Floods may be nearly as important as droughts for future carbon accounting

The plants play an important role in reducing climate change. They absorb about one third of carbon dioxide emitted by human activities, and store it in soil to prevent it from becoming a heat-trapping agent gas. This ecosystem service is affected by extreme weather, but floods are less studied than droughts when it comes to understanding the carbon uptake. However, new research suggests that they may be just as important.Stanford University researchers discovered that photosynthesis, the process whereby plants absorb carbon dioxide from the atmosphere, was affected by heavy rainfall and floods nearly as much as droughts. This paper was published in Environmental Research Letters, June 29. It highlights the importance to include plant responses to heavy rain in modeling vegetation dynamics and soil carbon stock in a warming world.Alexandra Konings, a senior study author and assistant professor of Earth system sciences at Stanford's School of Earth, Energy & Environmental Sciences, said that "these wet extremes" have been largely ignored in this field. "Specific areas might be more important than previously thought for flood impacts."According to researchers, more photosynthesis can result in higher soil carbon storage over time if it is combined with other factors. They used publicly available satellite data to determine the amount of photosynthesis in plants.Co-authors of the carbon accounting paper were shocked to discover that flooding affected photosynthesis in half of the areas. Although photosynthesis is affected by drought, it can also be affected by extreme weather conditions that either accelerate or decrease the process.Caroline Famiglietti (a PhD student in Earth systems science), is the lead author of the study. She said, "I think that drought side" is something many people understand because they can see soils drying out.The researchers used statistical analysis to divide the globe into regions and specific periods of photosynthetic activity that wouldn't have been caused by other factors like temperature or changes in sunlight. The researchers then used long-term soil moisture data to identify which areas were more susceptible to extreme wet or dry events. They found that central Mexico, eastern Africa, and the northern latitudes are all worth further investigation.Famiglietti stated that "everything observed in this master data set reflects the behavior and climate system as a whole." "This paper found something unexpected, but it doesn't answer all of the questions we still have."Extreme weather will become more severe, prolonged, and intense in a warmer world. However, the mechanisms controlling drought responses within plants are better understood than those controlling extreme wet responses. Konings believes that these findings offer an opportunity to address "a large component of uncertainty in future climate changes and its links with ecosystem carbon storage."Famiglietti stated that "if we can better understand these process, we can improve modeling to better prepare for future,"###Konings is also a Stanford Woods Institute for the Environment center fellow and assistant professor of geophysics. Anna Michalak, co-author, is an associate with the Department of Earth System Science at the Carnegie Institution for Science.The National Oceanic and Atmospheric Administration (NOAA) supported the research.