AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS
Aquatic Conserv: Mar. Freshw. Ecosyst. 22: 232–261 (2012)
Published online 17 January 2012 in Wiley Online Library
(wileyonlinelibrary.com). DOI: 10.1002/aqc.1248
Reefs and islands of the Chagos Archipelago, Indian Ocean: why it
is the world’s largest no-take marine protected area
C. R. C. SHEPPARDa,*, M. ATEWEBERHANa, B. W. BOWENb, P. CARRc, C. A. CHENd, C. CLUBBEe, M. T. CRAIGf,
R. EBINGHAUSg, J. EBLEb, N. FITZSIMMONSh, M. R. GAITHERb, C-H. GANd, M. GOLLOCKi, N. GUZMANj,
N. A. J. GRAHAMk, A. HARRISa, R. JONESi, S. KESHAVMURTHYd, H. KOLDEWEYi, C. G. LUNDINl, J. A. MORTIMERm,
D. OBURAn, M. PFEIFFERo, A. R. G. PRICEa, S. PURKISp, P. RAINESq, J. W. READMANr, B. RIEGLp, A. ROGERSs,
M. SCHLEYERt, M. R. D SEAWARDu, A. L. S. SHEPPARDa, J. TAMELANDERv, J. R. TURNERw, S. VISRAMd,
C. VOGLERx, S. VOGTy, H. WOLSCHKEg, J. M-C. YANGd, S-Y. YANGd and C. YESSONi
a
School of Life Sciences, University of Warwick, CV4 7AL, UK
b
Hawai’i Institute of Marine Biology, P.O. Box 1346, Kane’ohe, Hawai’i. 96744, USA
c
BF BIOT, Diego Garcia, BIOT, BFPO 485, UK
d
Biodiversity Research Centre, Academia Sinica, 128 Academia Road, Nankang, Taipei, 115, Taiwan
e
Royal Botanic Gardens Kew, Richmond, Surrey TW9 3AB, UK
f
Department of Marine Sciences, University of Puerto Rico, Mayaguez, P.O. Box 9000, Mayaguez, PR 00681
g
Department for Environmental Chemistry, Helmholtz-Zentrum Geesthacht, Zentrum für Material- und Küstenforschung GmbH,
Max-Planck-Straße 1 I 21502, Geesthacht I, Germany
h
Institute for Applied Ecology, University of Canberra, ACT 2601, Australia
i
Zoological Society of London, Regents Park, London, NW1 4RY, UK
j
Nestor Guzman: NAVFACFE PWD DG Environmental, PSC 466 Box 5, FPO AP, 96595-0005
k
ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, QLD 4811, Australia
l
IUCN Marine Programme, Rue Mauverney 28, Gland, 1196, Switzerland
m
Department of Biology, University of Florida, Gainesville, Florida, USA
n
CORDIO East Africa, #9 Kibaki Flats, Kenyatta Beach, Bamburi Beach, P.O.BOX 10135, Mombasa 80101, Kenya
o
RWTH Aachen University, Templergraben 55, 52056 Aachen, Germany
p
National Coral Reef Institute, Nova Southeastern University, Oceanographic Center, 8000 North Ocean Drive, Dania Beach, FL
33004, USA
q
Coral Cay Conservation, Elizabeth House, 39 York Road, London SE1 7NQ, UK
r
Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth, PL1 3DH, UK
s
Department of Zoology, University of Oxford, The Tinbergen Building, South Parks Road, Oxford, OX1 3PS, UK
t
Oceanographic Research Institute, PO Box 10712, Marine Parade, Durban, 4056, South Africa
u
Division of Archaeological, Geographical and Environmental Sciences, University of Bradford, Bradford, West Yorkshire BD7 1DP, UK
v
UNEP Division of Environmental Policy Implementation, UN, Rajdamnern Nok Av., Bangkok, 10200, Thailand
w
School of Ocean Sciences, Bangor University, Menai Bridge, Anglesey, LL59 5AB, UK
x
Department für Geo- und Umweltwissenschaften Paläontologie & Geobiologie, Ludwig- Maximilians-Universität, Richard-Wagner-Str.
10, 80333, München, Germany
y
Naval Facilities Engineering Command Far East, PSC 473, Box 1, FPO AP 96349, USA
ABSTRACT
1. The Chagos Archipelago was designated a no-take marine protected area (MPA) in 2010; it covers 550 000 km2,
with more than 60 000 km2 shallow limestone platform and reefs. This has doubled the global cover of such MPAs.
2. It contains 25–50% of the Indian Ocean reef area remaining in excellent condition, as well as the world’s
largest contiguous undamaged reef area. It has suffered from warming episodes, but after the most severe mortality
event of 1998, coral cover was restored after 10 years.
*Correspondence to: C. R. C. Sheppard, School of Life Sciences, University of Warwick, CV4 7AL, UK. E-mail: charles.sheppard@warwick.ac.uk
Copyright # 2012 John Wiley & Sons, Ltd.
CHAGOS LARGE MARINE PROTECTED AREA
233
3. Coral reef fishes are orders of magnitude more abundant than in other Indian Ocean locations, regardless of
whether the latter are fished or protected.
4. Coral diseases are extremely low, and no invasive marine species are known.
5. Genetically, Chagos marine species are part of the Western Indian Ocean, and Chagos serves as a
‘stepping-stone’ in the ocean.
6. The no-take MPA extends to the 200 nm boundary, and. includes 86 unfished seamounts and 243 deep knolls
as well as encompassing important pelagic species.
7. On the larger islands, native plants, coconut crabs, bird and turtle colonies were largely destroyed in
plantation times, but several smaller islands are in relatively undamaged state.
8. There are now 10 ‘important bird areas’, coconut crab density is high and numbers of green and hawksbill
turtles are recovering.
9. Diego Garcia atoll contains a military facility; this atoll contains one Ramsar site and several ‘strict nature
reserves’. Pollutant monitoring shows it to be the least polluted inhabited atoll in the world. Today, strict
environmental regulations are enforced.
10. Shoreline erosion is significant in many places. Its economic cost in the inhabited part of Diego Garcia is
very high, but all islands are vulnerable.
11. Chagos is ideally situated for several monitoring programmes, and use is increasingly being made of the
archipelago for this purpose.
Copyright # 2012 John Wiley & Sons, Ltd.
Received 4 August 2011; Revised 31 October 2011; Accepted 14 November 2011
KEY WORDS:
Chagos; British Indian Ocean Territory; marine protected area; coral recovery; reef fishes; seamounts; reef disease;
marine invasives; fisheries; island conservation
INTRODUCTION
This paper reviews the scientific work and historic
information that demonstrates the outstanding
ecological values of the Chagos Archipelago,
which led in 2010 to the creation of the world’s
largest marine protected area (MPA), and which
became fully a no-take MPA later the same year.
The archipelago (Figure 1) forms the British
Indian Ocean Territory (BIOT), created in 1965
for UK and USA defence purposes. It is a large
group of atolls and submerged banks in the central
Indian Ocean, lying at the southernmost end of the
Lakshadweep–Maldives–Chagos ridge. Its central
200 300 km area contains five atolls with islands,
one atoll which is awash at high tide, and a dozen
more which are submerged to depths of 6–25 m.
The Great Chagos Bank is the world’s largest atoll
in area, although it contains only eight islands on
its western and northern rim. The area within the
total BIOT 200 nm zone is about 550 000 km2.
During recent decades, most of the tropical
ocean has been heavily affected by pollution,
over-exploitation and various unwise forms of
development (Millennium Ecosystem Assessment,
2005). Almost all indicators of ‘ocean health’
continue to show worsening trajectories, and
many attempted remedial measures have failed
to arrest the decline of habitats and ecosystems
Copyright # 2012 John Wiley & Sons, Ltd.
essential for both human welfare and maintenance
of biodiversity and productivity. The world’s oceans
are affected by overfishing, pollution, agriculture
and industry, shoreline construction, and climate
change (Jackson et al., 2001). Coral reefs in
particular are overexploited because they support
growing populations of some of the world’s poorest
people (Wilkinson, 2008a; Burke et al., 2011). All
reefs are highly vulnerable to increasing intensity
of human exploitation, which reduces both biomass
and productivity, and consequences of reef
deterioration may be greater than previously
anticipated (Mora et al., 2011). Most conventional
forms of marine management are failing to arrest
the decline, so many marine science bodies,
conservation organizations and international
conventions have called for more and larger marine
protected areas (MPAs) that have effective levels of
protection (United Nations, 2002; Wood et al.,
2008; Nelson and Bradner, 2010). MPAs remain
one of the only extensive tools being used directly
for conservation purposes (Spalding et al., 2010).
A recent assessment (Toropova et al., 2010)
showed that there are about 5900 MPAs, covering
4.2 million km2, which covers only 1.17% of the
oceans. Recently their median size was only 5 km2
(Wood et al., 2008). The small proportion of ocean
covered by MPAs must be compared with estimated
Aquatic Conserv: Mar. Freshw. Ecosyst. 22: 232–261 (2012)
234
C. R. C. SHEPPARD ET AL.
Speakers
Bank
Blenheim
reef
Salomon atoll
Peros Banhos
atoll
Victory Bank
6S
Nelsons
Island
Three
Brothers
Danger Is
7S
Pitt
Bank
Chagos and the marine protected area
Great
Chagos
Bank
Eagle Is
Egmont
atoll
Diego
Garcia
atoll
50 km
71 E
72 E
Figure 1. The Chagos Archipelago. Inset shows location and MPA
boundary (circular shape with flattened northern border). Main map:
the five atolls with land are shown in bold, the islands on Great Chagos
Bank and submerged reefs and atolls are not bold. All are located in the
central area of the MPA.
need. The Convention on Biological Diversity called
initially for 10% of the world’s EEZ to be protected
by some form of MPA by 2010, though the target
date was later put back to 2020. The World Parks
Congress called for 20% of the oceans to be protected
by 2012, and the World Summit on Sustainable
Development called for a global network of
comprehensive, representative and effectively
managed MPAs by 2012 (United Nations, 2002).
In developed countries of the Atlantic, the
OSPAR Commission called for an ecologically
coherent, well managed network of MPAs also
by 2012. Most targets will manifestly fail, and
participating parties would need to create over
19 million of the median size MPAs to achieve
these targets. In 2010, 260 marine scientists made
an urgent call for more and larger MPAs (http://
www.globaloceanlegacy.org/), and a figure of 30%
(not 10–20%) has increasingly emerged as the area
needed to avert permanent damage.
Unfortunately, the meaning of ‘protected’ varies
widely, with most allowing only partial protection
Copyright # 2012 John Wiley & Sons, Ltd.
and many also allowing fishing (one of the most
ecosystem distorting activities), while many lack any
protection at all. The latter are commonly called
‘paper parks’ and, regrettably, human pressures make
this category the large majority. For coral reefs, only
6% are effectively managed, 21% are ineffectively
managed, and 73% lie outside any MPA (Burke
et al., 2011). Reasons for MPA failures range from
being declared solely to meet ‘targets’ which are then
inadequately resourced, to being simply overwhelmed
by close proximity to large human populations.
Chagos was occupied from the 18th century, during
which time most of its native vegetation was
converted to coconut plantations. This industry
lasted until the 1970s. Two of the five atolls were
abandoned for economic reasons and social problems
in the 1930s, and in the early 1970s the plantations on
the remaining three atolls were closed due to the
establishment of a military facility. The people
were moved to various countries, notably Mauritius
and the Seychelles, and some eventually to Europe,
especially England (Edis, 2004). The remaining
plantations were already in some decline given
diminishing world demand for coconuts and the
ascendency of palm oil from elsewhere, but
nevertheless political issues surrounding the
forced removal of the last inhabitants has been mired
in controversy ever since. For the last 40 years the
islands have been uninhabited except for the
southernmost atoll of Diego Garcia, the western
arm of which contains the military facility and at
least 1000 Asian contractors and others. That
facility does not depend on local food resources
but is provisioned and supported entirely from
outside the archipelago.
