How crops and forests are responding to changing rainfall patterns
Rainy days are becoming less frequent but more intense across much of the planet because of climate change. Even in years with similar rainfall totals, plants fare differently when rain falls in fewer, bigger bursts, a new study shows.
Scientists have found that how rain falls day to day throughout the year is nearly as important to the world’s vegetation as how much. Reporting Dec. 11 in Nature, the researchers showed that even in years with similar rainfall totals, plants fared differently when that water came in fewer, bigger bursts.
Overall, in years with less frequent but more concentrated rainfall, plants in drier environments like the U.S. Southwest were more likely to thrive. In humid ecosystems like the Central American rainforest, vegetation tended to fare worse, possibly because it was not adapted to the longer dry spells.
Scientists have previously estimated that almost half of the world’s vegetation is driven primarily by how much rain falls in a year. Less well understood is the role of day-to-day variability, said lead author Andrew Feldman, a hydrologist and ecosystem scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
Global warming is driving shifts in precipitation patterns that are producing stronger rainstorms – with longer dry spells in between – compared to a century ago. “That aspect of expected changes to future rainfall patterns is relatively well understood,” said study co-author Alexandra Konings, associate professor of Earth system science at the Stanford Doerr School of Sustainability. “So this new finding points to an area where further study might lead to significant improvements in our overall ability to predict future vegetation change.”
Consider how a houseplant might respond if you give it a pitcher of water each week – either portioned out every couple days, or dumped on the plant all at once, Feldman suggested. Scale that to the size of the Corn Belt or a rainforest and the answer could have implications for crop yields and ultimately how much carbon dioxide plants remove from the atmosphere.

Blooms in the desert
The team, including researchers from the U.S. Department of Agriculture and multiple universities, analyzed two decades of field and satellite observations, canvassing millions of square miles. Their study area encompassed diverse landscapes from Siberia in the north to the southern tip of Patagonia.
They found that plants across 42% of Earth’s vegetated land surface were sensitive to daily rainfall variability. Of those, a little over half fared better in years with fewer but more intense wet days. These include croplands as well as drier landscapes like grasslands and deserts, which more commonly showed increased growth. In contrast, broadleaf forests, which have trees such as oak, maple, and beech – and rainforests in lower and mid-latitudes tended to fare worse under those conditions. The effect was especially pronounced in Southeast Asian rainforests across the Pacific Islands.
On average, daily rainfall variability was nearly as important as annual rainfall totals in driving growth worldwide. That level of importance is several times higher than previous estimates; the scientists attribute the new finding to a longer data record.
Red light, green light
The new study relied primarily on a suite of NASA missions and datasets, including the Integrated Multi-satellitE Retrievals for GPM (IMERG) algorithm, which provides rain and snowfall rates for most of the planet every 30 minutes using a network of international satellites.
To gauge plant response day to day, the researchers calculated how green an area appeared in satellite imagery. “Greenness” is commonly used to estimate vegetation density and health. They also tracked a faint reddish light that plants emit when they feed. During photosynthesis, when a plant absorbs sunlight to convert carbon dioxide and water into food, its chlorophyll “leaks” unused photons. This faint light is called solar-induced fluorescence, and it’s a telltale sign of flourishing vegetation.
Invisible to the naked eye, plant fluorescence can be detected by instruments aboard satellites such as NASA’s Orbiting Carbon Observatory-2, or OCO-2. Launched in 2014, OCO-2 has observed the U.S. Midwest appearing to glow during the growing season.
As rising temperatures continue to alter weather patterns, Feldman said the findings highlight the vital role that plants play in moving carbon atoms around Earth – a process called the carbon cycle. Vegetation, including farmlands, forms a vast carbon sink, absorbing excess carbon dioxide from the atmosphere.
A finer understanding of how plants thrive or decline day to day, storm by storm, could help us better understand their role in that critical cycle, Feldman said.
This story was adapted from a press release originally published by NASA.
Additional co-authors are affiliated with Columbia University, Indiana University, University of Arizona, and NASA’s Jet Propulsion Laboratory.The research was supported by NASA, the Alfred P. Sloan Foundation, the U.S. National Science Foundation, and the Swiss National Science Foundation.
Explore More
-
Based on new analyses of satellite data, scientists have found that hydrologic conditions that increase flash drought risk occur more often than current models predict. The research also shows that incorporating how plants change soil structures can improve Earth system models.
-
In a 34-year global analysis, researchers found that photosynthesis – an important process for removing carbon dioxide from the atmosphere and storing it in soil – was controlled by extreme wet events nearly as often as droughts in certain locations.
-
New research suggests dry air combined with warmer temperatures may prompt bigger than expected changes in how water moves through plants. The adjustment may allow plants to survive with less water in future droughts, while downshifting how much carbon they absorb.