Sea Turtles in the Anthropocene

ABSTRACT: Sea turtle species have life cycles that have common features such as oviparity, nesting on sandy beaches, growing as juveniles in surface waters and moving to foraging grounds before migrating— often over long distances—to natal beaches to breed. They are therefore exposed to aquatic and terrestrial influences, both abiotic (e.g. temperature, weather) and biotic (e.g. food availability, predation). Humans have exploited sea turtles for millennia and pressure on their populations has increased dramatically during the ongoing Anthropocene as human influences have increased both in power and global reach. Fishing bycatches generated by powerful unselective gears have largely replaced direct fishing as an existential threat, but meat and egg poaching persist, while burgeoning global wildlife crime threatens sea turtles, especially hawksbills. Habitat loss caused by coastal development and exponential increases in beach-based tourism have reduced nesting success. Sustained losses of coral reef and seagrass habitats have removed foraging grounds for adult turtles and both habitat types are currently projected to disappear before 2100. Environmental degradation has taken several forms. Chemical pollution through the accumulation of organics and heavy metals have affected reproduction and facilitated the transmission of fibropapillomatosis. An emerging threat due to eutrophication also needs to be considered. Marine plastic pollution is already highly damaging to sea turtles; plastic fishing gears ‘ghost-fish’ indefinitely, capturing and killing all life-history stages except eggs, while ingestion of macro and microplastics blocks/damages guts. Rising global temperature has been identified as a potential existential threat for all species because of temperature-dependent sex determination and substantial sea level rise. However, climate change is also projected to cause an order of magnitude increase in the frequency of heat waves and extreme sea level highs, both of which can kill turtle embryos. This Praeger Review concludes with a description of sea turtle occurrences around the British Isles and the anthropogenic influences upon them.