Over the period of BIOT’s existence, there have
been a dozen scientific visits, involving more than
50 visiting scientists. It has become clear during this
period when coral reefs in most of the Indian Ocean
have become seriously degraded that those of
Chagos persist in an exceptionally good state. This
led increasingly to calls to extend its conservation,
and data to support the concept came from over
200 papers arising from both those scientific
expeditions and, to a lesser extent, from unpublished
information, from regional data and from modelling.
Recently, the Pew Ocean Legacy Program
included Chagos as one of five areas selected for
protection, and promoted efforts to convince the
UK Government to declare it a no-take MPA to
Aquatic Conserv: Mar. Freshw. Ecosyst. 22: 232–261 (2012)
CHAGOS LARGE MARINE PROTECTED AREA
the 200 nm boundary (Nelson and Bradner, 2010).
Part of this process was the creation of the Chagos
Environment Network (CEN), a loose association
of several leading UK science bodies and NGOs,
whose role was to support efforts to ensure that
Chagos’ globally important natural environment
would be conserved as a unique and valuable
resource for present and future generations. In
2010, CEN responded to the UK Government’s
Consultation, saying that only designation as a
no-take MPA ‘. . . guarantees full protection for the
ecosystems and species of the Chagos Archipelago
and its surrounding reefs, lagoons and waters. Only
[this] provides the complete protection needed to
underpin the Chagos Protected Area’s value as
an important global reference site for a wide range
of scientific ecological, oceanographic and climate
studies, as well as its continued benefits to humans
into the future’ (CEN, 2010).
BIOT is a UK Overseas Territory and as such
has its own government, which in this case is the
office of the BIOT Administration located in the
UK Foreign and Commonwealth Office in London.
The senior UK military officer in the archipelago is
the British Representative of the Commissioner.
The UK Foreign Secretary announced the creation
of BIOT as a no-take MPA, instructing the
Commissioner to declare it as such in April 2010
(http://www.fco.gov.uk/en/news/latest-news/
?view=News&id=22014096). The Commissioner,
in Proclamation Number 1 of 2010, proclaimed it such
235
‘in the name of the Queen’. Existing environmental
laws are currently being revised and consolidated to
accommodate this status. Diego Garcia atoll to its
3 nm boundary is excluded from the MPA. The
area thus excluded is less than 1% of the total
area although it has several pre-existing, strict
environmental laws of its own, and contains a
Ramsar site (see later). Existing tuna fishing licences
were discontinued, and the deficit for BIOT
finances of approximately $1 million per year was
subsequently replaced from private sources. It
is currently the largest MPA in the world
(Nelson and Bradner, 2010) and is now also part
of the ‘Big Ocean Network’, an information
exchange network of managers and partners of
existing and proposed large-scale marine managed
areas (www.bigoceanmanagers.org/). Monitoring
and enforcement are undertaken in large part
by a patrol vessel which serves as a mobile base
for both the military and civilian research
expeditions.
Island and reef areas
Figure 2(a) shows the areas of islands and reefs.
Diego Garcia contains half the total land area, the
rest being split among over 50 small islands, the
number varying to some degree with tidal height
and shifts of sand banks. All islands are very
low lying, and are typical coral cays constructed
of limestone. Beneath these lie freshwater lenses
sustained by high rainfall.
Figure 2. a) island areas in the Chagos Archipelago (scale in ha). The largest islands are named. b) area of submerged substrate in the archipelago
(scale in km2) (from Dumbraveanu and Sheppard, 1999).
Copyright # 2012 John Wiley & Sons, Ltd.
Aquatic Conserv: Mar. Freshw. Ecosyst. 22: 232–261 (2012)
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C. R. C. SHEPPARD ET AL.
In contrast to the small island areas, sublittoral
substrate in the photic zone is calculated to be
approximately 60 000 km2 (Figure 2(b)) (Dumbraveanu
and Sheppard, 1999). How much of this huge area
is actively growing reef is uncertain; more than
95% of the territory has never been studied, though
some areas are apparently eroding and others
support sand and/or large seagrass beds. There is
enormous opportunity for new discoveries: as
recently as 2010 an expedition discovered many
hectares of seagrass and a previously unknown
3 km2 mangrove forest. Other parts of Chagos
have been mapped using bathymetric or satellite
data-based modelling (Yesson et al., 2011, see later
Figures 9 and S12 in Supplementary Material).
REEF CONDITION
Coral cover and changes due to mortality episodes
There were no quantitative studies of reef condition
on Chagos reefs before the 1970s, although
descriptive studies, notably Stoddart and Taylor
(1971), described land and reef flat in Diego
Garcia. From the 1970s, episodic visits enabled a
series of coral cover measurements to be taken
on reef slopes.
Coral cover declined between the first survey
in 1978 (Sheppard, 1980a) and the next in 1996
(Sheppard, 1999a) (Figure 3). This was mainly due
to loss of shallow and mid-depth branching species,
particularly Acropora palifera and table corals
including Acropora cytherea, and causes were only
speculated upon at the time (Sheppard, 1999a).
Later, after much work globally and more surveys
in Chagos, the cause was suggested to be several
warming events. This modest decline occurred in
many Indian Ocean islands groups over this period
(Ateweberhan et al., 2011) and in Kenya (Muthiga
et al., 2008) though it was not universal.
Severe warming in 1998 then caused severe
mortality on all Chagos reefs (Sheppard, 1999b;
Sheppard et al., 2002; Figures 3 and S1 in
Supplementary Material) as it did throughout the
Indian Ocean (Ateweberhan et al., 2011). Coral
and soft coral mortality was almost total on several
Chagos ocean-facing reefs to clearly defined
depths, below which corals provided much higher
cover. This killed zone extended deeper in southern
atolls, and in Diego Garcia for example was
greater than 40 m depth, while in more northern
atolls it extended to only about 10–15 m depth
(Sheppard et al., 2002). Such variability was mirrored
in the Indian Ocean as a whole (Sheppard, 2006).
Lagoon reefs of Chagos atolls were much less
affected than ocean facing reefs (Figure S1 in
Supplementary Material), with many retaining
high coral cover, including stands of Acropora.
Post-1998, coral species diversity was greatest in deep
lagoon areas.
Coral recovery
Several ocean-facing transects around the atolls
have been monitored repeatedly from 1999 onwards
(Figure 4). On these, no increase of hard coral cover
was seen for 3 years following the mortality,
although by 2001 large numbers of juveniles were
present, at densities of up to 28 m-2, the highest
recorded globally at that time (Sheppard et al., 2002;
Harris and Sheppard, 2008). Coral spat provided 6%
cover on easily measured (but disintegrating) dead
coral tables, with a further 5% cover provided by
juvenile soft corals, indicating good recovery
potential (Figure S2 in Supplementary Material).
Increase in coral cover became evident by 2006,
Average reef cover and years with SST warming - El Nino events
Average all data to 20 m depth
79-80
80
70
82-83
86-87
88
95
91
Soft corals
False
corals
60
% reef cover
98
Others
50
40
Soft corals
Digitate corals
Others
30
Acropora tables
Digitate corals
20
Acropora tables
P.lutea
10
P.lutea
A. palifera
A. palifera
0
1979
1996
1999
2001
Year
Figure 3. Percentage coral on reefs by the main coral types in 4 years, for the major live categories identifiable by snorkelling in 1999. Arrows along the
top are dates and approximate relative severity (arrow thickness) of previous warming events (from Sheppard, 1999a).
Copyright # 2012 John Wiley & Sons, Ltd.
Aquatic Conserv: Mar. Freshw. Ecosyst. 22: 232–261 (2012)
237
CHAGOS LARGE MARINE PROTECTED AREA
70
significantly higher in lagoons (63.04 3.19%)
than ocean-facing slopes (39.69 2.03%). Soft
coral was higher on ocean-facing slopes (14.02
1.58%) than in lagoons (2.65 0.72%). Hard
coral cover decreased between 6 and 25 m, but
sponge and soft corals showed an increase with
depth. Dead standing coral at most sites was low
at 3–13%, and rubble did not change significantly
at different depths. Structural complexity was
reduced to 15 m in the outer atolls, and to deeper
zones on the Great Chagos Bank and Diego
Garcia atoll. By 2006 all shallow regions had
developed sufficiently to form a canopy, with
colonies competing with one another for space
(O’Farrell, 2007). Furthermore, deep lagoonal
areas exhibited the highest numbers of small,
juvenile coral colonies. Modelling studies indicate
that such deep reef areas could be responsible for
relatively rapid recolonization of denuded shallow
reefs (Riegl and Piller, 2003).
The past decade has seen further coral bleaching
events in Chagos, in 2003, 2004, 2005, and a mild
one in 2010. None were sufficient to cause mass
mortality, although species-specific coral mortality
was recorded of many Acropora cytherea tables in
2010 (Pratchett et al., 2010). Given that warming
episodes sufficient to kill corals are predicted to
increase (Sheppard, 2003; Hoegh-Guldberg et al.,
2007) it is likely that intermittent interruptions to
coral growth will continue. However, models
based on recruit availability scaled to the present
coral cover, suggest that Chagos reefs will long
be able to withstand recurring strong mortality
60
Coral Cover (%)
1978
50
1996
40
2010
30
2006
20
1999
10
2001
0
0
5
10
15
25
20
Depth (m)
Figure 4. Coral cover in depths to 25 m on ocean-facing slopes in
different years (Sheppard 1980a, 1999a,1999b; Sheppard et al., 2008;
Sheppard unpublished data). Data are of all ocean-facing transects in
this series measured on each date. Bars are error bars (error data lost
for 1978).
especially in shallow water (Harris and Sheppard,
2008; Sheppard et al., 2008) where restoration to
pre-1998 levels occurred by 2010. Deeper recovery
has been slower. Coral cover in 2011 reached
values recorded in 1978 in a few transects in Diego
Garcia, but most atolls were not surveyed during
that year.
In 2006, extensive video surveys were taken
and archived, showing mean percentage cover of
several benthic categories (Bayley, 2009) (Figures 5
and S3, S4 in Supplementary Material). These
showed no significant differences that year in hard
coral cover in pooled data between atolls, although
significant differences existed at depth and site levels
between ocean-facing reefs. Hard coral cover was
Mean % cover
60
GCB
50
DG
40
SAL
PB
30
20
10
Sa
nd
e
ub
bl
R
ro
ck
ra
l
ou
s
co
C
al
c
ar
e
ni
sm
ea
d
D
or
ga
Al
ga
e
th
er
O
Sp
on
ge
So
f
H
ar
d
co
ra
l
tc
or
al
0
Life form
Figure 5. Mean percentage cover values of life form and substrate categories pooled from all depths and all sites for each of four atolls (GCB:Great
Chagos Bank, DG: Diego Garcia, SAL: Salomon atoll, PB: Peros Banhos atoll), surveyed by video during 2006. Bars are error bars.
Copyright # 2012 John Wiley & Sons, Ltd.
Aquatic Conserv: Mar. Freshw. Ecosyst. 22: 232–261 (2012)
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C. R. C. SHEPPARD ET AL.
events – even each decade – and still maintain high
coral cover. Significant declines in cover are expected
only if both larval supply decreases and coral
mortality events increase in intensity and frequency.
Pre- and post-1998 studies have also revealed
some changes in the soft coral component. The
principal octocorals before and after the 1998
ENSO shared many common taxa (Reinicke and
van Ofwegen, 1999; Schleyer and Benayahu,
2010), but a few discontinuities in their biodiversity
indicate subtle changes in more persistent genera
(Lobophytum, Sarcophyton). Some fast-growing
‘fugitive’ genera (e.g. Cespitularia, Efflatounaria,
Heteroxenia) disappeared after the ENSO-related
coral bleaching (Reinicke and van Ofwegen, 1999;
Schleyer and Benayahu, 2010), suggesting that
such transient fugitives might be eliminated from
soft coral communities on isolated reef systems by
bleaching disturbance of this nature. Carijoa riseii,
a species often considered a fouling organism, and
even an invasive in some places (Concepcion et al.,
2010), was found in 2006. The observed post-ENSO
recovery gives cause for hope for soft coral survival
in the face of climate change.
