Frequently asked questions

How did CCT get started?

We began life as ‘Friends of the Chagos’, a grouping of scientists, past administrators and British representatives who had an interest in the Chagos Archipelago and an increasing awareness of its value to the Indian Ocean. 

What are CCT’s goals?

We are a UK charity that conducts and promotes conservation work, and scientific and historical research in the Chagos Archipelago.

Check out our Vision, Mission and Strategic Plan here.

What is Healthy Islands, Healthy Reefs?

1. What is Healthy Islands, Healthy Reefs?

Healthy Islands, Heathy Reefs is CCT’s flagship programme that will rewild 30 ecologically degraded islands in the Chagos Archipelago, returning them to sanctuaries for seabirds and building resilience in coral reefs.

2. Why is CCT focusing on this work?

CCT is the only non-government organisation solely dedicated to promoting and conducting world-leading scientific and historical research, and environmental conservation work in the Chagos Archipelago. 

The British Indian Ocean Territory Administration (BIOTA) has identified eleven conservation and environmental priorities to ensure the protection of the Chagos Archipelago’s environment for the future. CCT has been approached to help deliver two of these priorities (1) restoring the islands through eradicating invasive rats and controlling invasive plants, which threaten native seabird populations and impact the delicate balance of BIOT’s ecosystem, and (2) understanding more about BIOT’s unique terrestrial environment. 

CCT plans to deliver these priorities through our Healthy Islands, Healthy Reefs Programme. 

3. Who is CCT working with?

CCT is working in partnership with the BIOTA, and has convened a Stakeholder Advisory Committee of experts from RSPB, ZSL, RBG Kew, and several leading UK universities who have experience and knowledge of the Chagos Archipelago and/or eradication of invasive species or habitat rehabilitation to ensure this programme follows best practice and is as robust as possible.

Over the past five years the Bertarelli Programme of Marine Science, a collaboration bringing together scientists from all around the world to work in the Chagos Archipelago, have published numerous scientific papers based on research conducted in the archipelago. CCT is working closely with scientists from this programme to base conservation actions on sound science and have a positive impact on the archipelago and the biodiversity found there.

CCT also has the support of Island Conservation and the Island Eradication Advisory Group. Both organisations were third party, peer reviewers of the CCT feasibility study and environmental impact assessment.

4. How is CCT funding this work?

Healthy Islands, Healthy Reefs is being delivered in four phases:

1. Feasibility phase - CCT self-funded a Feasibility Study, that includes an Environmental Impact Assessment, to determine the most efficient method for eradicating invasive rats from the Chagos Archipelago’s outer islands. This phase was completed in September 2020.

2. Research and development phase - The Healthy Islands, Healthy Reefs Research and Development Project will provide CCT with the urgently needed knowledge and capacity to deliver the rat eradication component of the wider programme. CCT is currently fundraising for this phase.

3. Implementation phase – This is the main field component of the programme and will incur a significant cost of approximately £5 million. Through the research and development phase these funds will be secured.

4. Monitoring phase – Monitoring post rat eradication is vital and in line with international best practices. Tropical islands can only be officially declared as rat free using the internationally recognised minimum period before declaration of rat free status of one year. On-going monitoring after this period will be done in partnership with the BIOTA.

5. What is the research and development phase?

Our large-scale island restoration and rewilding programme, Healthy Islands, Healthy Reefs, has moved into phase two: research and development. This phase will provide CCT with the urgently needed knowledge and capacity to deliver the rat eradication component of the wider programme. 

The feasibility study highlighted a number of knowledge gaps that need to be filled and, once gathered, this data will inform the Healthy Islands, Healthy Reefs Operational Plan. Questions over the presence/absence of mice and rats, the amount of bait crabs take, and what specialist techniques are needed for baiting mangroves, all need to be addressed. It is vital to have this information to maximise the probability of successfully eradicating rats, which is key to the ecological restoration of the archipelago. 

We hope to look at which new technologies could help not only monitor newly rat-free islands to make sure there are no future invasions, but also to record the return of seabirds to these islands as a measure of success. 

Our ambitious programme requires a team that can ensure CCT has the expertise and funds to take it to the next phase. Building our team is an important step in the development phase. 

The rat eradication component alone is likely to cost approximately £4 million, therefore CCT needs to engage with the public about this important programme and ensure we can finance it into the future. In 2021, CCT will launch its Healthy Islands, Healthy Reefs Programme with a fundraising campaign to raise the £250,000 required to start the research and development phase. 

