[dramatic music] ♪ ♪ narrator: El Desemboque is a remote village in northern Mexico located where the Sonoran Desert meets the sea.

- [speaking Spanish] narrator: The Indigenous Comcáac people that live here have a deep, ancestral connection to the ocean.

In their origin stories, a sea turtle helped form the Earth.

narrator: Sea turtles have been around since the time of the dinosaurs.

But hotter conditions now threaten this ancient species.

narrator: To improve the turtles' odds of survival, their eggs are moved to a hatchery where they're protected from increasingly frequent storm surges that wash away the nests.

narrator: The olive ridley is the world's most abundant sea turtle, but their numbers are falling drastically.

Yazmín has come to check on a nest that was moved here over a month ago-- an extreme measure to save the baby turtles.

- [speaking Spanish] - No.

narrator: A turtle's sex is determined by the warmth of the sand around the nest.

The hotter it gets, the fewer males will hatch.

Above 91 degrees, the hatchlings will almost all be female and may struggle to find a breeding partner... bad news for a species already in decline in a warming world.

[bright music] ♪ ♪ [person shouts, cheers] narrator: Sea turtles help safeguard the overall health and resilience of marine environments, and by keeping the reefs healthy, they ensure a bountiful supply of fish for the Comcáac people.

[dramatic music] ♪ ♪ [waves crashing] ♪ ♪ - [singing in native language] narrator: The turtle guardians and many other Indigenous groups worldwide make a small but significant difference.

But rising temperatures have complex implications, such as affecting a turtle's sex.

It's a reminder that changes in one place can have surprising and far-reaching consequences.

♪ ♪