Reef fish
Biomass of reef fish around the northern atolls of
Chagos was quantified for the first time in 2010, using
underwater visual census (Graham, 2010). Biomass
estimates for Chagos exceed values from both fished
and protected reefs elsewhere in the region, such as
Kenya, Seychelles, Madagascar and even the Maldives,
by several orders of magnitude (McClanahan et al.,
2009; McClanahan, 2011; Graham, 2010). The
Chagos biomass estimates are matched only by
some remote, unfished locations in the Pacific Ocean
(Sandin et al., 2008; Williams et al., 2011).
With recent declines in coral cover globally
(Ateweberhan et al., 2011) there is growing concern
over impacts on reef fish assemblages (Pratchett et al.,
2008). Much work has followed the 1998 bleaching
event around the world in trying to document
changes to reef fish populations. A compilation of
short-term impacts (<3 years post-coral mortality)
of coral loss on fishes indicated that species displaying
population declines were those that specialized on
coral for food, shelter or settlement (Wilson et al.,
2006). However, subsequent studies have shown that
longer term effects of coral loss and reef structural
collapse on fish are much wider reaching, with a large
portion of the fish community affected, including
reductions in species richness, reduced abundance of
Copyright # 2012 John Wiley & Sons, Ltd.
many groups and changes in the size structure of the
community (Jones et al., 2004; Graham et al., 2006,
2007, 2008; Wilson et al., 2008). Reef fish surveys in
Chagos conducted in 1996 were repeated in 2006
using identical methodology. This was part of a study
across seven Indian Ocean nations. One of the groups
of fish most affected by coral loss is coral-feeding
butterflyfishes, but a comparison between Chagos
and Seychelles demonstrated that, although both
specialized and generalist coral feeding butterflyfishes
showed declines in abundance in the Seychelles
through the 1998 bleaching event, there was no
detectable difference in Chagos (Graham et al., 2009a).
Across the Indian Ocean as a whole there were
declines in fish species richness, and in the abundance
of corallivores, planktivores and small bodied fish
(<20 cm maximum attainable size) (Graham et al.,
2008; MacNeil and Graham, 2010) as a result of reef
degradation. In contrast, the populations of Chagos
remained remarkably stable (Figure 6). Changes in
fish species richness for Chagos were extremely small
and either side of zero, compared with the regional
decline. This highlights the temporal stability of
Chagos fish assemblages in response to a large-scale
disturbance, despite substantial negative responses
elsewhere in the ocean, and accords with findings
of Mora et al. (2011) and Sandin et al. (2008)
that reef fish assemblages are very vulnerable to
anthropogenic stressors.
Also of note are some different fish behaviours
that are very rarely seen elsewhere around the world
where human exploitation, coastal development,
and other impacts have changed abundances,
ecological interactions, and behaviour. One such
example is the daytime feeding behaviour of the
moray eel, Gymnothorax pictus, on shore crabs,
leaping clear of the water to capture their prey
(Graham et al., 2009b). Behaviours like this, and the
exceptional stability and abundance of the reef fish
communities, make Chagos a very important reference
area with which scientists can understand ecological
and behavioural changes elsewhere in the world.
Coral diseases
In 2006 a survey assessed corals along 37 transects
at eight sites across the archipelago (Figure 7).
Overall prevalence of disease was 5.2%, which sits
at the low end of the global spectrum where regional
averages for ‘white syndrome’ alone are around 5%
in parts of Australia, Palau, and East Africa, 8% in
the Philippines (Weil et al., 2002; Willis et al., 2004;
Raymundo et al., 2005) up to around 13% at some
Aquatic Conserv: Mar. Freshw. Ecosyst. 22: 232–261 (2012)
239
CHAGOS LARGE MARINE PROTECTED AREA
Figure 6. Change in reef fish species richness across seven countries in the Indian Ocean following the 1998 coral mortality event. Chagos sites
represented by filled circles. Adapted from Graham et al. (2008).
14
Health status (% of total coral)
bleached (%)
12
white
syndrome (%)
10
pigmentation
response (%)
predation (%)
8
spots (%)
6
ulcers (%)
4
2
0
Diego
Garcia
Salomon
Peros
Banhos
Eagle
Middle
Brother
North
Brother
Egmont
Danger
-2
Site
Figure 7. Percentage of adult colonies in different atolls showing disease or other adverse conditions. Bars are standard error bars.
sites in the Eastern Indian Ocean (Hobbs and Frisch,
2010), and 20% in the Caribbean (Weil et al., 2006;
Miller et al., 2009).
Temperature has been shown to be a key factor
triggering diseases, with infection occurring rapidly
at elevated temperatures (Ben-Haim and Rosenberg,
2002; Bruno et al., 2007; Harvell et al., 2007). Thus
the increasing frequency of raised temperature
episodes gives cause for concern. Coral diseases
often arise from changes to the normal, commensal
relationship between the coral and the bacterial
community in their mucus, skeleton, and tissues
(Rohwer and Kelley, 2004; Lesser et al., 2007).
Physiological stresses that cause corals to become
overwhelmed by bacteria are often anthropogenic
Copyright # 2012 John Wiley & Sons, Ltd.
in origin, coming from sediment deposition, nutrient
rise (Bruno et al., 2003; Kaczmarsky and Richardson,
2011), or sea temperature rise (Harvell et al., 2007;
Zvuloni et al., 2009). Other factors correlated with
the likelihood of coral disease include geographical
range and predator diversity (Diaz and Madin,
2011), while a higher density of individuals also
increases susceptibility (Willis et al., 2004; Bruno
et al., 2007). Although remoteness from people is
no guarantee of absence of disease, especially if
temperature rises (Williams et al., 2007), mitigation
of other human induced stress factors may reduce
disease prevalence (Bruno et al., 2003; Harvell
et al., 2007). At present, Chagos reefs have very
low disease levels.
Aquatic Conserv: Mar. Freshw. Ecosyst. 22: 232–261 (2012)
240
C. R. C. SHEPPARD ET AL.
Marine invasive species
Marine invasive alien species (IAS) are recognized
as one of the most significant threats to global
biodiversity (Wilcove et al., 1998; Bax et al., 2010)
and documented IAS are commonly significantly
underestimated. IAS pressure is driving global
declines in species diversity, with the overall impact
apparently increasing (McGeoch et al., 2010).
Notably, over 100 introduced marine species covering
14 phyla are known from ports in the Pacific (Coles
et al., 1999). Article 8(h) of the Convention on
Biological Diversity calls for prevention of
introductions and control or eradication of alien
species that threaten ecosystems, habitats or
species, and the recently agreed Aichi Biodiversity
Targets call for identifying pathways and putting
in place by 2020 measures to prevent species
introduction and establishment.
Ballast water and hull fouling provide the primary
vectors for marine species introduction (Cohen and
Carlton, 1998; Ruiz et al., 2000; Hewitt et al., 2004).
Navy and supply ships frequently arrive in Diego
Garcia, mainly from the USA, the Middle East, and
Singapore, but any ships, including recreational
yachts, may carry hull fouling organisms (Bax et al.,
2002). Therefore pathways for species introductions
to Chagos exist, as do preconditions for successful
establishment (Tamelander et al., 2009). While
most ships arrive at Chagos loaded, some may
be empty and ballasted. Ballast water exchange
occurs outside the lagoon and during mid-crossing
in keeping with IMO ballast water management
guidelines (IMO, 2004).
A survey of non-native marine biota in Chagos was
carried out in 2006 in all atolls (Tamelander et al.,
2009) based on standard port survey methods (Hewitt
and Martin, 2001) but with a lower sensitivity. Hard
and soft substrate benthic biota were sampled at 42
sites (19 sites in Diego Garcia, nine each on the Great
Chagos Bank and at Peros Banhos, and five in the
Salomon atoll). Twenty-four phyla were represented
in 2672 samples, with four phyla (Bryozoa, Mollusca,
Annelida and Porifera) each making up over 10% of
the total number of specimens.
No non-native species were detected in the
samples, the first time such a survey has not found
species introduced as a result of human activities
(Tamelander et al., 2009). This finding is testament
to the ecological integrity of Chagos’ marine
ecosystems. Shallow marine habitats are believed
to be particularly vulnerable to bioinvasions when
degraded (Heywood, 1995), but ecosystem health
Copyright # 2012 John Wiley & Sons, Ltd.
and high biodiversity confer higher resistance. Only
16% of marine ecoregions have no reported marine
invasions, although the true figure may be lower
because of under-reporting (Molnar et al., 2008).
Because controlling or eradicating a marine
species once it is established is nearly impossible
(Bax et al., 2002), management must focus on
precautionary measures (Thresher and Kuris, 2004;
Carlton and Ruiz, 2005). Successful prevention
and management of IAS threats in Chagos is a
prerequisite for effective management of the newly
established MPA (Pomeroy et al., 2004; Tu, 2009).
Further, this needs to be devised in the broader
context of climate change and the potentially greater
risk of species spread and establishment that this
may bring (Bax et al., 2010; Burgiel and Muir, 2010).
Chagos reef condition in the Indian Ocean context
Most Indian Ocean reef areas are heavily exploited
and many have shown limited recovery following the
1998 bleaching disturbance (Wilkinson, 2008b;
Harris, 2010). Many which declined catastrophically
in 1998 and which also suffer from local impacts have
not recovered significantly, or at all (Harris, 2010).
The 1998 bleaching event is the main determinant
of coral cover change in the Indian Ocean since the
1970s (Ateweberhan et al., 2011), and the central
regions, which had some of the highest coral cover
estimates before 1998, suffered the worst during the
bleaching event. Subsequent recovery for most of these
reefs now remains below average for the region, but of
the central Indian Ocean reefs, recovery in Chagos is
higher than elsewhere (Ateweberhan et al., 2011).
Globally, a third of reef-building corals are
threatened with extinction (Carpenter et al., 2008)
and today, in the Indian Ocean, only about a
third of reefs may be attributed to a ‘low threat
level’ category (Wilkinson, 2008a, 2008b). Chagos
reefs fall within this minority group and contain a
substantial proportion of reef area in very good
condition. Reef area estimations are difficult, and
have been subject to wide variation. Spalding et al.
(2001) suggested the Indian Ocean has 32 000 km2
of reefs (the Red Sea region and the Gulf region
adding 17 400 and 4200 km2 more, respectively),
and, based on this, Chagos has 3770 km2 of reefs
(Rajasuriya et al., 2004) meaning Chagos comprises
up to half of this ocean’s reefs in a ‘low threat level’
category (Figure 8). More recent calculations by
Spalding (pers. comm. and see Burke et al., 2011)
resulted in a revised estimate that Chagos provides
25% of reefs in the ‘low threat’ category. Even
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CHAGOS LARGE MARINE PROTECTED AREA
Chagos
Effectively Lost Reefs
(%)
Reefs at Critical Stage
(%)
Reefs at Threatened
Stage (%)
Reefs at Low Threat
level (%)
Figure 8. Percentage of reefs in different categories in the Indian Ocean.
Categories are those from Wilkinson (2008a). The probable proportion
occupied by Chagos (solid line to vertical) is about half of the reefs in
the ‘best’ category. From the dashed line to vertical is an alternative
estimate of the proportion of Chagos reefs according to Spalding using
slightly different categories (pers. comm.).
this ‘. . .25% of the region’s low threat reefs is still an
extraordinary proportion, and it is also worth
stressing that in addition to this, these are by far
the largest contiguous reef tracts considered to be
under low threat’ (Spalding pers. comm., 2011).
While both area values are much less than the area
of illuminated shallow limestone substrate which
was calculated from detailed bathymetric plotting
(Figure 2), the values used have the important
benefit that they were calculated consistently
throughout the world, thus permitting comparisons;
direct measurements based on bathymetry do not yet
have a counterpart in most other countries.
