The Temporal Ecological Disruption Index: Assessing climate change impacts on ecosystem functioning

Climate change is causing species range shifts and changing species compositions, altering the trophodynamics of ecosystems. Yet, while approaches such as species distribution models can be used to project assemblage change, there is limited knowledge of the consequences for ecosystem functioning. We developed the ‘Temporal Ecological Disruption Index’ as a framework for assessing potential shifts in ecosystem functioning that are quantified over time and can be compared between ecosystems or climate scenarios. The aim is to provide a simple and easy-to-interpret index that builds on existing efforts on quantifying functional diversity and has useful properties such as comparability and interpretability. We demonstrate this index by projecting changes in species assemblages for the present-day and end-century under two climate scenarios in two protected seascape sites in eastern Canada, illustrating how species composition shifts can be translated into potential ecological disruption, and are affected by different carbon emission trajectories. The approach provides a foundation for exploring the functional consequences of species range shifts due to climate change and identifying areas at greater risk. It can be used to link projected shifts from species distribution models to potential ecological disruption, thus helping to inform efforts to build ecological resilience in a warming world.