Drought in the Western U.S. has plunged the largest reservoir in the country into alarming shortage conditions that have rippling impacts for the region. Lake Mead, formed by the construction of the Hoover Dam on the Colorado River, delivers water and hydroelectric power to 25 million residents in the Southwest. But its viability has been pushed to the brink by intensifying drought, exacerbated by climate change, triggering emergency measures to conserve water in the basin.
The region has been in a “megadrought” since 2000, but recently, Lake Mead’s water levels have been breaking ever lower lows, unearthing old shipwrecks and other long-forgotten debris and leaving a “bathtub ring” around the reservoir’s edges. The drought signals a larger trend of dwindling snowfall and longer summers brought on by the growing climate crisis.
Water usage on the Colorado River operates on a tier system. When water levels in a reservoir drop below a certain point, usage by neighboring states is restricted. Lake Mead hit Tier 1 in August 2021 after the elevation of the reservoir dipped below 1,075 feet, leading to a reduction in water supplies that largely impacted agricultural users across counties.
This was the first time a shortage condition has been implemented on Lake Mead. The Tier 2 decision was announced in August of 2022—stating that the water level would fall below 1,050 by the end of the year, triggering a more intense shortage.
This emergency declaration for Lake Mead is part of a plan to increase the water levels in Lake Powell— an upstream reservoir and the second largest in the United States behind Mead. Dealing with shortages in the Colorado River Basin has required officials to weigh the needs of one region over another. The Bureau of Reclamation has indicated that at present, keeping water levels up in Lake Powell supersedes the requirements of Lake Mead. The generators at Powell have a total capacity of 1,320 megawatts and the reservoir is considered a ‘bank account’ for the region to draw on in times of drought—which are anticipated to worsen with climate change.
According to the US Drought Monitor, extreme droughts were rare in the historical climate—a 5.5% likelihood. In 2022 however, nearly all of the watersheds in the Colorado River experienced extreme drought. In a world warmed by 2 degrees C, the likelihood of 12 or more months of extreme drought in the Colorado River Basin becomes as high as 40%.
But Lake Mead also serves a massive population in the lower basin, and filling demand for water even during shortages means some major cities have to turn to reservoirs on other river systems. Arizona, suffering some of the steepest cuts in their allotment of Colorado River water (21%) , will draw from the Salt and Verde rivers. Other strategies include pumping groundwater and implementing more aggressive conservation and re-use strategies, which have so-far helped to spare Las Vegas from the worst effects of the shortage.
The Southern Nevada Water Authority also began using its low lake level intake in 2022, which allows the state to draw water even when the elevation of the lake falls below “dead pool” status— the point at which downstream water releases are no longer possible. But this is only a temporary solution, as the water in the reservoir keeps falling.
The next significant threshold for Lake Mead would be a drop to Tier 3 (1,025 feet) which some experts say could come as soon as 2024. At 950 feet, the reservoir would be considered an “inactive pool”, meaning the dam’s generators can no longer run. Energy shortages could kick off a vicious cycle, requiring backfilling with fossil fuels that would exacerbate the climate crisis and warming-driven drought conditions.
Reversing the drought in the Colorado River Basin will ultimately depend on snowfall in the Rocky Mountains, which will ultimately depend on getting the climate crisis under control. Experts estimate there would have to be several consecutive heavy snow years in the mountains to make back the current deficits further downriver. 2023 is currently experiencing above average snowpack, but if temperatures keep rising, that will be a less likely annual occurrence. Water rights and resource usage will have to adapt rapidly to support residents as reservoir levels continue to drop, but pulling out of emergency scarcity measures for good will require curbing the greater impacts of global climate change.
As the planet warms, drought is an increasing threat in many regions. Research led by Woodwell Research Assistant Isabelle Runde, modeled the frequency of drought across the globe, analyzing drought changes in forest, food, and energy systems as temperatures surpass 2, 3, and 4 degrees Celsius.
Models show that unlike in a stable climate, unreliable water resources and increasing temperatures make drought more likely in many places. For every increase of 0.5 degrees C, an additional 619 million people could become exposed to extreme drought 1 in every 4 years. This is in addition to the 1.7 billion people (nearly a quarter of today’s global population) who are already exposed to these conditions in a world that has warmed by a little more than 1 degree C.
Tropical forests are one of the planet’s key natural climate solutions— able to prevent 1 degree of warming through both carbon sequestration and regional cooling effects. Deforestation, fragmentation and degradation from things like fire, and disease threaten to turn these forests from a vital sink to a source of emissions.
In recent years, the Amazon has been a net carbon source due to increased extreme drought and deforestation, leaving the Congo rainforest as the world’s last remaining stable tropical forest carbon sink.
