Henley Spiers's Image

A red-eared slider turtle swims peacefully among the water lilies in the Aktun Ha cenote in Mexico.

The limestone rock of Mexico's Yucatán Peninsula is dotted by thousands of cenotes, freshwater pools linked by an underground river system. Some cenotes are underground caves while others, where the rock has fallen in, are open air pools.

Henley was spellbound by the marine world below the surface. 'It was only later that I found out this beautiful scene has a more troubling backstory,' he says.

This unique environment is home to many species of flora and fauna including fish and turtles, but what Henley didn't realise at the time is that the slider turtle in his image is not a native Meso-American slider, but a red-eared slider (native to the USA and northeastern Mexico).

It is likely that this turtle was once a pet, or the offspring of a former pet which was then released back into the wild. An increase in wild releases as a result of the booming pet trade has meant that slider turtles have now been successfully introduced to nearly every continent. They are now among the world's 100 most invasive species due to their interbreeding, altering freshwater habitats and carrying pathogens.

How you can help

• Learn about the world's wildlife and pet trade and the impact it has on the welfare of both humans and nature.
• Consider adopting a pet carefully, and never release your pets back into the wild. If you have to give them up, call a local wildlife organisation.
• Look after your local ecosystems, and learn about the species that keep them balanced.