For other Indian Ocean areas, Tamelander and
Rajasuriya (2008) report that ‘recovery of South
Asian coral reefs since the 1998 mass bleaching
has been patchy; Chagos has shown particularly
good recovery, reefs in the western atoll chain of
the Maldives and Bar Reef in Sri Lanka have also
recovered relatively well, while many reefs near Sri
Lanka and reefs in the eastern atoll chain of the
Maldives have shown little or no recovery. . . Coral
larval recruitment was very strong, such that the
lowest Chagos recruit densities were at least 10
times higher than rates of recruitment at most
other reefs in the central and western Indian Ocean.’
For island archipelagos further west, Wilkinson
(2008a) reported that ‘some reefs of the Seychelles
and Comoros that suffered major damage in 1998
have probably regained about half the lost coral
cover; there has also been virtually no recovery on
others’. Numerous other compilations (Wilkinson,
2008a; Burke et al., 2011) report patchy or poor coral
recovery in most other parts of the region.
Reasons for the good condition of Chagos reefs
are likely to include remoteness from compounding
Copyright # 2012 John Wiley & Sons, Ltd.
241
human activities, but some additional factors may
contribute. Strong light adapted ‘Clade A’ forms of
symbiotic zooxanthellae have been identified in
shallow corals in Chagos, occurring in approximately
half of the shallow water Acropora colonies that were
heavily affected by warming but which are now
recovering strongly (Yang et al., 2012; Figure S5
in Supplementary Material). Also, an array of
temperature sensors at different depths has identified
regular incursions of deep, cool water that rise to
cover reefs, including during the annual periods of
greatest warming (Sheppard, 2009).
But it is increasingly understood that direct human
pressures are the main cause of reef degradation and
this has often been underestimated in the past (Mora
et al., 2011). Such activities impede recovery, and
absence of herbivore extraction, pollution, and
sedimentation increase reef resilience (Hughes et al.,
2010). Most of Chagos has no human population
at all. Diego Garcia imports all its requirements
and for the last 15 years at least has had strong
environmental management. Lack of human
pressures is likely to be one major reason for the
present good condition of these reefs.
In the Indian Ocean as a whole, direct human
pressures can only increase further. Of this
region, a decade ago Spalding et al. (2001) noted:
‘Human populations . . . are rapidly increasing.
Most of the coastal populations are very poor,
and heavily dependent on the adjacent reefs for
food. Unfortunately there is little control over the
utilization of these resources, either through
traditional or formal management regimes, and
large areas of reefs have been degraded through
overfishing or destructive fishing techniques.’ With
annual population growth rates of 2.5% being
common in the region, compounded by migration
to the coast in some countries that have experienced
wars or drought, coastal populations and exploitation
of reefs have increased substantially since Spalding’s
(2001) account. As reefs degrade, the proportion of
healthy reefs of the Indian Ocean contained in
Chagos, already very high, continues to increase,
so that a precautionary approach to their protection
is merited.
DEEP-WATER ECOSYSTEMS
Yesson et al. (2011) determined that 86 seamounts
(conical topographic rises >1000 m elevation) and
243 knolls (conical topographic rises of elevation
200–999 m) are predicted to occur within the
Aquatic Conserv: Mar. Freshw. Ecosyst. 22: 232–261 (2012)
242
C. R. C. SHEPPARD ET AL.
Figure 9. Seamounts of the Chagos MPA as identified in Yesson et al.
(2011). Bathymetry data from shuttle radar topography mission 30
arc-second grid (http://www2.jpl.nasa.gov/srtm/).
Chagos MPA (Figure 9). Chagos thus contains
more than 10% of all Indian Ocean seamounts
and so the area is regionally important for these
features as well. Given that globally only 506
seamounts and 606 knolls lie in protected areas
(Yesson et al., 2011, based on the world database
of protected areas 2009), this means that the
Chagos MPA increased the world’s protection of
seamounts by 17% and knolls by 40%. Previous
emphasis of the Chagos MPA has been on
shallow-water ecosystems, but protection of its
seamounts is also important, especially considering
their high biodiversity, often representing entirely
unique ecosystems (Clark et al., 2006). Although
the geology of some of the seamounts and ridges
in the Indian Ocean has been explored, including
the Chagos-Laccadives Ridge, seamount fauna is
poorly known (Rogers et al., 2007). Some data on
fish exist, mainly resulting from exploratory or
commercial fishing, but no specific information
relates to the Chagos-Laccadive Ridge. Recent
modelling studies based on 30-arc second satellite
bathymetry data indicate that the Indian Ocean
hosts fewer seamounts than the Atlantic and Pacific
Oceans (Yesson et al., 2011), and many are
associated with ridges or originate at ridges.
The Indian Ocean suffers increasing pressure
from deep-sea fishing that threatens both seamounts
and other benthic habitats. The fact that there has
never been deep-water fishing or trawling in Chagos
makes it particularly important when considered in
a regional context. Deep-sea fishing in the Indian
Ocean was mostly undertaken by distant-water
fleets, particularly from the USSR. These fisheries
targeted redbait (Emmelichthys nitidus) and rubyfish
(Plagiogeneion rubiginosus) with catches peaking
about 1980 and then decreasing to the mid-1980s
(Clark et al., 2007). Fishing then switched to
Copyright # 2012 John Wiley & Sons, Ltd.
alfonsino (Beryx splendens) in the 1990s as new
seamounts were exploited. Some exploratory
trawling was also carried out on the Madagascar
Ridge and South-west Indian Ocean Ridge by French
vessels in the 1970s and 1980s, particularly targeting
Walter’s Shoals and Sapmer Bank (Collette and
Parin, 1991). In the late 1990s, a new fishery
developed on the South-west Indian Ocean Ridge
with trawlers targeting deep-water species such
as orange roughy (Hoplostethus atlanticus), black
cardinal fish (Epigonus telescopus), southern
boarfish (Pseudopentaceros richardsoni), oreo
(Oreosomatidae) and alfonsino (Clark et al., 2007).
This fishery rapidly expanded, with estimated catches
of orange roughy being approximately 10 000 tonnes,
until the fishery collapsed. Fishing then shifted to
the Madagascar Plateau, Mozambique Ridge, and
Mid-Indian Ocean Ridge, targeting alfonsino and
rubyfish (Clark et al., 2007). Most of these areas
therefore have probably been significantly affected
by past deep-sea bottom fisheries.
Deep-sea fishing in most of the Indian Ocean is
continuing and showing signs of increasing its
geographic spread, mainly targeting orange roughy
and alfonsino. Recent fishing has also taken place
on the Broken Ridge (eastern Indian Ocean), 90 East
Ridge, possibly the Central Indian Ridge, the
Mozambique Ridge and Plateau and Walter’s Shoal
(western Indian Ocean), where a deep-water fishery
for lobster (Palinurus barbarae) has developed
(Bensch et al., 2008). The banks around Mauritius
and high seas portions of the Saya da Malha Bank
have been targeted by fisheries for Lutjanus spp.,
and lethrinid fish (SWIOFC, 2009), and there are also
reports of unregulated gillnet fishing in the Southern
Indian Ocean such as at Walter’s Shoal, which target
sharks (Shotton, 2006). Currently, there is little or no
information available on impacts of deep-sea fishing
in high seas areas of the Indian Ocean on populations
of target or by-catch species, or on seabed ecosystems.
Reporting of data is complicated by issues
of commercial confidentiality in fisheries where
individual stocks may be located across a wide area
(e.g. the South-west Indian Ocean Ridge), and there
is no adequate regional fisheries management body
(see below). At present, new fisheries are developing
in the region with no apparent assessment of resource
size or appropriate exploitation levels to ensure
sustainability of fisheries, or to estimate impacts of
such fisheries on vulnerable marine ecosystems.
Global modelling studies are currently also being
undertaken of habitat suitability for deep-sea
Scleractinia and Octocorallia, at 30-arc second
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CHAGOS LARGE MARINE PROTECTED AREA
resolution (Davies and Guinotte, 2011; Yesson
et al., in press). These indicate that suitable habitat
for these organisms exist on deep slopes and
seamounts within the Chagos MPA (Davies and
Guinotte, 2011; Yesson et al., in press). Given
the lack of a history of deep-sea fishing in the
region around the Chagos Archipelago, it is likely
that associated communities of invertebrates and fish
are still largely intact, unlike on most other ridges in
the Indian Ocean that have been fished or which are
subject to continuing or expanding fisheries.
Given the lack of research in general on equatorial
seamounts, the MPA is thus particularly important
for deep-water ecosystem conservation, both at a
regional and global level. It also provides a unique
opportunity to investigate the energetic links between
production associated with shallow-water coral
reefs and deep-water ecosystems, an area of marine
ecology that has not been explored.
PELAGIC FISHING AND FISHERIES
While no deep-sea trawling has been recorded in the
Chagos EEZ, there have been impacts from fisheries
operating in both in-shore and pelagic environments.
These fisheries provided most income for Chagos until
the cessation of fishing licences after the MPA was
created, with the last licences expiring on 31 October
2010. The main fisheries were a longline and purse
seine fishery for tuna, and an inshore fishery. There
is also a small recreational fishery in Diego Garcia.
The longline fishery in Chagos waters was active
year-round, mainly under Taiwanese and Japanese
flagged vessels targeting large pelagic species,
including yellowfin tuna (Thunnus albacares) and
bigeye tuna (Thunnus obesus), swordfish (Xiphias
gladius), striped marlin (Tetrapturus audax) and
Indo-Pacific sailfish (Istiophorus platypterus), with
annual catches ranging from 371–1366 tonnes
over the last 5 years (Koldewey et al., 2010). The
purse-seine fishery targeted yellowfin and skipjack
tuna (Katsuwonus pelamis) and was highly seasonal,
operating between November and March with a
peak usually in December and January (Mees
et al., 2009). Log book records show that catches,
mainly by Spanish and French flagged vessels, were
highly variable, ranging from less than 100 to
around 24 000 tonnes annually over the last 5 years
(Koldewey et al., 2010).
The Mauritian inshore fishery targeted demersal
species, principally snappers, emperors, and groupers,
and logbook records indicated that catches were
between 200 and 300 tonnes per year for the period
Copyright # 2012 John Wiley & Sons, Ltd.
243
1991–1997, decreasing to between 100 and 150 tonnes
from 2004 (Mees et al., 2008).
The recreational fishery on Diego Garcia is much
smaller, taking (in 2008) 25.2 tonnes of tuna and
tuna-like species (76% of the catch), the remainder
being reef-associated species (Mees et al., 2009).
As with most fisheries, those in Chagos suffered
from poor documentation of by-catch and illegal
fishing. By-catch was inadequately recorded through
a log book system supported by limited observer
coverage – mean observer coverage was 1.24% per
season for longline fishing and 5.56% for purse-seine
fishing (Koldewey et al., 2010). Even with this
uncertainty, the by-catch in the Chagos was clearly
substantial, particularly for sharks, rays, and billfish
(Pearce, 1996; Anderson et al., 1998; Roberts, 2007;
Graham et al., 2010; Koldewey et al., 2010). There
is also evidence of marked harvesting effects on
holothurian (sea cucumber) populations as a result
of poaching (Price et al., 2010).
Illegal fishing remains a management issue
following the implementation of the MPA and
enforcement will be key to its effectiveness. Reef
sharks in Chagos have declined by over 90% in a
30 year period (1975 to 2006), attributed primarily
to poaching by illegal vessels (Anderson et al.,
1998; Graham et al., 2010). The size and location
of Chagos as an MPA is particularly important
as the western Indian Ocean has some of the most
exploited, poorly understood, and badly protected
and managed coastal and pelagic fisheries in the
world (Kimani et al., 2009; van der Elst et al., 2005),
while overall catches continue to dramatically increase
(FAO, 2010). Chagos is within the remit of the
Indian Ocean Tuna Commission (IOTC), although
this Regional Fisheries Management Organization
(RFMO) is recognized to have numerous legal and
technical weaknesses (Anon., 2009). Tuna in the
Indian Ocean are considered to be close to the
maximum sustainable yield (bigeye) or overexploited
(yellowfin) and even skipjack, which is generally
considered a highly productive and resilient species,
has been highlighted for close monitoring (IOTC,
2010). Illegal, unreported and unregulated fishing
is not a trivial component of the catch and adds
substantial uncertainty into assessments (Ahrens,
2010).
