Invasive alien species measured for the first time
Levels to which non-native invasive species have spread themselves around the world have been measured for the first time.
The report Global indicators of biological invasion: species numbers, biodiversity impact and policy responses.
Looking at 57 countries the report found, on average, there are 50 non-indigenous species in each country which have a negative impact on biodiversity.
The number of invasive alien species ranged from nine in Equatorial Guinea to 222 in New Zealand.
According to the report if left uncontrolled, invasive alien species can have a serious impact on native species.
The Yellowhead, a bird endemic to New Zealand, has suffered considerably in recent years due to a surge in the number of rats.
Two populations of the Yellowhead are now extinct and three more are significantly falling in number, leading to the species to move up from vulnerable to endangered on the IUCN Red List of Threatened Species.
Similarly, the pathogenic chytrid fungus, which was entirely unknown until 1998, is thought to be the cause of the decline and extinction of many amphibian populations around the globe.
The disease, caused by the fungus, can be spread by humans and a host of other species, ranging from exotic fish to African Clawed Frogs.
However, it's not all bad news with the Black-vented Shearwater, a seabird native to Natividad Island off the Pacific coast of Mexico, was under threat from cats, goats and sheep.
But since they've been eradicated, the status of the bird has been reduced from vulnerable to near threatened on the red list.
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