Michael Sheen strides across a grassy field, atop the hillfort of Castell Dinas, to deliver an uncomfortable truth. The skies above the Bannau Brycheiniog national park are emptying of birds. Its rivers are sluggish with pollution. Nature, within its boundaries, is struggling.

What’s surprising here is not the fact itself, but that a world-famous actor is shouting it from the hilltops. (In this case, in a promotional film announcing that the park, formerly Brecon Beacons, will now go by its Welsh name and has a bold new plan for how it will be managed.) Sadly, the Bannau is not unique: nature often fares worse inside national parks in the United Kingdom than in their surroundings. Parks aren’t holding back the demise of life across our islands.

On biodiversity, the picture is bleak. Only 26 per cent of Sites of Special Scientific Interest within English national parks are in “favourable condition”, meaning that their habitats are healthy and protected; the national average is 38 per cent. In the House of Lords, Katherine Willis described national parks as being in a “perilous state” for biodiversity. While they might seem “lush and green”, they are also getting “quieter and quieter”, she said, invoking Rachel Carson’s Silent Spring. The environmental journalist George Monbiot has called them “ecological disaster zones”.

In the Bannau, between 1995 and 2018 populations of eight “red list” species of birds, including the swift, yellowhammer and curlew, declined by more than 50 per cent. Familiar birds such as the chaffinch and blue tit declined by 25 to 50 per cent. These are the canaries in the coal mine, signalling the collapse of ecosystems. When officers of the park presented this evidence to a panel of local citizens, there was dismay. A senior officer tells me the group asked: “Who let this happen? Who let the park get into that state? Where are the people who are supposed to be looking after it? What have they been doing?”

Continue reading this feature on the Prospect website

You can also listen to me discussing this piece on the Prospect podcast episode called 'Biodiversity on the brink?'