Though the Endangered Species Act has very strong prohibitory language, in practice its bark is sometimes much worse than its bite. The U.S. Court of Appeals for the Fifth Circuit's recent decision in The Aranas Project v. Shaw, et al. has preserved the statute's status as a mere "paper tiger" by reversing a district court ruling which had the potential to preserve the dwindling wild whooping crane population.
Under the ESA, you can't "take" any endangered or protected species, including the whooping crane. "Take" is defined in the ESA to include any act which harasses, harms, wounds, kills, significantly modifies the habitat, or significantly disrupts the behavioral patterns of such species. The ESA does allow some leeway, however; "incidental take" permits are available where a "take" is attendant to an otherwise lawful activity (provided the permitee minimizes and mitigates impacts upon the species).
In 2008, the Texas Commission on Environmental Quality (TCEQ) issued a permit for water withdrawal from the San Antonio and Guadalupe Rivers, which lie upstream of the Aransas National Wildlife Refuge. The Refuge is the winter habitat of the last remaining wild flock of whooping cranes in the world.
When water was withdrawn, the resultant reduction in fresh water inflow (combined with seasonal drought) led to reduced freshwater inflow into the estuary and increased salinity in the Refuge's waters. This, in turn, caused a reduction in the blue crab and wolfberry populations. These two species comprise the whooping crane's primary food source. After the winter of 2008-2009, 23 of the flock's approximately 300 whooping cranes were reported dead.
After the whooping cranes' death, The Aransas Project brought suit, alleging that the TCEQ's water management practices constituted an unpermitted "take" of the species. The district court agreed, and on March 11, 2013 required TCEQ to apply for an "incidental take" permit and enjoined it from issuing any additional water permits in the interim.
On appeal, the Fifth Circuit disagreed, finding that the district court had held TCEQ responsible for remote, attenuated, and fortuitous events that followed the issuance of the water permits. The long chain of chain of causation that followed TCEQ's water withdrawal permitting and which eventually lead to the whooping cranes' mortality was too remote and based on too many contingencies to constitute a "taking" under the ESA.
The Fifth Circuit's decision emphasizes that the concepts of foreseeability and proximate cause are not abandoned in ESA cases. Though the ESA broadly defines the conduct which constitutes a "take," the range of results it prohibits is not as wide, and is bound by traditional legal principles. In the Fifth Circuit, only "takes" that are foreseeable, not accidental, and which are proximately caused by a defendant's actions, not reliant on "butterfly effects" or remote events in the ecosystem, will give rise to ESA liability.