Chagos Archipelago

Chagos coral reef

The British Indian Ocean Territory (BIOT) is one of the UK’s 14 Overseas Territories and one of the most amazing marine environments anywhere in the world. Located about 1,500km from the southern tip of India, 3,400km due east of Africa and 3,000km west of Indonesia the territory covers a total of 640,000km2 of ocean. At its heart is the Chagos archipelago a scattering of 55 tiny islands surrounded by 60,000km2 of coral reefs and the cleanest seawater ever recorded.

Why we are there

The open ocean, tropical coral reefs and islands of the territory contains has a huge abundance of marine and terrestrial species; it contains the largest living coral atoll anywhere on earth, the only populations of island-nesting seabirds that are increasing in size and eight times more reef fish biomass than anywhere else in the Indian Ocean.

The open ocean there teems with life, from large pelagic predators like Thresher sharks and tuna to huge pods of spinner dolphins. This incredible diversity, some of which is unique to the archipelago, is under pressure from threats such as climate change and illegal exploitation but it still represents some of the best examples of these habitats left anywhere in the world. 

The world's largest no-take Marine Reserve

Over 275,000 people and a number of NGO's called on the UK Government to establish the territorial waters of the British Indian Ocean Territory as a Marine Reserve in 2010. ZSL was amongst the organisations that contributed to the science case for the creation of the reserve and that helped ensure its establishment. This decision was one of the most significant ways the UK could make a landmark contribution to global marine conservation and contributes greatly to a number of globally agreed targets, such as the IUCN World Conservation Congress target to protect 30% of each marine habitat in highly protected marine reserves by 2030. 

The BIOT marine reserve into the future

From 2010 to 2016 the BIOT marine reserve was the largest in the world. Since then it’s been overtaken by even bigger protected areas, some of them in other UK Overseas Territories such as the enormous Pitcairn Marine Reserve which is 834,000 km2. ZSL has played a key role in the creation of many of these new protected areas as well.

Since 2010 ZSL has been working with many other organisations to research the astounding array of wildlife that lives in BIOT and has been making significant advances in marine science and conservation. We have worked closely with the BIOT administration in the Foreign and Commonwealth Office and with the Bertarelli Foundation to develop an ambitious programme of research to support better management of the marine reserve over the next few years.

A healthy Porites colony on the reef

The Bertarelli Programme in Marine Science

In 2017 the Bertarelli Foundation announced its new programme for marine science in BIOT. The programme builds on a series of expeditions, workshops and strategic plans to create a vision for the BIOT marine reserve as a global exemplar. From 2017 to 2020 the programme will be coordinated on behalf of the foundation by ZSL and comprises a team of 50 researchers from 14 institutions across the world studying all aspects of the animals and habitats of this amazing place.


Over the course of the programme will have teams in the field several times each year and we will be bringing information live from each trip. Read blogs from recent expedition here:

You can keep in touch with all the science going on in BIOT on twitter using the hashtag #BIOTscience

Connect Chagos: People and wildlife

As part of ZSL’s commitment to global and local conservation capacity building we designed a delivered a four year programme called Connect Chagos. This multi-phase project to build environmental skills and awareness within the Chagossian community in the UK and overseas was a great success and we learnt huge amount from working alongside each other. We continue to stay interested and involved in the communities are looking for ways to continue this work into the future.

Project information

Sentinel species

The team will be studying the ecology and distribution of the larger animals in the ecosystem – many of them top predators. These animals at the top of the food chain often drive the dynamics of populations blow them and understanding where they are and what they are doing can unlock incredible insights into the whole ecosystem. It also helps to figure out where and when they might be most vulnerable to poaching which can help with better targeted enforcement efforts. Our sentinel species groups are: 

  • Pelagic predators – open ocean sharks, rays and tuna
  • Reef sharks
  • Turtles
  • Seabirds

Coral reefs

There are at least 310 species of coral on the reefs of the Chagos Archipelago, including the Chagos brain coral (Ctenella chagius), a species endemic to these waters. Corals not only created the tiny atoll islands of the Archipelago but thick strands of branching species continue to protect them from waves and storm damage. Corals on these reefs have been hit hard by bleaching from rising sea temperatures during the El Nino events of 2015 and 2016 with widespread mortality. The team will be closely studying their recovery and resilience over the next three years. 

