The world is facing a severe biodiversity crisis, as almost half of the planet’s species are experiencing rapid population declines, according to a new study. The main cause is human activity, such as habitat destruction, overexploitation, pollution and climate change.
The study, published in the journal Biological Reviews, analyzed more than 70,000 species across the globe, spanning mammals, birds, reptiles, amphibians, fish and insects. It found that 48% of these species are declining in population size, with fewer than 3% seeing increases.
Co-author Daniel Pincheira-Donoso, from the School of Biological Sciences at Queen’s University Belfast, said their findings are a “drastic alert” on the global erosion of biodiversity.
“Other studies, based on considerably smaller numbers of species, have shown that the ongoing ‘extinction crisis’ is more severe than generally appreciated,” he told CNN. “Our findings provide a stark confirmation on a global scale.”
The study also revealed that 33% of the species currently classed as “non-threatened” on the International Union for Conservation of Nature’s (IUCN) Red List are in fact declining towards extinction. The Red List is the most widely used measure of biodiversity loss, but it only assesses whether species are under threat of extinction at a given moment in time.
“What our study shows is not whether species are currently classed as threatened or not, but instead, whether their population sizes are becoming rapidly and progressively smaller or not,” Pincheira-Donoso said.
Downward trends in population over time are a precursor to extinctions. Scientists have warned that we are entering the sixth mass extinction event in Earth’s history, this time driven by humans. The previous five mass extinctions include the asteroid strike that killed off the dinosaurs and many species in the sea.
“We’re the most dangerous species in global history,” said Elizabeth Mrema, the executive secretary of the Convention on Biological Diversity.
The loss of wildlife has serious consequences for the functioning of ecosystems that provide essential services for life on Earth, such as pollination, pest control, water purification and soil formation. It also poses risks for human health and well-being, as it increases the chances of disease outbreaks and reduces food security and cultural diversity.
Many factors are to blame for biodiversity loss, including changes in land use (e.g. deforestation, intensive mono-culture, urbanisation), direct exploitation such as hunting and over-fishing, invasive species, pollution and climate change associated with global warming. In each case, human beings and their activities play direct roles.
The study calls for urgent action to reverse the trend and protect nature. It urges governments to adopt ambitious targets to conserve biodiversity at the upcoming UN summit on biodiversity in Kunming, China. It also recommends increasing public awareness and education on the importance of wildlife and its conservation.
“We have no time to wait. Biodiversity loss, nature loss, it is at an unprecedented level in the history of mankind,” Mrema said.