Corn is one of the planet鈥檚 most important crops. It not only provides sweet kernels to flavor many dishes, but it鈥檚 also used in oils, as a sweetener syrup, and as a feed crop for livestock. Corn has been bred to maximize its yield on farms around the world.

But what will happen under climate change? Research led by the 天美影视传媒 combined climate projections with plant models to determine what combination of traits might be best adapted to future climates. The study used projections of weather and climate across the U.S. in 2050 and 2100 with a model that simulates corn鈥檚 growth to find the mix of traits that will produce the highest, most reliable yield under future conditions across the country.

The open-access was published in April in Environmental Research Food Systems. UW News asked senior author , a UW professor of atmospheric sciences and of biology, about the study and its findings.

Our future climate will be warmer, have drier air and have a higher concentration of atmospheric carbon dioxide. Is there a broad understanding of how all these changes together will affect plant growth?

Abigail Swann: For corn, a by our group found that higher temperatures and drier air have about the same size impact, with both leading to less corn yield, while more CO2 available for photosynthesis increased yield. The increase in yield from CO2 wasn鈥檛 enough to counteract the decrease from the other two changes, however, so corn yields went down overall.

Overall, hotter temperatures like those we expect in the future will make crops grow faster but be less productive. Of course, shifts in precipitation also affect their growth in different locations, though that has less impact overall, and particularly for agricultural crops that rely on irrigation.

Typically, many people think of climate change as something that will shift where certain crops can grow. Your study says the crop varieties we plant today aren鈥檛 ideal for any location in the future. Why is that?

AS: As climate continues to warm, we can adapt by moving existing crop varieties closer to the poles, where the air is cooler. But shifting existing varieties to new places isn鈥檛 enough to make up for the loss in crop yield that we expect in a hotter climate because the impacts of higher temperatures are so detrimental.

Our study looked at 100 possible corn varieties, and we find that those that will be most successful in the future are not varieties that are successful now 鈥� we need new crops for the new climate.

Can you describe the corn that will perform best in future climates, according to your study, compared to the varieties that do best today?

AS: Corn plants first grow leaves, and then switch to growing grain. We find that today, corn plants must make a tradeoff between growing a lot of leaves and still having enough time left in the growing season to grow a lot of grain. This means the most successful varieties today don鈥檛 grow very many leaves, so they can switch to growing grain early in the season.

Growing more leaves could potentially allow corn to increase how much the plant can photosynthesize, which would also increase how much grain it could grow, but today this comes at a cost of a shorter growing season.

In the future, it will be warmer overall, and corn may be planted earlier and harvested later in the season. This longer growing season relieves corn from this tradeoff and allows it to both grow more leaves and still have plenty of time to grow grain (there is an additional boost from faster growth under hotter temperatures).

So basically, in this sense the corn plants of the future can have their cake and eat it too. The varieties we simulated that took advantage of the ability to grow more leaves yielded more under future climate than the varieties with less leaf growth. This isn鈥檛 good news for corn, though. While corn will be able to grow more leaves and still have plenty of time to grow grain, the adverse impacts of hot temperatures and drier air will decrease the overall yields. Growing more leaves and having a longer growing season help buffer these adverse impacts, but overall, all of the corn plants we simulated did worse under future climate conditions.

Is there any way to verify these results on real plants before these climate conditions become reality?

AS: While the plants that we found would do best under future climate conditions don鈥檛 exist right now, plants with many of these characteristics can be bred quickly, using genetic techniques like CRISPR. Then they can be grown under controlled climate conditions to see if our findings hold up for real plants. That part of the process is surprisingly fast, so we can create and trial new plant varieties before they are needed.

Why is it helpful to use computer models, rather than just selective breeding as has been done in the past?

AS: Breeding new crop varieties is a very slow process. It can take decades to go from initial breeding to testing and adoption by farmers. The process starts with selecting among the existing crop varieties for desirable characteristics, including high yield. Then these new potential varieties are combined, grown and tested in multiple environments and with different management. Finally, the final varieties are released commercially and then can be adopted by farmers.

With simulations we can test a much wider range of possible combinations of characteristics that could work well for a new variety, and use that knowledge to guide the first stages of breeding. This can speed up the breeding process and accelerate our ability to adapt to a changing climate. It also gives us information about what characteristics we might try to create that are farther from our existing varieties.

