The scientific foundations of habitat conservation plans: a quantitative assessment

The number of habitat conservation plans (HCP) has risen dramatically since the first plan was written over 18 years ago. Until recently, no studies h ave quantitatively investigated the scientific foundations underlying these documents. As part of a larger study of HCPs, we examined 43 plans primari ly to assess the availability and use of scientific data and secondarily to determine the extent of involvement by, and influence of, independent scie ntists within the process. Specifically, our analysis focused on five key s teps taken when an HCP is developed: assessing status of a species, determi ning take, predicting the project effects, mitigating for those effects, an d monitoring of take and mitigation. In general, we found that the preparer s of HCPs utilized existing scientific information fairly well, with 60% of plans not missing any available information described by our study as "sta rkly necessary." The most common types of underutilized available data incl uded those describing the influence of stochastic processes and habitat qua lity or quantity on species persistence. For many species, however, data on biology or status simply did not exist, as demonstrated by the fact that w e could locate quantitative population estimates for only 10% of the specie s. Furthermore, for 42% of the species examined we had insufficient data an d analysis to determine clearly how predicted take might effect the populat ion. In many cases, mitigation measures proposed to offset take frequently addressed the most important local threats to the species with moderately r eliable strategies. Species with monitoring programs rated as sufficient ha d plans that proposed to collect a greater amount of "quantitative" data th an did those programs rated insufficient. Finally, when species "experts" w ere consulted, plan quality was generally higher. Overall, available scient ific information in a majority of categories was fairly well utilized, but for many species additional studies and more indepth analysis were required to provide adequate support for issuance of an incidental take permit.