Study: Earth's ecosystems face 'major transformation' from climate change

Researchers said this ancient city in Oman was once surrounded by dense woodland. The city was abandoned as the landscape became dry and desolate.   Credit: Sarah IvoryAll Rights Reserved.

UNIVERSITY PARK, Pa. — Warming that took place over thousands of years following Earth’s last ice age dramatically changed vegetation on much of the planet, according to a new study.

The same level of warming may occur in the next 100 to 150 years if greenhouse-gas emissions remain at current levels, potentially resulting in a “major transformation” of ecosystems worldwide, an international team of scientists has found.

“Depending on emission scenarios, unless we do a dramatic job limiting greenhouse-gas emissions in the next 100 years, they are likely to result in major global impacts to biodiversity and biological ecosystems,” said Sarah Ivory, an assistant professor in the Department of Geosciences at Penn State.

Ivory was one of more than 40 scientists who worked on the study, the largest of its kind, analyzing hundreds of fossil plant and pollen records from every continent but Antarctica dating as far back as 21,000 years, after the last ice age.

Using the fossil records, researchers compared changes in temperature and vegetation around the globe following the last ice age. The results can help them project how modern ecosystems will react under a range of future climate change scenarios.

“Throughout the world, a large percentage of ancient vegetation records saw very strong, large changes over the last 21,000 years,” said Ivory, an associate in the Earth and Environmental Systems Institute at Penn State. “And so what that amounts to, depending on the magnitude of climate change, we can expect a large-scale reorganizing of terrestrial ecosystems in the future.”

The researchers presented their findings in a recent issue of the journal Science. The corresponding author is Stephen Jackson, director of the U.S. Geological Survey’s Southwest Climate Adaption Science Center and adjunct professor at the University of Arizona.

Previous studies have used direct observation and computer models to predict ecological impacts of climate change. However, this study is unique in that it uses paleoecological records — including ancient plant and pollen fossils — to analyze how ecosystems transformed under climate change since the last ice age and how it may happen in the future.

“Observations over the last 50 years don’t capture the magnitude of temperature change we are projected to see in the future,” Ivory said. “They are limited in how much they can help us constrain future change.”

The study draws on fossil records from 594 sites around the world. Regional experts reviewed the records and analyzed how much vegetation changed during a period of thousands of years following the last ice age when warming rapidly occurred.

By comparing the data to previously published climate records, the researchers found places that warmed the most following the ice age — areas like glacier-covered North America and Europe — also had the most significant changes in vegetation.

"We used the results from the past to look at the risk of future ecosystem change," said Connor Nolan, a doctoral student at the University of Arizona and first author on the paper. "We find that as temperatures rise there are bigger and bigger risks for more ecosystem change."

The scientists said Earth warmed between 7 and 13 degrees Fahrenheit in the thousands of years following the ice age. Climate change estimates show the planet could face similar warming in the next 100 to 150 years.

In the paper, the team reported that “business-as-usual” emissions levels would result in a 60 percent chance of large-scale ecosystems changes worldwide. With efforts to reduce emissions levels to targets established by the 2015 Paris Agreement, the odds improve to 45 percent.

“If we allow climate change to go unchecked, the vegetation of this planet is going to look completely different than it does today, and that means a huge risk to the diversity of the planet,” said Jonathan Overpeck, dean of the School for Environment and Sustainability at the University of Michigan. Overpeck developed the study along with Jackson.

Such significant changes to ecosystems would threaten biodiversity and harm ecosystems services — like the ability of forests to sequester carbon from the atmosphere, Ivory said.

“We owe billions in our economy to services vegetation provides for us, from cleaning our water to stopping erosion because of root networks,” she said. “They are very valuable to us in a practical way that we sometimes take for granted.”

Ivory, a doctoral student at the University of Arizona when the five-year study began, was tasked with analyzing fossil records from tropical Africa.

“To me the tropics are very important,” she said. “The tropics are a very at-risk area because of a lack of infrastructure. People have a tendency to live off the land, and these things become more important to them.”

Funding for the study came from the National Science Foundation, the U.S. Department of the Interior Southwest Climate Adaptation Science Center, the Russian Academy of Sciences and the Russian Foundation for Fundamental Research.

Last Updated September 05, 2018