As warming surpasses 2 degrees, the annual likelihood of drought in the Congo rainforest begins increasing faster than in the Amazon. Drought can make a forest more susceptible to further degradation, such as fire or disease, and reduces carbon sink capacity by stressing or killing trees and placing the ecosystem under stress.
Global crop production is highly concentrated in key breadbasket regions— nearly 72% of the world’s maize, wheat, rice, and soy are produced in just 5 countries. Extreme drought can reduce the productivity levels of these staple crops, among others, potentially triggering widespread food insecurity, hunger and economic disruption.
By 2 degrees of warming, the probability of drought in the breadbasket regions of both China and the United States will be greater than 50% — meaning an extreme drought roughly every other year.
Disruption will be much higher in countries where jobs in agriculture comprise a large segment of the economy. In Mexico, one of the world’s top 10 producers of maize, 12% of the workforce is in agriculture and at 1 degree, the country already has among the greatest areas of cropland exposed to drought. 90% probabilities—indicating near-annual drought—begin to emerge in some parts of the country at 2 degrees of warming.This kind of recurrent extreme drought will stress water resources for agriculture.
The Mediterranean also is a drought hotspot. Drought probability in Mediterranean croplands will increase rapidly between 2 and 3 degrees of warming, rising from just 10% to over 50% of cropland affected by drought in 3 out of 4 years.
Hydroelectricity supplies a sixth of global energy demand, and is a low-cost, low-emission alternative to fossil fuels. The overwhelming majority of new hydropower plants since 1990 have been constructed in fast-growing, developing nations.
High dependence on hydropower makes countries like Brazil and China vulnerable to energy disruption during periods of drought. Brazil draws nearly two thirds of its energy from hydroelectric resources. During a three year drought between 2012 and 2015 in Brazil, hydroelectric generation declined by 20% each year. If warming exceeds 3 degrees C, more than half of Brazil’s hydroelectric capacity will experience a likelihood of annual drought greater than 50%.
Extreme drought can also be counterproductive to reducing carbon emissions. During years of drought, expensive fossil fuel based energy is often brought in to fill demands. In addition, droughts often coincide with extreme heat events, when electricity demand peaks to run air conditioners. Beyond 3 degrees of warming, more than a third of the planet’s hydroelectric capacity will likely be exposed to extreme drought every other year.
Current international climate goals aim to limit warming to between 1.5 and 2 degrees C, but without urgent intervention, we are on track to push past that limit to at least 2.5 degrees C. Projections past 2 degrees of warming show a future where extreme drought is common, exposing already-vulnerable people, places, and economies to greater water shortages, while making it even harder to curb emissions. In order to guard water resources and the systems that depend on them, emissions need to be cut rapidly. And places already feeling the impacts of warming will need to brace to adapt to a hotter, dryer version of the world.
The city of Chelsea, Massachusetts persevered through the American Revolution and two great fires. Now its resilience is being tested by climate change, as rising sea levels and more intense storms have begun sending frequent flood waters into the city.
Woodwell Climate Research Center recently conducted a thorough analysis of flood risk in Chelsea, identifying where flooding is likely to increase with climate change. The picture it paints is one where the city’s most vulnerable citizens get hit the hardest.
Located north of Boston where Chelsea Creek merges into the Mystic River and the Boston Harbor, Chelsea is vulnerable to two forms of flooding— storm surge from the harbor and extreme rainfall events. Currently, 15% of the city falls within an area of potential flooding. That number will more than double to 34% by 2081.
The return interval of high intensity flooding events will also increase. Scientists use the term “1-in-100 year events” to refer to the kind of large-scale flooding that has a 1% likelihood of occurring over the course of a century. Woodwell calculated that today’s 1-in-100 year rainfall events could become three times as likely by mid-century, and 1-in-100 year storm surge events could be annual occurrences by 2081. That would be like the city of Chelsea experiencing flooding proportional to Hurricane Sandy every year.
Chelsea was settled on a salt marsh punctuated by five hills. The city was developed from the high ground down, and much of the marsh and wetlands around Island End and Chelsea Creek were filled in over the city’s history. These low lying areas form the city’s vulnerable floodplain.
According to Woodwell’s analysis, that floodplain contains much of the city’s vital industry. Two oil terminals sit on Chelsea’s waterfront— the Chelsea Sandwich and Gulf Oil terminals. Here, petroleum, natural gas, and other petrochemicals are stored before being transported to their final destinations. The southeastern waterfront is also a designated port area for commercial shipping.
On the western side of the floodplain is the New England Produce Center, a massive regional hub for food distribution, as well as a major employer.
“Our waterfront has been industrial for 200 years and will continue to be industrial. But we’re very concerned that industry and flooding aren’t compatible,” says Karl Allen, a planner in Chelsea’s Department of Housing and Community Development who worked with Woodwell on the analysis.
