A 30-year study on ground beetles from the KBS LTER reveals significant declines in beetle abundance and community composition in agricultural systems. Rates of decline were must faster in fields with chemical inputs, compared to organic systems.
Data that spans multiple decades has the potential not only to reveal long-term trends, but also provide answers to new and exciting questions. This is particularly important in agricultural systems, where the impacts of different management practices can take many years to be seen.
Recent research from by KBS LTER graduate student Cindy Fiser (PhD Candidate with Doug Landis, Michigan State University) provides novel information on how differing management practices impact ground beetles, which act as important predators in the ecosystem and useful indicators of arthropod diversity in many kinds of agricultural settings.
The study sampled beetles across plots in the Main Cropping System Experiment (MCSE) that engaged in conventional farming practices with either reduced fertilizers and pesticides or with no synthetic inputs at all. Crucially, similar data collected at the MCSE in 1994-95 provided a baseline for comparison, and allowed for a decades-long perspective on changes in arthropods.
When Cindy compared her data to this historic dataset, she found beetle abundance declined at least 58-74% across all species. Rates of beetle decline were much faster in agricultural fields that used chemical inputs when compared to organic fields. In addition, the four most dominant beetle species declined 94-98% over the time period. After decades of management, sites without chemical inputs had greater diversity and abundance of beetles compared to sites with reduced inputs, but community structure still shifted from predatory to granivorous species.
This information provides one more piece to the puzzle in determining how differing farming practices affect ecosystem service and health in Michigan landscapes and throughout the Midwest. The continuing collection of data over many years provides a strong foundation for education, collaboration, and innovation in science.