6. Why do the corals of the Chagos Archipelago need our help?

In 2015 and 2016 two ocean heatwaves led to mass coral bleaching and the death of approximately 70% of the hard corals that form the foundations of the archipelago’s reefs. To give the reefs the best chance of recovery and build their resilience to future bleaching events, we must now focus our efforts on the wildlife found above the water – the archipelago’s seabirds.

7. How do seabirds help corals?

Scientists have recently proven a direct relationship between healthy seabird populations on islands and healthy reefs. The researchers found that after seabirds forage for food in the ocean they return to the islands and their droppings act as a natural fertiliser for the surrounding corals. In essence the seabirds provide food for the corals, which help them grow and build resilience to events such as bleaching.

8. What is ecological restoration?

Ecological restoration in the Chagos Archipelago is man intervening to make good the historic environmental damage he has done to the islands. Nature left alone is not capable of repairing the damage invasive species and native habitat clearance has caused. Intervention in the Chagos Archipelago will be eradicating rats and converting abandoned invasive coconut plantations back to native habitats conducive to breeding seabirds. 

9. What are the biodiversity benefits of ecological restoring the Chagos Archipelago?

• Restoration will triple the amount of habitat available to nesting seabirds.

• Seabirds densities on rat-free islands are 760 times higher than on rat-infested islands.

• Increase in coral resilience.

• Coral reefs around rat-free islands have almost 50% more fish compared to rat-infested islands.

• Increase in native forest cover – only through intervention.

10. What is an invasive non-native species?

Invasive non-native species are organisims that have been introduced (deliberately or accidentally) by people, which are having a detrimental impact on the environment. After habitat loss, invasive non-native species are the second biggest threat to biodiversity worldwide, and on islands are considered to be the biggest threat.

11. What does eradication mean?

Eradication means the complete removal of the target species from the site of interest, usually an island. Eradication of rats has been successfully conducted on over 600 islands around the world, and is a proven and enduring method for protecting or increasing the biodiversity of those islands. 

12. Why is CCT focusing on eradicating rats?

After habitat loss, invasive non-native species like rats are the second biggest threat to biodiversity worldwide, and on islands are considered to be the biggest threat. Currently, within the Chagos Archipelago, over 50% of the islands (30), which constitute 93% of the landmass, have rats.

On the reefs around the rat-free islands in the Chagos Archipelago, fish numbers and coral reef productivity is higher than rat-infested islands, with evidence that this may also provide some resilience to coral bleaching. This research demonstrated that removing rats is the highest priority conservation management action to restore species and build reef resilience, and is now the focus for CCT.

13. How were rats introduced to the Chagos Archipelago

When humans first colonised the archipelago in the late 1700s they introduced several invasive species including rats. Rats eat seabird eggs, chicks and adult birds. This has led to the decimation of seabird populations and most islands with rats now have very few seabirds.

14. How do you eradicate rats?

CCT commissioned a feasibility study that looked at the most efficient ways to eradicate rats from islands using international best practice guidelines. It identified that, currently, the only efficient  way to eradicate rats is by aerial baiting, coupled with targeted hand-baiting in some small areas such as mangroves or former settlements where buildings remain. 

An additional option is to delay eradication of rats until other control tools are developed.  Although there has been a substantial amount of research conducted on other more humane control tools than poison baits no commercially viable tools have been forthcoming in recent times and appear unlikely to be available in the foreseeable future.

Similarly, research on biological control of rats has not achieved any tangible advances recently, and no method for biological control of rats in the field at a landscape scale is presently available. 

Moreover, there are considerable issues and risks with possible techniques, such as gene drives. These include the fact that gene drives currently only work in any sense in mice in a laboratory setting and transfer of the technology to rats is fraught with difficulty, the possibility of inadvertent release elsewhere and the extinction of rattus as a genera worldwide, along with significant doubts about deployment techniques into an existing population.

15. What risks does rat bait pose to the native wildlife?

On the outer islands of the Chagos Archipelago, there are no native mammals. The avifauna is composed primarily of seabirds that would not forage rat pellets. One bird, the striated heron, could be impacted by the operation if they scavenged on rat carcasses or rats that have ingested poison. This is a common species globally and it is likely the Chagos Archipelago population would rapidly recover if impacted.


