A decade of research finds corridors effectively increase species movement, fitness, and richness

Corridors are strips of habitat connecting previously fragmented habitats, and are a popular strategy to restore migration and gene flow.

When habitats are fragmented due to human activity, such as building roads that bisect natural areas, wildlife populations become fragmented as well. Fragmented populations experience reduced gene flow and are at greater risk for local extinction, leading to loss of biodiversity. 

Corridors are strips of habitat connecting previously fragmented habitats, and are a popular strategy to restore migration and gene flow. While corridors are intuitively appealing, and extensive research has been done to test their efficacy, there is still doubt as to whether corridors function as intended. For example, just because an overpass is built across a road to help wildlife avoid vehicles, does not mean they will choose to use it. 

Meta-analyses on corridor efficacy combine data from across these wide variety of studies, looking for an overall effect of corridors. A previous corridor meta-analysis, by Gilbert-Norton and colleagues in 2010, found that corridors do in fact increase movement between habitat patches and restore gene flow, but lacked sufficient data to look at population-level effects. A call was put out for more studies that not only study movement between patches, but also the effects of corridors at the population and community level.

Shows results from the 2019 meta-analysis by Resasco. Effect size (d) summaries for studies assessing corridor effectiveness. Values of d > 0 indicate positive effects of corridor treatments on ecological response variables compared to unconnected control treatments. The dashed vertical lines demarcate d = 0. The top panel (A) is a histogram representing the 56 d values from this meta- analysis. The bottom panel (B) shows estimates of d from meta-analysis models for different levels of organization as well as for all levels of organization combined (“overall”) in filled gray dots. Error bars represent ± SE values from meta-analysis models.

Almost ten years later, to follow up on this work, a new study reviewed the current literature in corridor research. This new meta-analysis compared data from fragmented habitats connected by corridors, to those with no corridors. Not only did they study restoration of gene-flow, but because corridor research had become more popular, were also able to test whether these effects translated to increased stability for populations and overall biodiversity. 

The study found that, though not all corridors worked as planned, overall corridors effectively increase species movement, fitness, and richness. This further translated into an increase in community biodiversity. Similar to the previous meta-analysis, not all taxa responded in the same way, and corridor effects depended on details of their construction, like size or whether they were man-made or created by preserving existing habitat. Corridor effects were also variable over time, and this review called out the need for corridor research over longer time periods.

Resources 

Resasco, J. 2019. Meta-analysis on a decade of testing corridor efficacy: What new have we learned? Current Landscape Ecology Reports. DOI: 10.1007/s40823-019-00041-9.

Gilbert-Norton L, Wilson R, Stevens JR, Beard KH. 2010. A meta-analytic review of corridor effectiveness. Conservation Biology 24(3): 660–8.

2019-09-19T12:24:07-04:00 August 12th, 2019|

About the Author:

Elizabeth Schultheis
I am a postdoctoral researcher at Michigan State University. My work includes research in plant biology and science education, professional development for scientists on science communication, and teacher professional development on data in the classroom. I am a co-founder of Data Nuggets, an innovative approach to bring cutting edge research and authentic data into K-16 classrooms.