Guest post by Richard Bradbury from the RSPB's Centre for Conservation Science

The latest IPCC report presents evidence that climate change is having widespread and profound impacts on the world’s wildlife and ecosystems, on land and at sea. Climate change in the UK is arguably less extreme than in many other parts of the world, yet even here wildlife is responding – acting as the ‘miner’s canary’ to alert us to further changes to come.

One example is the Dartford warbler. At first, this looks like a climate change good news story. But the truth is more complicated.

Dartford warbler

Dartford warblers are very sensitive to the cold, especially in winter, and historically were found in the UK only on lowland heathland in the extreme south of England – places like the RSPB reserve at Arne in Dorset and the Thames basin heaths. This is the extreme north of the species’ small global range, which extends down through France into Iberia. In the extreme winter of 1962/3, Dartford warblers nearly went extinct in the UK, with just a few individuals hanging on in Dorset.

But this picture has changed dramatically, as revealed by a series of national surveys in 1974, 1984, 1994 and 2006. The Dartford warbler has been charging northwards, picking out the remaining fragments of its favoured heathland habitat in which to settle. It has moved north to the midlands, Cannock Chase for example, and the heaths of coastal East Anglia. It has moved uphill, now being found up to 400m up hills in south-west England and south Wales. Birds have even set up territory in the Peak District.

 So, is this a response to climate change? Well, it’s hard to say for sure, but as for many other species that are moving north (like little egret and a host of butterflies and dragonflies), it looks the most plausible explanation. And it is exactly what we projected would happen in the ‘Climatic Atlas’ that we recently produced with Durham University, where we used the strong relationship between this species’ range and the climate to predict where suitable climate conditions for this species would be in the future.

Modelled current (top) and late 21st century (bottom) range of the Dartford warbler (blue present, yellow absent)

So, is it all good news for Dartford warblers? Well, unfortunately not. The Climatic Atlas suggests that UK advances will be offset by retreats at the southern edge of the species range. And monitoring reports from Spain suggest they are already declining rapidly. Again, whether this is due to climate change, or an interaction between climate change and other problems, is not yet known. What is clear though is that, if these patterns continue, the UK will have a greater share of the world’s Dartford warblers, and a greater responsibility for their global stewardship.

So, RSPB is fighting for Dartford warblers on two fronts. First, we continue to restore heathland, for instance at our Lodge reserve, so that Dartford warblers may have safe havens. Second, with Cambridge University, we are researching how best to help Dartford warblers to spread and consolidate their new range. And I can’t forget to mention monitoring. This is often undervalued, as unsexy science, but it is crucial that we continue to invest in monitoring the natural world if we are to detect, and then act on, the changes that are predicted to come.

Heathland restoration at the Lodge nature reserve