RESUMEN
Water policymakers internationally face the challenge of adapting to climate, supporting environmental resource needs, and meeting irrigation demands for food security in the world's arid and semi-arid regions. Much recent work has assessed the economic performance of environmental river flows to support endangered species habitat protection. However, little published work to date has systematically formulated and applied methods to identify the economic performance of various policy measures that adapt to climate, support endangered species, and meet irrigation demands for water. This work's original contribution with international relevance is to address those gaps by identifying the economic performance of various water shortage sharing methods for handling climate water stress while supporting protection of critical habitat to protect the endangered Southwestern willow flycatcher (Empidonax traillii extimus) along with Willow tree (Salix bonplandiana) habitat in the middle part of the Rio Grande Basin in North America, a region facing a number of conflicts between commercial uses of water and protection of key ecological assets. It develops a hydroeconomic optimization model containing information on crop water use and endangered species requirements in that region to identify the economic performance of three climate adaptation policy scenarios for handling water shortages while respecting endangered species habitat protection requirements. Results show how water shortages as well as policy responses for handing those shortages affect the economic value of water in agriculture for food security both with and without critical habitat to support the endangered flycatcher. This work's international relevance comes from its capacity to inform policy debates on the costs of protecting endangered species habitat under various climate scenarios and climate policy adaptation measures. Findings provide a general framework to address existing gaps in understanding and measuring the economic performance of measures to promote environmental resilience.