Threats to the Chagos Archipelago

Threats to the Chagos Archipelago

While the archipelago has not been as devastated as other ecosystems around the world, it still needs protection from several threats.

Climate change

Rising global temperatures have had a dramatic effect on coral reefs. Warming seawaters have caused coral colonies to "bleach", by affecting the symbiotic algae which are sensitive to light exposure, temperature and acidity. The depletion of algae and coral leads to the loss of vital habitats for a variety of species.

While the condition of the Chagos Archipelago's reefs was exceptionally good in the 1970s, they, similarly to coral reefs the world over, were notably affected by moderate warming over the next two decades. A severe warming spike in 1998 pushed surface temperatures up 30 degrees celsius, killing large quantities of coral.

A rapid recovery has been seen in some parts of the archipelago, while in other areas it is less pronounced. The negative effects of global warming have here and elsewhere been repeated since, and an increase in such incidents are likely to have a dramatically negative effect on biodiversity, as well as the natural breakwaters that protect the islands from erosion.

Illegal fishing

Before the designation of the marine reserve, an estimated 10,000 sharks and 10,000 rays were killed annually by the licensed fishing industry. While protection has ended legal fishing within its waters, illegal fishing continues to affect sharks and other valuable species such as tuna and grouper.

It is often hard to detect the small illegal boats, which hail from Sri Lanka and more recently India. Patrol vessels are tasked with policing more than half a million kilometres of ocean. But modern technology is being employed to address the problem, and a £100,000 fine can be imposed on those who are apprehended.

However, the very richness of these waters, compared with the increasingly over-fished and impoverished waters elsewhere in the Indian Ocean, means that the Chagos Marine Reserve is likely forever to be attractive to poachers.

Indian Ocean shark numbers have decreased by 90% over the last three decades

Invasive species

Over half of the islands in the archipelago have been degraded because of introduced, invasive species. For example, black rats that arrived with colonists are now rife on some islands, preying on seabird and turtle eggs as well as young turtles. It is one of the aims of the Trust to address this problem so native species can thrive again.

Unmanaged coconut plantations have also become rampant. Native forests were removed and replaced with coconut trees, which have in turn taken over native vegetation. The resulting monoculture has led to the loss of seabirds, as they are unable to build nests in coconut palms.

It is one of the aims of the Trust to address these problems so islands are restored to their original natural condition and native species can thrive again.

Invasive species - including black rats - have affected the native species and habitats of over half the islands