Sea turtles have roamed our oceans for over 100 million years, outliving the dinosaurs and witnessing the evolution of life on Earth. Yet today, all seven species are threatened or endangered. In this article, we dive into their deep evolutionary past, vital role in marine ecosystems, and the growing threats they face—and explore what we can do to ensure their survival.
One of my most treasured memories: a sea turtle gliding past me in the blue. Graceful, slow, eternal — 100 million years of evolution in one quiet breath. And yet, it could all end with a single plastic bag.
Sometimes I wonder: will they survive us?
1. Sea Turtles Through Time
Sea turtles separated from their reptilian ancestors around 260 million years ago. Fossil evidence suggests that modern-like sea turtles existed 240 million years ago. The leatherback turtle, the largest species, has existed for 110 million years, while hard-shelled turtles evolved between 30 and 50 million years ago.
To put it in perspective: dinosaurs lived between 235 and 66 million years ago, while modern humans (Homo sapiens) only emerged 200,000–300,000 years ago.
2. How Long Do Sea Turtles Live?
Sea turtles can live up to 100 years in the wild. However, reaching that age is a rare feat due to numerous natural and human-induced threats throughout their lives.
3. Why Sea Turtles Are Vital to Ocean Health
Sea turtles play a critical role in maintaining marine ecosystems:
- Green turtles graze on seagrass, keeping it healthy and promoting biodiversity.
- Leatherback turtles control jellyfish populations.
- Hawksbills feed on sponges in coral reefs, preventing them from overgrowing and smothering corals.
- Their eggs provide nutrients to beach ecosystems, enriching coastal plant life.
- Through long migrations, they transport nutrients like nitrogen and phosphorus from ocean waters to beaches.
4. Reproduction and Nesting
After 20–30 years, female sea turtles return to their birthplace to nest, crossing entire oceans guided by Earth’s magnetic field. Each lays 100–200 eggs in a carefully dug 70 cm-deep nest. Factors like moisture, sand composition, and temperature are critical. Temperature even determines the hatchlings' sex: higher temperatures result in more females, lower in more males.
Only 1 in 1,000 hatchlings survives to adulthood.
5. Threats to Sea Turtles
5.1 Natural Predators
Once hatched, baby turtles face a gauntlet of predators: birds, crabs, fish, and lizards. As adults, their only natural threats are sharks, orcas, and humans.
5.2 Wild Harvesting and Poaching
Turtles are hunted for their meat, eggs, and shells. Hawksbills are critically endangered due to the demand for tortoiseshell products like jewelry and combs.
5.3 Coastal Development and Tourism
Urbanization and tourism destroy nesting beaches:
- Beach furniture blocks paths
- Umbrellas damage nests
- Noise and activity cause stress
- Vehicle tracks and vibrations hinder hatchlings
5.4 Light Pollution
Hatchlings instinctively move toward the brightest horizon—usually the ocean. Artificial lights from resorts, homes, and roads disorient them, leading many to their deaths.
5.5 Fishing Industry & Boats
Thousands of turtles die annually as bycatch in fishing nets. They drown when unable to surface for air. Boat strikes and propeller injuries are also fatal.
5.6 Pollution & Plastic Waste
Turtles mistake plastic bags for jellyfish. Many die from ingesting plastic or getting entangled in discarded fishing gear. Microplastics and pollutants weaken their immune systems.
5.7 Climate Change
Rising temperatures affect hatchling sex ratios (too many females), destroy nesting beaches, and eliminate feeding grounds like coral reefs and seagrass beds.
