Evidence and Uncertainty in the Future Pathways of Insects Under Global Change

Christie A Bahlai , Kayla I. Perry, Erica Fleishman, Robert Guralnick, Joseph Millard , Timothy C Bonebrake, Tim Newbold, Kyle Haynes, Paul Manning, Matthew Bulbert, Christopher Halsch, Chris Elphick, David Wagner, Jessica Lee Ware, Eliza M. Grames

Insects are essential for life on Earth, yet anthropogenic environmental changes have led to declines in insect biomass, abundance, and species richness. Projecting future insect trajectories can inform conservation and policy but is complicated by variation in life histories and traits, nonlinear population dynamics, extreme population fluctuations, and interacting natural and anthropogenic drivers. Limited long-term, spatially representative data further constrain the accuracy of projections, while human-driven factors such as land-use change and policy shifts add layers of uncertainty. Understanding these uncertainties is essential for interpreting current evidence, prioritizing research, and developing robust policies that remain effective under a range of plausible future scenarios. This synthesis integrates evidence on insect responses to global change, bounding outcomes under plausible best- and worst-case scenarios of greenhouse gas emissions, environmental change, and social and economic pathways over 10- and 50-year horizons. Across case studies of functionally diverse taxa with conservation, economic, and public-health relevance, uncertainty is a central feature, reflecting variation in species traits, environmental drivers, and social systems. We identify five pathways—agricultural deintensification, increasing food-system efficiency, urban greening, mitigation of light pollution, and landscape restoration—that can alter future trajectories of insect populations while providing benefits for humans. Combined with rapid climate mitigation and habitat protection, these interventions offer the greatest potential to stabilize and restore insect populations and their ecological functions. Recognizing insects as central to biodiversity planning and explicitly addressing uncertainty are critical for effective conservation, policy design, and long-term sustainability.