Global Insect Threat-Response Synthesis (GLiTRS): a comprehensive and predictive assessment of the pattern and consequences of insect declines

With increasing recognition of the importance of insects, there are growing concerns that insect biodiversity has declined globally, with serious consequences for ecosystem function. Yet, gaps in knowledge limit progress in understanding the magnitude and direction of change. Information about insect trends is fragmented, and time-series data are restricted and unrepresentative, both taxonomically and spatially. It is therefore difficult to evaluate stories about "insectageddon", to understand the ecosystem consequences, to devise mitigation strategies, or predict future trends. To address the shortfalls, we will bring together other sources of information, including experimental data, meta-analyses, correlative relationships and expert judgement. We will integrate diverse lines of evidence on how insect biodiversity changes in response to anthropogenic threats, and how responses vary according to functional traits, with spatial grain, and across biodiversity metrics (e.g. species abundance, occupancy, richness and biomass); and how insect trends drive further changes. By challenging this "threat-response model" to predict trends for taxa and places where high-quality time series data exist, we will assess the degree to which change in insect biodiversity is predictable or idiosyncratic, and at what scales. This knowledge will allow projections - with uncertainty estimates - of how insect biodiversity has changed globally, across all major taxa and functional groups. This global perspective on recent trends will provide the basis for an exploration of consequences for a range of ecosystem functions and services, as well as how biodiversity and ecosystem properties might be affected by plausible scenarios of future environmental change at various scales. The research will be conducted in four work packages (as well as cross-cutting policy-relevant syntheses): WP1: Data Compilation of a) time-series on insect biodiversity from across the globe, b) insect functional traits, c) spatial layers of drivers of change, and d) trophic interactions. We will explore the relationship between biodiversity metrics, and across spatial scales. WP2: Build a comprehensive threat-response model for insect taxa and functional groups in a flexible database using information from correlational models (e.g. space-for-time substitution), meta-analyses, experimental manipulations and expert judgement. WP3: Validation and hindcasting of the threat-response model, by challenging it to predict trends in the time-series from WP1, thus identifying the potential (and limits) of the model for prediction. This exercise will inform hindcasting to taxa and ecosystems for whom time-series do not exist, and provide a basis for the best available view of insect declines across ecosystems. WP4: Consequences of a) recent changes for ecosystem function & services; b) future changes in environmental pressures, and c) interactions among species for network and community-level properties.