Marine mammals and sea turtles listed under the U.S. Endangered Species Act are recovering.

Abel Valdivia,Kieran Suckling,Shaye Wolf,Graeme Hays

doi:10.1371/journal.pone.0210164

Abstract

The U.S. Endangered Species Act (ESA) is a powerful environmental law protecting imperiled plants and animals, and a growing number of marine species have been protected under this law as extinction risk in the oceans has increased. Marine mammals and sea turtles comprise 38% of the 163 ESA-listed marine “species”, which includes subspecies and distinct population segments, yet analyses of recovery trends after listing are lacking. Here we gathered the best available annual abundance estimates for geographically delimited populations of all 62 marine mammal and sea turtle species listed under the ESA. Of these, we chose representative populations of species that were listed before 2012, occur and reproduce in U.S. waters, and have data of sufficient quality and timespan for trend analyses. Thus, we quantitatively analyzed population trends, magnitude of population change, and recovery status for 23 and 8 representative populations of 14 marine mammal and 5 sea turtle species, respectively. Using generalized linear and non-linear models, we found that 18 marine mammal (78%) and 6 sea turtle (75%) populations significantly increased after listing; 3 marine mammal (13%) and 2 sea turtle (25%) populations showed non-significant changes; while 2 marine mammal (9%), but no sea turtle populations declined after ESA protection. Overall, the 24 populations that increased in abundance were from species listed for 20 years or more (e.g., large whales, manatees, and sea turtles). Conservation measures triggered by ESA listing such as ending exploitation, tailored species management, and fishery regulations, and other national and international measures, appear to have been largely successful in promoting species recovery, leading to the delisting of some species and to increases in most populations. These findings underscore the capacity of marine mammal and sea turtle species to recover from substantial geographical population declines when conservation actions are implemented in a timely and effective manner.

Highlights

IntroductionMarine mammals and sea turtles listed under the Endangered Species Act are recovering habitat loss and degradation [4], pollution [5], and climate change [6,7]
18 out of 23 of marine mammal populations (~78%) and 6 out of 8 sea turtle populations (75%) analyzed that met our selection criteria significantly increased in abundance after Endangered Species Act (ESA) listing (Fig 1A)
Marine mammal and sea turtle populations that significantly increased were from species listed between two to five decades and increasing population trends was positively associated with time since listing (p = 0.036)

Summary

Introduction

Marine mammals and sea turtles listed under the Endangered Species Act are recovering habitat loss and degradation [4], pollution [5], and climate change [6,7]. The Endangered Species Act (ESA) of the United States is a powerful environmental law, expressly designed to prevent extinction and promote recovery of imperiled species [14]. The ESA’s tools include critical habitat designation, recovery planning with concrete and measurable goals, a science-based consultation process for federal agencies to prevent jeopardizing listed species or adversely modifying their critical habitat, and a prohibition on killing or harming listed species Species protected under the ESA generally receive tailored federal and state conservation efforts with increased funding for management [16] and may have better chances for recovery

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