Life on Earth is in the throes of a new wave of mass extinction, unlike anything since the demise of the dinosaurs. In the last 500 years, 844 species – like the passenger pigeon, auk, thylacine, and quagga – are known to have died out, and up to 16,000 others are now known to be threatened. Two thirds of turtles could be gone by the 2025, great apes have recently declined by over 50% in parts of Africa, half of marsupials and one in three amphibians are in jeopardy, and a staggering 40% of Asia’s plants and animals could soon be lost. But this may only be a fraction of the true number facing extinction. Though only 1.5 million species have been described, there could be between 5 to 30 million in total. Of these, some experts predict that one could be falling extinct every 20 minutes – or 27,000 a year.
Conservationists argue that humans have an ethical obligation to protect other species, that diversity and natural beauty are highly prized by mankind, and that biodiversity is a vital resource: we rely on ecosystems to provide food, oxygen and natural resources, recycle wastes and fertilise soils for agriculture. The total value of services provided to man by nature has been estimated at $33 trillion annually. Plants and animals are also an essential source of new foods and medicines – up to 20,000 plants are used in medicines worldwide. Preserving species could help protect us from disease. Natural disasters and processes were behind the five major mass extinctions in geological history, but the current “sixth extinction” is caused by success of one species – humans. The six billion (and counting) people crowding the Earth, are driving out biodiversity in a variety of ways. Species form and die out naturally as a part of evolution. However, many experts argue the current extinction rate is as much as 100 or 1000 times higher than the “background” rate. Bird extinctions were the first to hint at this, but in 2004, studies of declining butterflies and plants confirmed it. Humans began to destroy ecosystems in a major way about 10,000 years ago with the development of agriculture. But within the last 100,000 years, the hunting and burning practices of Palaeolithic people, along with climate change, drove many large mammals and birds to extinction. North- and South America and Australia lost up to 86% of large mammals soon after humans arrived – species such as giant wombats, killer ducks, ground sloths, mammoths, sabre-tooth cats and moas.
The most common reason for extinction is habitat loss. Ecosystems from wetlands to prairies and cloud forests to coral reefs are being cleared or degraded for crops, cattle, roads and development. Even fragmenting habitats with roads or dams can make species more vulnerable. Fragmentation reduces population size and increases inbreeding, increases disease and opens access for poachers. The Amazonian rainforest is today being cleared at rate of 24,000 km2 per year – equivalent to New York City’s...