There are a lot of great examples of corridors and connectivity projects – Y2Y in North America, crab crossings in Australia, the Jaguar Corridor Initiative in Central and South America. Most of these, however, are targeted toward larger, more mobile species. With invertebrates accounting for over 95% of all known animal species, there are plenty of smaller species in need of connected spaces. How can we better design corridors to support this type of biodiversity? Three recent studies give insight on corridor planning for the small but abundant part of the world.
In the first, researchers compared the behavior of over 700 butterflies from five different species as the butterflies moved through corridors versus arable land in southern Germany. They found that habitat quality was a key characteristic that influenced movements such as flying, perching, and visiting flowers. Butterflies spent more time in flight when in the matrix compared to in high quality corridors, and they preferred corridors over the matrix even when the corridor was of lower quality. Corridors can be beneficial for butterflies, particularly specialists, when they are created and maintained with high quality habitat that provides a refuge from the surrounding matrix.
A second study looked at how varying the length of narrow riparian tree corridors affects benthic macroinvertebrate communities in northern California. When land use changes necessitate restoration work to repair degraded streams, adding in riparian corridors can mitigate the loss of surrounding habitat. The study found that sites with longer riparian corridors had higher percentages of invertebrates sensitive to disturbance and streams with lower water temperatures and less fine sediment. In areas where it’s impractical to create wide riparian corridors, increasing the length of narrow riparian corridors can still improve streams and benefit the aquatic communities they support.
A third study goes one step smaller to look at corridors for soil fauna in the tropics of northeast Brazil. Soil fauna provide ecosystem services such as nutrient cycling, pollination and decomposition, and corridors have the potential to promote these functions when the landscape is fragmented by agriculture. In collecting over 85,000 individuals, researchers found that corridors show marked difference according to season and soil fauna taxa.
While corridors were not equally effective across all taxa, they did increase the abundance of some taxonomic groups in cultivated areas. During the rainy season, the most abundant taxa included Acari, Chilopoda, Oligochaeta, Orthoptera and Psocoptera, while during the dry season, the most abundant taxa included Dermaptera, Diplura, Diptera, Collembola, Formicidae larva, Lepidoptera and Lepidoptera larva. Including corridors that specifically promote healthy soils in agricultural regions of the tropics has the benefit of supporting even the smallest of species, who in turn can provide stability and balance to the larger ecosystem.
Habel, J.C., Ulrich, W. and Schmitt, T. 2020. Butterflies in corridors: quality matters for specialists. Insect Conservation and Diversity 13(1): 91-98.
Stanford, B., Holl, K.D., Herbst, D.B. and Zavaleta, E. 2020. In‐stream habitat and macroinvertebrate responses to riparian corridor length in rangeland streams. Restoration Ecology 28(1): 173-184.
Portela, M.B., Rodrigues, E.I., de Sousa Rodrigues Filho, C.A.D.S.R., Rezende, C.F. and de Oliveira, T.S. 2020. Do ecological corridors increase the abundance of soil fauna? Ecoscience 27(1): 45-57.