A recent study revealed trees take between two and four years to recover from extreme drought and help remove planet-warming carbon dioxide from the atmosphere.
In the past, scientists assumed trees and other plant life could quickly bounce back from the damage done by droughts, but this new research suggests those assumptions are too optimistic, Princeton University reported. The idea that trees take longer to recover from these conditions suggests they are not capable of storing as much carbon dioxide as past climate models have predicted.
"This really matters because future droughts are expected to increase in frequency and severity due to climate change," said lead author William Anderegg, a visiting associate research scholar in the Princeton Environmental Institute. "Some forests could be in a race to recover before the next drought strikes. If forests are not as good at taking up carbon dioxide, this means climate change could speed up."
To make their findings, the researchers examined the recovery of tree-stem growth after severe droughts at over 1,300 forest sites across the globe since 1948. The findings showed some forest in California and the Mediterranean had higher than expected rates of growth following a drought, but the majority of forests looked at in the study took longer than predicted to return to normal growth rates. For these forests, growth was about 9 percent slower than expected during the first year of drought recovery, and 5 percent slower in the second year. The effects of droughts were most dramatic in dry ecosystems and among pine trees.
The researchers are unsure of exactly how these droughts cause long-lasting harm to trees, but suggest it could have something to do with factors like: loss of foilage and carbohydrate reserves that later hinder growth; pests and diseases that build up in drought conditions; and lasting damage to the trees' vascular tissues caused by lack of water.
The scientists estimated the delayed drought recovery could reduce carbon-storage capacity in semi-arid ecosystems alone by about 1.6 metric gigatons over a century, a phenomenon that is not factored into current climate models.
"In most of our current models of ecosystems and climate, drought effects on forests switch on and off like a light," Anderegg said. "When drought conditions go away, the models assume a forest's recovery is complete and close to immediate. That's not how the real world works."
The findings were published in a recent edition of the journal Science.