Illegal, unregulated and unreported fishing

Like any protected area the animals of BIOT are under threat from poachers. Understanding why people break the rules, where they come from and how they work is key to figuring out how to better protect the biodiversity of the marine reserve. We will be conducting socio-economic studies across the region to inform management and ensure the reserve is well protected. 

People involved at ZSL

ZSL has been actively working in BIOT for more than 10 years and our efforts there are collaborative across our departments. In the Marine and Freshwater Conservation Department Heather Koldewey manages ZSL's work in the BIOT marine reserve with Rachel Jones as Project Manager of the Bertarelli Programme in Marine Science. Matthew Gollock has been involved with pelagic fish studies over many years and co-ordination has come from Kirsty Richards.

In the Institute of Zoology there are several researchers working on aspects of BIOT science: 

  • David Curnick is investigating the role of large marine protected areas as a conservation strategy for pelagic tunas and sharks.
  • David Jacoby is studying the behaviour and ecology of reef sharks a group of species under particular pressure from poaching activities.
  • Tom Letessier is working to understand how Illegal, Unreported and Unregulated (IUU) fishing impacts the marine reserve and how fishers that break the rules there perceive the risks and benefits of doing so.

By combining our work on both the fishers and the species that are fished we hope to contribute to improved protection of the reserve.

Malcolm Nicoll, Robin Freeman, Peter Carr and Hannah Woods are all working on aspects of seabird biology and ecology across the region.

Partners and sponsors

The Bertarelli Programme in Marine Science is kindly supported by the Bertarelli Foundation.

Previous work in BIOT has been funded by: PEW Charitable Trusts; Darwin Initiative - Overseas Territories Challenge Fund; PEW Environment Group; Defra; FCO; Waterloo Foundation; Blue Marine Foundation;; University College London; Rufford Small Grants Foundation. 

Our partners include: Chagos Conservation Trust; Marine Resources Assessment Group; CEFAS; Marine Management Organisation; University of Bangor; University of Western Australia; University College London;, University of Oxford; University of Exeter; University of Montpellier; Stanford University; Scottish Association of Marine Science; Natural History Museum; Deakin University; Manta Trust; University of Swansea; University of Lancaster; Australian Institute of Marine Science. 

Connect Chagos 2015

The Project 

The Connect Chagos Project was created in 2012 to engage with Chagossian communities based in the UK in order to increase environmental awareness and to contribute to the conservation of the Chagos Archipelago.

Staff from the Connect Chagos Project worked in Crawley and Manchester, hosting events such as Environmental Open Days and Tailored Sessions to actively engage with the community and to increase awareness of the extraordinary environment of the Archipelago.

Each summer an Environmental Training Course was run, in partnership with many conservation organisations, which covered a variety of nature-related topics from bird monitoring, habitat management and marine conservation. Individuals who successfully completed the training course were then invited to apply for bursaries to fund advanced training and to join a scientific expedition to the Chagos Archipelago.

From 2012 – 2015 the project actively engaged with >700 community members from Crawley and Manchester. 42 ambassadors completed the environmental training course, 19 of which went on to carry out advanced training which included chainsaw training and gaining SCUBA diving qualifications. 7 ambassadors have joined scientific expeditions and one individual has recently represented the community at a “Big Oceans” meeting in Hawaii. 

Connect Chagos 2015

The Connect Chagos Book

The book was created as a lasting legacy of the project and as a resouce for the community. It's colourful pages contain information on each of the topics covered during the training course. Starting with an "Introduction to Conservation" it not only educates the reader on the wonderful environment of the Chagos Archipelago but provides useful hints and tips for learning about our wildlife here in the UK. A PDF version can be downloaded below, or contact Kirsty Richards to be sent a hard copy.

PDF icon The Connect Chagos Book (5.36 MB)



Connect Chagos Environmental Training Course Film 2014.


Contact Connect Chagos:

Kirsty Richards

Connect Chagos : People & Wildlife 2014 Booklet

PDF icon Connect Chagos 2014 Booklet (9.49 MB)


Foreign and Commonwealth Office

Chagos Conservation Trust

Darwin Initiative

Partners & Supporters

Bangor University



Manchester Museum

Blue Ventures

Yu Diving

London School of Diving

The Deep Aquarium

The Horniman Museum

City of London

The Ness Botanical Gardens

Natural England

Sayers Croft