Planet Earth is home to an astonishing variety of life, from bacteria that live in the extreme heat of volcanic lava to ice-cap dwelling polar bears, from city-based humans to luminous fish in deep ocean trenches. All are interconnected in a fragile web of life called ‘biodiversity’.

Life on earth first evolved in the oceans over 2.5 billion years ago. Perhaps half a million years ago, one species of primate became more and more successful, and humanity spread throughout the world. By 10,000 years ago we were domesticating plants and animals; and by the 20th century our high-energy technologies and productive activities meant we were capable of the total transformation of ecosystems, something unprecedented in history.

The number of species threatened with extinction is a clear indicator of the state of the world’s ecosystems. Extinction means the death of birth. Five mass extinctions have happened in the past 500 million years. The sixth and greatest extinction in the history of our planet is happening today. It is almost entirely due to human activity, and is faster than any in history: we are losing species at a rate of up to 1,000 times the natural rate of extinction. Between a third and a half of terrestrial species are expected to die out over the next two centuries if current trends continue unchecked.

Humanity’s threats to biodiversity are manifold, from habitat loss to destruction of grasslands and forests, from overfishing, pollution and contamination to global climate change. The inter-relatedness of ecosystems means that a small loss in one area can affect many other species around it: for example, the decline of the honeybee leaves many fruit crops and flowers unpollinated. For in nature, diversity breeds diversity: trees in turn provide homes and food for birds, insects, other plants and animals and fungi.

This interrelatedness of all beings includes us. Human beings rely directly on the planet’s biodiversity for food, shelter and health; and indirectly for clean water, pure air and fertile soils. The lesson we need to learn urgently is this: we cannot do without the rest of the planet’s biodiversity, but it can do very well without us.

New Internationalist

Red-eyed tree frog Tree frogs are found on every continent except Antarctica; the red-eyed variety, Agalychnis callidryas, lives in the forests of Central America. Photo: Klein / Still Pictures

Egret, Japan As many as 12 per cent of the world's birds are now threatened with extinction, mainly from loss of habitat. We have, for example, already lost the Atilan and Colombian Grebes, the Wake Island Rail and the Canary Islands Oystercatcher. Photo: R Kawakami / UNEP / Still Pictures

Tubu pastoralist, Chad Tubu (Teda) people are pastoralists, herding camels and donkeys across the hot, arid lands of northern Chad where the Sahara encompasses the volcanic Tibesti mountain range. The area remains littered with landmines from the 1980s Libya/Chad war, and today is the stage for clashes between the Movement for Democracy and Justice in Chad (MDJT) and Chad's military-backed government. Photo: Sven Torfinn / Panos Pictures

Forest, Sabah, Malaysia Rainforests are the foremost ecosystem in terms of species diversity; they cover only about six per cent of the earth's surface yet hold over half the world's species, many still unidentified. Photo: Ed Hoogervorst / Panos Pictures

Migrant family, Brazil Photo: Mark Edwards / Still Pictures

Plastic bags, England This non-biodegradable substance is a growing problem. But in Ireland a tax of 15 cents per bag, introduced in 2002, cut the use of plastic bags by more than 90 per cent as well as raising millions of euros in revenue. Photo: Philippe Hays / Still Pictures

View of Hong Kong In 1999 the population density of Hong Kong Island was 17,527 per square kilometre. Photo: Cornelius Paas / Still Pictures

LIFE – THE FACTS
• The Millennium Ecosystems Assessment considered four different scenarios for global development over the next 50 years. In all four, the pressures on ecosystems continue to grow and biodiversity continues to be lost. Between 10% and 15% of plant species may be extinct by 2050.

• Some 23% of mammal species, 12% of bird species and 32% of amphibian species are threatened with extinction.

• Over the past few hundred years, humans have increased the species extinction rate by as much as 1,000 times the background rates typical over the planet’s history.

• In some sea areas the total weight of fish available to be captured is less than a hundredth of that caught before the onset of industrial fishing.

• The distribution of species on Earth is becoming more homogenous. For example, a high proportion of the 100 or so non-native species in the Baltic Sea are native to the North American Great Lakes, while 75% of the 175 recently arrived species in the Great Lakes are native to the Baltic.

Source: Millennium Ecosystem Assessment 2005