As the global human population continues to grow with ever more mouths to feed, many remaining wildlife habitats continue to shrink to make way for yet more agricultural land.
Already mammals, birds and amphibians around the planet have seen their natural habitat range shrink by 18% on average over just three centuries. Unless drastic measures are taken, this loss of wildlife habitats could increase considerably by the end of the century, according to a team of scientists who analyzed changes in the geographical range of nearly 170,00 species from the year 1700 to today.
Tropical areas, which have been especially biodiverse, have particularly been affected by habitat loss as jungles have been cut down at a rapid pace in favor of oil palm plantations and other uses over the past decades.
“We estimate that species have lost an average of 18% of their natural habitat range sizes thus far, and may lose up to 23% by 2100,” the scientists write in a new study. “Our data reveal that range losses have been increasing disproportionately in relation to the area of destroyed habitat, driven by a long-term increase of land use in tropical biodiversity hotspots.”
The experts predict various changes by the end of the century under 16 different climate and socio-economic scenarios, but what they all have in common is that habitats will continue to shrink if our destructive practices are maintained.
“The habitat size of almost all known birds, mammals and amphibians is shrinking, primarily because of land conversion by humans as we continue to expand our agricultural and urban areas,” warns Robert Beyer, an author of the paper who works at the University of Cambridge’s Department of Zoology.
As a rule of thumb, the smaller the geographical range of a threatened species already is, the more at risk of extinction it is if that range continues to shrink. Troublingly, an estimated 16% of species have lost more than half of their estimated natural historical range over the centuries, and this loss could rise to as much as 26% by 2100 in the worst-case scenario.
“Species’ geographical ranges were found to have recently shrunk most significantly in tropical areas. Until around 50 years ago, most agricultural development was in Europe and North America,” the scientists note. “Since then, large areas of land have been converted for agriculture in the tropics: clearance of rainforest for oil palm plantations in South East Asia, and for pasture land in South America, for example.”
The repurposing of forested lands in tropical areas is affecting a large number of species because these forests are especially biodiverse and the natural ranges of resident species tend to be smaller to begin with. “The tropics are biodiversity hotspots with lots of small-range species,” Beyer says. “If one hectare of tropical forest is converted to agricultural land, a lot more species lose larger proportions of their home than in places like Europe.”
Add to that the effects of climate change with rising temperatures and changing rainfall patterns and entire tropical ecosystems could change irreversibly with forested regions like the Amazon turning into savannah.
“Species in the Amazon have adapted to living in a tropical rainforest. If climate change causes this ecosystem to change, many of those species won’t be able to survive, or they will at least be pushed into smaller areas of remaining rainforest,” Beyer says. “We found that the higher the carbon emissions, the worse it gets for most species in terms of habitat loss.”
To forestall this bleak prospect, strident measures worldwide will need to be enacted to protect existing wildlife habitats, especially in the tropics, while we must also seek to mitigate the effects of climate change by lowering our carbon emissions.
“Whether these past trends in habitat range losses will reverse, continue, or accelerate will depend on future global carbon emissions and societal choices in the coming years and decades,” says Prof. Andrea Manica, an expert at the University of Cambridge’s Department of Zoology,
“While our study quantifies the drastic consequences for species’ ranges if global land use and climate change are left unchecked, they also demonstrate the tremendous potential of timely and concerted policy action for halting — and indeed partially reversing — previous trends in global range contractions. It all depends on what we do next,” Manica stresses.
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