How does your study fit into the broader field of climate adaptation?

AS: We will need to adapt agriculture in many ways to support a growing population with a growing demand for food, combined with the loss in crop yield that we expect as climate gets hotter. Our study helps to jumpstart the process of breeding climate-resilient crops by envisioning what those crops should look like. Our study also provides a blueprint for how to do this analysis for other crop types, besides corn.

Although we focus on corn for this study, we see our work as a demonstration of an approach that can be applied to any crop, and so more of a blueprint of how we can incorporate the expected impacts of climate change into the breeding of new crop varieties.

In the U.S. we heard recently about population leveling off due to lower birth rates and about shifts to less resource-intensive, plant-based diets. Can you explain why, worldwide, we still expect an increase in demand for corn?

AS: Worldwide population is still growing, and in addition to growing in total number, the global population is growing more affluent and increasing its consumption of meat. In the U.S. our diet is already very meat-intensive, and so shifts towards less resource-intensive and plant-based diets make a lot of sense from a health and environmental standpoint.

But meat consumption in many parts of the world is currently very low. As these populations increase their wealth, we expect that in some cases meat consumption will grow. This increase in wealth is a good thing for the well-being of those people. By adapting agriculture, we hope to buffer the losses in yield expected from hotter temperatures and help provide enough food for everyone.

What鈥檚 next for this research?

AS: We would like to work with breeders to create some of the corn varieties our study proposed, and do similar studies on other major global food crops. We are currently seeking additional funding sources to conduct these next steps.

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Lead author did the work as part of her UW doctoral degree in biology. Co-authors are , UW professor of environmental and forest sciences; at the U.S. Department of Agriculture; and at Colorado State University. The research was funded by the National Science Foundation, the U.S. Department of Agriculture and the UW鈥檚 Royalty Research Fund.

For more information, contact Swann at aswann@uw.edu.

How plants will fare as carbon dioxide levels continue to rise is a tricky problem and, researchers say, especially vexing in the tropics. Some aspects of plants鈥� survival may get easier, some parts will get harder, and there will be species winners and losers. The resulting shifts in vegetation will help determine the future direction of climate change.

To explore the question, a study led by the 天美影视传媒 looked at how tropical forests, which absorb large amounts of carbon dioxide, might adjust as CO2 continues to climb. Their results show that multiple changes occurring in plants鈥� leaves and competition between species could preserve these ecosystems鈥� ability to absorb carbon dioxide from the atmosphere. The resulting was published Jan. 16 in the journal Global Biogeochemical Cycles.

鈥淥ur findings suggest that plants with some types of responses, like making their leaves thicker, will ultimately grow better in tropical forests than their competitors,鈥� said senior author , a UW associate professor of atmospheric sciences and of biology. 鈥淚f these better-growing plants become more common in the forest, the total rates of water and carbon exchange could stay closer to what they are now.鈥�

A previous study by Swann鈥檚 group showed that tropical plants leaves鈥� becoming thicker as CO2 climbs would worsen climate change, because thicker leaves might also be smaller. Plants would then capture less sunlight for photosynthesis, absorb less carbon dioxide from the air and emit less water vapor, all exacerbating the heating due to climate change.

The new work expands the scope of this question to include competition between plant species, and the ratio of carbon and nitrogen in their leaves. Higher carbon dioxide in the atmosphere makes it a bit easier for plants to photosynthesize. But if nitrogen can鈥檛 keep up, the plant becomes less efficient at producing energy.

鈥淎lthough it is observed to happen, the verdict is still out on why exactly plants grow thicker leaves under high CO2,鈥� Swann said. The new modeling study suggests an explanation: 鈥淭hicker leaves can concentrate the nitrogen so that photosynthesis rates per area of leaf are high.鈥�

The authors ran simulations for , a forested tropical island in Panama where the model had been well tested against conditions on the ground. The simulations included one or two species of broad-leaf evergreen tropical trees, such as wild cashew and Ecuador laurel. The trees were programmed to have various responses to the higher carbon dioxide and could compete with one another for space.

