Wanting to get the most bang for your buck isn’t an uncommon goal. When putting conservation plans into practice, there’s often a hope that conservation goals will benefit more than just the target species. For example, placing grassland buffers around row-crop fields may have the direct goal of benefiting grassland birds such as northern bobwhite. With buffers in place, though, can forest birds that inhabit adjacent forest corridors and patches also benefit from the softened edges that grassland buffers around row-crop fields provide?
A recent study by Riffell et al. in the Journal of Applied Ecology looks at these potential indirect effects of grassland buffers to non-target species. Buffers along forest edges and corridors may influence the movement of birds, increase potential resources, or affect predator-prey interactions, and any of these mechanisms could increase the abundance and richness of certain bird guilds along forest edges. The study collected bird counts conducted inside the buffers and looked at biodiversity within different bird guilds (forest interior species, forest generalist species, and edge species) when buffers were adjacent to forest corridors or forest blocks.
The results show that indirect benefits to the non-target species (i.e. forest birds) were real, although neither pervasive nor strong. Edge species responded positively to buffers near both blocks and corridors, whereas forest interior birds only responded positively when buffers were adjacent to corridors; there was not much of a response when buffers were near forest blocks. There was no response among forest generalist birds. While the benefits for grassland birds were previously shown as substantial and ubiquitous, the benefits for non-target species were measurable, but small and more highly variable.
What does this mean for management? If your objectives are to benefit guilds like northern bobwhite and certain grassland birds by placing buffers around row-crop fields, there is an added benefit when buffers are also placed adjacent to forest edges for edge and forest interior birds (along corridors). However, the added benefits are likely small and may not justify placing buffers solely for the benefit of edge and forest interior birds, especially if there are negative impacts of placing buffers near forest edges for grassland birds (e.g., greater nest failure due to brood parasitism and predation). Managers should be aware of how conservation practices may impact non-targeted species, and balance the positive and negative effects when implementing adjacent conservation practices.
Riffell, S. K., A. P. Monroe, J. A. Martin, K. O. Evans, L. W. Burger Jr., M. D. Smith. 2015. Response of non-grassland avian guilds to adjacent herbaceous field buffers: testing the configuration of targeted conservation practices in agricultural landscapes. Journal of Applied Ecology 52(2): 300-309.