Study: Climate change could transform ecosystems
After the end of the last ice age, as sea levels rose, glaciers receded and global average temperatures soared as much as 7 degrees Celsius, Earth’s ecosystems were utterly transformed.
Forests grew up out of what was once barren, ice-covered ground. Dark, cool stands of pine were replaced by thickets of hickory and oak. Woodlands gave way to scrub, and savanna turned to desert. The more temperatures increased in a particular landscape, the more dramatic the ecological shifts.
It’s about to happen again, researchers report Thursday in the journal Science .A sweeping survey of global fossil and temperature records from the last 20,000 years suggests that Earth’s terrestrial ecosystems are at risk of another, even faster transformation unless aggressive action is taken against climate change.
“Even as someone who has spent more than 40 years thinking about vegetation change looking into the past … it is really hard for me to wrap my mind around the magnitude of change we’re talking about,” said ecologist Stephen Jackson, director of the U.S. Geological Survey’s Southwest Climate Science Adaptation Center and the lead author of the new study.
“It is concerning to me to think about how much change and how rapidly the change is likely to happen, and how little capacity we have to predict the exact course,” he continued.
Jackson has spent most of the past four decades studying ecological changes as the Earth transitioned from an ice age to the current “interglacial” period between 20,000 and 10,000 years ago. His experience suggested that no corner of the planet made it through that upheaval unchanged, but being a scientist, he wanted actual evidence.
So Jackson brought together a group of more than three dozen ecology experts from around the globe to assess how vegetation in various regions had been altered after the end of the last ice age. The scientists analyzed preserved bits of plant pollen from nearly 600 sites on every continent except Antarctica. For each metric, they ranked the change at their site as “low,” “moderate” or “large.”
Indeed, some of the predicted ecological shifts are already happening, Jackson said. Where he lives in the Southwest, severe wildfires are destroying ponderosa pine forests that have existed for generations; constant high temperatures and prolonged drought prevent the pines from regenerating in the aftermath.
“Instead of these beautiful, open, shady cool stands of ponderosa pine forest, we have oak shrubs that are very dense and maybe three to five feet high,” he said.
The scientist said it would be difficult to predict exactly how individual ecosystems will change in the years to come. The ecological disruption caused by temperature increases is compounded by pollution, deforestation, and other human activities.
“That is a unique combination, and that’s what makes it more scary,” Jackson said. “It’s going to take the natural adaptive capacity that’s out there and strain it, and we will probably have to adapt too.”