Trees that were programmed to have more carbon relative to nitrogen in their leaves became less efficient at photosynthesis, which helps them to grow, and emitted less water vapor, which helps trees stay cool. But tree species whose leaves also thickened were better at absorbing carbon and producing water vapor, helping them to grow tall and stay cool, and could also outcompete their neighbors.

鈥淥ur work suggests that by shifting which plants are growing in the forest there may be less dire consequences of higher CO2 than other studies have suggested,鈥� Swann said. 鈥淭here is a lot we still don鈥檛 know about how plants are responding to climate change 鈥� this work really sets up some best guesses about which plants will grow best in future tropical forests that we can test with more observations.鈥�

This research was funded by the National Science Foundation and the U.S. Department of Energy. Lead author was UW graduate student Marlies Kovenock; co-authors are Charles Koven and Ryan Knox at Lawrence Berkeley National Laboratory; and Rosie Fisher at the National Center for Atmospheric Research.

For more information, contact Swann at aswann@uw.edu.

The 天美影视传媒’s is honored by Science News on its list of 10 promising early- and mid-career scientists. Read about all the who were announced Oct. 2.

Each scientist included on the list is age 40 or younger and was selected by Science News staff for their potential to shape the science of the future. Each was originally nominated for consideration by a Nobel laureate, recently elected member of the National Academy of Sciences or, for the 铿乺st time, a scientist previously named to the SN 10 list.

Swann, an associate professor of atmospheric sciences and of biology, studies how plants influence the climate at global and geologic timescales, and how larger climate shifts influence vegetation. One recent study looked at how large-scale tree loss can affect climate across North America.

“I am, of course, honored to have been chosen,” Swann said. “In particular it is humbling to be chosen for a broad award such as this one, which is not specific to a single scientific discipline.”

Swann was also named the inaugural winner of the $1,000 Jon C. Graff, Ph.D. Prize for Excellence in Science Communications. She was selected “for her mastery of conveying complex ideas with clarity.” The selection committee also considered “the scientists’ use of media, acknowledgement of scientific research as iterative and ability to communicate the long-term value of their work.”

The October issue of the magazine includes profiles of the 10 winners. The cover shows a cartoon version of each of the honorees doing their research.

In her research, Swann “builds whole planets, some of them very odd and all of them simulations inside a computer,” reads the . “She has turned her garage creativity to developing computer models for testing ideas about Earth鈥檚 atmosphere.”

鈥淲e so often cover the results of scientists鈥� work, but not how they did that work, or what motivates them through the long, often frustrating research process,” said Nancy Shute, editor in chief of Science News magazine. “We鈥檙e thrilled to be able to recognize the work of these outstanding scientists, and to give people a glimpse into their remarkable lives.鈥�

, an assistant professor in the Paul G. Allen School of Computer Science & Engineering, was named to the list in 2016.

Plant scientists have observed that when levels of carbon dioxide in the atmosphere rise, most plants do something unusual: They thicken their leaves.

And since human activity is raising atmospheric carbon dioxide levels, thick-leafed plants appear to be in our future.

But the consequences of this physiological response go far beyond heftier leaves on many plants. Two 天美影视传媒 scientists have discovered that plants with thicker leaves may exacerbate the effects of climate change because they would be less efficient in sequestering atmospheric carbon, a fact that climate change models to date have not taken into account.

In a published online Oct. 1聽by the journal , the researchers report that, when they incorporated this information into global climate models under the high atmospheric carbon dioxide levels expected later this century, the global “” contributed by plants was less productive 鈥� leaving about 5.8 extra petagrams, or 6.39 billion tons, of carbon in the atmosphere per year. Those levels are similar to the amount of carbon released into the atmosphere each year due to human-generated fossil fuel emissions 鈥� 8 petagrams, or 8.8 billion tons.

“Plants are flexible and respond to different environmental conditions,” said senior author , a UW assistant professor of atmospheric sciences and biology. “But until now, no one had tried to quantify how this type of response to climate change will alter the impact that plants have on our planet.”

In addition to a weakening plant carbon sink, the simulations run by Swann and , a UW doctoral student in biology, indicated that global temperatures could rise an extra 0.3 to 1.4 degrees Celsius beyond what has already been projected to occur by scientists studying climate change.

