Sea turtles are ancient marine reptiles that have navigated the world’s oceans for over 100 million years, playing integral roles in maintaining healthy marine ecosystems, such as balancing coral reefs and seagrass beds and transporting nutrients. All seven species face significant challenges, with many populations classified as endangered or vulnerable by the IUCN Red List. The decline across global sea turtle populations stems directly from various human activities.
Coastal Development and Habitat Destruction
Human development along coastlines directly impacts sea turtle habitats, particularly their nesting beaches. Construction of buildings, resorts, and infrastructure encroaches upon sandy shores where female turtles lay their eggs. This reduces available nesting area, forcing turtles to use less suitable sites or forgo nesting.
Erosion control structures like seawalls and jetties degrade nesting habitats by blocking beach access and altering sand dynamics, leading to increased erosion. Beachfront lighting from coastal properties disorients both nesting females and emerging hatchlings. Hatchlings naturally navigate towards the ocean’s horizon, but artificial lights draw them inland, increasing vulnerability to predators, dehydration, and vehicle traffic.
Human activities in coastal waters also affect critical foraging grounds. Dredging for navigation channels or development can directly destroy seagrass beds and coral reefs, which are food sources and shelters for sea turtles. Increased boat traffic poses a direct threat through collisions, causing severe injuries or fatalities to surfacing turtles. Human activity and noise can also disrupt nesting, causing females to abandon attempts or select less secure locations.
Widespread Ocean Pollution
Various forms of pollution significantly harm sea turtle populations across their life stages. Plastic pollution poses a substantial threat, as turtles often mistake plastic bags for jellyfish. Ingesting plastic can lead to internal injuries, digestive blockages, and starvation.
Beyond ingestion, sea turtles frequently become entangled in discarded plastic debris, including abandoned fishing gear known as ghost fishing gear. Entanglement restricts movement, hinders foraging, prevents surfacing for air, and can result in drowning or severe injuries. Microplastics also infiltrate nesting sands, potentially affecting developing hatchlings.
Chemical pollution, originating from sources like agricultural runoff, industrial waste, and untreated sewage, compromises sea turtle health. These pollutants degrade water quality, leading to diseases, reduced fertility, and damage to food sources. Contaminants accumulate in turtle tissues, impacting immune function and reproductive success.
Oil spills represent an immediate threat to sea turtles. Direct contact with oil causes external contamination, leading to skin/eye irritation, respiratory issues, and hypothermia. Ingesting oil can result in internal organ damage, immune suppression, and long-term health problems.
Fisheries Interactions
Interactions with commercial and artisanal fisheries are a foremost threat to sea turtle populations. Bycatch, the accidental capture of non-target species, is a leading cause of mortality. Turtles become inadvertently caught in various fishing gear types, including trawl nets, longlines, and gillnets.
Trawl nets, often used for shrimp, can ensnare turtles, leading to drowning if they cannot surface for air. Longlines, extending for miles with thousands of baited hooks, can hook turtles. Gillnets, set near coastal areas, can entangle turtles, preventing them from swimming or breathing.
Many bycaught turtles suffer injuries, suffocation, or drowning before release. Even if released, some may succumb to injuries or stress. Some fishing practices, such as bottom trawling, can also damage critical sea turtle foraging habitats like coral reefs and seagrass beds, indirectly affecting food availability.
Ghost fishing, caused by abandoned, lost, or discarded fishing gear, poses a significant danger. These derelict nets and lines drift for years, entangling and killing turtles and other marine life. This highlights the lasting impact of fishing waste.
Climate Change Impacts
Human-induced climate change significantly impacts sea turtle populations. Rising sand temperatures on nesting beaches, a direct consequence of global warming, severely affect temperature-dependent sex determination in sea turtle eggs. Warmer temperatures favor female hatchlings, leading to skewed sex ratios with fewer males.
This feminization threatens breeding success and genetic diversity, potentially leading to a decline in reproductive output. Sea level rise and increased extreme weather events also directly affect nesting habitats. Rising sea levels erode beaches, reducing available nesting area.
More powerful storms can inundate or wash away nests, destroying eggs and hatchlings. These events disrupt nesting cycles and lead to significant reproductive losses. Climate change also impacts sea turtle foraging grounds.
Ocean acidification, caused by increased atmospheric carbon dioxide, can harm coral reefs, food sources for some species. Warming ocean temperatures can also alter prey distribution, potentially forcing turtles to seek new foraging grounds or face reduced food.
Direct Exploitation
Direct, intentional harm continues to threaten sea turtle populations. Poaching and illegal trade are significant pressures. Turtles are illegally harvested for meat and eggs.
Hawksbill turtle shells are highly prized for decorative items and jewelry, contributing to illegal wildlife trade. These products are sold on black markets despite international protections. Trade in turtle parts for traditional medicine also contributes to exploitation.
Historically, widespread harvesting significantly reduced populations before protective measures. While many countries now have laws protecting sea turtles, illegal remnants persist. This ongoing exploitation, though localized, can disproportionately impact vulnerable populations, hindering recovery.