There is virtually no record of this type of bait causing mortality in seabirds, even at locations with large and diverse seabird populations. There has been one study that recorded a single sooty tern chick pecking at and possibly ingesting a non-toxic bait pellet but it was an extremely rare incident.

Land birds

Of the land bird species present, visiting or vagrant wader species are probably the most common and wader deaths from secondary poisoning through consumption of invertebrates have been recorded. However, the likelihood of significant mortality in this group is virtually eliminated by undertaking the eradication operation during their breeding season when they are absent from the archipelago (southern winter = northern summer) and has been a risk-reduction method for this guild in other tropical rat eradications.


There is generally little concern for populations of lizards during rat eradications, with little evidence of reptiles being susceptible to the bait. 


Land crabs, including the coconut crab, will ingest the bait and indeed pose a risk to operational success due to the amounts of bait they can eat. However, they have a different blood clotting system, so are not susceptible to these types of bait and show no adverse effects at an individual or population level from rat eradication operations using these baits.


As these baits are largely insoluble in water there will be no uptake of the toxin by plants. There will be no impact on plant growth.

Marine environment

Some bait pellets are likely to enter the marine environment. At other tropical rat eradications there has been little recorded impact from the few rat baits that enter the sea. It is possible that intertidal marine animals will consume small amounts of toxin, particularly filter feeders, but also some fish whilst pellets are still relatively intact. The impacts of the bait on tropical marine ecosystems will be reviewed as part of the Healthy Islands, Healthy Reefs research and development phase, which occurs before any baiting takes place. If funded, the BPMS bid will produce a scientific paper on this.

16. What are the benefits of eradicating rats?

Currently, over 50% of the islands, that constitutes 93% of the landmass, of the Chagos Archipelago are in a degraded state caused by habitat destruction and invasive rat presence, resulting in a marked reduction of biodiversity. Without healthy seabird populations supplying nutrients, the coral reefs are less likely to thrive. 

Eleven rat-free islands hold some 92% of the estimated half a million individual seabirds breeding in the Chagos Archipelago. On the reefs around these rat-free islands, there are more fish and coral reefs function better, with evidence that this may also provide some resilience to coral bleaching. Research demonstrates that removing rats is the highest priority conservation management action to restore species and build reef resilience, and is now the focus for CCT.

17. What expertise does CCT have in eradicating rats?

CCT was the first organisation to successfully eradicate rats from the archipelago. Ile Vache Marine is a small island within the eastern Peros Banhos Strict Nature Reserve. It lies amidst six islands that are IUCN Important Bird and Biodiversity Areas, designated for their breeding seabird populations. Ile Vache Marine was rat-infested and had very few breeding seabirds. 

In 2014 CCT conducted an invasive rat eradication operation as part of the Ile Vache Marine Restoration Project. The island was officially declared rat-free, in 2017, using the internationally recognised guidelines. This was the first successful eradication of an island in the archipelago and formed the basis of CCT’s Healthy Islands, Healthy Reefs programme.



1 Graham, N.A.J., Wilson, S.K., Carr, P. et al. Seabirds enhance coral reef productivity and functioning in the absence of invasive rats. Nature 559, 250–253 (2018). 

2 Carr, P, et al (2020). Status and phenology of breeding seabirds and a review of Important Bird and Biodiversity Areas in the British Indian Ocean Territory. In production.

3 https://chagos-trust.org/news/news-first-successful-invasive-rat-eradication-in-the-chagos-archipelago 

4 Benkwitt C.E., Graham N.A.J. and Wilson S.K. (2019) Seabird nutrient subsidies alter response of coral reefs to bleaching events. Global Change Biology. DOI:10.1111/ gcb.14643 

5 Head, C.E.I., Bayley, D.T.I., Rowlands, G. et al. Coral bleaching impacts from back-to-back 2015–2016 thermal anomalies in the remote central Indian Ocean. Coral Reefs 38, 605–618 (2019). 

6 http://www.nonnativespecies.org

Where does CCT receive its funding from?

We are a not-for-profit, charitable incorporated organisation registered in the UK. We rely on membership fees, donations and funding through grants from the British government, trusts and foundations, and other charitable giving organisations to fund research and conservation work in the Chagos Archipelago.

Our founder, John Topp, generously provided an endowment that enables us to pay for administration costs leaving any other funding received to go directly into achieving the organisation’s vision and mission.

