Protecting biodiversity around the world

Islands and their surrounding marine areas are the focus of this year's International Day for Biological Diversity on May 22. Islands are unique ecosystems with plant and animal species that are often found nowhere else on Earth. They are also home to one-tenth of the world's human population and are increasingly coming under population and climate pressure.

Of the 724 recorded animal extinctions in the last 400 years, about half were island species, according to the UN's Convention on Biological Diversity. Over the past century, island biodiversity has been subject to intense pressure from invasive species, habitat change and over-exploitation, as well as, increasingly, from climate change and pollution caused by humans.

The brown tree snake is infamous for being the invasive species that devastated the majority of the native animal population on the Pacific island of Guam. With no natural predators, its accidental introduction is thought to have caused the extinction of 12 native bird species. It has also negatively affected vegetative species diversity and even affected the economy, experts say.

For three decades, conservationists have been working to rebuild the original ecosystem of Mauritius on the tiny island of Ile aux Aigrettes. They've now managed to eradicate most foreign animals like rats, rabbits and goats, and have replanted forests. In some cases authorities replaced extinct animals, like the original giant tortoise, with a similar animal to maintain the ecosystem's balance.

A biodiversity hotspot is a region under threat from human activities which also has a high level of endemic species. While hotspots are spread all over the world, the most are in forest areas and located in the tropics. Madagascar's dry deciduous forests and lowland rainforests have complex ecosystems, but many of the forests have been almost entirely destroyed by overgrazing and deforestation.

Over the last 50 years, conditions on the German island of Heligoland have dramatically changed. Scientists at the Biological Institute Heligoland say the average water temperature has increased by 1.7 degrees Celsius in half a century. There are now around 60 species that were not present in local waters before, including types of hermit crabs, sea slugs, bristle worms and jellyfish.

Before European colonization, Norfolk Island was once covered with subtropical rainforest. The Norfolk Island palm made up part of the forest undergrowth, while the famous Norfolk Island pine formed the canopy. Now, only one small area of the original rainforest remains on the island, which has now been declared a national park. The forest remains infested with several introduced plants.

Taiwan is home to a huge range of plant and animal species. That's partly due to the various natural landscapes that stretch between the coastal regions and high mountain ranges. Most of the 17 bird types that are unique to Taiwan live in the high mountain ranges, shielded from the rapid urban development in the country below. One of them, the Mikado pheasant, lives only above 1,800 meters.

The Hawaiian monk seal is the only native seal left in Hawaii and is highly endangered. The small population of about 1,100 is threatened by human encroachment and fishing, low levels of genetic variation, and marine debris. The National Marine Fisheries Service in the United States has had a Hawaiian Monk Seal Recovery plan in place since 1983, but numbers are still dangerously low.

As part of the UN's Decade on Biodiversity, countries are required to implement the 20 so-called "Aichi Biodiversity Targets." The targets are meant to reduce loss of biodiversity worldwide. A workshop for small developing island states to better tackle invasive alien species is due to be held in Montreal in June. It will examine one how island ecosystems can be better protected.