There is increasing evidence that large MPAs
like Chagos can benefit pelagic species that exhibit
highly mobile behaviours (reviewed in Game
et al., 2009; Koldewey et al., 2010). In fisheries
management, the phrase ‘highly migratory’ often
has little biological meaning, with studies of
Aquatic Conserv: Mar. Freshw. Ecosyst. 22: 232–261 (2012)
244
C. R. C. SHEPPARD ET AL.
tuna mobility demonstrating they would benefit
from national-level closures (Sibert and Hampton,
2003). Pelagic fish demonstrate considerable
stability and persistence, and predictability of
some habitat features does occur within the pelagic
realm (Hyrenbach et al., 2000; Baum et al., 2003;
Worm et al., 2003; Etnoyer et al., 2004; Alpine,
2005). Migratory predators like tuna do not move
randomly, but associate with certain environmental
and/or physical features (Hughes et al., 2010;
Schaefer and Fuller, 2010), meaning that positive,
measurable reserve effects on pelagic populations
exist (Hyrenbach et al., 2002; Roberts and Sargant,
2002; Baum et al., 2003; Worm et al., 2003, 2005;
Jensen et al., 2010). Several studies have shown that
migratory species can benefit from no-take marine
reserves (Polunin and Roberts, 1993; Palumbi, 2004;
Beare et al., 2010; Jensen et al., 2010).
Pelagic MPAs are an important tool in marine
conservation management (Game et al., 2009) and
are rapidly becoming a reality (Pala, 2009),
although some of the challenges relating to their
implementation may be both costly and difficult
(Kaplan et al., 2010). Large MPAs are considered
necessary to protect migratory species such as large
pelagic fish and marine mammals (Wood et al.,
2008) as well as offsetting the concentration of
fishing effort outside them (Walters, 2000) and
maintaining ecological value (Nelson and Bradner,
2010). Their importance for top predators has been
highlighted by the most comprehensive, decade-long,
open ocean tagging study in the Pacific that clearly
demonstrated that top predators – including whales,
seals, tuna, sharks, seabirds and turtles – exploit their
environment in predictable ways, providing the
foundation for spatial management of large marine
ecosystems (Block et al., 2011). Extending to
200 nm, the Chagos MPA offers an extremely
valuable opportunity to understand the effects of
large-scale protection on pelagic, migratory species,
both within the MPA and within a regional context.
Ranges of skipjack and yellowfin tuna have not been
measured in the Indian Ocean, but if their ranges in a
Pacific archipelago (Sibert and Hampton, 2003) are
superimposed onto the Chagos MPA, it is seen that
the latter encompasses as much as the median lifetime
displacement of these two key species (Figure 10).
Figure 10. The median lifetime displacement of skipjack (red) and
yellowfin tuna (yellow), superimposed on a map of the Chagos MPA
(ranges from Pacific: Sibert and Hampton, 2003).
east, with Indonesia another 1000 km further on.
To the west, distances to shallow reefs are much
less, 1700 km to the Seychelles and only 1050 km
to the commonly overlooked Saya de Malha
submerged banks at the northern end of the
‘Shoals of Capricorn’ between the Seychelles and
the Mascarenes (Figure 11). Ocean currents passing
across Chagos flow towards south-east Asia from
approximately January to April, and towards the
western Indian Ocean for much of the rest of the
Lakshadweep
Socotra
Maldives
Granitic
Seychelles
Seychelles
atolls
Chagos
Saya de Malha
Nazareth Bank
Cargados Carajos
(St Brandon)
Mascarenes
BIOLOGICAL CONNECTIONS OF CHAGOS
IN THE INDIAN OCEAN
To the east of Chagos, there is no shallow water
until the Cocos-Keeling islands 2750 km to the
Copyright # 2012 John Wiley & Sons, Ltd.
Figure 11. Reef substrate or limestone banks within the photic zone in
the central and western Indian Ocean.
Aquatic Conserv: Mar. Freshw. Ecosyst. 22: 232–261 (2012)
CHAGOS LARGE MARINE PROTECTED AREA
year, with fluctuations (Couper, 1987). At a speed of
0.5 m s-1 (Bonjean and Lagerloef, 2002) planktonic
larvae from reef species would need 65 days to reach
shallow habitat in the east, but only 35 and 25 days
to reach the Seychelles and Saya de Malha reef
systems, respectively, well within the pelagic larval
duration of many reef organisms. Due to its
location, Chagos is thus likely to be an important
‘stepping-stone’ for marine organisms in the
Indian Ocean.
Fifteen years ago, mapping methods in which
geographical distances were replaced by similarities
of coral presences, showed that Chagos does appear
to function as an east–west stepping stone for corals
(Sheppard, 1999c). Another study has shown recent
colonization of a fish species from the east, consistent
with this stepping-stone function, especially with reefs
in the southern part of the group (Craig, 2008).
Genetic programmes to examine connections
between Chagos and other Indian Ocean reef sites
have been initiated recently for numerous species,
including about 24 reef fish species and several
invertebrates. For hawksbill turtles (Eretmochelys
imbricata), genetic linkages were demonstrated for
nesting females and foraging juveniles between
Chagos and Seychelles, but no linkages were
demonstrated with hawksbill rookeries of Western
Australia (Mortimer and Broderick, 1999; Mortimer
et al., 2002). In the wider Indian Ocean, Vargas et al.
(in press) subsequently identified nine genetic
groupings, with those nesting in Chagos and
Seychelles forming a single grouping distinct from
those in the Arabian Gulf and from easterly sites
including Western Australia (Vargas et al., in press).
Analyses of DNA indicate that most foraging
hawksbills in Chagos derive from rookeries in
Chagos and Seychelles, which also contribute
substantially to foraging aggregations in Cocos
Keeling (FitzSimmons, 2010, unpublished report).
Although most mtDNA haplotypes found in the
Chagos and Seychelles were not found elsewhere,
some uncommon haplotypes were identical to those
observed from Iran, Oman, and Australia, supporting
the stepping stone model.
The crown-of-thorns starfish, an important coral
predator, was previously believed to be a single
species, Acanthaster planci, but Vogler et al. (2008)
have shown that the species includes four highly
differentiated lineages with restricted distributions,
which together form a species complex. Two of
these lineages are found in the Indian Ocean, and
data indicate (Figure 12(a)) that crown-of-thorns
starfish from Chagos belong to the Southern Indian
Copyright # 2012 John Wiley & Sons, Ltd.
245
Figure 12. (a) Crown of thorns genetic groupings. (b) peacock hind
(Cephalopholis argus). (c) brown surgeonfish (Acanthurus nigrofuscus).
(d) coconut crab (Birgus latro). Colour coding for the crown of thorns
(Vogler et al., 2008, in prep.) and peacock hind (Gaither et al., 2011)
indicate distinct genetic lineages. Dashed lines for the brown
surgeonfish (Eble et al., 2011) indicate genetically independent populations.
Photo credit: www.aquaportail.com. Image 12(b) and 12(c) reprinted from
Gaither et al. (2011) and Eble et al. (2011) with permission from the
authors. For (d) solidity of arrow lines represents relative amounts of gene
flow, so that for this terrestrial crab flow is mainly eastwards during the
Equatorial Counter Current flow.
Ocean lineage. A more detailed phylogeographic
study (Vogler et al., in prep.) reveals that there is
high gene flow among populations of the Southern
Indian Ocean lineage, indicating high connectivity
among these geographically distant populations.
In other parts of the Pacific, larvae have been found
to extend their developmental period to seven weeks
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246
C. R. C. SHEPPARD ET AL.
in marginal food regimes (Lucas, 1982). Although
the occurrence of a facultative teleplanic larva
remains to be confirmed (Birkeland and Lucas,
1990), the low productivity found over most of
the southern Indian Ocean (<130 gC m-2 day-1;
Reid et al., 2006) could result in extended larval
durations there too, and hence the observed high
connectivity. This would contribute to the low
levels of genetic structure observed in the Southern
Indian Ocean lineage, despite the geographic
distances among populations.
Genetic surveys of reef fish species (Eble et al.,
2011; Gaither et al., 2011) show an affinity with
the western Indian Ocean. The peacock hind
(Cephalopholis argus, Figure 12(b)) and brown
surgeonfish (Acanthurus nigrofuscus) (Figure 12(c))
demonstrate genetic similarity within sites in the
western Indian Ocean and much less similarity with
sites further east.
Preliminary examination of the coral Platygyra
daedalea with five microsatellite loci, including
samples from Chagos (Macdonald et al., personal
communication), revealed the intuitive result that,
while the Chagos population had the lowest allelic
diversity among the sites studied, it proved to be a
source of genetic diversity for this species. The role
of Chagos as a stepping stone between the east and
the west of the Indian Ocean, or a recipient of larvae,
is further suggested by coral species diversity patterns
(Obura, unpublished; Figure S6 in Supplementary
Material). Based on consistent field samples from
2002–2010, the coral fauna of Chagos is more similar
to that of the western Indian Ocean continental
coastline, including northern Madagascar, than it is
to the smaller and more dispersed islands in the central
Indian Ocean (Seychelles, Mauritius, Reunion). In
terms of species richness it groups with the continental
sites, potentially due to both connectivity and habitat
area (Figure S6 in Supplementary Material).
Despite being geographically part of the Indian
Ocean, the eastern Indian Ocean locations at
Cocos- Keeling and Christmas Islands, and Western
Australia are more closely affiliated with the
Pacific ichthyofauna, with only 5% of species
at Cocos-Keeling being exclusively of Indian
Ocean origin (Allen and Smith-Vaniz, 1994). The
latter islands are considered to be a part of the
Indo-Polynesian Province stretching from the eastern
Indian Ocean to Easter Island (Briggs and Bowen,
2012) and have been shown to be sites of hybridization
between Indian and Pacific Ocean populations of
reef fishes (Hobbs et al., 2009). Exceptions to
this pattern include a dispersive snapper (Lutjanus
Copyright # 2012 John Wiley & Sons, Ltd.
kasmira; Gaither et al., 2010), trumpetfish (Bowen
et al., 2001) and two moray eels (Genus Gymnothorax,
Reece et al., 2010) which freely intermix across all
their Indo-Pacific range and Chagos may act as a
bridge between western Indian Ocean and Pacific
populations of these species.
For the coconut crab, Birgus latro, which is
terrestrial but which breeds in the sea, mitochondrial
genetic work has compared Chagos with sites in the
Seychelles and East Africa, and showed that the
Chagos population was significantly differentiated
(P <0.05) from Seychelles and East African
populations (Table S1 in Supplementary Material).
Asymmetric gene flow, favouring migration from
East Africa to Seychelles, and Seychelles to Chagos,
comes from estimates on direction and mean number
of migrants per generation between regions. The rate
of immigration to Chagos from the west was measured
at about five effective females per generation (breeding
age commences after about 5 years), using a measured
mean effective female population size in the study of
about 3000, or about 0.1–0.2% per generation
(NB this is not the counted population of individuals,
which is orders of magnitude greater). Thus for this
species, Chagos receives more larvae from the west
than flow from Chagos to the west (Figure 12(d);
Tables S1–S3 in Supplementary Material) partly
because egg release coincides with the period of
current flow towards the east, and there is a high level
of genetic connectivity. Additionally, a strong genetic
connectivity among three sites was also seen through
population structure analysis. The data also show that
there is a clear differentiation between the Indian
Ocean clade and the west Pacific clade (Figure S7 in
Supplementary Material).
Taken together, these results confirm that Chagos
is part of the western Indian Ocean province as
described by Briggs (1974), although Briggs and
Bowen (2012) comment that it has faunal affinities
with the Indo-Polynesian province, with respect to
fishes, as well as to the western Indian Ocean.
