As global temperatures warm, many species are already on the move to track suitable climatic conditions. But habitat loss and fragmentation—coupled with rapid rates of warming—make that a tricky proposition. It’s no surprise that enhancing landscape connectivity is one of the most important climate-adaptations strategies we have for protecting biodiversity under climate change.
However, approaches typically used for connectivity modeling may not sufficiently address the obstacles unique to climate-driven movements—for example, the fact that the availability of suitable habitat is likely to shift. Given these challenges, a range of connectivity modeling approaches that explicitly incorporate climate change has recently emerged. These approaches all have a common objective—to support climate-driven movement—and share some common principles, but their underlying theories and analytical tactics diverge:
- Approaches that use projected future ranges explicitly identify where species are likely to be under future climate conditions, typically using species distribution models (SDMs). By modeling species ranges at different points in the future, one can identify overlapping areas of climatic continuity – or even simulate dispersal across SDMs – to highlight important corridors.
- Other approaches rely on climate analogs—in other words, locations in the future that will harbor the climates of today—or paths climate conditions are likely to take, termed climate trajectories. Routes across the landscape that link climate analogs or trace trajectories may help a range of species move—that is, assuming species will track climatic conditions and can keep pace with rates of change, which may be unrealistic.
- The third class of approaches use existing environmental and climatic gradients for identifying important movement routes—for example, corridors that span elevations to connect areas that are relatively warmer now to areas that are relatively cooler now. To date, many observed climate-driven movements have indeed tended to follow this rule of thumb of shifting along climatic gradients—for example, towards higher latitudes or elevations.
- The fourth class of approaches relies on connecting a diversity of enduring geophysical features—for example, geological formations and landforms that experience slow rates of change—far slower than contemporary climate change. By linking a diversity of abiotic conditions in corridor networks, it’s assumed that a sufficient range of environments will be captured to support biodiversity into the future, even as climate conditions and ecological community change.
Each class of approaches has some strengths and some shortcomings. But still, they are collectively improving our ability to identifying connectivity needs under climate change.
Questions, of course, still remain. How can we better account for the continuous unfolding of climate changes in time and in space—not to mention other processes such as land-use change? Where are climate refugia that may serve as stepping-stones within connectivity networks? How will population dynamics, biotic interactions, and habitat requirements constrain movement? And how much biological realism do we really need for these connectivity models to be useful in conservation planning? Above all, do connectivity enhancements based on these approaches actually work?
These are the frontiers that connectivity modelers and planners are facing. But time is of the essence and we cannot wait to devise the “perfect” approach. Instead, supporting species’ movements by applying the best connectivity tools available is one of the most effective strategies we have for preventing climate-driven extinctions.
Littlefield, C.E., M. Krosby, J. Michalak, and J.J. Lawler. 2019. Connectivity for species on the move: approaches to aid climate-driven range shifts. Frontiers in Ecology and the Environment. DOI:10.1002/fee.204.