Who runs the CCT?

We are largely voluntary with the Board of Trustees made up from a diverse group of scientists, conservationists, campaigners and finance specialists with one thing in common: working to protect the Chagos Archipelago.

In 2015 the trust decided to hire a director to drive and expand the organisation. The director works closely with the board and other institutions and organisations to further the goals of the CCT and ensure the trust has a sustainable future.   

Does CCT work with Chagossian groups?

As vital stakeholders in the Chagos Archipelago, CCT has worked and engaged with Chagossian groups (wherever they are based) for many years. Chagossian's history and culture play an important part in the islands, and CCT supports Chagossian communities to ensure this continues. 

For example, CCT works closely with the UK community through the group Chagossian Voices, where we develop new ways to engage and build capacity. We are currently helping to build a community website.

CCT also includes Chagossians in conservation activities, including supporting scholarships for students to join scientific expeditions. 

Through our partnership with ZSL,  and with the support of other members of the Chagos Environment Network, we ran an outreach and training programme for Chagossians based in Crawley and Manchester. The programme allowed Chagossians to learn more about the Chagos environment about diving and the protection of coral reefs.

“I will do my ‘A’ level biology and then I hope to go to university to do marine biology. In the future I might do research out here [in Chagos].” Pascaline Cotte, 19, Chagos Conservation Trust scholar. 

You can learn more about the Chagossian Community Environment Project and ZSL’s other work in Chagos Archipelago on the ZSL website.

What is the Chagos Archipelago?

The Chagos Archipelago is made up of a collection of 58 tiny island and coral reefs surrounded by open sea. It is located in the central the Indian Ocean and is a British Overseas Territory known as the BIOT.

The land area totals only about 40 km2 spread over 640,000 sq km of ocean, which is twice the size of the Britain. The largest island located in the far southeast of the archipelago and comprising of about half the land area is Diego Garcia.

When did the Chagos Archipelago become a marine reserve?

On 1st April 2010 the Chagos Archipelago was designated by the British government as a fully no-take marine reserve.  

The combination of tropical islands, unspoiled coral reefs and adjacent oceanic abyss makes this area globally important. As a fully protected marine reserve, all extractive activities, such as industrial fishing and deep-sea mining, are prohibited. This decision will safeguard the rich diversity of marine life found in the area.

Why protect the Chagos Archipelago? Why does it deserve recognition and protection?

The Chagos Archipelago contains the world’s largest coral atoll and the greatest marine biodiversity by far under UK jurisdiction. It also has one of the healthiest reef systems in the cleanest waters in the world.

The reserve helps to maintain the pure and unpolluted waters and provides a safe refuge for its rich marine life, including many threatened species, such as turtles and sharks, and globally important populations of seabirds. It also provides a temporary refuge for migratory species, such as tuna, from exploitation.

The archipelago is one of the few marine locations in the world where there are almost no ongoing, direct human impacts over almost all of its area. The marine reserve serves as a reference site for global scientific research to aid in our understanding of such things as climate change, tropical marine ecosystems and the impacts of commercial fisheries.

The creation of the Chagos Marine Reserve represents an important contribution by the UK to at least seven international environmental conventions. It also contributes to the UK’s global commitments, such as slowing the decline of biodiversity by 2010, establishing marine protection networks by 2012, and restoring depleted fish stocks to sustainable levels by 2015.

Why is a no-take marine reserve necessary?

There are very few wild places left on earth that are still in good condition. The Chagos Archipelago is one of these places.

In 2009-10 the British government held a consultation to inform its conservation policy in the Chagos Archipelago. As there were no people living within the proposed MPA1, it was possible for the government to consider the highest possible level of marine protection – a no-take marine reserve, where all fishing and other extractive activities would be banned.

A number of high-profile conservation organisations, including CCT, agreed that a no-take marine reserve was the best option. These included the RSPB, ZSL, the Royal Botanic Gardens, Kew, the Linnean Society of London and the Royal Society. Read more about our partners in the Chagos Environment Network (CEN) who helped establish the marine reserve.

Achieving the highest level of protection in this part of the world is crucial to allow the Chagos Archipelago ecosystem to continue to thrive and benefit communities all over the world.

1. The US military base on Diego Garcia, and the water to three miles from its shoreline, is not part of the MPA - though it has numerous protection measures specific to that atoll, recreational fishing here is permitted.

