Bird species losing ground in Ethiopia

Climate change poses a serious threat to thousands, if not millions, of species around the planet. But two - the White-tailed Swallow and Ethiopian Bush-crow, are particularly at risk. Scientists are predicting that both of these birds will suffer an extreme loss of their native habitats, even under the most optimistic global warming scenarios. Cambridge University’s Andrew Bladon has been leading this study, and spoke with Chris Smith...

Andrew Bladon - These two species are really interesting because they have incredibly small global ranges. Both of them are only found in a tiny area of Southern Ethiopia. And the interesting thing is that both species, the area in which they are found is cooler and drier than surrounding areas. And this seems to be the determining factor in limiting the distribution.

Chris Smith - And how did you realize that there was this threat?

Andrew Bladon - For a long time, scientists were puzzled as to what was going on with these species. So when they were first described, people sort of talked about the fact that the habitat inside and outside of their range all looked the same, and there was no obvious reason why they would be found in only one location. And then we started a project a few years ago now, looking into this and looked at how temperature impacts the behavior of the birds. So we looked at the foraging behavior of the Ethiopian Bushcrow and found that when temperatures get too high, they really struggled to forage. They don't get enough food. And for the White-tailed Swallow, it appears that there's some impact on their breeding success. So when it gets warmer, they struggle to breed in the nest, start to fail. And so this begins to suggest that when you get to the edge of their distribution in areas where it's generally a bit warmer, they struggled to survive, and that's why they're not there. And then we underpin that with some big distribution models where we compared climate in the areas where they are found and the areas where they're not found and found that indeed the areas where they're not found are warmer and a bit wetter than the areas where they are.

Chris Smith - Can you use models like that then to look at ways or explore ways in which you might be able to reverse some of the threats or, find alternative places for them to live?

Andrew Bladon - Yeah, so one thing that these models allow us to do is to look at the areas that are likely to remain the most suitable. So we can project these models into the future under different climate scenarios and see how the climate is likely to change and which areas are going to remain the most suitable for the species. And those areas are probably the places that we want to target for conservation, i.e. for protection of the habitat, perhaps for habitat improvement and mitigation strategies to try and create the sort of optimal habitat that maybe provides cooler environments for the species. But the problem is that we're talking about such a small area and such a rapid rate of change that actually the suitable climate is probably just going to disappear too quickly. So the other kind of option is to then start looking at where else in the world might the climate be suitable? And can we introduce them into a different habitat, but that comes with its own sort of set of risks and it's quite controversial.

Chris Smith - Presumably these animals are just the canaries in the coal mine in many respects, aren't they? There must be thousands to millions of species, similarly, imperiled by climate change with very, very rigid constraints on where they can exist. And it's just going to be an impossibility for us to find new homes, and then rehome quite that many species.

Andrew Bladon - Yeah. So the real advantage of these two species is because their range is so small, and appears to be entirely predicted by these climate factors. It's very easy for us to build these models and sort of say, well, this is what's driving their distribution. For a lot of species, they will be similarly threatened by climate change. But if they have wider distributions, that might be an area where they're sort of actually limited by unsuitable habitat and an area where they're actually limited by some competition with other species. And so it makes it harder for us to predict what's going on. So one option that we have with these spaces is by actually monitoring the rate at which they decline in the coming years, we can try and validate the models that we've built. And that could be really important because these models are really commonly used for predicting what's going to happen to species in the future.

Andrew Bladon - But we don't actually have very good data on how well they produce those predictions. And so if we can use data from the Swallow and the Bushcrow to validate these models and validate the predictions that they make over the next 20 or 30 years, we might be able to apply that to other species where we're working with a slightly wider time window. So for these two species, we're looking at the potential disappearance of their entire distribution within the next 40 or 50 years. Whereas for other species where we might be talking about 80 or a hundred years, we've got a bit more time to think, well, if we can validate these models, we know that they're accurate and then we can work with what they're telling us to try and better conserve other species,

Chris Smith - A silver lining to what is though, a very, very dark cloud.

Andrew Bladon - Yes, indeed. It's quite sobering to work on two species for sort of six or seven years. And then to realize that the end result of this is actually, they're probably both going to go extinct and there's very little we can do about it.