Human activity is leaving some migratory species like green turtles facing extinction, a UN report says.

More than 40 years ago many of the world’s nations signed an agreement to protect the world’s migrating species, known as the Convention on the Conservation of Migratory Species of Wild Animals (CMS).

Now, a first global assessment has been undertaken looking at the numbers and health of these animals.

Of the 1,189 species assessed the researchers found one in five are threatened with extinction. For some species the situation is much worse - 97% of fish listed under the convention are at risk.