Interestingly, Chagos shows less connectivity in some
groups than might be expected (considering the much
shorter distances) with the much closer Maldives
to the north, which may be a function of the
predominantly east–west currents. The pattern is
clearly complex: earlier fish surveys (Winterbottom
and Anderson, 1997) in the Chagos Islands delineated
the archipelago into two distinct assemblages, with
the northern portion sharing affinities with the eastern
Indian Ocean and the southern portion (including
Diego Garcia) more closely aligned with faunal
assemblages further west.
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CHAGOS LARGE MARINE PROTECTED AREA
Thus the results from the genetic and distribution
data indicate that Chagos is an important
biogeographic crossroad between the eastern and
western Indian Ocean. The so-far limited molecular
data show that the distances between Chagos and
the western banks and Seychelles is much less of a
barrier than is the much larger expanse of water
to the east. Development of so-called ‘teleplanic
larvae’ by which many species show greatly expanded
larval durations, especially in conditions of low
nutrients (such as exist in the central Indian Ocean)
and lack of suitable substrate, has been long
recognized (Scheltema, 1988). Some coral larvae
may be competent for up to 105 days (Wilson and
Harrison, 1998), and while the pelagic larval
duration of reef fishes averages about one month, it
varies enormously (Brothers and Thresher, 1985;
Sale, 2002). Although it is probable that Chagos is
an important stepping stone in the western Indian
Ocean, the rate at which this happens for most groups
is still not known (though values show appreciable
mixing of the island-requiring coconut crab as noted
above). In fact, the number of migrants needed to
maintain genetic coherence between populations is
small (Slatkin, 1977, 1982). As noted by Hellberg
(2007), for management purposes we need to
know whether or not connections are made every
several thousand generations, or if only a single
founding event occurred, or whether connections
occur in ecologically frequent intervals. Patterns
of connectivity as they exist today are especially
important for designing management strategies to
restore and conserve reef populations. If Chagos is
mainly a net recipient of larvae then its rich and
relatively undamaged state affords it a very high
conservation value. If Chagos is also a source of
biological diversity for the over-exploited sites
further west, then its value would be even greater.
ISLANDS OF THE MPA
Because of its relatively large land size (29.7 km2)
Diego Garcia has been the site of most terrestrial
research (Stoddart and Taylor, 1971). During its
plantation period, Diego Garcia, along with most
other islands of Chagos, was heavily planted
for coconut at the expense of the native plant
communities. Stoddart (1971) expressed surprise
at the large proportion of land area used for
coconut production: ‘. . .almost the whole area of
the atoll (6250 out of 7488 acres) was being
cropped for coconuts’ and
Copyright # 2012 John Wiley & Sons, Ltd.
247
“Little attention has been paid at Diego Garcia
to conservation: the atoll has simply been used as
a supplier of coconut products, and to a lesser
extent of dried fish and turtles, for Mauritius.
Both the Green and Hawksbill turtle used to nest
here in some numbers. . . The early settlers found
the frigate birds, boobies, noddies, terns, herons
and tropicbirds to ‘breed on these islands. They
are considered good eating; the feathers too,
make excellent bedding’ (Anon. 1845, 483).”
The island was severely damaged in ecological
terms. Guano mining and habitat destruction
accompanying the plantations destroyed most birds
and nesting habitats, including some huge tern
colonies, along with other species now listed in the
IUCN Red List such as turtles and coconut crabs
(IUCN, 2011). Stoddart reports that the first practical
conservation measures were taken by a manager in
the 1870s, but ‘in the absence of enforcing authority
or of any clear need for conservation it is unlikely that
much attention was paid to it.’ The same lack of
conservation ethic applied to other Chagos atolls
too, as with coral islands throughout the ocean.
The military facility was constructed mainly in
the early 1970s. It was built on former coconut
plantation – little or no intact natural vegetation
or bird colonies remained. Partly because of
conservation requirements developed over the last
20 years, Diego Garcia has several conservation
sites and issues of its own (Figure 13). It is one of
the most enclosed atolls in the world, being open
in the north only, with three small islets in the
mouth. The military facility is located on the western
arm. The eastern arm is part of a Ramsar site
(JNCC: Ramsar Site UK61002), which extends
3 nm to seaward, encompassing most of the lagoon
also. There are four Strict Nature Reserves: on the
eastern arm south to line ‘A’ in Figure 13, and
around the three islets, into which access is
prohibited. Access to the part of this arm south
of line ‘A’ is permitted. ‘Turtle Cove’ has special
conservation status and restrictions because of its
large aggregations of foraging juvenile and subadult
hawksbill turtles, which have been the subject of
mark–recapture, genetic analysis, blood hormone
analysis, and population research (Mortimer and
Broderick, 1999; Mortimer and Crain, 1999;
Mortimer and Day, 1999; Mortimer et al., 2002).
Underwater, the northern and deepest third of
the lagoon was subjected to significant blasting
and removal of surface-reaching coral growths, to
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248
C. R. C. SHEPPARD ET AL.
Figure 13. Map of Diego Garcia atoll. The military facility is on the
western arm. Gray line shows the Ramsar site, which encompasses most
of the lagoon, extending seaward on the eastern side. The eastern arm
south approximately to the line where the Ramsar boundary intersects
the coast is a ‘Nature Reserve’ which covers land only. From the top of
the eastern arm to the line marked ‘A’, plus the three circled islets in the
mouth of the atoll, are ‘Strict Nature Reserves’, which each cover land
plus the sea area extending out 200 m from shore.
create the present large anchorage. This caused
much damage in that area at that time, though a
brief survey of eight locations in 1979 (Sheppard,
1980b) showed that by that time coral cover had
recovered in areas where there was no anchoring,
being similar to values in the northern atolls where
no activities of any kind had occurred for several
years. During the 1970s, there was no indication
that coral growth was other than vigorous in
most of the world, though the extent of the lagoon
recovery was more rapid than expected. To the
authors’ knowledge, no further dredging or blasting
activities have taken place after that initial period.
Pollution monitoring
Extensive pollution monitoring takes place in Diego
Garcia. ‘Final Governing Standards’ and routine
procedures require regular analyses in US laboratories
of over 100 metals and organic substances according
to US operating procedures. Almost all analyses
report levels below detectable or reporting limits.
None have been found to be of concern, including oil
and oil residues (data held by BIOT Administration).
Copyright # 2012 John Wiley & Sons, Ltd.
In addition to the US monitoring, several specific
projects have set out to measure emerging compounds
of particular interest or concern (see Supplementary
Information text for more detail about all substances
summarized below).
Hydrocarbons have been particularly focused
upon, and most have a natural origin (Readman
et al., 1999). There was negligible evidence of
contamination from petroleum. Polycyclic aromatic
hydrocarbons (PAH) were similarly very low, and
Readman et al. (1999) also found no evidence
of sewage contamination. PCBs and organic
pesticides were mostly below instrument detection
levels. Similarly, extremely low levels occurred for
polyfluorinated compounds, brominated, chlorinated
and organo-phosphorus flame retardants, fluorinated
tensides, and surfactants (PFOS) (Wolschke et al.,
2011). Antifouling booster biocides and triazine
herbicides (Guitart et al., 2007) also were negligible,
with levels generally below the limit of detection.
The same pattern occurred with most metals, though
of interest is that some elevated copper was detected
in 1996 in some northern waters, attributed to
copper in fungicides used in coconut agriculture
several years earlier (Everaarts et al., 1999).
Comparisons with Antarctic and remote deep sea
samples for many showed this area to have the
least chemical contamination so far recorded
(Supplementary Information).
There has been no oil or tar seen on Diego
Garcia beaches to date, although a little has been
seen on some northern islands. Lagoon water near
ships is likewise monitored and is also devoid of
these substances. In summary, from a chemical
contaminant perspective, the marine environment
surrounding the Chagos Archipelago can be
considered to be near pristine and in chemical
pollution terms, Diego Garcia is likely to be the
cleanest inhabited atoll in the world.
Shoreline debris
Despite their near pristine chemical status, Chagos
beaches have a surprisingly high number of pieces
of debris. Observations were made in 1996, 2006,
and 2010 at 20 sites in the outer atolls, and one in
Diego Garcia (Price, 1999; Price and Harris,
2009). Median scores of the number of litter pieces
were high in all years; >1000 items per 500 m linear
beach. Items were mainly plastics, polystyrene
(Styrofoam) and rope, much being lost fishing gear
or debris discarded from ships, most commonly of
south-east Asian origin. Levels in Diego Garcia in
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CHAGOS LARGE MARINE PROTECTED AREA
all years were two orders of magnitude less than in
other atolls, reflecting periodic clean-up events in
that inhabited atoll. The method did not determine
size categories or weight; most items were a few cm
in size or less, but several northern islands appear to
collect substantial volumes of larger flotsam.
Similar numbers are found in remote Pacific atolls
(Price and Harris, 2009) where ocean current gyres
are the main transport vector. Driftwood and lost
timber from ships was low on beaches in all years,
but decreased over time from 1996 to 2006, attributed
to use for fuel by illegal fishing camps on the islands
during this period of increasing fishing pressure (Price
and Harris, 2009; Price et al., 2010). Oil slicks were
never seen, but tar balls were seen at eight beaches
in 1996, at three in 2006 and at one in 2010, none
being seen in Diego Garcia. The decrease may
reflect improved international ship ballast cleaning
measures over that period (Price, unpublished data).
Terrestrial flora
Being geologically young, remote, isolated, flat, and
never connected to a continental land mass, the
Chagos islands have a naturally impoverished
native flora. There are probably 45 native species
of higher plants, 41 flowering plants (12 trees) and
four ferns, none of which are endemic (Topp and
Sheppard, 1999), most having a widespread
distribution across the region. There are several
important native vegetation community types with
examples remaining intact, especially on islands too
small to have been used in plantation times. These
include Pisonia forest and Lumnitzera mangroves
on Moresby Island; Scaevola-Argusia beach
communities on many islands and Calophyllum
thickets on Ile Takamaka. Most plants, especially
on Diego Garcia, were introduced for fruit or
ornament, or accidentally as unwelcome passengers
of incoming cargo (Topp and Sheppard, 1999). Some
species are problematic. The native dodder (Cassytha
filiformis), a parasitic vine, is spreading rapidly and
over-topping some of the native vegetation. Pipturus
argenteus, a shrub whose origin is in doubt, is
spreading widely and is having some negative
impacts on regenerating native trees such as Pisonia
grandis (Clubbe, 2010).
Introduced plant species are far more numerous
than the native species. An updated vascular plant
checklist (Clubbe, unpublished data; Hamilton
and Topp, 2009) shows that 232 non-native species
have been recorded, with 128 listed as only occurring
on Diego Garcia (Hamilton and Topp, 2009). Of
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249
these, few show signs of invasiveness and most are
unlikely to pose significant problems. However, there
are some species where control measures are needed.
Most significant is coconut (Cocos nucifera), which
was widely cultivated previously. Young palms form
a dense understorey which exclude virtually all other
plants. Control measures underway in a pilot scheme
on Diego Garcia involve the removal of palms to
enable regeneration of native species from either
a recently established seed bank or from those
few plants that are able to survive in the low-light
environment created by the coconuts. Regeneration
is supplemented by enrichment planting of key
native tree species including Barringtonia asiatica,
Cordia subcordata, Guettarda scabra and Calophyllum
inophyllum, all of which provide important nesting
sites for seabirds. In Diego Garcia, there is a ‘two
for one’ policy whereby any coconut or other tree
removal is replaced by two hardwood trees collected
from seedlings beneath established trees or from the
seed bank. If successful, this approach will be applied
to northern islands also. Some species of introduced
plants are spreading invasively, some associated
specifically with former settlement, e.g. Tabebuia
heterophylla, while others not specifically associated
with settlement areas, e.g. Casuarina equisetifolia,
exist on several islands. The latter, introduced for
timber in plantation times, poses a threat to native
trees on some of the islands since it exerts a tenacious
hold, out-competing other trees owing to the ability
of its roots to fix nitrogen and because of the litter it
creates.
More work is needed to fully understand the
distribution of non-native species and the potential
impact of invasive plants in Chagos. Preliminary
analyses indicate, however, that the spread of
non-native species from Diego Garcia to other
atolls is slow and there has not been a noticeable
increase in the number of non-native species on
the outer islands since the 1980s (Clubbe, 2010).
