Biodiversity Below Safe Levels Across More Than Half Of World
Above photo: Enormous swaths of dry forest in Paraguay’s sparsely populated Chaco Boreal region have been cleared for cattle ranching. Photograph: Planet
Habitat destruction has reduced the variety of plants and animals to the point that ecological systems could become unable to function properly, with risks for agriculture and human health, say scientists.
The variety of animals and plants has fallen to dangerous levels across more than half of the world’s landmass due to humanity destroying habitats to use as farmland, scientists have estimated.
The unchecked loss of biodiversity is akin to playing ecological roulette and will set back efforts to bring people out of poverty in the long term, they warned.
Analysing 1.8m records from 39,123 sites across Earth, the international study found that a measure of the intactness of biodiversity at sites has fallen below a safety limit across 58.1% of the world’s land.
Under a proposal put forward by experts last year, a site losing more than 10% of its biodiversity is considered to have passed a precautionary threshold, beyond which the ecosystem’s ability to function could be compromised.
“It’s worrying that land use has already pushed biodiversity below the level proposed as a safe limit,” said Prof Andy Purvis, of the Natural History Museum, and one of the authors. “Until and unless we can bring biodiversity back up, we’re playing ecological roulette.”
Researchers said the study, published in the journal Science on Thursday, was the most comprehensive examination yet of biodiversity loss. The decline is not just bad news for the species but in the long term could spell problems for human health and economies.
“If ecosystem functions don’t continue, then yes it affects the ability of agriculture to sustain human populations and we simply don’t know at which point that will be reached,” said Dr Tim Newbold, lead author of the work and a research associate at University College London. “We are entering the zone of uncertainty.”
He added that while to an extent people could use technological solutions to replicate the functions of nature, such as pollinators, there were limits to how much humans could compensate for the loss of species.
“Such widespread transgression of safe limits suggests that biodiversity loss, if unchecked, will undermine efforts toward long-term sustainable development,” the paper said.
Dr Tom Oliver, who was not involved in the study, wrote in a separate commentary in Science that: “It is a tricky problem to say how much biodiversity loss is too much. However, we can be certain that inaction commits us to a future with substantial costs to human wellbeing.”
The study found that different types of habitat had lost more biodiversity where they were biomes that humans lived in, such as grasslands. Tundra and boreal forests, by contrast, were the least affected. The biggest cause of natural habitats being changed was due to agriculture, rather than urbanisation.
The study does come with some caveats. Foremost is that scientists cannot say exactly what a dangerous degree of biodiversity loss would be – it could be the 10% threshold agreed on, but the authors admit that as much as a 70% loss in variety could count as the safe limit.
The team looked at 1sq km-sized sites around the world, using the latest records that would give a geographically comprehensive picture, including species data from 2005 and human population numbers from 2000, when there were 6 billion people worldwide.
Since then, the global population has grown to 7 billion and governments have been lambasted for failing to stem biodiversity loss, suggesting the real world percentage of sites passing the safety threshold today is even higher.
Newbold said that while losses in the interim would not be uniformly true, because of conservation efforts in certain parts of the world, “on average, we would predict in intervening period, there has been further loss.”