Declining biodiversity

Plants and animals depend on each other for survival. Find out why this biodiversity is so important—and why it's in trouble.

A green sea turtle glides through the Great Barrier Reef off the northeastern coast of Australia. Millions of species live in and around coral reef ecosystems, where these plants and animals rely on each other for survival. Scientists call this mix of different species biodiversity.

An environment works well with a wide variety of species. Here’s an example: Green sea turtles love to chomp on sea grass—but they can’t hang out in one spot for too long because tiger sharks patrol the area, hunting for sea turtles. Without tiger sharks, sea turtles would eat all the best sea grass, destroying that habitat for all the other animals that depend on it. If one species—turtle, shark, or sea grass—disappears, other plants and animals that are connected to that species could go extinct too. Losing just one species can harm many others.


There are possibly billions of different species of plants, animals, bacteria, and other living things throughout the world—but we’ve only documented about two million of them. Many of these known and unknown species have uncertain futures though. Climate change, pollution, poaching, and habitat destruction change the number of plant and animal species that live in a habitat, known as declining biodiversity.

Due in part to declining biodiversity, almost one-third of Earth’s animals are at risk of extinction, according to the International Union for Conservation of Nature.


By preventing the decline of biodiversity, you can help keep Earth safe. Some animals such as sharks are especially important to protect. Scientists call these animals keystone species because they’re the key to keeping whole ecosystems healthy. So if you save animals like sharks, you protect other critters. Check out all the ways to protect biodiversity in your backyard and beyond.