It is an immense achievement. But it still leaves much to be done. The protected areas are unevenly spread: one fifth of all the world’s countries have designated less than 1 per cent of their land. There are major gaps; less than a tenth of a per cent of the original forest in the Southern Pacific islands is protected for example, along with less than 1 per cent of the forests of Central Africa’s Cameroon Highlands and of the mangroves of the Gulf of Guinea. More striking still, less than 1 per cent of the seas and oceans that cover 70 per cent of the globe is covered by protected areas.

Many parks exist only on paper, lacking management and legal title. Many that are properly enforced are too small to function effectively. Many more are damaged by threats ranging from poaching to air pollution, from illegal mining and logging to uncontrolled fires – often because they have been set up without the participation of local people, who believe they do not benefit from them. And global warming threatens to erode and destroy their value, as species are unable to cope with the changing climate.

These threats are driven by the forces endangering the world’s environment and security as a whole, such as poverty, overconsumption and overexploitation. The protected areas of the globe will only continue to do their invaluable work if these underlying problems are tackled – and if the local people have reason to value them and participate in their conservation.

Geoffrey Lean