“If this single trait 鈥� leaf thickness 鈥� in high carbon dioxide levels has such a significant impact on the course of future climate change, we believe that global climate models should take other aspects of plant physiology and plant behavior into account when trying to forecast what the climate will look like later this century,” said Kovenock, who is lead author on the paper.

Scientists don’t know why plants thicken their leaves when carbon dioxide levels rise in the atmosphere. But the response has been documented across many different types of plant species, such as woody trees; staple crops like wheat, rice and potatoes; and other plants that undergo , the form of photosynthesis that accounts for about 95 percent of photosynthetic activity on Earth.

Leaves can thicken by as much as a third, which changes the ratio of surface area to mass in the leaf and alters plant activities like photosynthesis, gas exchange, evaporative cooling and sugar storage. Plants are crucial modulators of their environment 鈥� without them, Earth’s atmosphere wouldn鈥檛 contain the oxygen that we breathe 鈥� and Kovenock and Swann believed that this critical and predictable leaf-thickening response was an ideal starting point to try to understand how widespread changes to plant physiology will affect Earth’s climate.

“Plant biologists have gathered large amounts of data about the leaf-thickening response to high carbon dioxide levels, including atmospheric carbon dioxide levels that we will see later this century,” said Kovenock. “We decided to incorporate the known physiological effects of leaf thickening into climate models to find out what effect, if any, this would have on a global scale.”

A by researchers in Europe and Australia collected and catalogued data from years of experiments on how plant leaves change in response to different environmental conditions. Kovenock and Swann incorporated the collated data on carbon dioxide responses into Earth-system models that are widely used in modeling the effect of diverse factors on global climate patterns.

The concentration of carbon dioxide in the atmosphere today hovers around 410 parts per million. Within a century, it may rise as high as 900 ppm. The carbon dioxide level that Kovenock and Swann simulated with thickened leaves was just 710 ppm. They also discovered the effects were worse in specific global regions. Parts of Eurasia and the Amazon basin, for example, showed a higher minimum increase in temperature. In these regions, thicker leaves may hamper evaporative cooling by plants or cloud formation, said Kovenock.

Swann and Kovenock hope that this study shows that it is necessary to consider plant responses to climate change in projections of future climate. There are many other changes in plant physiology and behavior under climate change that researchers could model next.

“We now know that even seemingly small alterations in plants such as this can have a global impact on climate, but we need more data on plant responses to simulate how plants will change with high accuracy,” said Swann. “People are not the only organisms that can influence climate.”

The research was funded by the National Science Foundation and the UW.

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For more information, contact Swann at +1 206-616-0486 or aswann@uw.edu.

DOI: 10.1029/2018GB005883

Grant numbers: AGS-1321745, AGS-1553715.

A 天美影视传媒-led published May 16 in shows that forest die-offs in specific regions of the United States can influence plant growth in other parts of the country. The largest impacts seen were from losing forest cover in California, a region that is currently .

“These smaller areas of forest can have continental-scale impacts, and we really need to be considering this when we’re thinking about ecological changes,” said first author , a UW assistant professor of atmospheric sciences and of biology.

Such far-off effects are accepted in the atmospheric sciences community, Swann said, but the idea is only beginning to be accepted by ecologists.

A 2016 study from the same UW group looked at what removing trees from , would mean for worldwide plant growth. This study took the same approach on a regional scale.

The project divided the mainland U.S. into the 18 regions used in the . Researchers then ran a climate model to look at what removing the existing forest cover from the 13 most-heavily-treed regions would mean for growing conditions across the country.

Of all the regions, the Pacific Southwest region, which covers most of California, has the smallest total area of tree cover. But removing those trees had the biggest influence on growing conditions nationally, by reducing vegetation in the Eastern U.S.

The precise mechanisms would require further study, Swann said, but in this case it seemed to make Eastern summers slightly warmer, which was harmful to plant growth.

“Forest loss is disrupting or changing the flow patterns in the atmosphere that is leading to a slightly different summertime climate in the eastern part of the country,” Swann said. “It’s very analogous to El Ni帽o or ‘the blob,’ something that’s occurring that causes the atmosphere to move around, which causes these warmer or cooler conditions, or wetter and drier conditions, somewhere else.”

