Insights into effects of roads on amphibians from citizen science
Roads may be particularly harmful to amphibians because roads can divide terrestrial and aquatic habitats, cause direct mortality from vehicular collisions, and negatively affect the quality of roadside habitat. We linked 20 undergraduate biology classes across two years to study the effects of roads and habitat composition on frog distributions in the eastern and central U.S. Undergraduate students compiled occupancy data and characterized landscape structure at sampling locations from the North American Amphibian Monitoring Program (NAAMP). NAAMP is a monitoring initiative that uses standard methodology for citizen scientists to collect amphibian occupancy data along randomly-selected driving routes. We used NAAMP data to first identify aspects of road disturbance and habitat composition that had general effects on frog distributions across geographic regions. We then examined how effects of road disturbance and habitat composition varied among regions and at multiple spatial scales.
We found that road disturbance was the most consistent aspect of landscape structure constraining frog species richness across regions. Structural equation models indicated that species richness was limited by both traffic volume and density of roads around sampling locations. The negative relationship between road density and species richness was strongest within 1000 m of sampling locations, and species richness was limited more by the density of primary and secondary roads than rural roads. Negative associations between road density and species richness were stronger in the North than in the Midwest or South. Our project illustrates how networks of undergraduate students can work together to analyze large databases and provide insights into ecology and conservation biology.