Is the presence of the military base a threat to the ecosystem?

The island of Diego Garcia where the military base is located is in the far southeast of the archipelago, and is tens of miles, and in many cases more than one hundred miles, away from most other islands, reefs and their surrounding waters. Whilst there has been damage to some reefs close to the military area of Diego Garcia, it is not highly significant in the context of the vast area of reef in the entire Chagos Archipelago ecosystem. Even around the Diego Garcia military base, ecological and water chemistry results show that the area remains in good condition.

What do we know about the history of the Chagos Archipelago?

The Chagos Archipelago has been a British territory since 1814 when it was ceded to Britain with Mauritius, which then included the Seychelles. Following the French practice, it was administered as a dependency of Mauritius until 1965, when by agreement it was detached to form the new British Indian Ocean Territory. Three other island groups, formerly part of the Seychelles, were made part of the Seychelles, when the Seychelles gained independence in 1976.

The islands were uninhabited until the late 18th century, when the French established coconut plantations using slave labour. After emancipation, many slaves became contract employees and remained on the islands. Following the decision in the 1960s that the islands should be set aside for defence needs, the UK purchased the freehold title to the land in the islands in 1967. The copra plantations were run down as their commercial future was already unviable and the last of the contract workers and their families left the territory in 1972-3. The islanders (originally called Ilois but now more often termed Chagossians) were relocated to Mauritius and the Seychelles. Successive British governments have expressed regrets about the way resettlement was carried out and provided compensation.

Although many Chagossians still live in Mauritius, with a small community with Chagossian links in the Seychelles, some have moved to the UK when they gained British citizenship under the UK Overseas Territories Act 2002. Over recent years some Chagossian groups have brought a number of claims against the British government and there have been several court judgements on this matter.

Does the marine reserve prevent Chagossians returning to the islands?

The Chagossian communities were removed from the islands many decades before the Marine Protected Area (MPA) around the Chagos Archipelago was declared in 2010, and was not connected to the removal of the population.

The MPA creates a zone that is closed to commercial fishing, but when it was created it was anticipated that rules around fishing would need to be changed to accommodate any future re-settlement by the Chagossian community. There is precedence all over the world for MPAs that continue to support subsistence fishing from local communities.

In fact, the marine reserve presents neither a legal nor a practical barrier to Chagossian return, if that were granted, because the current conservation arrangements can be adapted to accommodate the needs of any future communities.

CCT believes strongly in the role that local communities play in the conservation and protection of the resources on which they depend, and would seek to fully support the Chagossian communities in playing that role.

What is CCT’s position on any resettlement back to the Chagos Archipelago?

We will continue to work with the Chagossian community, as we have for many years, on research and conservation of this unique archipelago and look forward to continuing to do so. The question of resettlement is a government matter and we hope that any decision will be made using the best scientific information.

As a conservation organisation we will to continue to include Chagossians in expeditions to the Chagos Archipelago and share the importance of conservation to their future and those of the islands. We believe that any return to the Chagos Archipelago must be sustainable and not used as a cover for exploitation of this unique marine environment.

Can I visit Chagos Archipelago as a tourist/volunteer/photographer/journalist etc?

Unfortunately, these islands are very remote making visiting them impractical. There are no commercial tours to the Chagos Archipelago. Rules regarding private visits are very strict and it is only possible to visit one or two sites by private yacht – and then only with permission of the BIOT administration. Most non-government visitors are highly skilled scientists who land a coveted position on one of the occasional research expeditions to the area. Therefore unfortunately there is almost no possibility of visiting or volunteering on these islands.

For further information on visiting the Chagos Archipelago visit the BIOT administration’s website.

If you would like to do more to help conservation of the Chagos Archipelago you can become a supporting member of the CCT. To find out how to become a member, please visit our Join CCT page.

How do I provide feedback or raise an issue with CCT?

At the Chagos Conservation Trust we take engagement with our supporters, partners and stakeholders seriously and welcome your feedback.

CCT commits to responding to all issues and feedback, if requested, in a timely manner and in confidence. To raise any issues or provide any feedback please contact the CCT Secretary.



In writing

CCT Secretary
23 The Avenue
UK, SG19 1ER

If your issue is not resolved to your satisfaction it can be elevated to the CCT board, on request in writing, where it will be reviewed at the quarterly board meeting and responded to accordingly.