What good is a rattlesnake? What purpose do animals serve? All species play a vital role in their biological communities, and the removal of just one can have a noticeable and catastrophic ripple effect. Yet social and political pressures frequently pit species conservation against economic progress and prosperity, and scientists fear that we may be in the midst of a mass extinction event. Brian R. Chapman and William I. Lutterschmidt make the case that the effort to preserve animals is the responsibility of every Texan and that biodiversity contributes enormous economic value to the citizens of Texas. Texans on the Brink brings together experts on eighty-eight endangered and threatened animal species of Texas and includes brief descriptions of the processes that state and federal agencies employ to list and protect designated species. Species accounts include a description of the species accompanied by a photograph, an easy-to-read account of the biology and ecology of the species, and a description of efforts underway to preserve the species and its required habitat. Sobering examples of species that were once part of the Texas fauna but are now extinct or extirpated are also given to further demonstrate just how vulnerable biodiversity can be. All species require healthy habitats, and every species—even a rattlesnake—provides important services for the biotic communities in which they live. It is imperative to learn as much as we can about these animals if we are to preserve biodiversity successfully in Texas.

The Edwards Aquifer in south-central Texas is the primary source of water for one of the fastest growing cities in the United States, San Antonio, and it also supplies irrigation water to thousands of farmers and livestock operators. It is also the source water for several springs and rivers, including the two largest freshwater springs in Texas that form the San Marcos and Comal Rivers. The unique habitat afforded by these spring-fed rivers has led to the development of species that are found in no other locations on Earth. Due to the potential for variations in spring flow caused by both human and natural causes, these species are continuously at risk and have been recognized as endangered under the federal Endangered Species Act (ESA). In an effort to manage the river systems and the aquifer that controls them, the Edwards Aquifer Authority (EAA) and stakeholders have developed a Habitat Conservation Plan (HCP). The HCP seeks to effectively manage the river-aquifer system to ensure the viability of the ESA-listed species in the face of drought, population growth, and other threats to the aquifer. This report is the third and final product of a three-phase study to provide advice to the EAA on various aspects of the HCP that will ultimately lead to improved management of the Edwards Aquifer. This final report focuses on the biological goals and objectives found in the HCP for each of the listed species.