By Sonal Butala
Although they can easily be considered commonplace among the billions of animal species and pale in comparison to the mighty tiger or majestic elephant, turtles are in fact a remarkable species. Surviving the extinction of dinosaurs over 2.6 million years ago and thriving in what is now the Anthropocene, an age of great human acceleration, turtles have endured all that nature has thrown at them. Yet, scientists Jeffrey E. Lovich, Joshua R. Ennen, et al. recently discovered that approximately 61% of the world’s 365 turtle species have become extinct or are in danger of becoming extinct.
Turtles are an integral part of the ecological system, and their loss could lead to the collapse of many ecosystems. Ecologically, turtles have left their footprint on the environments they inhabit through their high biomass, which reflects the energy stored within the flora and fauna of an ecosystem. As they continue to disappear, their biomass dwindles, damaging the entire ecosystem. Because turtles contribute such a significant portion of biomass to an ecosystem, they are strongly linked to ecosystem health and function through resource subsidies, mineral cycling, and top-down food web effects. Evidence of turtle-related ecosystem collapse has been reported in many island regions. For instance, the extinction of the Aldabra tortoises in the Mascarene Islands has severely damaged the ecosystem, putting at risk countless species of animals and aquatic life.
Due to turtle nest predation rates, turtle eggs enable the redistribution of energy and nutrients in both aquatic and terrestrial habitats, creating resources for other species. However, many situations are often unrelated to predation. For example, American beach grass, which stabilizes dune nesting habitats for turtles, is capable of absorbing nutrients directly from the eggs of diamond-backed terrapin nests. This transfer of energy depends on the presence of turtle eggs; their declining numbers are thus responsible for the devlie of American beach grass and consequently much of the entire ecosystem.
Furthermore, turtles play a crucial role in mineral cycling, which transfers elements such as calcium between organisms and their surrounding environment. Given their long lifespan, their high percentage of slowly developing bone creates is an imperative link in the calcium cycles of ecosystems. Notably, Agassiz’s desert tortoises have been observed to “mine” and eat calcium carbonate deposits, distributing calcium equally throughout the ecosystem. Without their presence, the flow of minerals is abruptly disrupted.
Uniquely, turtles occupy trophic positions as herbivores, carnivores, and omnivores. Many are the top predators of their communities. As consumers, turtles can have substantial top-down food effects, and their removal can alter the biomass of the environment, reducing community function and allowing invasive species to ravage the ecosystem, which harms all the organisms living there.
Ultimately, it’s become clear that turtles are dying and that they will continue to do so unless a conservation effort is made. They are vital to ecosystems across the globe, and their disappearance is only worsening the state of the entire planet. At the rate at which they are going extinct, one question does come to the forefront: How long before they all go extinct?
Reference: Jeffrey E Lovich, Joshua R Ennen, Mickey Agha, J Whitfield Gibbons; Where Have All the Turtles Gone, and Why Does It Matter?, BioScience, , biy095, https://doi.org/10.1093/biosci/biy095