The California drought's impacts on agriculture, water systems and infrastructure are well known. Now new research demonstrates that there is a negative carbon impact too – and that this may continue for several years.
William Anderegg is an ecologist at Princeton University. He and his colleagues examined tree-ring data from more than 1,300 sites around the world. And by comparing the rings with known drought records, they found that trees don't simply kick back into gear as soon as rains return.
That drought 'hangover' causes tree growth to lag 5 to 10 percent below normal for several years following the dry spell.
Tree growth is, of course, what removes carbon dioxide (CO2), the air trees breath, from the atmosphere. If trees grow 5 to 10 percent more slowly, it means that they are using 5 to 10 percent less CO2, meaning a significant carbon sink is being lost, and more CO2 is being left in the atmosphere as a greenhouse gas. California, which has huge swaths of primary and secondary forest, is one of the most important carbon sinks in the United States, thus this will affect America's overall carbon emissions picture.
There is little, if anything, we can do to stop this now. The drought has already been going on for more than four years. California's trees will likely suffer for some time to come in order to recover from such a long period of limited rainfall and high stress.
What this does do, though, is demonstrate the continued importance of investing in, and maintaining, healthy and resilient ecosystems. Unfortunately, years of intensive water usage by farms and cities reduced the natural water flows into nature, which made many of our forests more vulnerable to drought – hence the already rampant wildfires across the state, which experts expect to get much worse before they get better.
So, what can we do to reduce the future carbon impacts of California forests? Simply, we can invest in forest preservation in other parts of the world. Deforestation is a major problem in countries like Indonesia, Brazil and Russia, where it is a top source of carbon emissions. The impacts of losing these vast carbon sinks is incredibly complex and has not been studied enough, but is thought to play a significant role in global climate.
Because carbon mixes uniformly in the atmosphere, reducing carbon elsewhere will mean less CO2 in our air here. Thus, we can mitigate, at least, one impact of the drought. This is the reason that carbon credits exist: They allow us to invest in preserving carbon stock elsewhere and get benefits globally.
In the long-term, this just shows that we need to think more holistically about climate, nature and our impact on it. Now, at least, we have a better understanding of the role that trees play in regulating carbon. Hopefully that will help us better value the regenerative nature of forests and plan more effectively for future droughts.
Image credit: Pixabay