A plant’s ‘glow’ can predict drought weeks in advance: UConn

Our planet is heating up. Just look at summer 2022 for proof.

A cluster of wildfires scorched hundreds of parched acres in the normally lush forests of the Shawangunk Mountains in New York’s Hudson Valley in August. Fires were rare in this part of the country as drought baked the tri-state area for weeks.

Elsewhere in the United States, wildfires raged amid unprecedented heat waves in the Pacific Northwest and the Colorado River, a source of drinking water for 40 million people, continued to shrink. Overseas, countries like France, Spain and China have been ravaged by wildfires, while similar and persistent drought conditions in East Africa have pushed populations to the brink of survival.

Droughts and the disasters that follow often take communities by surprise – displacing people from their homes, destroying crops and leaving governments scrambling to find resources. But researchers at the University of Connecticut have stumbled upon a curious new way to predict flash droughts weeks before they start.

They use radiation from plants. As elementary school taught us, plants make chlorophyll – a green pigment in their leaves that absorbs energy from the sun and turns it into sugars, carbohydrates and starch. But that’s not all chlorophyll does.

“Plants that perform photosynthesis absorb solar radiation, and a small portion of it is re-emitted by plants as fluorescence,” said Guilang Wang, professor of environmental engineering at UConn.

In other words, the plants glow. This radiation is not harmful to humans, but plants produce enough of it in mass to be seen from space. “This glow can be captured by satellite,” Wang said.

In a new study from UConn’s Center for Environmental Sciences and Engineering, Wang and his colleagues monitored this electromagnetic radiation – known as solar-induced chlorophyll fluorescence (SIF) – over time using data of the European Space Agency’s GOME-2 satellite instrument.

They found that if SIF levels rose or fell more slowly than normal, flash drought was more likely to occur. Flash droughts are happening at a rapid rate, said Dennis Todey, director of the USDA Midwest Climate Hub, based in Ames, Iowa. “We’re talking about drought conditions developing on the order of weeks,” he said.

Wang and his team were able to predict flash droughts two weeks to two months before they started, compared to forecasts from the US Drought Monitor. This prediction tool could provide several weeks of lead time for preparation and recovery, they said. Their report was published last month in the Proceedings of the National Academy of Sciences.

“Indeed, we were surprised because we thought the plants were responding to the drought. Therefore, we expected to see a lagged response around the plants, instead of the plants leading the drought signal by as much,” Wang said.

Previous studies have measured SIF levels as a way to monitor arid conditions, as well as the impact of drought on plant health.

“The problem is that when the SIF is below normal, the plants are already very stressed,” Wang said. “And by then it’s too late to predict the drought.” His team, on the contrary, checks the progress of the trend over time.

Wang and his team used two flash droughts as case examples: the flash drought in the Northern Plains in 2017 and another in the Central Great Plains in the summer of 2012, which resulted in $30 billion in agricultural losses.

USDA’s Todey called the 2012 flash drought the worst in recent memory. “We had a fairly quick drought in May, into June, which affected much of the Great Plains and much of the Midwest,” he said. “We have seen widespread losses of corn and soybeans.”

In the United States, flash droughts are most common in the Midwest and Southeast regions, said Andrew Hoell, research meteorologist at the NOAA Physical Sciences Laboratory and co-lead of the NOAA Drought Task Force.

Agricultural losses and forest fires are too often the result of flash droughts, he said. “In this country, they tend to happen in the hot season, and because of that what we’re seeing is a reduction in agriculture,” Hoell said, along with crop shortages that drive prices up. . “So economically they can be very expensive,” he said.

Hoell agreed that SIF could serve as a useful method for predicting flash droughts in the future. “I think it’s another tool in our toolbox,” he said.

Scientists typically use hydrometeorological data such as soil temperature and moisture to predict drought. And the NOAA Climate Prediction Center’s drought outlook is the primary source for forecasting drought in the United States, Hoell said.

But Wang noted that weather data is not always available in some parts of the world where drought occurs often and with increasing intensity. Wang cites Africa and Southeast Asia as examples.

Sun-induced fluorescence, on the other hand, can be recorded around the world, Wang said. “Because it’s coming from the satellite, which can capture information on a global scale, it doesn’t really have the limitation (of) ground data,” she said.

Wang hopes the team’s research can help inform climate agencies and mitigate agricultural damage caused by flash droughts – which are expected to intensify in the coming years.

“Early warning won’t prevent drought, but it gives time for farmers to prepare better,” Wang said.