BBC Sounds Music Radio Podcasts Hello and thanks for downloading the More or Less podcast. We're the programme that looks at the numbers in the news and in life and in the sky. I'm Charlotte McDonald. If there's one thing Donald Trump definitely doesn't like, it's wind turbines or windmills as he calls them. You know the windmills. Boom, boom, boom. They kill so many birds you look underneath some of those windmills it's like a killing field of birds. It's been suggested that Trump's dislike of windmills goes back to a golfing dispute. In the early 2010s, a brave soul proposed building a wind farm off the coast of a golf course he owns in Scotland. Trump fought back, labelling the wind turbines monsters and even testifying against the plan to the Scottish Parliament. But it's the cost to bird life that now seems his main concern. But I've restricted windmills in the United States because they also kill all your birds, you know, they wipe out, you know, it's interesting. If you shoot a bald eagle in the United States, they put you in jail for five years. And yet windmills knock out hundreds of them. They don't do anything. Rrrrr. You know, the thing makes it so. And of course, it's like a graveyard for birds. If you love birds, you'd never want to walk under a windmill. Because it's a very sad, sad site. It's like a cemetery. We put a little. We put a little statue for the poor birds. Earlier this year, he posted on TruthSocial claiming wind turbines were killing birds by the millions. But is he right? Do wind turbines kill millions of birds a year? It's not completely wrong. I think with this statement that S on the millions is probably doing some heavy lifting. This is Dr Hannah Ritchie, deputy editor at Our World in Data and senior researcher at the University of Oxford. I think my best estimate is that in the US wind turbines probably kill between 1 and 2 million birds every year. So with the million statement that's broadly right but I think it's missing a lot of context. Okay, let's get into the details of this number and let's start with the basics. We're going to focus on the United States because that's what Trump's comments were referring to and it's where we have reasonable data. How do we count how many birds are killed by wind turbines each year? It turns out those bird cemeteries Trump was talking about aren't far from the truth. Yeah, so figuring this number is very difficult. I mean there's no big national database where we store all of the different birds killed by wind turbines every year. It's often extrapolated from the smaller scale studies so what researchers will do is that they'll go out to a wind farm and they'll basically count the number of bird carcasses that they find. Sounds like a fun way to spend your weekend? It's important to note that these studies only measure the birds killed by onshore wind farms. It's much harder to measure birds killed by wind turbines in the ocean and the data on that isn't reliable. Anyway, you can use the data from Counting Dead Birds to calculate a rate of deaths per wind turbine. Hannah found all the studies she could that did this to see if they agree. They did not. So most of the studies I looked at were in the range of 4 to 18 birds killed per wind turbine per year. So that's a fourfold difference so the difference there is large. The problem is that dead birds are hard to count. Sometimes small birds get missed, sometimes wild animals eat dead birds before they're counted. The number and type of dead birds also varies depending on the location. Some particular species such as eagles, raptors, shore like birds, they tend to be at higher risk. And that's for a couple of reasons. The main one being that they will often use kind of ridgetops to get lift when they're flying. And that's obviously a very, very good spot to put a wind turbine. It's very windy there. You'll also get migratory birds that will go through the same spot over and over again through migration patterns and they also tend to be at higher risk. To account for the bird count problems, scientists try to model the number of birds that might die but not be counted. Hence the big range of answers. So if we take the range of figures for the number of birds killed per turbine per year in the US, so 4 to 18, we multiply that by the number of turbines in the US. We get this estimate between 300,000 and about 1.3 million birds killed across the US every year. Hannah thinks that because there's a risk of underreporting in the dead bird count, the higher numbers are more likely to be in the right ballpark. So naturally picking the higher number is maybe more honest and adjust for that. So Hannah reckons a figure of maybe 1 to 2 million birds being killed every year looks justifiable. President Trump is roughly right, as long as you think millions means 2 million and not 100 million. But as so often on this programme, the numbers don't tell the whole story. Yeah, so my estimate is that wind turbines probably kill between 1 to 2 million birds every year in the US. But to put that in context of other hazards, kind of top of the list is cats. Now cats probably kill just over 2 billion, so a thousand times higher than my estimates for wind turbines. Those figures come with a lot of uncertainty, they're not precise in any way. I tried to figure out how many birds do they kill per cat and it works out at around 20 per year for a kind of feral outdoor cat. Now that probably seems reasonable to me. And it's not just cats that are more deadly for birds than wind turbines. Buildings and cars and trucks are also very high on that list, so they kill maybe 600 million for buildings and around 200 million for cars and trucks. There are other big hazards like pesticides, communication towers, they are kind of in the order of magnitude of millions to tens of millions. And obviously these hazards just don't get the same attention in terms of policy and media attention as wind turbines do. So I think the number is maybe correct, but I think the context surrounding it is missing to help us understand whether there should be a barrier to us deploying wind power or not. One thing that's definitely not true is that wind turbines are killing all the birds. The back of an envelope calculation is even harder for the total US bird population, but Hannah had a look at the data to try and give us a rough idea. Some of the best estimates I've seen have been in the range of maybe 10 to 20 billion. So when you're thinking about the threat from wind turbines, you're talking about maybe 1 million relative to 10 to 20 billion birds in total. So as a share of the total bird population, the threat is reasonably small. Birds also often reproduce pretty fast and have quite short lifespans, so there's a lot going on in this number. So what's the final verdict? Should the number of birds being killed make us reconsider our use of wind turbines? I don't think the death toll from wind turbines should stop us from deploying wind power for a couple of reasons. I think the first one is that we are actually deploying clean energy for a reason, and part of that reason is to mitigate climate change and also it has the side benefit of mitigation air pollution. And both of those are relatively large threats to birds and wildlife at large. So there is some downsides in terms of bird loss to wind turbines, but on the flip side, the problem we're trying to solve also has downsides for this wildlife. I think what it does mean though, and I think this comes back to the types of birds that are most at risk, is that I think we also need to think carefully about where we're putting wind turbines and what we're putting in place to try to mitigate those risks. I don't think this is purely about total numbers. I think there are genuine risks to specific and often rarer species, and I think we do need to take that selection process quite carefully. Until next week, goodbye.
