Under the pressures of both rapid human development and climate change, wildlife habitat has diminished and become fragmented, at times compromising the ability of many species to persist. Conservation biologists have pushed for the creation of systems of protected areas but to function these areas must be linked. Currently, many of these protected areas are disconnected, but concerted effort has been made in recent years to create conservation corridors between these isolated protected areas. Preserving and restoring habitat connectivity has been identified as a key conservation priority for government agencies and conservation organizations.
The protection of wildlife corridors can increase dispersal and gene flow providing demographic and genetic rescue, and offsetting random catastrophic events. Many of these wildlife corridors are managed for providing optimal habitat for a single target species. However, often there are several species of concern or interest in these protected areas and ideally the corridors should serve the needs of more than one species. Until now, multi-species optimization was a challenge and this research shows that designing corridors for single species based on purely ecological criteria can lead to extremely expensive linkages that are sub-optimal for multi-species connectivity objectives. Similarly, acquiring lands or easements within budget constraints creates opportunity costs associated with the purchase decisions.
To evaluate conservation strategies that minimize expenditure while achieving connectivity for multiple species, we developed algorithms for finding the multi-species corridors with minimum landscape resistance to movement subject to budget constraints. We then apply our approach in western Montana to demonstrate how the solutions may be used to study trade-offs in connectivity for two species (wolverine and grizzly bears) with different habitat requirements and different core areas.
We show that designing corridors for single species based on purely ecological criteria tends leads to extremely expensive linkages that are sub-optimal for multi-species connectivity objectives. Similarly, acquiring what is inexpensive leads to ecologically poor solutions.
By imposing budget constraints on the ecological optimization process, we achieve linkages with resistance scores close to the unconstrained optimum, spending marginally more than the minimum expenditure to acquire a linkage. Joint optimization for multiple species leads to similar efficiencies.
Our results demonstrate the economies of scale and complementarities conservation planners can achieve by optimizing corridor designs.