Affordable housing is also at risk. Much of the city’s affordable housing was built in the 50’s and 60’s in the lowest-lying areas of the city, where marshes were filled in to create land for their construction. These communities are already familiar with bearing the burden of environmental damages— a rail line bisects the city through a designated environmental justice corridor. At only a few feet above sea level, the rail line serves as a major inundation pathway. Without adaptation measures, climate change will hit these lower income areas hardest.
“I can say that the one thing that’s been very common for municipal and state agencies is a sense of moving goalposts,” says John Walkey, the Director of Waterfront and Climate Justice Initiatives for GreenRoots. GreenRoots is a community organization dedicated to improving urban environmental and public health in Chelsea. Walkey and Greenroots facilitated the collaboration between Woodwell and the city.
“We are now at the stage where climate processes are moving faster than our bureaucracy can,” said Walkey. That could have been a paralyzing realization, especially backed up with analysis results outlining the intensity of increased flooding. Instead, the City’s planning leaders have decided to confront the floodwaters head on, using the analysis to change the way they think about implementing routine infrastructure updates.
Of course, Water doesn’t care where one municipality begins or ends; it will flow into any accessible space. The success of Chelsea’s adaptation measures will depend on collaboration with nearby localities— Everett, Revere, Boston. For example, there are plans in the works to construct a flood defense between Chelsea and nearby Everett that sits across the Island End River. Both cities hope this landscaped wall will protect the area from major flooding until at least 2070.
Having a thorough flood risk analysis also puts the city in a good position to lobby for adaptation on a larger scale. In mid-April, Woodwell and Chelsea hosted a briefing for the offices of Massachusetts Senators Ed Markey and Elizabeth Warren and Congresswoman Ayanna Pressley on the results of the flood analysis and the regional security issue it represents.
“Chelsea is facing a severe threat from climate change over the course of the next 50 years,” said Chelsea City Manager, Tom Ambrosino during the briefing. “So we are working hard to try to be prepared for it. But a lot of these projects are beyond our immediate capability.”
There are hundreds of Chelseas across the United States facing similar, and increasingly urgent, threats from flooding, drought, heat, or extreme weather. Many communities are scrambling to adapt as disasters hit, without knowing how much more change is on the horizon. Replicating climate risk analyses like the one in Chelsea could help them get a more specific picture of what they are facing.
“When you tell people well, ‘you’ve got to design for conditions in 2070’, they say ‘what does that mean? What kind of storm are we designing for?” says Allen. “This analysis has given us a better understanding of what kind of disasters we’ll be looking at, and with what frequency, so we have a design target.”
Risk analyses are invaluable to a municipality’s ability to plan for the shifting goalposts of climate change. Yet the availability of these analyses is uneven. Cities with more resources are able to pay private companies for risk assessments, while non-profits like Woodwell work to fill in the gaps. The Center has already partnered with 14 communities in the U.S. and abroad to produce tailored analyses. But there are nearly 20 thousand municipalities in the U.S. alone. Each will experience their own unique version of climate change.
“It really highlights the need for a national climate service,” said Woodwell Research Associate Dominick Dusseau who worked on the analysis for Chelsea, “something that can provide a nationwide standard service, rather than a piecemeal thing.”
Woodwell’s analysis is a prototypical version of what could be possible with more uniform risk assessment services, as well as a model of successful community engagement. Woodwell will continue to grow its partnerships with individual cities, but the scope of climate change will require a larger, more coordinated response.
“We’re doing a lot, there’s just so much more to do,” says Dusseau.
When and where precipitation falls can determine whether or not people have enough drinking water, aquifers can support agriculture, and rivers keep running. Climate change is breaking down the predictability of weather patterns across the globe. Two new releases this week, from the Woodwell Climate Research Center and Probable Futures, flesh out our understanding of how the shifting seasonality of precipitation might impact our future.
A new volume of maps, data, and educational materials launched on the Probable Futures platform today. The volume provides information that helps readers better understand local, regional, and global precipitation trends, showing how they will change with climate change.
The impact of a warmer world on precipitation patterns is not uniform—in some places dry spells will become more common, in others, intense storms, and some places will fluctuate between both. Rainy seasons may start earlier or later in different parts of the world, which will have impacts on growing seasons and agricultural yields.
“Climate change is reshaping both local precipitation patterns and the global water system—and everyone on Earth will be affected,” said Alison Smar, executive director of Probable Futures. “It may seem counterintuitive, but knowing that the future is less predictable is a valuable forecast. Communities need to be more resilient, adaptable, and prepared. It’s within our power today to prepare for the events that are probable, and prevent those with irreversible impacts.”
