The lungs of the Earth

Study eyes forest ecosystem tipping points that can drive climate change

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The tipping point of forest ecosystems can, in turn, drive climate change by altering the global carbon cycle. @bberwyn photo.

Staff Report

Tropical forests are the Earth’s lungs, helping drive global respiration and transpiration – key steps in the climate cycle. That’s been the case for millennia, according to a University of California, Davis-led study that tracked atmospheric CO2 levels from 330 to 260 million years ago by examining fossilized leaves and soil-formed minerals.

The last time Earth experienced both ice sheets and carbon dioxide levels within the range predicted for this century was a period of major sea level rise, melting ice sheets and upheaval of tropical forests, where dramatically dynamic forest regeneration cycles were a big factor in driving the climate between warmer and cooler phases.

The ancient record shows more accurately shows swings in CO2 cycles are similar to some projections for the 21st century. The study is published in  the journal Nature Geoscience.

“We show that climate change not only impacts plants but that plants’ responses to climate can in turn impact climate change itself, making for amplified and in many cases unpredictable outcomes,” lead author Isabel Montañez said in a statement releasing the study. The fossil and soil record suggests that repeated shifts in tropical forests in response to climate change could shift CO2 levels in the atmosphere by as much as 100 to 300 parts per million.

The findings suggest that major climate models are underestimating the forest-atmosphere CO2 flux, said  Montañez, a Chancellor’s Leadership Professor with UC Davis Department of Earth and Planetary Science.

Co-author William DiMichele, a paleobiologist with the Smithsonian Institution, said the study suggests forest ecosystem tipping points toward “rapid and irreversible biological change.”Co-leading author Jenny McElwain, professor of paleobiology at University College in Dublin, Ireland, said the study indicates that shifts in atmospheric carbon dioxide impacted plant groups differently.

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