Regarding algae, mosses, liverworts, cyanobacteria,
fungi, and lichens, diversity is relatively low in
Chagos, although these provide high cover and
are ecologically important (Seaward, 1999; Seaward
and Aptroot, 2000; Watling and Seaward, 2004;
Seaward et al., 2006). Cyanobacteria extensively
clothe limestone, thin sandy soils and tree trunks,
and fix nitrogen directly in the otherwise poor
soils. The mosses and liverworts are important in
stabilizing soils, and are often the primary stages
in the succession of higher vegetation in exposed
areas. In wooded areas, the mosses and liverworts
clothe the bark of living trees; the nature of
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C. R. C. SHEPPARD ET AL.
this epiphytic flora changes with age; as the trunks
die, different mosses and liverworts support the
decomposition process undertaken mainly by fungi.
Lichens colonize all available tree bark surfaces, as
well as being found on the living leaves of various tree
species, the long-lived evergreen nature of the leaves
allowing these slow growing organisms to establish
themselves.
There are no endemic species of these groups.
However, due to the geographical setting of the
islands their establishment is remarkable, not only
in terms of the distances travelled by the spores
and propagules, but also in terms of their origin,
and there are interesting affinities of these floras
with south-east Asia, India or Africa, as yet to be
fully determined. A new liverwort, Cololejeunea
planissima var. chagosensis, known only from Chagos
(Seaward et al., 2006), is likely to occur elsewhere, but
there is always the possibility that it has disappeared
(or will disappear) from its original site(s).
Terrestrial fauna
There are no native mammals, amphibians or
endemic birds. Of invertebrates recorded to date,
most are widespread species with distributions
across the Indo-Australian tropics and include some
human commensals (Barnett and Emms, 1999).
There are thought to be three endemic sub-species
and one endemic species of Lepidoptera (Barnett
and Emms, 1999).
The black rat (Rattus rattus) is the main invasive
animal, and was reported to be of plague proportions
as early as the late 1700s. Only smaller islands which
were not planted have no rats and have numerous
birds, and even islands close to rat-infested islands
remain uninvaded.
Other species introduced at various times in the
islands’ history include sheep Ovis aries, cattle Bos
sp., horses Equus ferus, donkeys Equus africanus
asinus and (having the worst impact on the birds),
dogs Canus lupus., pigs Sus sp., cats Felis catus, as
well as the rats (Edis, 2004; Carr, 2011a). Most have
gone, but remaining invasive animals include the
cane toad (Bufo marinus), feral cats, donkeys and
several birds (Carr, 2011b). Dates of introduction
for most terrestrial invasives are unknown, one
exception being the garden lizard (Calotes versicolor)
in Diego Garcia. This was first observed on Diego
Garcia in May, 2001, and is believed to have been
introduced via cargo. It is arboreal, diurnal and
adaptable (Daniel, 2002) and is one of the most
widespread non-geckonid lizards in the world
Copyright # 2012 John Wiley & Sons, Ltd.
(Matyot, 2004). It has a population density of 172
lizards ha-1 (95% CI: 154–237) in the inhabited area,
has since spread south and is likely to spread island
wide. This illustrates the rapidity at which such
species may spread. Since that time, strict quarantine
measures have been introduced for imported
materials, including rock for construction of
hardened shorelines to combat shoreline erosion.
Seabirds
In contrast to the generally poor terrestrial
fauna, the breeding seabirds of the Chagos are of
international importance (Carr, 2006, 2011a).
Islands never planted, inhabited or rat infested
give a glimpse of what the islands used to look like
because significantly higher bird abundances occur
on these (Symens, 1999; Price and Harris, 2009).
Population trends and the seabirds’ breeding
phenology are poorly understood. Comprehensive
censuses were undertaken of breeding seabirds in
February/March 1996 (Symens, 1999) and again
in March 2006 (McGowan et al., 2008; Figure S8
in Supplementary Material). Eighteen seabird
species breed in Chagos (Carr, 2011a), five in
globally important numbers, resulting in ten islands
being classified as Important Bird Areas (IBAs)
(Carr, 2004, 2006, 2011b), with two further islands
being proposed as IBAs (McGowan et al., 2008).
Recently more regular monitoring of the Chagos
IBAs showed that many species of seabird either
breed continuously throughout the year with spikes
in breeding in certain months, e.g. red-footed (Sula
sula) and brown (Sula leucogaster) boobies, or breed
at different times of the year on different atolls, e.g.
lesser noddy (Anous tenuirostris) and sooty tern
(Sterna fuscata) (Figure S8 in Supplementary
Material). This realization of continuous breeding
has increased the estimates of some of the breeding
populations of some species, making the Chagos
seabirds an even more important asset than was
previously believed, to both the Indian Ocean and
globally. Diego Garcia and its three associated islets
hold one of the Indian Ocean’s largest breeding
colonies of red-footed booby, which has grown from
three or four pairs in 1984 to over 5000 pairs in
2011, spread over 30 km of shoreline (Carr, 2011b).
This growth may be attributable to the area being
out of bounds to all personnel since 1984.
The suggestion has been made that the ten IBAs
should be clustered into four grouped IBAs, which
would ‘. . . be consistent with IBA philosophy in
designating inter-connected, proximal, protected
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CHAGOS LARGE MARINE PROTECTED AREA
habitats for species that . . . appear to utilise different
islands for breeding in different seasons’ (Carr,
2011b). These four would consist of Diego Garcia,
the Western Great Chagos Bank Islands, Nelson’s
Island in the northern Great Chagos Bank, and
the eastern islands of Peros Banhos atoll. To
initiate successful conservation management plans
for seabirds, a thorough understanding of their
breeding phenology is essential, including breeding
triggers and dietary requirements. Long-term,
scheduled monitoring is required to achieve this,
in order to preserve and protect one of the last
seabird strongholds in the Indian Ocean.
Coconut crabs
The coconut or robber crab (Birgus latro) has a
wide distribution throughout the Indian and Pacific
Oceans but is usually over-harvested. The largest
land dwelling invertebrate in the world, it can
exceed 5 kg. They mate on land but the female
releases eggs in the ocean after a few months, where
they immediately hatch, the oceanic larval stage
usually lasting 2–3 weeks (Fletcher and Amos,
1994). Once on land their growth is slow; they
may be mature at 5 years but it takes approximately
8–10 years (depending on diet quality) for crabs to
reach a size of ~500 g, with maximum size at
40 years (Fletcher and Amos, 1994).
Many of the northern islands in the 1970s had
very few coconut crabs, and they were virtually
absent from some. Those seen had a size positively
correlated with the length of time that the island
had been uninhabited, ranging from the 1930s when
the first two of the five atolls were abandoned, to the
1970s (Sheppard, 1979). In 2010 in Diego Garcia,
crab populations showed an overall average density
in the Ramsar area of 298 crabs ha-1 (95% CI:
229–387, Figure S9(a) in Supplementary Material),
the highest average number ever recorded, with two
transects containing 467 and 489 crabs ha-1 (Vogt,
unpublished). The southern tip of the island had an
average 147 crabs ha-1 (95% CI: 95–226), while the
side containing human habitation had only 39 crabs
ha-1 (95% CI: 24–63) indicating capture despite
regulations, and the inhabited side also lacked
crabs in the largest size classes (Figure S9(b)
in Supplementary Material). The Ramsar side
appears to be unharvested, a rarity for this species.
Turtles
Hawksbill (Eretmochelys imbricata) and green turtles
(Chelonia mydas) nest in Chagos, and surveys
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251
conducted in 1996 and 2006 recorded both species
at each of the five atolls. Estimated numbers of
females nesting annually were 400–800 green turtles
and 300–700 hawksbills in 1996 (Mortimer and
Day, 1999). Diego Garcia, by far the largest island
in the group, has nesting populations of both species
that rival those of any of the other atolls, and nesting
density and habitat quality are particularly good
along the east coast.
Historical records indicate that nesting numbers
of both species declined significantly over the period
of human settlement (Mortimer and Day, 1999;
Mortimer, 2009). In 1786, more nesting green
turtles were captured at Salomon atoll in 4 days
than were estimated to nest there annually in 1996
(Mortimer and Day, 1999). Likewise for hawksbills:
trade statistics show that at the turn of the 20th
century nearly as many were killed annually to
provide shell for export, as were estimated to nest
each year in 1996 (Mortimer, 2009; Figure S10 in
Supplementary Material). A comparison of nesting
census data from 1996 and 2006 (Mortimer, 2007)
indicates little change in hawksbill nesting activity
in the northern atolls, but a possible increase at
Diego Garcia. Levels of green turtle nesting recorded
at all island groups were greater in 2006 than in
1996. However, this does not necessarily indicate
population increase, given that green turtle nesting
activity oscillates from year to year and trends can
only be discerned when nesting activity is monitored
consistently over extended periods of time (usually
more than 10 years).
Island prospects, erosion and sea levels
Though tiny in total area compared with marine
habitats, the islands are central to conservation
measures. Much has been discussed recently about
loss of coral islands from climate change; indeed
the nearest archipelago, the Maldives, has taken a
lead among small nations in this matter. Controversy
about island erosion and sea level rise has been
strenuous because the subject has many apparent
contradictions.
Sea-level rise in the southernmost atoll Diego
Garcia has been recorded by tide gauges since 1988
(Figure S11 in Supplementary Material). The data
are in two series, (1988–2000 and 2003 to present),
the former being ‘research grade’, the latter being
‘fast delivery’ data only at present. Both series have
gaps and, while the graph shows a substantial rise,
both series are short. The two nearest tide gauges to
Chagos are on Gan in the southern Maldives, 475 km
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C. R. C. SHEPPARD ET AL.
north at about 1oS and on the capital Malé at about
4oN (Singh et al., 2001). These show rises of similar
order to that in Diego Garcia. Further, there are
marked seasonal differences in monthly averages, both
in Diego Garcia and in the Maldives, which Singh et al.
(2001) link to the monsoon cycle. Highest monthly
average tides in Diego Garcia occur in November–
February, and the lowest ones between April and July.
Newer satellite altimetry data shows a much
smaller rise compared with tide gauge measurements
for the central Indian Ocean (www.sealevel.colorado.
edu), including both Chagos and the Maldives. Local
land movements may account for an unknown
proportion of the discrepancy between gauges and
satellite altimetry, but whether gauges or satellite
altimetry are more correct, it is high tides, not
monthly averages, which cause flooding, and
several other oceanographic and climate driven
changes may be more important. Further, different
atolls may respond slightly differently to Diego Garcia
in terms of relative sea level rise because the area is
tectonic, lying on a minor plate margin (Figure S12
in Supplementary Material). Local effects are also
dependent on supply of sediments, which is likely to
have changed markedly following the massive coral
mortality of 1998.
The important immediate consideration is
erosion of shores and inundation by the sea, rather
than sea-level rise per se. Coral islands have long
been known to have mobile shores because of
natural annual or decadal shifts in sedimentation
driven by climate, which affects wave height, swell,
and swell direction (Young et al., 2011in press) as
well as sea level. Chagos has suffered considerable
overall erosion of many shorelines, most notably
in the last decade. This has not yet been studied in
detail, although in Diego Garcia it is most noticeable
if only because of the high cost of sea defence
measures employed there. In parts of the northern
atolls, horizontal attrition may exceed 1 m yr-1 in
several areas although this high rate is episodic
and spatially patchy. On several islands, remnants
of mature coconut trees are now in the intertidal
zone, and pits dug for coconut cultivation are now
at or below high tide levels in some places, all
indicating net erosion over the past 100–150 years
in such places. Blenheim atoll in the north used to
have three low sandy islands, with low bushes
(report by Archibald Blair, 1787) but this atoll is
now submerged, with only some sections of its
western rim emergent at low tide. This atoll’s coral
and algal ridge growth are as prolific as on nearby
islanded atolls, so a deficiency in reef growth is an
Copyright # 2012 John Wiley & Sons, Ltd.
unlikely cause of the drowning. In contrast, Egmont
atoll, was known in the 19th century as the ‘Six
Islands’ (each named separately), yet today most
have fused to form only three islands at low tide,
possibly because of tectonic movement or because
of changing sedimentary patterns, although erosion
as described above also occurs in some sectors.
