Biodiversity has dropped below the “safe limit” across 58% of the Earth’s surface according to the most comprehensive analysis of global data to date.
The international study, published recently in the journal Science, suggests that the degree of lost biodiversity across more than half of the world’s surface is substantial enough to question the ability of many ecosystems to support human societies.
“We’ve found that across most of the world, biodiversity loss is no longer within the safe limit suggested by ecologists,” said lead researcher Dr Tim Newbold of University College London.
“We know biodiversity loss affects ecosystem function but how it does this is not entirely clear.
“What we do know is that in many parts of the world we are approaching a situation where human intervention might be needed to sustain ecosystem function.”
Other environmental experts said the research was impressive in its scope. But they said it is too soon to say we are on the verge of an ecological disaster and more work is needed at a local level.
Previous work has proposed a threshold whereby continued loss of biodiversity may impair an ecosystem’s ability to function.
“The main implication of crossing the safe limit of biodiversity intactness is that the ability of biodiversity to support important ecosystem functions ~ things like food production, nutrient cycling and pollination ~ becomes uncertain,” said Dr Newbold.
To assess the extent to which these limits had been crossed, Dr Newbold and a team of international researchers analysed a database of some 2.3 million records covering more than 39,100 species living in 18,600 sites.
Global map of biodiversity intactness
Their global map (above) reveals that the average abundance of original species in much of the world has fallen to 84.6%.
The analysis suggested at least seven of the 14 terrestrial ecosystem types ~ or biomes ~ have crossed the suggested safe limit for biodiversity. Grasslands, savannahs and shrublands were most affected by biodiversity loss.
“This is where a lot of the world’s farmland is currently,” explained Dr Newbold.
Tundra and boreal forests were the least affected.
According to the global map, much of Australia is below the safe limit.
“Generally the most change in biodiversity has occurred in places where there are more people, but this isn’t always so,” said Dr Newbold. “In the case of Australia, the maps of the different land uses … suggest that a lot of Australia’s area is used for grazing livestock. This probably reflects reality to some extent, but is perhaps an overestimate [as] the extent of grazing land has proven difficult to estimate by global models.”
Professor Hugh Possingham, director of the ARC Centre of Excellence for Environmental Decisions at the University of Queensland, said the link between biodiversity and species abundance within ecosystems is still not well understood.
“I wouldn’t like to think because we’ve crossed these safe operating boundaries it’s a disaster” he said, adding that many ecosystems around the world had experienced significant losses of original species but had not collapsed.
Professor Possingham said it was important to quantify biodiversity loss, but the question is what to do about it.
He said conservation decisions needed to be based on factors such as what actions could be taken to restore the abundance and richness of species; how much those actions were likely to cost; were they likely to succeed; and whether or not there is a net benefit.
Repost — Global map reveals ‘unsafe levels’ of biodiversity across 58pc of Earth’s surface | ABC News
See also — Has land use pushed terrestia biodiversity beyond the planetary boundary? | Science
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