The essential premise of the theory of natural selection is that some species live and some species die. If survival of the fittest is the rule, the unfit don't survive.
But what makes a species "unfit," and who or what should make that decision? It is human nature to alter our environment. If we change the environment faster than other species can adapt to those changes, what is our obligation to protect those other species from our behavior?
In a purely Darwinian world, we wouldn't have any such obligation. We'd survive, the other species wouldn't, we'd be the biological winners. But the reality is more complicated. Humans are part of a complex system of interdependence, where our species needs to interact with a vast spectrum of other species in order to survive. The extinction of the dodo or the passenger pigeon may not have imperiled the long-term survival of homo sapiens, but how do we know? We've only been studying this stuff in any meaningful way for about 200 years.
Every ecosystem is both resilient and fragile, in ways we can't always predict. Even before the oil spill, the Gulf of Mexico was home to five endangered species of whale, three endangered and two threatened turtle species, one threatened and one endangered species of fish, and two threatened species of coral. Nine additional types of fish had been identified as "species of concern." Beyond that, dozens of bird species live around or migrate through the Gulf of Mexico; cruelly, the brown pelican just came off the threatened list last November.
The complete list of endangered marine life is available here, but these are five representative species.
1. Sperm whale (Physeter macrocephalus). The NOAA Fisheries Service lists five whale species as endangered in the Gulf, but some of these are theoretical at best: while blue whales can live in any ocean, only two sightings have ever been reported in the Gulf. Sperm whales, on the other hand, do live in the Gulf of Mexico; as of last fall, government scientists estimated the population at 1,665. Like the brown pelican, they had been in recovery, although the recovery was always fragile. Three human-related deaths a year would be enough to push them back into decline. They are among the deepest-diving mammals, they mostly eat squid, and they give birth once every three to six years (pregnancy takes 14-16 months). A sperm whale can live to be 70 years old.
2. Kemp's Ridley Turtle (Lepidochelys kempii). They are the smallest marine turtles, averaging about 100 pounds and about two feet across. The females nest in colonies called "arribadas;" by far the largest of them is a beach near Rancho Nuevo, Mexico. To escape predators, hatchlings must scramble to the water immediately, and let the currents carry them far out into the Gulf or even to the Atlantic Ocean. They eat crabs, fish, jellyfish and mollusks. The Kemp's Ridley Turtle is an example of a species that has simply collapsed, with the Rancho Nuevo colony declining from more than 42,000 in 1947 to as few as 200 in the early 1990s. The species had been starting to recover, with 7,866 nests counted in Rancho Nuevo in 2006.
3. Leatherback Turtle (Dermochelys coriacea). The largest marine turtle also makes its home in the Gulf of Mexico. Leatherbacks can grow to be almost seven feet long, and can weigh a ton. They live all over the world, and follow migration paths that span the globe. They prefer nesting areas that offer temperatures in the mid-80s, which makes the Gulf attractive; interestingly, higher temperatures produce larger populations of female hatchlings, while colder temperatures produce more males. No one really knows how long they can live — it's the stuff of legend — but scientists estimate that only one in 1,000 lives to adulthood. Unique in their diving abilities and their unusual non-shell carapaces, they are the last surviving relic of a family of reptiles that dates back 100 million years.
4. Smalltooth sawfish (Pristis pectinata). Nature is amazing, and the Creator has a sense of humor. Sawfish belong to the same family as sharks, skates, and rays — they are most closely related to rays, with bodies that look more like sharks. The "saw" is a long, flat snout used to find and kill prey (mostly fish); they breathe through gills on their underside. Like other types of shark, they give birth to live young — that is, they carry their eggs inside until the eggs hatch, at which point the young emerge. They can grow to 25 feet in length, and live as long as 30 years; they reach maturity around the age of 10. Their habitat is shallow coastal waters and estuaries, and in the Gulf of Mexico, they live almost exclusively along the coastline of the Everglades. The mangrove forests protect young sawfish, and the development of these areas is a major factor in the sawfish's endangered status.
5. Elkhorn coral (Acropora palmata) used to be one of the most common species of coral in the Caribbean and the Florida Keys, but disease, bleaching, predation, climate change and human activity had killed as much as 95% of it by 2005. That year the National Marine Fisheries Service recognized it and staghorn coral, a related species, as endangered, and the species have been on the Endangered Species List since 2006. Healthy colonies grow very fast, but organized restoration efforts have had only mixed results. Elkhorn coral provides habitats for dozens of species, including lobsters and parrotfish.