Recent headlines about declines in insect populations around the world and the threat of mass extinction are alarming. According to a recent study, three-quarters of flying insects in nature reserves across Germany have disappeared over the last 25 years. Scientists studying in Puerto Rico have reported astonishing losses of insects on the ground — a reported 98% loss over 35 years.
The Allegheny Front’s Kara Holsopple spoke with John Wenzel, a career entomologist and director of Powdermill Nature Reserve, part of the Carnegie Museum of Natural History, to find out what’s known and unknown about insects declines here and across the globe.
LISTEN to the full conversation:
Kara Holsopple: Is the situation as dire as these stories suggest?
Josh Wenzel: I don’t think we can really say that yet. Some of the situations really are terrible crises. Other ones we’re just discovering and we don’t really know how bad they are. The research needs to be compared to something else. Do it again two years from now, that kind of thing. Also when we talk about loss, there are two kinds of loss. There’s a loss where the species disappears completely and then there’s a loss where they’re just not as frequent as they were. Both of those are important to measuring this crisis.
KH: So these stories are not necessarily telling the full picture of what’s happening?
John Wenzel, director of Powdermill Nature Reserve in front of a Carnegie Museum of Natural History display. Photo: Kara Holsopple
JW: It certainly is more complicated than any of the sort of simple cries to arms make it out to be. The two studies you mentioned I think are important for very different reasons. In the German study, what they found was even within protected nature reserves, there is this collapse. What this means is our nature reserves aren’t working. And apparently the human environment around the margin of the reserve is enough to degrade the preserved area. So it isn’t functioning properly anymore. That should be a great concern.
The study from Puerto Rico is rather different. We don’t think that is due to manmade influences around the island of Puerto Rico. Rather that seems to be the result of climate change, where the rainy and dry seasons have changed a little bit. So with really increasing duration and frequency of dry periods, these forest insects [that] like wet forests are disappearing because of the wet forest is drying out. So you have both manmade causes and natural causes. Of course, these conspire in some places to create really a very grave situation where the insects and the plants they rely on, all kinds of other things, can’t really live the way they used to live.
KH: What kind of data do we have and what’s needed?
JW: Well, obviously, the best data are from places where people have been paying attention for a long time. So that’s mostly northern Europe and eastern North America, where we usually have the best records. England and the British Isles generally have the best records and they can be known almost to completion. So we often turn there for the best information.
Going forward, there are several things that we want to do to generate good information. One is to do new research on what the change in population or impact is. So for example, here at the Carnegie Museum, we recently got a grant to study chimney swifts which are fast flying nocturnal birds that eat mosquitoes and other small insects at night. So we want to take the feces of Chimney Swifts and evaluate what they’re actually eating. You can do that over agricultural fields or urban areas or forested areas. Presumably, we can see the change in insect fauna in that fashion and predict what the effects would be on these other animals that rely on insects.
“If you were to remove the insects, the ecosystem that we know particularly here in eastern North America, for instance, would collapse in a year.”
Another one is to restore them. In some places in Europe and Britain, they’ve had really good results in restoring habitat or bringing back populations of things that were rare. In doing that, you learn what is causing the trouble and then you can undo it to try to help out.
Here at the Carnegie Museum, we’ve been working jointly with the National Park Service at the Flight 93 Memorial. We’ve been trying to restore what was a strip mine to a healthy pollinator habitat to recover the bees and butterflies and flies and things that would be out in a natural or nature like environment that’s healthy. So instead of the strip mine we can make it back to be something like a forest edge or a prairie and hopefully bring back the insects and then the birds and the mammals and everything that rely on that.
KH: What do we know about why population declines are happening in different regions?
JW: Different regions of course have different causes of decline. I think we casually like to blame insecticides for instance and sometimes that must be true that the insecticides have had a tremendous impact. Certainly, the intensification of agriculture where we are spraying herbicides and insecticides all over the place that will have a very grave impact on nearby natural areas that are downstream or downwind.
I think for the European studies, I think it’s clear that it’s some kind of a chronic effect of human activities: turning things into agriculture or urban environment or building highways or straightening the rivers or all those things that we do. Somehow that changes the environment. All of those changes together often have a much greater effect than any individual little change.
One of the things that’s been observed particularly in Britain is the abandonment of the family farm seems to have an effect. We can probably measure this in eastern North America. Family farms are actually pretty good places sometimes for wildlife, because the edge of the field provides a place for weeds and little places for animals to live. They often have water all year round. So little family farms are not such a bad way to generate a margin for animals and plants to live in. Now, we’ve done away with those and we have gigantic monoculture that’s industrial. That’s a very different landscape. A lot of these changes are probably catching up with us all at once.
KH: What’s the impact of insects on the ecosystem? What role do insects play and how that loss might be felt?
JW: The entire terrestrial ecosystem relies ultimately on plants, fundamentally. Then the next step is insects. Insects either pollinate the plants or control the weeds. Or they simply feed on these leaves and then a bird eats the insect that eats the leaves.
If you were to remove the insects, the ecosystem that we know particularly here in eastern North America for instance, would collapse in a year. The entire thing would be very unlike what we know today because the insects are fundamental. Regulating many of these processes are being the critical link in the food chain between plants and higher animals. So without those insects, essentially, every fundamental process in terrestrial ecosystems would fail. Leaves would fall to the ground and they wouldn’t turn into soil anymore, they just be dead leaves on the ground. Everything that you think of would be disrupted.
KH: Do you think dramatic headlines that we’ve seen recently are harmful or do you think they get people interested?
JW: Well, I don’t think those are alternatives. I think they are a little harmful and they get people interested. When you consider how people view changes in the natural environment, people are always alarmed by that. Any change seems to be dramatic and dangerous. So sometimes I think that the dramatic headlines are undeserved.
But this is something that we’re still just figuring out. And every time we measure it, it seems to look worse than we thought. So I think maybe the dramatic headlines here, maybe they really are called for. But it’s important to state that we haven’t quite figured this out yet.
Also truthfully, if there are many, many causes, then we need to write many articles with scary headlines instead of just one.
