A largely inconspicuous portion of the food web called ground beetles plays a role in the success of North American crops, from corn to Christmas trees. The number of ground beetle species in North America is close to 2,000.
As the environment changes, some of these insects may thrive while others may suffer, according to recent research performed by Penn State. The research team discovered that the reaction will mostly depend on the characteristics and habitats of the species and may have substantial effects on conservation efforts.
“We know that climate change influences everything from coral reefs in the ocean to trees on land, but there’s less information available on how it affects insects,” said Tong Qiu, assistant professor of multifunctional landscapes at Penn State. “Ground beetles are everywhere in your backyard, in your garden. They eat the pests and weed seeds that damage crops and are important food sources for birds. They are small insects, but they have large ecosystem impacts.”
The idea for the project came after Qiu and his colleagues read two studies with diverging findings. By combining the results of previous research, both studies examined the changes in insect populations, with one showing a reduction in terrestrial insect numbers over the past century and the other showing no change.
Qiu and his collaborators wondered what the picture would look like if they examined species as a group, or “community,” but allowing for their differing traits, using raw data that were collected across the continent.
The researchers studied 136 ground beetle species found in diverse habitats across North America, Puerto Rico and Hawaii. They retrieved ground beetle count data from the National Science Foundation’s National Ecological Observatory Network (NEON) and 11 previously published studies to measure the beetles’ distribution across the continent.
To generalize the species’ responses to climate change, the researchers divided the species into groups based on characteristics including body size, preferred habitat, and whether they fly, burrow, climb, or sprint.
Ground beetles are very beneficial to ecosystems, but they’re largely invisible to the average person. In this paper we’re showing the broad impacts they have on whole communities in forested and agricultural ecosystems.Professor Tong Qiu
The scientists collected habitat information such as gaps in forest canopy and the density of plants and logs on the forest floor from NEON’s Airborne Observation Platform (AOP). AOP conducts low-altitude flights with imaging instruments that measure a wide spectrum of light to create detailed 3D images of landscapes.
To investigate how ground beetles react to a changing climate, researchers incorporated information about the species and their habitat into a sophisticated statistical model and ran scenarios with varying levels of greenhouse gas emissions.
According to their findings, less mobile, non-flying beetle species may eventually become extinct, but habitat preservation might sometimes counteract the effects of climate change and reverse the trend. They reported their findings today (March 23) in the journal Global Ecology and Biogeography.
“We found that nonflying carnivores, which are critical pest control agents, are more likely to decline over time in a warmer, dryer climate,” said Qiu, who is also an associate of Penn State’s Institute for Computational and Data Sciences. “If you have fewer carnivores, you’ll have more of the pests that can impact agriculture.”
According to the researchers, habitat characteristics can actually counteract the tendency and have a significant impact on beetle population change. Many ground beetles, which need open ground to hunt their prey, benefit from gaps in the forest canopy.
Other habitats, such as those with dense understory plants and fallen tree logs, offer important microclimate conditions that help to mitigate the effects of climate change, said Qiu.
“We hope conservation biologists will use the information in this paper and the online map that we created to better manage habitats for insects in general,” he said. “Ground beetles are very beneficial to ecosystems, but they’re largely invisible to the average person. In this paper we’re showing the broad impacts they have on whole communities in forested and agricultural ecosystems.”
Aaron Bell, University of Saskatchewan; Jennifer Swenson, Duke University; and James Clark, Duke University and Université Grenoble Alpes, contributed to this work.
The National Science Foundation, Belmont Forum, NASA, and the Programme d’Investissement d’Avenir under project FORBIC supported the study.