Compared to an El Ni帽o cycle, Swann said, “the changes we made here were smaller and over land, but it’s very analogous.”

The results also showed other Western regions, such as the Northern Rockies and the Great Basin region, as having negative effects on plant growth in the eastern half of the country. These regions are currently losing tree cover: California forests have lost more than 130 million trees since 2010, largely due to the combined effects of drought, warm temperatures, insects and disease.

“In some case trees may be killed by drought, but in many cases they’re being weakened by the drought and then being finished off by the beetles or other stresses,” Swann said.

The study suggests that current forest loss in Western regions is big enough to trigger changes in plant growth, though it might not be possible to detect these small changes over large areas of the country.

“There’s some pretty extensive, widespread forest loss going on,” Swann said. “The changes we made in the model are bigger, but they’re starting to converge with things that we’re actually seeing.

“These results show that we need to start thinking about how altering vegetation in one place can affect plants elsewhere, especially in the context of climate change.”

The research was funded by the National Science Foundation. Other co-authors are Marysa Lagu褢, a UW doctoral student; Elizabeth Garcia, a former UW postdoctoral fellow now at Seattle Public Utilities; Jason Field, David Breshears, David Moore, Darin Law and Scott Saleska at the University of Arizona; Scott Stark and David Minor at Michigan State University; and Juan Villegas at the University of Antioquia in Colombia.

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For more information, contact Swann at aswann@uw.edu or 206-616-0486.

NSF grants: EF-1550641, EF-1550756, EF-1550686

Major forest die-offs due to drought, heat and beetle infestations or deforestation could have consequences far beyond the local landscape.

Wiping out an entire forest can have significant effects on global climate patterns and alter vegetation on the other side of the world, according to a led by the 天美影视传媒 and published Nov. 16 in PLOS ONE.

“When trees die in one place, it can be good or bad for plants elsewhere, because it causes changes in one place that can ricochet to shift climate in another place,” said lead author , a UW postdoctoral researcher in atmospheric sciences. “The atmosphere provides the connection.”

Just as conditions in the tropical Pacific Ocean can have distant effects through what we now understand as El Ni帽o, the loss of a forest could generate a signal heard around the world 鈥� including by other plants.

Forest loss is known to have a nearby cooling effect, because without trees the Earth’s surface is more reflective and absorbs less sunlight, and loss of vegetation also makes air drier. These local effects of deforestation are well known. But the new study shows major forest losses can alter global climate by shifting the path of large-scale atmospheric waves or altering precipitation paths. Less forest cover can also change how much sunlight is absorbed in the Northern versus the Southern hemispheres, which can shift tropical rain bands and other climate features.

“People have thought about how forest loss matters for an ecosystem, and maybe for local temperatures, but they haven’t thought about how that interacts with the global climate,” said co-author , a UW assistant professor of atmospheric sciences and of biology. “We are only starting to think about these larger-scale implications.”

The new study focused on two areas that are now losing trees: western North America, which is suffering from drought, heat and beetle infestations that span from the southwestern U.S. to Alaska, and the Amazon rainforest, which has been subject to decades of intense human development. The researchers ran a climate model with a drastic forest-loss scenario to investigate the most extreme potential climate effects.

Results show that removing trees in western North America causes cooling in Siberia, which slows forest growth there. Tree loss in the western U.S. also makes air drier in the southeastern U.S., which harms forests in places like the Carolinas. But forests in South America actually benefit, because it becomes cooler and thus wetter south of the equator.

In the second test case, removing most of the Amazon rainforest also caused Siberia to become colder and more barren, but it had a slight positive impact on southeastern U.S. vegetation. Losing Amazon forest had a significant positive impact on the neighboring forests in eastern South America, mostly by increasing the precipitation there during the Southern Hemisphere summer.

The study shows that when it comes to forests, one plus one does not always equal two. Removing both forests had different impacts than the combined effects of removing the two separately, since the effects can either reinforce one another or cancel each other out.

“I think it’s really interesting that these effects happen through different mechanisms depending on where you look,” Swann said.

