Quantifying multiple threats to endangered species: an example from loggerhead sea turtles

© The Ecological Society of America www.frontiersinecology.org T US Endangered Species Act requires that a recovery plan be developed for each species listed as threatened or endangered with extinction, with the aim of helping the species to recover so it can eventually be removed from Federal listing (ie delisting). Tremendous effort and considerable funds have been invested in the development of species recovery plans. However, the effectiveness of these plans has “come under increased scrutiny in both political and academic arenas as species are continually added to the endangered species list but few are removed” (Hoekstra et al. 2002). As a result, a comprehensive assessment of 181 recovery plans for threatened and endangered species was undertaken (Kareiva 2002). One of the major conclusions of that assessment was that quantification and prioritization of threats have received insufficient attention (Clark et al. 2002). Furthermore, the lack of knowledge regarding the relative importance of threats that each species faces leads to long “shopping lists” of management-related interventions that ultimately contribute to the failure of recovery plans (Lawler et al. 2002). On the basis of these conclusions, and with US Federal agency guidance (NMFS 2007), we undertook the development and implementation of a detailed analysis of threats in one particular plan: the Recovery Plan for the Northwest Atlantic Population of the Loggerhead Sea Turtle (Caretta caretta) (NMFS and USFWS 2008). Loggerhead sea turtles have complex life histories (Figure 1), are highly migratory, and can be found in temperate and tropical regions of the Atlantic, Pacific, and Indian oceans (Bolten and Witherington 2003). Most loggerhead nesting occurs on beaches located along the western rims of the Atlantic and Indian ocean basins, with nesting aggregations in Florida and Oman accounting for the majority of nesting worldwide (Baldwin et al. 2003; Ehrhart et al. 2003). However, observed nesting activity in Florida has declined by 43% over the past decade (Witherington et al. 2009), highlighting the need for identifying and quantifying the threats to loggerhead sea turtles so that conservation actions can be prioritized relative to their impact on population growth rate ( ). A quantified threats analysis supports objective development of management priorities. Here, we describe the process we used to identify, categorize, and quantify threats to the Northwest Atlantic CONCEPTS AND QUESTIONS