Plants emit a faint 'glow' when flash droughts are imminent

Ever heard of plants glowing? No, it’s not a scene from a sci-fi movie. Plants have a hidden talent – they emit a faint, invisible light known as solar-induced fluorescence (SIF). It’s like a secret language, whispering tales of their health and activity. 

NASA scientists are eavesdropping from space, using satellites like the Orbiting Carbon Observatory-2 (OCO-2) to decode these luminous messages and predict flash droughts.

Flash droughts

Flash droughts, as their name suggests, strike with lightning speed. Unlike traditional droughts that develop over months, these stealthy adversaries can parch the land in mere weeks, leaving farmers and ecosystems scrambling. These sudden and intense droughts come without warning, rapidly drying out soil and vegetation.

Remember the devastating 2012 drought across the U.S.? That was a flash drought, causing widespread crop failure and resulting in a staggering $30 billion in agricultural losses. The rapid onset and severe impact of flash droughts make them particularly challenging to manage and predict.

Predicting these disasters has been a challenge, until now. Scientists have struggled to find reliable early warning signs for flash droughts, leaving farmers vulnerable to sudden and severe water shortages. However, recent advancements in technology and research have provided a breakthrough.

By monitoring plant fluorescence and soil moisture from space, researchers can now detect early signs of flash droughts, offering valuable lead time for mitigation efforts. This innovation marks a significant step forward in our ability to combat this unpredictable threat.

Plant glow linked to flash drought

In a recent study, NASA researchers uncovered a surprising pattern. Before a flash drought strikes, plants go through a sudden and intense growth spurt.

During this period, they absorb carbon dioxide at an accelerated rate, almost as if they are preparing for an impending shortage.

This frantic feeding frenzy results in a significant increase in their solar-induced fluorescence (SIF) signal, which creates an unusual glow detectable by satellites from space.

This unexpected growth surge, however, is a double-edged sword. While the rapid growth indicates healthy and thriving plants, it also has a hidden cost.

As plants vigorously absorb water to support their accelerated growth, they rapidly deplete the soil moisture.

This depletion leaves the soil dry and vulnerable. When extreme heat strikes, the already diminished moisture levels plummet further, setting the stage for a flash drought.

Significance of plant glow

The rapid depletion of soil moisture due to the plants‘ growth spurt acts as a precursor to the flash drought. The plants’ initial thriving phase, marked by the intense SIF signal, is followed by a sudden downturn as the drought takes hold.

This pattern of initial growth followed by rapid drying highlights the complex and interconnected nature of flash droughts, making early detection and prediction crucial for mitigating their impacts.

“Plant fluorescence shows promise as a reliable early warning indicator of flash drought with enough lead time to take action,” explains Nicholas Parazoo, NASA Earth Scientist.

This discovery is a game-changer. By monitoring the SIF signal, scientists can potentially predict flash droughts weeks or even months in advance, giving farmers and water managers a crucial head start in preparing for the dry spell.

Beyond SIF signal

The SIF signal is just one piece of the puzzle. To confirm their findings, the scientists turned to another NASA satellite, SMAP (Soil Moisture Active Passive). 

SMAP measures soil moisture from space, and its data perfectly matched the pattern revealed by the glowing plants. 

When the SIF signal was high, SMAP showed a corresponding decrease in soil moisture in the weeks leading up to a flash drought. This correlation held true across diverse landscapes, from forests to grasslands.

Carbon cycle and flash droughts

The study also shed light on how flash droughts impact the carbon cycle. Plants are natural carbon sinks, absorbing carbon dioxide from the atmosphere during photosynthesis. This process is crucial in reducing atmospheric carbon levels.

However, as drought stress sets in, plants’ ability to capture carbon diminishes. The stress from drought conditions hampers their photosynthetic activity, leading to a reduced intake of carbon dioxide.

The researchers anticipated a noticeable spike in atmospheric carbon dioxide levels during flash droughts due to the decreased carbon uptake by stressed plants. Surprisingly, the study revealed a different outcome.

They discovered a balance in the carbon cycle that they did not expect. The initial growth spurt of plants before the drought resulted in a higher than usual carbon uptake.

This increased absorption of carbon dioxide before the drought effectively compensated for the subsequent decline in carbon uptake during the drought stress period.

As a result, the overall carbon balance remained stable despite the occurrence of the flash drought. This finding highlights the complex interactions within the carbon cycle and suggests that plants’ response to pre-drought conditions plays a significant role in mitigating the potential increase in atmospheric carbon dioxide levels during flash droughts.

OCO-2’s legacy

The OCO-2 satellite, celebrating its 10th anniversary in space, has been instrumental in this research. Its three high-precision spectrometers can detect the faint glow of SIF and measure carbon dioxide levels with remarkable accuracy.

This wealth of data has allowed scientists to unravel the intricate connection between plants, water, and carbon, and to develop new tools for predicting and mitigating the impacts of flash droughts.

Lesser flash droughts using plants

The implications of this research are far-reaching. With early warning systems based on plant fluorescence and soil moisture data, farmers can make informed decisions about irrigation, crop selection, and planting schedules. This could significantly reduce crop losses and ensure food security in the face of a changing climate.

“While early warning can’t eliminate the impacts of flash droughts, farmers and ranchers with advanced operations can better use water for irrigation to reduce crop impacts, avoid planting crops that are likely to fail, or plant a different type of crop to achieve the most ideal yield if they have weeks to months of lead time,” notes Jordan Gerth, National Weather Service Scientist.

So, next time you gaze at a field of green, remember the secret glow hidden within those leaves. It’s not just a sign of life, but a beacon of hope, guiding us towards a future where we can outsmart even the most elusive droughts.

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