A group from University of Bonn, University of California San Diego and University of Applied Sciences Eberswalde found that islands located in oceans were nine times more valuable than an equally sized piece of mainland.

By compiling the largest collection of data on plant and vertebrate animal species they used the number of each species and their rarity to calculate an index. The index ranks the island of New Caledonia as the most important place on the planet in terms of biodiversity. New Caledonia is home to 3,270 plant species – two thirds of these are only found on the island and nowhere else in the world. Unique bird species are also found there – the Kagu, for example, is the only surviving species of an entire major group of animals.

Dr Holger Kreft from University of California in San Diego said: “Although islands have been known since Dawin’s day for their unique flora and fauna, until now there was no global analysis comparing their value for nature conservation with continents.”

Although islands are key to maintain biodiversity, some mainland areas also have a high biodiversity index. The southern tip of Africa, known as Capensis, and many mountains in the tropics are also very valuable. “It would in fact not make any sense now for protective measures to simply focus on islands because three quarters of all plant species are nevertheless found on the continental mainland,” Dr Kreft commented.

The researchers also investigated the threats to biodiversity due to human impact. They found that deforestation and expansion of farmland have an amplified effect on islands but islands are affected less by climate change due to the buffering effect of the oceans. However, if sea levels continue to rise then many smaller islands will simply be sucked in to the sea.

Dr Gerold Kier who was also involved with the study said: “Climate change remains one of the main threats to the biodiversity of the earth. If we cannot slow it down significantly, protected areas will not be much help.”

By Leila Sattary