Coral mortality from warming, discussed earlier, is
likely to lead to massive if temporary changes in
sand production, known to have had marked
consequences on shorelines elsewhere in the Indian
Ocean for example (Sheppard et al., 2005).
Island heights and cross-sections are likely to be
important to future events. The highest points of
probably all islands occur on the rims. Profiles of
several Chagos islands (Figure 14) show a central
depression, caused by acidic rain eroding the
Figure 14. Cross-sections of (a) Sipaille, (b) Lubine, (c) Sudest islands in
Egmont atoll, (d) Isle de Coin on Peros Banhos atoll, and (e) Ile
Boddam on Salomon atoll. Y-axis is metres above mean high tide in
(a)–(c), and from a relative datum in (d)–(e). (a) Lagoon is on right,
total width is 500 m, (b) lagoon on right, total width 450 m, (c) lagoon
is on left, total width 250 m. (d) and (e) have no horizontal dimensions
but are larger islands. Solid horizontal lines are mean high water
springs. (a)–(c) from Sheppard (2002), (d)–(e) from Royal Haskoning
(2002). Dashed lines in (d)–(e) are estimated flooding levels following
severe storm overtopping.
Aquatic Conserv: Mar. Freshw. Ecosyst. 22: 232–261 (2012)
CHAGOS LARGE MARINE PROTECTED AREA
coral limestone rock (Sheppard, 2002), and by
accumulation of sand around island rims. Future
erosion patterns are unlikely to be smoothly
progressive, and may be episodic. There is evidence
of this in several locations, and a broach could
destroy the freshwater lens in that area. Figures 14
(d)–(e) also shows potential inundation levels in
two islands in two northern atolls, determined
by Royal Haskoning (2002) in a resettlement
feasibility study. In Diego Garcia atoll also,
similar central depressions are evident on both
western and eastern sides, although much of the
eastern arm is very narrow and low lying too, such
that extensive flooding occurs at high spring tides.
A further phenomenon, noted over 100 years ago
but which has been largely overlooked, is that of
‘self-gravitation’, whereby the large volume of ice
added to the poles creates significant gravitational
attraction of its own (Vermeersen, pers. comm.;
Vermeersen and Schotman, 2009), raising water
level nearer the poles. Thus, when ice melts and
water redistributes, polar gravitational attraction
lessens, so sea-level rise increases the further the
distance from the ice sheet (along with a marked
fall near the poles). The magnitudes are likely to
be significant to tropical coral islands because, in
the absence of the Greenland ice sheet’s gravitational
attraction, sea-level rise in equatorial regions would
probably be 10–20% greater than would occur from
ice volume melt alone (Vermeersen, pers. comm.).
CLIMATE AND LONG TERM
ENVIRONMENTAL MONITORING
PROGRAMMES
Work is increasingly needed on climate change
projections, yet the Indian Ocean forms a very large
gap in many global monitoring programmes. Chagos
is situated in a key region of climate variability. It lies
at the eastern margin of an oceanic feature known as
the ‘Seychelles–Chagos thermocline ridge’ (Hermes
and Reason, 2008), along which the thermocline rises
close to the surface and upwelling of cold water from
below the thermocline occurs (Vialard et al., 2009).
In contrast to most upwelling regions, surface water
of the Seychelles–Chagos ridge is extremely warm.
In austral summer, the main rainy season, sea surface
temperature (SST) varies between 28.5 C and 30 C
only, a range in which the atmosphere is very sensitive
to small oceanic changes (Timm et al., 2005). The high
SST combined with the shallow thermocline makes
the Seychelles–Chagos ridge a region with very strong
air–sea interactions.
Copyright # 2012 John Wiley & Sons, Ltd.
253
However, climate observations from this region are
extremely sparse due to the paucity of measurements
in most Indian Ocean countries and to the remoteness
of Chagos. Further, instrumental SST data are
associated with errors that are as large as the
SST anomalies across a range of time scales
(Annamalai et al., 1999). There is currently only one
weather station at Diego Garcia, whose weather
records contain several gaps (Sheppard, 1999d).
‘Conventional’ infrared satellite measurements of
SST are not adequate to capture important SST
perturbations that occur in the rainy season when
convective activity and cloud cover is highest
(Vialard et al., 2009), and only the increased use
of orbiting microwave instruments in the late
1990s allowed better quality SST to reveal the role
of Chagos with respect to air–sea interactions
(Vialard et al., 2009). Therefore, a continuous
monitoring programme of important climatic and
oceanographic parameters at Chagos is needed
for a better understanding of air–sea interactions
that are crucial in global climate issues.
The Seychelles–Chagos region has a distinct
oceanic and atmospheric variability at multiple time
scales, each with significant climatic consequences.
It has the strongest intraseasonal SST variance in
the Indo-Pacific warm pool, because the shallow
thermocline is very responsive to atmospheric
fluxes (Vialard et al., 2008, 2009). SST cooling of
1–1.5 C, lasting for 1 to 2 months, may occur
during austral summer, followed by a short lag
and sharp increase in atmospheric convective
activity (Vialard et al., 2009) associated with
the Madden–Julian–Oscillation (MJO, Madden
and Julian, 1994). The MJO has a time scale of
30–80 days, and it explains much of the variance of
tropical convection, and modulates cyclonic activity.
On interannual time scales, the Seychelles–Chagos
ridge is affected by the El Nino-Southern Oscillation
(ENSO) and the Indian Ocean Dipole (IOD)
(Saji et al., 1999; Webster et al., 1999). ENSO
events lead to a displacement of the West Pacific
warm pool and affect the Indian Ocean via the
so-called atmospheric bridge. Anomalous subsidence
over Indonesia during El Nino years leads to a
cooling over the maritime continent and a
basin-scale warming of the Indian Ocean, particularly
the western part. The IOD is a coupled
ocean–atmosphere instability centred in the tropical
Indian Ocean that affects the climate of the countries
that surround the Indian Ocean basin (Marchant
et al., 2007). A positive IOD period is characterized
by cooler than normal water and below average
Aquatic Conserv: Mar. Freshw. Ecosyst. 22: 232–261 (2012)
254
C. R. C. SHEPPARD ET AL.
rainfall in the eastern Indian Ocean, Indonesia and
over parts of Australia, while warmer water and
increased rainfall is observed in the western Indian
Ocean and equatorial East Africa. A negative IOD
period is characterized by warmer than normal water
and above average rainfall in the eastern Indian
Ocean sector and cooler than normal water and
below average rainfall in the western Indian Ocean.
Some studies suggest that positive (negative) IOD
events may be triggered by El Niño (La Niña), while
others find that IOD events occur independently
although they may overlap with El Niño/La Niña
events, e.g. the strong 1998 ENSO (Saji and
Yamagata, 2003). The IOD has two ‘centres of
action’: one off the coast of Sumatra, in the eastern
Indian Ocean sector, and one at the Chagos
Archipelago (Saji and Yamagata, 2003). Reliable
instrumental records of the IOD are currently
limited to the past 50 years.
On decadal and longer time scales, information
on climate variability at Chagos has been gained
from geochemical proxies archived in long-lived
corals (Pfeiffer et al., 2004, 2006, 2009; Timm
et al., 2005). These data suggest that changes in
the mean climate may influence the impact of
large-scale climate phenomena at Chagos, possibly
affecting climate in other countries surrounding
the Indian Ocean. For example, a shift towards
higher mean SSTs occurred in 1975 (Timm et al.,
2005; Pfeiffer et al., 2006, 2009), after which small
SST changes induced by ENSO caused much larger
precipitation anomalies (Timm et al., 2005; Pfeiffer
et al., 2006). Similar changes in rainfall variability
have been found in South Africa (Richard et al.,
2000), Sri Lanka and southern India (Zubair and
Ropelewski, 2006).
The long-term variability of the IOD has also been
investigated with coral proxies from the Seychelles
and Indonesia (Abram et al., 2008). The coral
reconstruction suggests an increase in the strength
and frequency of IOD events during the 20th
century, which may also influence the distribution
of rainfall in the tropical Indian Ocean. The work
highlights the importance of the Chagos Archipelago
for climate variability research in the Indian Ocean
sector and beyond, and emphasizes the need for
high-quality in situ data recording of climatic
parameters at Chagos.
CONCLUSIONS
The Chagos Archipelago is unquestionably a
very valuable biological asset in an ocean showing
Copyright # 2012 John Wiley & Sons, Ltd.
significant and continuing decline. The exceptionally
good condition of the Chagos marine ecosystems is
important in terms of biodiversity and productivity,
and for its likely biogeographic role in the ocean. Its
protection is of great and increasing importance given
that global pressures from overfishing and other
activities resulting from human population growth
are increasing. In this it joins a small handful of
other large, protected sites in the world (Nelson and
Bradner, 2010), and is the only one in the Indian
Ocean. The importance of the Chagos MPA was
further underpinned by a recent report across marine
science disciplines suggesting that the world’s ocean is
at high risk of entering a phase of disturbance
unprecedented in human history (Rogers and
Laffoley, 2011). Indeed, many more effective and
very large MPAs need to be created if international
goals for protecting the oceans are to be met,
although the number of locations where this will be
possible is diminishing. Regarding terrestrial value,
several smaller islands that were not ravaged by
coconut plantations remain intact and, by using
them as source areas, much restoration is possible
and indeed has been commenced.
The MPA therefore is needed for multiple
reasons. It has met with opposition from various
sources, including the oceanic fishing industry,
the government of Mauritius that claims the
territory, and from Chagossians who were removed
approximately 40 years ago, and some of their
representatives. While the decision to remove the
inhabitants at that time was based on politics and
defence rather than for any reasons of conservation,
the present good condition of such a large area has
been a fortuitous if unplanned consequence of the
subsequent lack of exploitation of the area. The
MPA was created ‘without prejudice’ to any future
resettlement, and if resettlement does occur then
management must be adequate to avoid the problems
which almost all past global experience has
demonstrated could too easily happen.
The high value of relatively undisturbed areas
encompassing a range of functionally linked
ecosystems is becoming increasingly recognized at
the same time that their number world-wide is
diminishing (http://www.globaloceanlegacy.org/).
Whereas there are many ‘managed’ reef sites
elsewhere in the tropical oceans, almost all are
themselves in a poor condition compared with
places like Chagos and a few Pacific sites. The
‘shifting baseline syndrome’ (Pauly, 1995) applies
to marine management and in many places has led
to situations where decisions are taken that are
Aquatic Conserv: Mar. Freshw. Ecosyst. 22: 232–261 (2012)
CHAGOS LARGE MARINE PROTECTED AREA
highly disadvantageous to both the natural systems
and to the people dependent on them. Most reefs
remain unprotected or protected in name only.
The huge scale of the interconnected network of
atolls and banks in Chagos, and its effective
governance, are likely to become increasingly
important both directly and as a scientific reference
site in the Indian Ocean. BIOT has, at present and
the foreseeable future, governance which will
enable this situation to persist. Priorities now are
management in an effective manner, whatever
the political future holds for the area, so that the
benefits of a well protected MPA are likely to
extend to peoples and ecosystems far beyond the
boundaries of the Chagos MPA.
ACKNOWLEDGEMENTS
The authors thank the Administration of the British
Indian Ocean Territory for permission to visit the
area on various occasions, the military commanders
and personnel for much assistance on site, and to
the officers and crew of the BIOT Patrol Vessel
Pacific Marlin for exceptional help on all visits to
atolls away from Diego Garcia. The OTEP fund
provided core funds for most visits, and all scientists
involved received funding from numerous sources
to carry out their own programmes of work in the
archipelago. For assistance with genetic work we
thank Jiddawi Norriman and Mohammed Suleiman
Mohammed (Zanzibar), and Nancy Bunbury
(Seychelles).
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