Land cover as an indicator of amphibian species richness in Frederick County, Maryland wetlands
Amphibians are often used as environmental indicators because their populations are often affected when undesirable environmental conditions occur. Many amphibian species require forested corridors for migration to wetlands where breeding occurs in spring and summer months. Other land covers, specifically those influenced by humans, deter amphibians from reaching their wetland destinations. While past studies have explored the effects wetlands have on amphibians, this research focuses on the effect land cover, adjacent to wetlands, has on amphibian species richness, in particular whether certain land covers promote migration to wetland breeding grounds. Amphibian species richness at 14 wetland sites in Frederick County, Maryland was observed for five years. A 200-m buffer of adjacent land cover around wetland sites was manually digitized using ArcMap™ 10.1. Land cover categories consisted of agriculture, impervious, lawn, natural cover, and water. The area of each type of land cover around wetlands was compared to the amphibian species richness found at that site.
Overall, the wetland sites surrounded by increased natural cover promoted greater amphibian species richness. A multiple linear regression conducted between land cover area and amphibian species richness found that natural cover was highly significant in predicting amphibian species at wetlands. Linear regressions indicated that agriculture and lawn were highly significant negative predictors of amphibian species richness while natural cover and water were highly significant positive predictors. Impervious surface showed a negative correlation to amphibian species richness, although not significant. This research supports the idea that various amphibian species require vegetative and aquatic areas as migration corridors to reach wetlands, especially the most sensitive species. Increased agriculture, impervious cover, and lawn prohibit amphibians from successfully reaching wetlands. Deforestation, development, and the depletion of natural habitat lead to fragmentation, thus impeding amphibians from breeding successfully and replenishing their populations. As indicator species, amphibians represent a multitude of organisms that depend on natural corridors and they highlight the necessity of natural cover restoration and protection.