Reposted from Cristina Eisenberg's Huffington Post blog with permission. The Endangered Species Act (ESA), created in 1973 to prevent extinction, is one of the most powerful environmental laws on Earth. The U.S. federal government designed it to function like Noah's Ark: you bring aboard species that risk extinction, a process called listing, and then use the best science to save them. the sixth extinction. We're living in a brave new world unimaginable in 1973. Additionally, we now know that preventing extinction isn't just about preserving individual species so they can propagate and survive. It's about preserving these species' ecological roles and relationships with entire ecosystems. The ESA's biodiversity clause mandates that we ". . . provide a means whereby the ecosystems upon which endangered species and threatened species depend may be conserved." This clause opens the door to fully considering keystone species effects when setting recovery goals.