The strongest influence of climate change in reducing biodiversity will likely come through the interaction between climate change and habitat fragmentation. As climate warms, species are naturally expected to shift their ranges to cooler places. When landscapes were vast and uninterrupted by cities and farms, these shifts in response to climate were easier. Given the level of landscape fragmentation, how can species adapt their ranges to new climates? Climate corridors have become the most popular strategy for landscape conservation in the face of climate change (see Heller and Zavaleta 2009). Paul Beier makes a convincing case that, in many landscapes, focus on complexity in geography or perhaps plant communities, so called coarse-filter approaches, through relatively short corridors (<30km in length) will provide the additional places needed for species to move and keep up with climate change.
A key part of Beier’s argument is that, in many landscapes, climate variability already exists in large conservation blocks, or could be conserved in corridors, to provide the future climates that most species need. Riparian drainages and mountains that vary in topographic complexity and aspect should provide cooler spaces that species need. Further, when these factors are taken into account, the dominant direction of range shifts may not be uniformly upslope or poleward, as assumed in most discussions about corridors and climate change.
Coarse filter approaches like those that Beier recommends overcome the uncertainty that plagues more complex, fine-filter approaches that take into account the ranges and dispersal of individual species. Such approaches depend on understanding the rate of future climate change and the impacts on species dispersal and distribution. Current understanding of these factors is uncertain, to the point where Beier thinks our ability to predict responses of individual species is impractical. Further, there are many reasons to design corridors, with climate being just one – by orienting corridors with respect to predominant temperature gradients, we may reduce corridor effectiveness in relation to other gradients in land use, moisture, or wind. Although I am more optimistic that modeling approaches can be useful, the burden is clearly on modelers to reduce uncertainty in their projections, and until they can, I agree with Beier that coarse filter approaches will be more practical.
Beier’s argument is clear and compelling, especially in mountainous landscapes where there are large protected blocks. His recommended approaches are less clearly applied in flat landscapes with little topographic complexity. Flat places are often urban or farmed, and so are also the places that have fewer small protected blocks that are more widely separated.
This article provides the clearest articulation I have read of the logic supporting climate corridors, alternative approaches to their design, and nuances of how they should work as climate changes.
Beier, P. 2012. Conceptualizing and designing corridors for climate change. Ecological Restoration 30:312-319.
Heller, N. E. and E. S. Zavaleta. 2009. Biodiversity management in the face of climate change: a review of 22 years of recommendations. Biological conservation 142:14-32.
This article is part of a series in the December 2012 Special Issue of Ecological Restoration on The Design of Ecological Corridors. We have posted other Digests from this Special Issue including: