Global ecosystems 'face collapse'
Current global consumption levels could result in a large-scale ecosystem collapse by the middle of the century, environmental group WWF has warned.
The group's biannual Living Planet Report said the natural world was being degraded "at a rate unprecedented in human history".
Terrestrial species had declined by 31% between 1970-2003, the findings showed.
The loss was a result of resources being consumed faster than the planet could replace them, the authors said.
They added that if the world's population shared the UK's lifestyle, three planets would be needed to support their needs.
Paul King, WWF director of campaigns, said the world was running up a "serious ecological debt".
"It is time to make some vital choices to enable people to enjoy a one planet lifestyle," he said.
"The cities, power plants and homes we build today will either lock society into damaging over-consumption beyond our lifetimes, or begin to propel this and future generations towards sustainable one planet living."
The report, co-produced by the Zoological Society of London (ZSL) and the Global Footprint Network, is based on data from two indicators:
Living Planet Index - assesses the health of the planet's ecosystems
Ecological Footprint - measures human demand on the natural world
The Living Planet Index tracked the population of 1,313 vertebrate species of fish, amphibians, reptiles, birds and mammals from around the world.
Humans are placing ever greater demands on natural resources (WWF-Canon/Jurgen Freund)
It found that these species had declined by about 30% since 1970, suggesting that natural ecosystems were being degraded at an unprecedented rate.
The Ecological Footprint measured the amount of biologically productive land and water to meet the demand for food, timber, shelter, and absorb the pollution from human activity.
The report concluded that the global footprint exceeded the earth's biocapacity by 25% in 2003, which meant that the Earth could no longer keep up with the demands being placed upon it.
One of the report's editors, Jonathan Loh from the Zoological Society of London, said: "[It] is a stark indication of the rapid and ongoing loss of biodiversity worldwide.
"Populations of species in terrestrial, marine and freshwater ecosystems have declined by more than 30% since 1970," he added.
"In the tropics the declines are even more dramatic, as natural resources are being intensively exploited for human use."
The report outlined five scenarios based on the data from the two indicators, ranging from "business as usual" to "transition to a sustainable society".
Under the "business as usual" scenario, the authors projected that to meet the demand for resources in 2050 would be twice as much as what the Earth could provide.
They warned: "At this level of ecological deficit, exhaustion of ecological assets and large-scale ecosystem collapse become increasingly likely."
To deliver a shift towards a "sustainable society" scenario would require "significant action now" on issues such as energy generation, transport and housing.
The latest Living Planet Report is the sixth in a series of publications which began in 1998.