Diego Garcia Military Base and British Indian Ocean Territory Bill

Debate between Lord Craig of Radley and Baroness Foster of Aghadrumsee

Committee stage
Tuesday 18th November 2025 Lords Chamber

[Lord Craig of Radley (CB)]

My Lords, I will speak to Amendment 53 in my name and that of the noble and gallant Lord, Lord Houghton of Richmond, who unfortunately cannot be here this evening. It is clearly a probing amendment to give the Committee an opportunity to consider the implications for the UK of another possibility affecting Article 11, the economic partnership of the treaty. That possibility is that, within the 100 years-plus of the treaty, the Diego Garcia military base might become unusable, due to natural causes or because of a sea level rise triggered by global warming. While the loss of use would have military consequences, due to the wording of the treaty the UK’s financial obligations to Mauritius would appear not to be affected.

As I mentioned at Second Reading, the treaty makes some valiant assumptions about the steadfastness of relationships between the countries concerned. That aside, it would be helpful to understand why, if only as a precautionary principle, no mention of this possibility —the functional failure of the base—or how it might be handled is covered in the treaty. I assume that the possibility was considered by His Majesty’s Government and the United States in their preparations for negotiation. Can the Minister confirm this? Was it decided, based on historical records, that the risk of an earthquake, tsunami or other natural cause was so remote that these need not be considered?

Indeed, in his response in the debate on 30 June, the Minister mentioned that, like all small atoll islands, it is naturally dynamic. While not wishing to speculate on future erosion, he said that scientific surveys had concluded that the overall natural land area of the island had decreased by less than one per cent over the last 50 years. But what about sea level rise? There is a widespread presumption that sea levels will rise in the future. The amount of rise, its timing and spread in the world’s oceans is still speculative, but, based on realistic IPCC global warming projections, estimates for the Chagos atoll indicate rises that would impact on the functioning of the Diego Garcia base. They suggest that, within 100 years of the treaty, the runway and hard standings will not be covered, but some of the domestic and fuel storage areas could become submerged, either intermittently by diurnal tides or on a permanent basis. There could also be difficulties with quayside berthing and the present availability of fresh water. This is but a résumé of findings that were sent to FCDO officials in January, before the treaty was signed in May this year.

Maybe the United States, having done its own assessment, believes that it will be possible gradually to strengthen the sea defences as necessary to maintain the base’s operational capabilities. It would be helpful if the Minister could indicate what assessments the United States has made of sea levels. Looking at the wording of the treaty, as I mentioned at Second Reading, there will be the opportunity to attempt to resolve any issue about payment by the arrangements for settling disputes contained in it. But, whatever arrangement might be accepted by both parties today, it does not follow that the same consensus might be possible later, due to changes in the individuals and their perceptions then. There seems therefore to be good reason to have an agreement with Mauritius now, before ratifying the treaty, on how the eventuality of the base becoming unusable would affect Article 11.

[Baroness Foster of Aghadrumsee (Non-Afl)]

My Lords, I rise very briefly to commend the noble and gallant Lord on his amendment. It is an incredibly sensible amendment that should not be contentious because, if there are difficulties arising out of natural causes or disaster, it would be unthinkable for His Majesty’s Government to have to continue to pay large sums of money to the Government of Mauritius. I hope that that will be taken on board.

Secondly, I will refer to the treaty, which, at Article 11, talks about the economic partnership between the United Kingdom and Mauritius. There are three parts to that. The first is the annual sum that has to be paid: there has been lots of conversations around what that is and what it might amount to. The second is the trust fund, which the Minister knows I take a particular interest in and which we will discuss in the eighth group of amendments. The third is the multiyear funding as part of a development framework for projects to be undertaken by the Mauritius Government across 25 years. We have heard very little about this multiyear funding. I wonder whether the Minister could elucidate that and give us some details in relation to what that is and what it is thought to be. In the treaty, it says that the amounts, payments and modality for all those three issues will be agreed separately. So it is important for the House to have some clarity in relation to that and I look forward to hearing from the Minister.