The model’s parameters for forest changes are still preliminary, so the exact mapping of cause and effect at each location is not set in stone. The researchers are conducting field studies to better characterize the temperature and humidity changes from altering different forest types. They also hope to pinpoint which locations are most sensitive to triggering such shifts, or to being affected by the changes.

“The broader idea is that we must understand and include the effects of forest loss when modeling global climate and trying to predict how climate will change in the future,” said Swann.

Swann’s previous research looked at how a hypothetical in the Northern Hemisphere to slow global warming could have the unintended effect of changing tropical rainfall. More recent has shown how European deforestation over the past thousands of years may have reduced rainfall over modern-day Africa.

“This study shows that local events like forest die-offs in one part of the globe influence climate and ecology in other, often distant locations,” said Tim Kratz, program director at the funding agency, the National Science Foundation. “Unraveling these far-reaching effects is critical to understanding how nature works at continental to global scales.”

The study was also funded by the U.S. Department of Energy. Co-authors are Juan Villegas at the University of Antioquia in Colombia; David Breshears, Darin Law and Scott Saleska at the University of Arizona; and Scott Stark at Michigan State University.

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For more information, contact Garcia at esgarcia@uw.edu and Swann at 206-616-0486 or aswann@uw.edu.

A study led by the 天美影视传媒 shows that popular long-term drought estimates have a major flaw: They ignore the fact that plants will be less thirsty as carbon dioxide rises. The shows that shifts in how plants use water could roughly halve the extent of climate change-induced droughts.

“Plants matter,” said , a UW assistant professor of atmospheric sciences and biology. “A number of studies assume that plant water needs are staying constant, when what we know about plants growing in lots of carbon dioxide suggests the opposite.”

Swann is lead author of the study published the week of Aug. 29 in the .

Recent studies have estimated that more than 70 percent of our planet will experience more drought as carbon dioxide levels quadruple from pre-industrial levels over about the next 100 years. But when Swann and her co-authors account for changes in plants’ water needs, this falls to 37 percent, with bigger differences concentrated in certain regions.

“It’s a significant effect,” Swann said.

The reason is that when Earth’s atmosphere holds more carbon dioxide, plants actually benefit from having more of the molecules they need to build their carbon-rich bodies. Plants take in carbon dioxide through tiny openings, called stomata, that cover their leaves. But as they draw in carbon dioxide, moisture escapes. When carbon dioxide is more plentiful, the stomata don’t need to be open for as long, and so the plants lose less water.聽 The plants thus draw less water from the soil through their roots.

Global climate models already account for these changes in plant growth. But many estimates of future drought use today’s standard indices, like the , which only consider atmospheric variables such as future temperature, humidity and precipitation.

“I had a very strong suspicion that you would get a different answer if you considered how the plants were responding,” Swann said.

The study compares today’s drought indices with ones that take into account changes in plant water use. It confirms that reduced precipitation will increase droughts across southern North America, southern Europe and northeastern South America. But the results show that in Central Africa and temperate Asia 鈥� including China, the Middle East, East Asia and most of Russia 鈥� water conservation by plants will largely counteract the parching due to climate change.

Planners will need accurate long-term drought predictions to design future water supplies, anticipate ecosystem stresses, project wildfire risks and decide where to locate agricultural fields.

“In some sense there’s an easy solution to this problem, which is we just have to create new metrics that take into account what the plants are doing,” Swann said. “We already have the information to do that; we just have to be more careful about ensuring that we’re considering the role of the plants.”

Is this good news for climate change? Although the drying may be less extreme than in some current estimates, droughts will certainly increase, researchers said, and other aspects of climate change could have severe effects on vegetation.

“There’s a lot we don’t know, especially about hot droughts,” Swann said. The same drought at a higher temperature might have more severe impacts, she noted, or might make plants more stressed and susceptible to pests.

“Even if droughts are not extremely more prevalent or frequent, they may be more deadly when they do happen,” she said.

The co-authors are Forrest Hoffman at Oak Ridge National Laboratory, Charles Koven at Lawrence Berkeley National Laboratory and James Randerson at the University of California, Irvine. The research was funded by the National Science Foundation and the U.S. Department of Energy.

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For more information, contact Swann at 206-616-0486 or aswann@uw.edu.

Grant numbers: NSF AGS-1321745, EF-1340649