It’s one thing to agree that connecting landscapes is one of the best ways to protect biodiversity. It’s another thing to go out and actually build a corridor in the landscape that is successful. Where should it go? How big should it be? What habitat should be included in it? While there’s no one answer for how to design the optimal corridor, new research can provide insights into how to make decisions and determine which configurations are most effective.
Some corridors function as short-term passages for species that are dispersing in a single generation, rather than long-term dwellings for multiple generations to inhabit. Movement corridors designed for passage species can vary greatly in complexity, both in spatial design and composition. A new study uses an individual-based model to simulate different corridor-matrix scenarios and evaluate which designs are most effective in promoting dispersal through movement corridors.
Simulations show that corridors with poor quality ground cover improve dispersal, since individuals perceived the corridor as poor habitat and were more likely to move through it quickly. A contrasting buffer (or even multiple buffers) around the corridor could prevent dispersing individuals from completely abandoning it and encourage direct movements. With this “onion-like” design, connectivity increases when the buffer is a mosaic of habitats, but decreases when the corridor itself is a mosaic of habitats. In agricultural landscapes, for example, this design could benefit connectivity by incorporating the surrounding farmland as a buffer.
In addition to buffers and habitat heterogeneity, corridor width can be a major consideration. A common method of designing corridors with geographic information systems is to use least-cost path analysis, which calculates the most effective patch through interconnected cells on a cost surface such as habitat type. However, this method often ignores the fact that corridors are rarely narrow paths, and are computationally wider than a single cell.
A new mathematical analysis compares the traditional path-based model with an updated wide-path-based model that considers the corridor as a wider swath of cells. Results show that the wider-path-based model is an improvement in design without being more difficult to implement or compute. Wide-path-based effective distances are also significantly greater than, but highly related to, path-based effective distances. Corridor design can be improved by using this newly validated least-cost wide-path algorithm, although it would be most effective when used in combination with multiple design methods.
Looking for more resources on corridor design? Check out our Toolbox, which features 20 of the most widely used connectivity programs and websites for designing and implementing corridors. Or search our Library, which contains almost 400 publications from 30 years of research on connectivity and corridors.
Delattre, T., J. Baudry, and F. Burel. 2018. An onion-like movement corridor? Possible guidelines emerging from small-scale movement rules. Ecological Informatics 45:48-58.
Shirabe, T. 2018. Buffered or bundled, least-cost paths are not least-cost corridors: computational experiments on path-based and wide-path-based models for conservation corridor design and effective distance estimation. Ecological Informatics 44:109-116.