Experts on Camera

Dr. John J. Wiens: Hot days, disappearing species

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Extreme temperatures have been linked to the endangerment and local extinction of many species of plants and animals. Thousands of species around the world may be threatened, including at least 90 in North America.

On August 26, 2021, SciLine interviewed: Dr. John J. Wiens, a professor of ecology and evolutionary biology at the University of Arizona, studying responses of species to climate change. See the footage and transcript from the interview below, or select ‘Contents’ on the left to skip to specific questions.

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JOHN J. WIENS: My name is John J. Wiens, and I am a professor of ecology and evolutionary biology at the University of Arizona.

Interview with SciLine

In general, how has climate change affected plant and animal populations?


JOHN J. WIENS: So there’s been all sorts of changes in plant and animal populations related to climate change. But probably the most important one are local extinctions. And that means that the species isn’t found where it used to be found, right? So think about one local place, right? They’re not there anymore. And so we’ve done analyses looking at this, where people have done surveys over time. We looked – a few years ago, we looked at 976 species. And there were local extinctions in 47% of those – right? – so almost half the species. There’s already been local extinctions, even though the amount of climate change that’s happened at that point has actually been pretty modest, pretty small relative to what’s predicted in the future. So that’s obviously really bad and does not bode well for the future. So those local extinctions – right? – them disappearing from a given locality – that’s the most – probably the most important change. But there’s lots of other changes, also. Some species are getting smaller because of climate change. Some species are shifting their ranges, so they’re found at higher elevations now than they used to be or at higher latitudes. They’re closer to the North Pole. They’re closer to the South Pole if they’re in the Southern hemisphere. Lots of species are active at different times of the year. So a lot of species – spring is coming earlier, so plants are flowering earlier in the year. It’s getting warmer, so winter is ending sooner. All sorts of changes like that are happening all over the world.

In particular, how have extremely hot days contributed to the local disappearances of species?


JOHN J. WIENS: So last year, a grad student of mine, ‪Cristian Roman-Palacios, and I tried to figure out what the – what are the specific changes in climate that seem to be causing these local extinctions? And we basically isolated that it seems to be these hottest days, right? So the change in the mean annual temperature – that doesn’t – that’s actually positively misleading, but it’s these hottest days that seems to best predict where local extinctions are going to happen. So we think that that is the big driver, that specific change in the climate that causes these local extinctions, right? So what’s actually happening on the ground, we don’t know, right? So we look across, you know, hundreds of species across the planet based on resurvey data, so we don’t necessarily know what’s happening in each location – could actually be a lot of different things, right? So it might be as simple as they just overheat, and so they die, right? It might be that simple, or it might be more complex, right? It might be that the heat weakens them, and then they get attacked by parasites. We know that in the case of coral reefs, it gets really hot. They eject the proteins that they need for food – right? – and then they starve to death. So it’s a pretty complicated thing. And probably, in general, there’s just lots of different things happening in lots of different species. But the heat stress that you might imagine – that comes from when we’re kind of at the maximum heat, the maximum temperatures.

What is biodiversity, and how does climate change affect biodiversity?


JOHN J. WIENS: Biodiversity is this very broad term that means the diversity of life. And it can mean diversity in lots of different things. It can – the genetics and the phenotypes. That is what they look like. But really, we often – most often use biodiversity to mean the same thing as the number of species, right? So when we worry about climate change, you know, one of the big things we worry about is how it’s going to affect the number of species on the planet. And so some of the analyses that we’ve done, you know, looking at hundreds of species of plants and animals, you know, basically suggests that the impact of climate change on biodiversity is pretty much up to us, right? So if we, for example, are able to follow the Paris Accord – right? – and keep climate change below 1.5 degrees Celsius, keep it down to that level, maybe we’re losing only 1 in 6 species, which is horrible but it’s a lot better than some of the alternatives. There are scenarios where we could lose half the plant and animal species on the planet, right? So which of those futures comes to pass is really up to us. This is human caused. And so we’re human, so we can determine what’s going to happen. It’s a pretty clear relationship, though. Once, you know, you get to a certain temperature, it seems like they can’t take it anymore, and they die. And that’s happening already.

If climate change continues along its current trajectory, what does the future hold for plants, animals and other species?


JOHN J. WIENS: It kind of depends on what the current trajectory is, and it’s – and I really couldn’t say. But I could tell you that if it goes – if we get a 3 degrees Celsius increase, that would be really, really bad. We basically know from the analyses we’ve done that most plant – animals and plants can’t survive that. So a local population that experiences a 3 degrees Celsius increase is probably not going to survive, right? So if that happens over the whole planet, that’s terrible, right? On the other hand, as I said, if we keep it down to, you know, like, a less than 1.5 degrees Celsius increase, that could reduce extinction to maybe 1 in 6 species or less. So it’s kind of up to us. And it’s – you know, think about it somewhere between, like, 1.5 and 3 degrees Celsius, 3 degrees Celsius is terrible, and 1.5 is not so bad.

Can anything be done at a large scale to help wild plants and animals adapt to warming temperatures, rather than go extinct?


JOHN J. WIENS: If you had asked me two years ago, I would have probably said that the most important thing was to create corridors along mountain slopes where things could naturally move up faster – right? – so basically move up to higher elevations where temperatures are cooler, kind of try to stay in there under the conditions that they’re adapted to. Now, having done this work with my former student, ‪Cristian Roman-Palacios, you know, we’ve sort of – we don’t run the analyses, we do the numbers, it doesn’t seem like things move fast enough to be able to stay cool enough as climates are warming. It’s really important to preserve natural habitats. It’s also important to preserve corridors of habitat along mountain ranges. But I’m not sure that that’s enough. Yeah, kind of – I’ll say this, and I’ll, you know, say it again that I think the most important thing is just to stop this level of climate change. It’s really hard to protect, I think, species from it.

Is there anything that individual people can do to help reduce climate change in general?


JOHN J. WIENS: The best thing that people can do to help wild plants and animals from going extinct is to try and reduce global warming, I think, right? And – ’cause it’s not really clear how you can help animals adapt. So but there’s lots of things that people can do to try and reduce warming. The most important thing is actually voting – just large, you know, structural change. But then there’s all sorts of everyday things. So basically, you know, almost everything that we do is – kind of has a carbon footprint associated with it, and that’s the bad news. But the good news is that, you know, for everything that you do, you can tweak it so that it has less of a carbon – you know, has less of an impact. So some of the best things you can do are flying less, driving less, eating less beef and lamb, using less electricity at home and at work, getting your home electricity from wind and solar and not from coal. And just remember that every little thing helps. It doesn’t have to be, you know, everything 100% all the time, right? So for example, in terms of people’s diets, you don’t have to be 100% vegan all the time to reduce climate change by eating less beef, right? You can have chicken instead of beef or just have beef once a month or something, right? It’s all – anything can help.

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