Life on Earth may have taken billions of years to appear, but humans are doing an impressive job of destroying it in double quick time, according to a study published this week in the journal Science. After studying species numbers in a variety of habitats, the researchers have reached the rather grim conclusion that biodiversity across most of the Earth’s surface has now fallen below safe levels, meaning ecosystems may soon cease to function and become incapable of sustaining life.
Their work comes on the back of previous research that revealed how the removal of large numbers of species from certain environments leads to a decrease in ecosystem viability, and therefore accelerates further species loss. Though it is not entirely clear how reductions in biodiversity bring about this drop in ecosystem function, the Planetary Boundaries framework suggests that a 10 percent loss of species abundance represents the safe limit, and that surpassing this could leave parts of the planet incapable of supporting life.
In a statement, study co-author Andy Purvis summed up the gravity of this threat, saying “decision-makers worry a lot about economic recessions, but an ecological recession could have even worse consequences – and the biodiversity damage we've had means we're at risk of that happening.”
After analyzing 2.38 million records for almost 40,000 species, collected by hundreds of scientists at over 18,500 sites around the world, the study authors were able to estimate how biodiversity levels have changed across the globe since before humans began modifying habitats through agriculture and industrialization. In doing so, they found that species numbers have dropped to below safe levels across 58.1 percent of the Earth’s land surface, representing an area that is home to more than 70 percent of the human population.
Levels of species intactness across the globe. T. Newbold et al., Science
On average, the number of originally present species has dropped by 15.4 percent globally as a result of humanity’s changing modes of land use, with biodiversity having transgressed the safety boundary in nine of the world’s 14 biomes – which include desserts, grasslands, forests, and other types of environment.
Though the destructive impact of human activity varies between biomes – with grasslands being the most affected and tundra and boreal forests being the least affected – the researchers insist that, unless something is done to alleviate this alarming trend, ecosystems across the world could soon begin to collapse. In other words, as Purvis explains, “until and unless we can bring biodiversity back up, we’re playing ecological roulette.”
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