Study: Butterfly Declines Linked To Climate Change

Mar 8, 2021

A study published in Science last week shows butterfly populations are declining by almost two percent a year in the Western U.S. The authors say that’s driven by climate change. KNAU’s Melissa Sevigny spoke with lead author Matt Forister of the University of Nevada-Reno about the findings, which came from decades of community science data from the North American Butterfly Association.

Credit Jeffrey Glassberg, North America Butterfly Association


How do you go about tracking the number of butterflies in such a huge geographical area?

It’s really remarkable, this network of people that are organized every year to go out to the same spots every year, and they basically take whatever team of volunteers they can get, and they search a certain area and they count up all the species of butterflies they can find… and that’s what we used to ask how butterflies are doing out in the wild spaces of the West.

Looking at all this data from the past four decades, what did you found out?

The biggest message is that butterflies, like many insects in many parts of the world, are declining at a subtle but important rate per year. The big finding here is to see that decline out in the open spaces of the West. Because previous long term data sets that have been used to answer this question have most often been closer to human habitation, for example, from Northern Europe where you have very intensely managed landscapes. In those areas it’s harder to separate the signal of agricultural development, urban development, climate change etc. We know that agriculture practices and urban development can be very bad for butterflies in the West. This study is not about that. This is about the other part of the picture, which we have the ability to look at in the West because we have so many open spaces where we can go look at natural communities.

When you say the other part of the picture, you’re talking about climate change?

Climate change, right. It really has been an open question. A lot of folks have thought, and there was reason to think, maybe if natural communities are left to their own devices that insects could shift around and adjust to climate change. We know that some species can move up slope, for example in mountains, to find cooler areas, or go to more northern latitudes, and sure, some species do that, but what we have found is there is still this an overall signal, when you take a massive region like the West and you dry it out and warm it up, that is going to have widespread consequence for insects.

Why do you think it’s important to understand what’s happening with butterflies? Can you talk about their importance to ecosystems?

As all insects, they are part of the glue that holds ecosystems together. Caterpillars connect plants to other parts of food webs like birds that need caterpillars to raise their young. Butterflies are of course pollinators, as are many other insects. We also generally take butterflies to be a representative of other insects, because a lot of other insect groups are just not easy to track in the same way that butterflies are…. Also butterflies are just pretty important parts of life, who doesn’t love butterflies? The thought of fewer butterflies out in the natural parks of the West is pretty shocking.

If we wanted to stop the downward trend, what would we need to do?

Climate change is very important, so voting is important, keeping action going at governmental levels and national levels to fight climate change is super important. But we all know a certain amount of change is locked in… I think there the interesting lesson is, if butterflies are suffering out there in protected areas, counterintuitively, that elevates the importance of land closer at hand.….They’re suffering our there, you could think twice about spraying poisons in your background, because our backyards are good butterfly habitat…. I do believe we can help…They’re different than other animals that are suffering because of human activity specifically because butterflies will respond to very small-scale things we do.

Matt Forister, thank you so much for speaking with me.

Thanks, nice to talk to you.