The resilience of North America’s plant biomes is declining — indicating that today’s landscapes are “primed to herald a major extinction event” not seen since the retreat of glaciers and arrival of humans 13,000 years ago, scientists reported in a new study published in the journal Global Change Biology.
The research analyzed 14,189 fossil pollen samples from 358 sites across North America, allowing scientists to reconstruct the “landscape resilience” — defined as “the ability of habitats to persist or quickly rebound in response to disturbances” — of 12 major plant biomes over the past 20,000 years.
The retreat of North American glaciers at the end of the Pleistocene era, for example, destabilized ecosystems, causing widespread shifts in plant composition and large herbivores such as mammoths to struggle for food supplies. Combined with the arrival of humans, the events were “a one-two punch that resulted in the extinction of large terrestrial mammals on the continent,” Jenny McGuire, a climate scientist at the Georgia Institute of Technology and a coauthor of the study, said in a statement.
“Today, we see a similarly low landscape resilience, and we see a similar one-two punch: humans are expanding our footprint and climates are changing rapidly,” said Yue Wang, a postdoctoral researcher at Georgia Tech who led the study. “Though we know that strategies exist to mitigate some of these effects, our findings serve as a dire warning about the vulnerability of natural systems to extinction.”
Wang, McGuire, and their colleagues found that over the past 20,000 years, forests persisted longer than grasslands — lasting an average 700 years versus 360 years — but they also took longer to reestablish after disruptions, 360 years versus 260 years. The research also found that ecosystems shift more rapidly when temperatures are changing quickly. Only 64 percent of biomes regain their original ecosystem type, the study found, and the process can take up to three centuries. Of all the biomes, Arctic ecosystems were the least likely to recover.
But the scientists said strategic conservation efforts could help counteract or slow down the impacts of climate change on ecosystems in the coming decades. “Conservation strategies focused on improving both landscape and ecosystem resilience by increasing local connectivity and targeting regions with high richness and diverse landforms can mitigate these extinction risks,” the scientists wrote.