Intertidal Zone

By Safina Center Fellow Alex Chege

©Alex Chege

For tens of thousands of years, humans have maintained a long relationship with coastal environments.

Understandably we more commonly associate coastal living with humans, sandy beaches, and marine life. But long before our major cities dotted the coastlines, before our even more modest settlements bordered oceans and rivers, terrestrial animals thrived at this intersection where land meets the sea.

Through remarkable ingenuity, humans exploited the ocean for its bountiful resources. One such cultural technology—fishing—is one of the oldest human practices, one that many indigenous populations around the world continue to practice, coexisting sustainably with aquatic life.

When the torrential waves crashing on the coral's surface subside, the gentle swish of the ebbing tide takes over and transforms the ephemeral intertidal zone into a vibrant habitat teeming with life. As the tide recedes, marine crab communities emerge and scatter across the reefs. ©Alex Chege

But humans are not the sole terrestrial species to make use of the ebbing tides to locate food. For example, so-called ‘maritime mammals’ such racoons, wolves, baboons, and macaques, and reptiles such as marine iguanas regularly forage near coastal shores and on the intertidal zone where the marine and terrestrial worlds come together. These terrestrial species target clams, crabs, and algae that are left exposed on intertidal and subtidal areas to supplement their terrestrial diets.

While working in the field on and near the intertidal habitats of Kiwayu Island in Kenya’s Lamu Archipelago, these immersive scenes of terrestrial life interacting with the marine realm inspired my photo series, Intertidal Zone. During the East African monsoon season in July last year, the torrential downpour and upwelling surf brought deep-sea fish closer to land, making sea foods easily accessible from the safety of Kiwayu’s reefs. Similarly, Kiwayu’s vervet monkeys used this period to forage on the abundant marine crabs trapped between the land and raging sea.

A resident troop of vervets on the southern side of Kiwayu, Shimo, forages for crabs during the morning high tide. This southern group regularly searches for crabs in this productive and diverse area of the island. ©Alex Chege

A cautious pleated rock crab (Pachygrapsus plicatus) cowers in a burrow. Though vervet monkeys do not seem to target this prey species, it is one of the crab species found within Kiwayu’s intertidal community. ©Alex Chege