Complex Measures of Habitat Fragmentation and Edge Can Complicate Biodiversity Conservation

Understanding habitat fragmentation effects on wildlife is critical to promoting effective conservation practices. There are many metrics of habitat fragmentation, from simple (number of habitat patches) to complex metrics designed to summarize many aspects of landscape patterns. To make meaningful inferences, we must understand how complex metrics are related to landscape patterns, especially to habitat amount. Here, we examine the behavior of the Edge Influence index, a metric that has been used in several influential recent studies and is designed to assess fragmentation and edge effects. Contrary to expectation, this index does not primarily quantify fragmentation or edge but rather habitat amount. Therefore, researchers should take this into consideration when interpreting the results of studies based on the Edge Influence index. To guide meaningful conservation action in fragmented landscapes, we recommend using simple, direct measures of fragmentation and separating the effects of habitat configuration from the effects of habitat amount.