Ecological connectivity for a changing climate.

A frequently proposed strategy to reduce the negative effects of climate change on biological diversity is to increase ecological connectivity (Heller & Zavaleta 2009)— the flow of organisms and ecological processes across landscapes (Taylor et al. 1993). Traditionally, conservation professionals have sought to maintain or restore connectivity to ensure gene flow among isolated populations and promote recolonization of vacant patches (Hanski 1998). Given the rapid emergence of connectivity enhancement as a climate-change adaptation strategy, we considered whether connectivity should be emphasized in conservation strategies as global or regional temperatures increase and what principles for connectivity enhancement could be applied to maximize the usefulness of the strategy. The best historical analogue for the ongoing rise in global temperatures occurred 55 million years ago at the Paleocene and Eocene boundary, when the average global temperature rose 5–6 ◦C in 10,000–20,000 years (Wing et al. 2005). At that time, species’ ranges shifted and subtropical cypress swamps, complete with alligators, existed on Ellesmere Island in the Arctic (Estes & Hutchison 1980). A similar rise in temperature has been projected within the next 100–200 years (IPCC 2007), two orders of magnitude faster than previous warming events. Movements of some species, however, are now restricted by human-caused fragmentation and other barriers. The primary rationale for increasing connectivity is that if the effects of land-cover fragmentation can be mitigated, this should enhance the ability of species to move into new regions as climate changes (Fig. 1), thereby decreasing the probability of extirpation or extinction. Here, increasing connectivity refers to management actions that facilitate dispersal of species among natural areas, for example, through the establishment of landscape corridors or stepping-stone reserves or through actions that increase matrix permeability. Because funds