Questions About Forests As Carbon Sinks


We have featured articles about forests so many times for multiple reasons. Even when we hint that we do so just out of pure love, it is almost always about the value of forests to our future on the planet. As always, when a Yale e360 article can help illuminate further on a topic, here goes:

This map shows the height of forests worldwide. Taller forests typically store more carbon. NASA

Climate Change Will Limit How Much Carbon Forests Take Up, New Research Shows

Governments are increasingly looking to forests to draw down carbon pollution, but worsening droughts threaten to stunt tree growth, while larger wildfires and insect infestations risk decimating woodlands, two new studies show.

The first study, published in the journal Science, challenges thinking that rising carbon dioxide levels will spur forests to grow faster by fueling photosynthesis. A survey of tree ring data in the U.S. and Europe found no link between photosynthesis and growth. However, scientists found, trees were highly sensitive to drought, suggesting that more frequent and severe dry spells expected with climate change will slow forest growth, limiting how much carbon trees take up.

The second study, published in Ecology Letters, finds that rising emissions will lead not only to more intense dry spells, but also to more insects killing drought-afflicted trees, as is happening with bark beetles across the American West. More pernicious than either of these threats, however, is the risk of wildfires, which are expected to grow fourfold by the end of this century if temperatures rise by 3.6 degrees C (6.5 degrees F), the middle climate scenario explored in the study.

Scientists used satellite observations and data collected from tree plots across the U.S. to estimate the risk that wildfires, insects, and drought pose to forests in different emissions scenarios, as shown in the interactive map above. The results suggest that limiting emissions would have a sizable impact on how well forests survive this century and, consequently, how much carbon they absorb.

“Together these studies suggest that the benefits carbon dioxide has for growth won’t be nearly as large as people thought, and the risk of climate stress, particularly wildfire, drought, and insects, will be much larger than people anticipate,” William Anderegg, an ecologist at the University of Utah who was involved in both studies, told The Conversation. “This tells us it’s probably not a great idea to count on forests for a widespread carbon sink through the 21st century, particularly if societies don’t reduce their emissions.”…

Read the whole article here.

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