In our continuing series of articles about endangered species, we once again return to the theme of interdependence, ecosystems, and the harmful effects of species loss from human encroachment. Encroachment means going beyond the boundaries of what may be considered another species' habitat or domain. The domain in question can be that of humans as well as of animals (bears wandering into places established by humans for human enjoyment as well as environmental conservation is an example of this sort of dilemma) and it can also encompass cultural practices involving certain species—practices that have persisted for hundreds or even thousands of years but which are no longer viable because the balance that maintained the dynamic between cultural practices and species survival has been thrown off course.
Turtles are essential for the maintenance of healthy ecosystems. In marine environments, they are vital to the health of both coastal and open ocean domains. At each phase of life, they contribute in essential ways to the balance of the ecosystem.
Coral reefs are living organisms on the ocean floor that provide an environment for hundreds of types of fish. Pollution and other man-made problems are endangering the very survival of coral reefs the world over. But coral reefs are in danger from native factors in their environments as well. Sponges growing on a coral reef can multiply out of control and take over an entire reef, covering it and killing it. Hawksbill Turtles graze on sponges as a primary food source, keeping their growth in check. The dwindling population of Hawksbills is thus posing a real threat to the health of coral reefs and making them more vulnerable to the many adversarial factors they must contend with: disease, algae overgrowth, overfishing, climate change, and pollutants.
Green Turtles graze almost perpetually on sea grass, which promotes the growth rate and general health of the sea grass beds. And if you like fish for dinner, you can thank the Leatherback Turtle for the continued presence of commercial fisheries; Leatherbacks' favorite food is the jellyfish, whose favorite food is larval fish (that's fish eggs to you and me and caviar to someone else). The fewer Leatherback Turtles there are to eat up the jellyfish, the fewer larval fish get to reach maturity. Even the cycle of turtle procreation has vital benefits for the environment. The thousands of eggs that are laid inshore, as well as the many hatchlings who are eaten by predators, provide nutrition for other coastal species. For those eggs that don't hatch, as well as the empty shells that are left behind, there are other roles to play in the nutritional maintenance of invertebrates and microorganisms essential to the health of sand dunes and their plant life, which in turn stabilizes dune structure and protects against coastal erosion.
The gender of a turtle is not fixed by genetics but is determined by the temperature of the sand where it developed as an egg—high temperatures produce a preponderance of females, while low temperatures produce more males. It is important to have a balance, as too few of a given gender could mean even fewer turtles than there already are, and the ability of turtles to lay their eggs in the variety of coastal regions that have been their breeding domain for generations is imperative to the continuation of the species, especially as only females ever come ashore and they generally lay their eggs in the same area in which they themselves were hatched.
