Towards the light


Key Points:

  • Artificial lighting in urban areas disorients sea turtle hatchlings, resulting in high mortality.
  • Over time, this has led to fewer sea turtle nests in urban areas, however nesting populations can still be found in several major cities.
  • While ‘turtle-friendly lighting’ is already being marketed by several manufacturers, it’s currently unclear whether these are effective.

Mother sea turtles are stalwart about where they lay their eggs – only their only place of birth will do, even if that place has since grown into a bustling metropolis. Once they lay their eggs, they have no further contact with their offspring.

(c) H. Kiera

After two months of incubating in their sandy nest, baby turtles hatch from their eggs, dig to the surface, and must quickly find their way to the sea to avoid getting gobbled up by hungry shore birds and other predators.

In those few crucial moments, hatchlings orient themselves with light and sprint towards the lightest point visible, which on undeveloped beaches is the horizon over the sea.

But on urban beaches, this instinct leads them astray. Bright lights of the city can take them inland, into hardscapes and across roads, where they fall into sewer gutters and encounter cars and predators. Those that survive the dangerous obstacles of the city eventually run out of energy reserves and become too exhausted to continue.

Over time, mortality of juvenile turtles from light pollution has led to decreases in the number of nests on developed beaches and contributed to declines in sea turtle populations. While ‘turtle-friendly lighting’ is already being marketed by several manufacturers (example), their effectiveness has yet to be thoroughly tested. In at least some cases, they do little to improve survivorship, but other studies hold out hope that they could improve sea turtle conservation in urban areas.