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 Central Park being destroyed every hour. Worldwide, 90,000 km2 of forest is cleared annually. In East Africa deforestation is destroying game parks, Singapore has lost 95% of its tropical forests, South East Asia may lose 74% by 2100. More than quarter of Earth’s land is under cultivation and in 54 countries 90% of forests have been felled. Some endangered species also have to contend with exotic invaders – the second biggest threat to rare species. Introduced species prey on them, eat their food, infect them or otherwise disrupt them. Human seafarers have spread cats, dogs, rats, foxes, rabbits and weasels to new places, contributing to the McDonaldisation of Earth’s biota. In Australia, rabbits and foxes are driving native marsupials to extinction; In New Zealand, weasels have been pushing the flightless Kakapo parrot to its doom; In North America, tiny European zebra mussels arrived in the 1980s with shipping, and clog waterways; In the US, once-ubiquitous chestnuts were decimated by an introduced blight. In Kenya’s Lake Victoria, the Nile perch has miraculously managed to eat its way through 200 cichlid fish species since 1959.And in Maryland, US, the voracious south-east Asian snakehead fish has been chomping its way through native fish and waterfowl since 2002. Often exotic species, such as the cane toad, have even been introduced intentionally, to control other species with disastrous consequences. One unusual way to eradicate invaders could be for people to eat them.
Exploitation – hunting, collecting, fishing or trading – is another factor driving extinctions. American bison were hunted down from a population of 30 million before Europeans arrived, to just 750 animals in 1890. Whales were exploited so fiercely that the International Whaling Commission voted in 1986 to place a moratorium on most whaling. Blue whales, for example, were hunted down from a population of perhaps 300,000 to just a few thousand by the 1960s. Today we continue to rape the oceans through overfishing. The UN claims that 15 of the top 17 fisheries are in decline. Exploited species include: the tuna, swordfish, red snapper, Atlantic salmon, Atlantic cod, sharks and lobsters. Now, overfishing of the smaller species that fleets have switched to may inhibit the recovery of the more-prized species that prey on them. Canada’s Atlantic cod fishery was closed in 1992 following its collapse. Better management and stock modelling may help reverse the trend, but others argue that many fisheries are already doomed. Other species are unintentionally killed as bycatch, by drift nets, longlines and deep-sea trawlers. Surveys reveal that 300,000 dolphins and small whales and as many as half of all remaining turtles are snared as bycatch each year. Overfishing could even put a strain on terrestrial wildlife.
Another significant challenge to conservation is the international trade in rare species. Second only to the illegal drug trade, it is thought to be worth more than illegal arms, and may net $10 billion a year. Tropical fish, birds (particularly parrots), and other animals are captured and sold as pets. Some – like turtles, whales and sharks – are prized as delicacies. Others – such as tigers, rhinos and saiga – are killed to supply bones, gall bladders, horns and other body parts for traditional medicine. Horns, feathers, eggs and other trophies are smuggled to unscrupulous collectors. Trade in elephant ivory was banned in 1990, but despite the ban 4000 are still killed illegally each year. The UN’s Convention on International Trade in Endangered Species (CITES) was set up in 1975 to stem the flow. Another body, TRAFFIC, monitors trade in rare species. One US forensics lab is dedicated to uncovering the illegal trade. Detection kits for bear tissue and different kinds of fur may help uncover illegal imports. However, some experts argue that we must allow limited trade of species in order to save them. Pollution is another serious issue. If it does not kill animals outright, pollution can affect reproduction, mess with sexual development and trigger bizarre behaviour. Mercury, dioxins, flame retardants, synthetic hormone, pesticides and other hydrocarbons such as DDT and PCBs are ubiquitous and carried far and wide. Carcinogenic pollutants are behind cancers in Canadian beluga whales. Sewage is ravaging Caribbean corals, while acid rain is killing fish and trees in Europe. Radioactive waste is found throughout oceans and ecosystems. Oil spills continue to kill seabirds, marine and coastal life in regions such as Spain, Pakistan and the Galapagos islands. Between 1993 and 2002, 580,000 tonnes of oil spilt into the sea in 470 separate accidents.
The World Conservation Union (IUCN) publishes the Red List – an annual index of threatened species. The IUCN, governments and conservationists try to protect these species by fencing them off and educating local people. In 1872 Yellowstone National Park, in the US, became the world’s first modern reserve. During the last century 44,000 protected areas were designated, covering 10% of Earth’s land. Marine reserves only cover 1% of oceans, and more are needed. The identification of biodiversity hotspots may help focus resources. Ecotourism may also be part of the solution, but could be part of the problem too. Returning the stewardship of forest reserves and other habitats to their indigenous inhabitants could help. In Africa, 2 million km2 is designated as protected: reserves such as Aberdare, Tsavo and the Masai Mara in Kenya; Quiçama in Angola; Kruger in South Africa; Garamba and Virunga in Congo; Queen Elizabeth in Uganda and the Serengeti in Tanzania. In 2002 Brazil created the vast Tumucumaque National Park, the largest tropical forest reserve in the world, the same year that Australia created the world’s largest marine reserve. Reintroducing species such as golden tamarin moneys, wolves and condors, has been a success. Some researchers even advocate reintroducing large animals such as lions and elephants to the US and wolves to the UK. Failing these methods, if we collect genetic material now, we may be able to reincarnate extinct species by cloning them in the future.