A new article about conservation corridors is a must read for researchers who want to make progress in understanding how corridors work, and for land managers who want to understand whether their corridors are accomplishing desired outcomes. Gregory and Beier have published a new paper in Conservation Biology that nicely encapsulates the ultimate functions of corridors and, in doing so, they highlight what has not been learned (and what should be learned) about the effects of corridors on populations.
For starters, this paper nicely formalizes the functions of corridors. In addition to providing clarity to the discussion that follows, it helps to consider merits and priorities for creating conservation corridors in the first place. The functions include conserving seasonal migration; restoring gene flow; promoting demographic rescue; permitting recolonization after local extinction; and providing pathways that permit species to shift ranges in response to climate change.
A second feature of this paper is to lay out research and monitoring strategies to actually measure when corridors achieve these functions. The authors find that some types of measures, like species presence in a corridor, essentially do not work, as they are only related to the conservation goal after other steps are fulfilled. Other measures, such as movement between connected vs. unconnected patches, are more directly linked to corridor functions, but they still lack measures of ultimate responses that precisely link movement to corridor functions. New research should focus more intently on gene flow, patch occupancy, and species richness as the most direct and relevant measures.
A third achievement of this paper is to provide practical guidance on the use of all measures, specifically in relation to the costs of obtaining such data, and the time needed between corridor creation and observed response (lag time). Studies of movement can be moderately costly, but can be achieved almost immediately after corridor creation; still, these studies are only useful when they link directly to a desired function. For studies of higher relevance to conservation goals, those of gene flow are less costly than those of occupancy and species richness. Yet, both types of functions require substantial lag times for responses, and thus take awhile to determine whether corridors have worked.
Understanding the most relevant responses to conservation corridors has proven difficult. This paper helps to point the way toward deeper understanding, advancing beyond studies of movement that have dominated research in the past two decades. Plans to follow the roadmap provided by this paper should be furthersupported by, for example, the reduced costs and advancing methods in measuring gene flow; and by the growing presence of corridors created for large scale conservation on the landscape where corridor functions can be measured.