Biodiversity prioritization: A comparison of data types
The identification of important areas for biodiversity is essential for effective allocation of limited conservation resources. Prioritizing regions for conservation based on biodiversity is typically done using global biodiversity maps created using range map data for one or more taxa. While the use of range maps makes pragmatic sense since large-scale survey data is rarely available, it is important to understand the sensitivity of the results to the use of range map data. We studied how prioritizations may change between data types using the North American Breeding Bird survey (BBS) and BirdLife International range maps as a comparison case study.
Diversity maps were generated using the North American Breeding Bird survey data for both total species richness and the richness of rare species. Rarity was defined as species present at less than the median number of sites. To account for spatial sampling bias in the location of BBS routes, maps were created based on a subsampling of sites within 100 square kilometer grid cells. For comparison, similar maps were generated using range maps for equivalent species.
Analyses of the Breeding Bird Survey data showed that for all species diversity was highest in the eastern and southern United States, the Rocky Mountains of Colorado, and southern California, with lowest diversity in the Midwest and Great Basin Desert regions. When analyzing only rare species the highest diversities were concentrated on the west coast and in the Four Corners states. Sites ranged in diversity from 8 to 81 species, with an average richness of 46 species. These richness values were significantly lower than those obtained from range maps (range from 16 to 120) and the range map data showed a stronger diversity peak in the Rocky Mountains. Detailed comparisons of the geographic differences between survey and range map diversity peaks and the implications of these differences for prioritizing regions for conservation of diversity will be discussed.