Source: Fortune
Summary
A study published in Science reveals that forests during the Paleocene-Eocene Thermal Maximum (PETM) 56 million years ago lost 60% of their canopy due to rising temperatures and drought. Researchers used fossilized leaf cuticles to measure canopy density and found that forests took over 100,000 years to recover. The study suggests that while forests can rebound, the process is far slower than human timescales. The findings highlight the risks of current climate change, which is occurring much faster than past warming events.
Our Reading
The numbers tell one story.
Forests lost 60% of their canopy during the PETM.
Recovery took over 100,000 years.
Current warming is faster than past events.
Forests may reach thresholds that take millennia to recover.
Author: Evan Null
Reading the Forest from Fossil Leaves
Scientists use fossilized leaf cuticles to determine ancient forest canopy density. By analyzing cell shapes, they can estimate how much sunlight reached the forest floor. This method was tested on modern forests to calibrate the findings. The study shows that canopy density directly affects ecosystem function, including temperature and water retention.
When Forests Reach Their Limits
The PETM began with dense forests, but rising temperatures and drought caused rapid canopy thinning. Trees died, and the forest remained in a weakened state for over 100,000 years. The loss of canopy altered water and sediment movement, changing the landscape. This shows how forests and their environments are deeply interconnected.
Lessons for Today
Higher CO2 levels can initially boost plant growth, but only if temperatures and water availability stay within limits. Beyond those thresholds, heat, drought, and other stressors can overwhelm any benefits. Many forests today are already showing signs of decline due to rising temperatures and deforestation.
Forests Recovered, But It Took Over 100,000 Years
As the climate cooled, weathering processes removed carbon from the air, allowing forests to recover. Over time, canopies became denser than before. This suggests that forests are resilient but require long periods to rebound. However, current warming is happening too fast for such recovery to occur within human lifetimes.
Human-Caused Warming Is Unfolding Faster
Today’s carbon emissions are 10 times faster than during the PETM. This means forests may not have enough time to recover before reaching irreversible thresholds. The fossil record shows that forests can rebound, but only if humanity avoids pushing them beyond limits that take tens of thousands of years to recover from.
