Massive carbon dioxide emissions will cause the Earth’s forests to wither and die rather than flourish, according to a new study published in the journal Science that challenges claims that fossil fuel pollution will green the planet. Researchers reconstructing forest responses from the Paleocene-Eocene Thermal Maximum 56 million years ago found that rapid global heating caused canopies to collapse and standing biomass to drop by about 60%.
Fossil Evidence and the PETM Precedent
To understand how modern ecosystems respond to rapid atmospheric changes, researchers analyzed fossilized leaf cells from the Paleocene-Eocene Thermal Maximum, known as the PETM. During this prehistoric event, enormous amounts of carbon entered the atmosphere over a 130,000-year period, driving global temperatures up by as much as 8 degrees Celsius (14 degrees Fahrenheit). According to Regan Dunn, a researcher at La Brea Tar Pits and the Natural History Museum of Los Angeles County who led the study, forests initially grew very dense before collapsing dramatically. “Around 60% of the biomass of the standing vegetation was gone; it was a huge loss,” Dunn said. Scientists used fossilized leaf cuticle fragments to measure canopy density over time, revealing that ancient trees retreated as the planet browned rather than greened under extreme heat.
Contasting Modern Emissions With Prehistoric Warming
While the PETM provides the closest historical comparison to current climate shifts, researchers emphasize that today’s carbon release is vastly faster and poses a severe threat. Trevor Keenan, a scientist at the University of California, Berkeley who was not involved in the research, noted that ancient carbon release occurred over thousands of years, whereas human-driven emissions are happening over decades. “Faster forcing gives ecosystems less room to adjust,” Keenan said, adding that modern forests face intense warming alongside fragmentation, logging, and altered fire regimes. According to grandgoldman.com reporting, the PETM temperature increase of up to 8 degrees Celsius unfolded over 130,000 years, while the modern industrial era has warmed the planet roughly 1.2 degrees Celsius so far in about 250 years.
Did you know?
While plants require carbon dioxide to build structures, excessive atmospheric CO2 traps more heat, causing trees to struggle with extreme temperatures, drought, and pest outbreaks. According to the study, the shift from greening to browning forests occurred around 2000 as heat stress overtook the physiological benefits of extra carbon.
Political Claims vs. Scientific Reality
The new findings directly counter assertions from political figures who argue that burning fossil fuels benefits the environment by feeding plant life. Doug Burgum, the interior secretary, claimed earlier this year that carbon dioxide was never a pollutant and that plants thrive with more CO2, while Chris Wright, Trump’s energy secretary, similarly claimed last year that a warmer planet with more carbon dioxide is better for growing plants. Experts have rejected these claims as false. The Science paper demonstrates that trees require much more than carbon dioxide to survive, and that extreme heat, drought, and lack of key nutrients trigger widespread tree mortality in Europe, North America, and the Amazon.
Frequently Asked Questions
Do carbon emissions green the planet?
What was the Paleocene-Eocene Thermal Maximum (PETM)?
The PETM was a period approximately 56 million years ago when massive carbon releases heated the Earth by up to 8 degrees Celsius over 130,000 years, serving as a historical analog for current climate change.
Why are modern forests more vulnerable than ancient ones?
Today’s carbon emissions are happening much faster than during prehistoric eras, leaving ecosystems less time to adjust. Furthermore, modern forests must contend with rapid warming alongside logging, habitat fragmentation, and severe wildfires.
To explore more environmental news, check out our latest coverage on global climate thresholds and forest conservation strategies, or subscribe to our weekly newsletter for updates.