What routes will species take to track suitable climatic conditions?
Key Points & Overview
- Including climate projections in connectivity models for species movement substantially shifts the road-map to a smaller, more constrained proportion of the landscape than when connectivity is based solely on human modification.
- Approximating the continuous unfolding of climatic changes in time – instead of representing changes in one fell swoop or averaged over many years – shifts the relative importance of movement pathways.
Many species are already responding to global warming by shifting their ranges to track suitable climatic conditions. We know from paleoecological records that this was an important adaptive response to climatic changes in the past, too. But with today’s rapid rates of warming, habitat fragmentation, and land-use change, are these suitable climatic conditions within reach? To answer this question, we mapped connectivity between climate analogs across a human-modified landscape.
Using current climate datasets and future projections, we mapped movement routes that link where current climate conditions are to where those conditions will be in the future. In other words, we linked climate analogs. We did so using Circuitscape—a model based on electrical circuit theory—with a moving-window algorithm. Our approach accounted for species’ dispersal capabilities as well as the effects of human modification of the landscape on species’ movement. Typically, connectivity models primarily rely on human modification, but in capturing the accessibility of climate analogs, too, we hoped to better represent how species may (or may not) successfully track suitable climatic conditions.
What did we find? Incorporating climate projections substantially shifted and shrunk the roadmap for species movement compared to connectivity maps based solely on landscape permeability (as they traditionally are). Our climate-informed approach highlighted a smaller number of specific locations important for movement whereas connectivity maps without climate projections depicted more movement options. What does this mean? Excluding climate projections from connectivity models may give an overly optimistic view of species’ ability to successfully shift their ranges and may undervalue specific important connections.
Furthermore, representing climate change in one fell swoop—from the past or present to a point in the future—obscured pathways that are important when two successive timesteps are used. Basing conservation decisions on a single, extended timestep will likely miss important movement routes, particularly over shorter time periods and for dispersal-limited species for whom intermediate stepping-stones will be important. Our models don’t represent climate change continuously, but our results suggest a broader need in conservation decision-making to consider climate change as a dynamic process that unfolds continuously.
So what? Conservation decision-making is challenged by considerable uncertainty surrounding the rates, magnitudes, and ecological consequences of climate change. And yet, conservation planners are necessarily prioritizing areas to protect to facilitate movement. Although planners may choose to avoid models that include future climate projections due to their uncertainty, our results suggest that, in doing so, planners may overlook critical locations. That’s because human modification of the landscape and the accessibility of climate analogs severely restricts movement options for species responding to climate change. Routes needed to track changing climatic conditions will likely differ from those that connect present-day landscapes. Prioritizing areas for enhancing connectivity in a climate-informed manner will therefore be critical for protecting biodiversity under a changing climate.