Given limited conservation funds, allocating money effectively and economically towards connectivity projects is critical. However, the finances of corridor design are often not discussed by biologists or the scientific literature. A recent paper by Torrubia et al. in Frontiers in Ecology and the Environment addresses this gap. They develop a “return-on-investment framework for connectivity restoration” that weighs the potential of land parcels to enhance connectivity and their cost. In their paper, Torrubia et al., described this framework and put it into practice using a case study of the Washington ground squirrel (Urocitellus washingtoni), a species of conservation concern in central Washington, USA whose habitat has been degraded and fragmented by human land-uses. They compared one prioritization scenario, where enhancing connectivity is the only objective, to another, where the objective is to maximize connectivity per dollar spent by incorporating land acquisition and restoration costs.
They began with a previously developed map of habitat patches, landscape movement resistance (the degree to which landscape type restricts or facilitates movement), and potential corridors connecting habitat patches using least-cost path. The information to parameterize landscape resistance was based on expert opinion and U. washingtoni occurrence data. They then identified potential barriers to movement using the Barrier Mapper tool in Linkage Mapper software. This software identifies areas of high resistance in the landscape where restoration could create short-cuts to reduce least-cost path distance between patches. The simulated restored landscape least-cost path distance can then be compared to the original least-cost path distance to get an improvement score. Sites were sequentially selected for restoration in a simulation based on their improvement score until 13 sites were restored. The 13 sites totaled 809 ha, which is approximately the annual restoration target area for the region. For the second scenario, they then added another prioritization criterion into the site selection algorithm, the cost of land purchase (based on 2011 tax-assessed parcel value) and restoration (estimated at $1131.74 per ha). As before, they selected 13 sites, but this time selection was based on improvement score per dollar of purchase and restoration cost.
Accounting for land and restoration costs resulted in dramatic savings. For example, for an increase in connectivity by 147 resistance-weighted kilometers, considering land and restoration costs resulted in a >50% ($2.4 million) reduction in cost and a 30% increase in area protected. These results underscore the importance of considering land costs in corridors site selection plans. Because this framework is flexible and can work with other existing connectivity tools (e.g., circuit theory) it could be a powerful tool towards helping corridor project managers get the most connectivity for their buck.
Torrubia S., B. H. McRae, J. J. Lawler, S. A. Hall, M. Halabisky, J. Langdon, and M. Case. 2014. Getting the most connectivity per conservation dollar. Frontiers in Ecology and the Environment 12: 491–497.