Human Activity Is Driving Earth's 'Sixth Great Extinction Event'
Population growth, pollution and invasive species are having a disastrous effect on species in the southern hemisphere, a major review by conservationists warns
Earth is experiencing its "sixth great extinction event" with disease and human activity taking a devastating toll on vulnerable species, according to a major review by conservationists.
Much of the southern hemisphere is suffering particularly badly, with Australia, New Zealand and neighbouring Pacific islands destined to become the extinction hotspots of the world, the report warns.
Ecosystems in Oceania, which includes Polynesia, Micronesia and Melanesia, need urgent and effective conservation policies, or the region's already poor record on extinctions will worsen signficantly.
Researchers trawled 24,000 published reports to compile information on the flora and fauna of Australasia and the Pacific islands, home to six of the most biodiverse regions on the planet. Their report identifies six major causes that are driving species to extinction, almost all of which are linked in some way to human activity.
"Our region has the notorious distinction of having possibly the worst extinction record on Earth," said Richard Kingsford, an environmental scientist at the University of New South Wales in Sydney and lead author of the report. "We have an amazing natural environment in our part of the world, but so much of it is being destroyed before our eyes. Species are being threatened by habitat loss and degradation, invasive species, climate change, over-exploitation, pollution and wildlife disease."
The review, published in the journal Conservation Biology, highlights destruction and degradation of ecosystems as the single greatest threat to the region's wildlife. In Australia, agriculture has altered or destroyed half of all woodland and forests. Around 70% of the remaining forest has been damaged by logging. Severe loss of suitable habitats is behind 80% of threatened species, the report claims.
The arrival of invasive animals and plants has devastated native species on many Pacific islands and contributed to the extinction of birds and mammals. The Guam Micronesian kingfisher is now thought to be extinct in the wild following the introduction of the brown tree snake, which preys on the birds. The impact of invasive species is often compounded by pollution from rapid development and burgeoning human populations on the islands, which have outstripped their capacity to deal with waste. Plastics and fishing gear are an ongoing danger to seabirds and marine animals, the report says.
The impact of humans on wildlife is likely to increase in Australasia and the Pacific islands, where populations are predicted to rise substantially. By 2050, the population of Australia is expected to have risen by 35%, and in New Zealand by 25%. Other islands with rich biodiversity are predicted to see an even more dramatic population rise, with Papua New Guinea predicted to be home to 76% more people by 2050 and New Caledonia having 49% more.
More than 2,500 invasive plant species have colonised Australia and New Zealand, threatening local species by competing for sunlight and nutrients. Many have been introduced by governments, horticulturalists and hunters. In addition, the report says Australia has seen increased average temperatures, especially since the 1950s, in line with climate change predictions, forcing some species towards Antarctica and others to higher, cooler ground.
The report highlights several studies that point to serious threats from diseases such as avian malaria and the chytrid fungus, which has been linked to large declines in frog populations. One of the most devastating animal diseases is an infectious form of facial cancer that is spreading rapidly among Tasmanian devils, the world's largest marsupial predator. Populations of the animals are believed to have fallen by more than 60% because of the disease.
Plants have also fared badly as a result of new diseases. For example a root fungus that was deliberately introduced into Australia has destroyed several plant species.
The report sets out a raft of recommendations to slow the decline of species by introducing new laws to limit land clearing, logging and mining; restricting the deliberate introduction of invasive species; reducing carbon emissions and pollution; and placing strict limits on fisheries. The report raises particular concerns about fisheries that cause disproportionate destruction to ecosystems by bottom trawling, and using cyanide and dynamite.
It also calls for the establisment of early-warning systems to pick up diseases in the wild.
"The burden on the environment is going to get worse unless we are a lot smarter about reducing our footprint on the planet or the human population," said Kingsford. "Unless we get this equation right, future generations will surely be paying more in terms of quality of life and the environment we live in. And our region will continue its terrible reputation of leading the world in the extinction of plants and animals."