Woodwell Associate Scientist, Dr. Anna Liljedahl and Assistant Scientist Dr. Jenny Watts, were co-authors on a paper also released today that documents the impacts of earlier snowmelt in the Arctic. The Arctic is warming more rapidly than anywhere else on earth, which has led to earlier snow melts and longer growing seasons in the tundra.
Conventional hypotheses have predicted that lengthening summers would allow more time for vegetation to grow and sequester carbon, perhaps offsetting emissions elsewhere.
“Our results show that the expected increased CO2 sequestration arising from Arctic warming and the associated increase in growing length may not materialize if tundra ecosystems are not able to continue capturing CO2 later in the season,” said Dr. Donatella Zona, lead author on the paper from the University of Sheffield’s School of Biosciences and the Department of Biology at San Diego State University.
Dr. Liljedahl says that the results highlight the fact that the impacts of climate change will be complex across ecosystems.
“This work shows how important it is to continually assess our assumptions and terminology on how the Arctic system will respond to warming. We often say that warming will lead to a “longer growing season”. We need to be more careful in making that connection,” said Dr. Liljedahl.
Though droughts and bad harvest years are occasional risks for farmers, modern agriculture is built on the assumption of a predictable and stable climate. Rising temperatures are breaking down that assumption, leaving the future of food uncertain. Two new studies put the increasing risks in sharp relief.
Seventy-two percent of today’s staple crops—maize, wheat, soybeans and rice—are grown in just 5 countries, in regions of the world known as breadbaskets. From the plains of North America to the river valleys of India and China, these regions earned their distinction for supporting hundreds of years of agricultural production with their climatic suitability.
“These regions have developed this way for centuries in the same way that human settlements have developed around water, because that’s where the resource was,” says Woodwell Research Assistant, Monica Caparas.
Caparas works on agricultural risk models. Last year, she led an analysis of crop failures in global breadbaskets, projecting the likelihood of declining yields in the upcoming decades. Her results conjured a world where these centuries-old food producing regions may no longer be so reliable. By 2030, crop yield failures will be 4.5 times higher. By 2050, the likelihood shoots up to 25 times current rates.
By mid-century, the world could be facing a rice or wheat failure every other year, with the probability of soybean and maize failures even higher. A synchronized failure across all four crops becomes a possibility every 11 years.
If that sounds like rapid, drastic change, that’s because it is. The immediacy of increasing failures surprised even Caparas.
“The fact that by 2050—which we are almost halfway to already— there could be a wheat failure every year. It’s startling.”
One major component of crop failure predictions is water scarcity. In a warmer world, water is a critical resource. Climate change will shift precipitation patterns, drying out some regions and inundating others. Most of the world’s breadbaskets are headed in the drier direction.
Caparas factored water availability into her analysis, finding the likelihood of crop failure much higher in water scarce sections of breadbaskets. Wheat is especially water dependent, particularly in India where 97% of wheat crops are growing in areas already experiencing water stress. Irrigation could make up for some lack of rain, but groundwater stores are already overdrawn in many places.
In Brazil, agriculture is already showing signs of declining productivity from changing precipitation. Woodwell Assistant Scientist Dr. Ludmila Rattis works in Mato Grosso, where she researches the impacts of agriculture and deforestation on the regional climate. Central Brazil is a major breadbasket for soybeans and maize—as well as cattle— and as crop demand increases, farms and ranches have advanced into the Amazon rainforest and the Cerrado, the Brazilian Savanna.
Clearing and burning forests not only releases carbon that contributes to rising global temperatures, it can also have drying effects on the local watershed. In recent years, farmers in Mato Grosso and the Cerrado have reported issues with dry spells, though they would not attribute it to climate change. Dr. Rattis wanted to quantify these anecdotes to show that they were connected.
“I was trying to see why they were denying the climate changing at the same time they were feeling the climate changing. Were they feeling that in their pockets? Was it affecting the finance of their business?”
Dr. Rattis modeled temperature and precipitation changes along Brazil’s Amazon-Cerrado frontier. Her results not only predicted that by 2060, 74% of the region’s agricultural land would fall outside of the ideal range of suitability for rainfed agriculture, they showed that nearly a third of farms already did.
The changes are affecting crop productivity. When the temperature gets warmer, plants grow faster, releasing more water vapor into the air from their leaves as a byproduct of photosynthesis. If there isn’t a steady supply of soil moisture available to replace the lost water, plant growth is stunted. Rainy seasons are also starting later, limiting the possibility for planting two rounds of crops in a single season, which cuts into farmer’s profits and encourages further expansion via land clearing.
Caparas notes that increasing crop failure doesn’t necessarily mean we are headed for a world without maize or soybean. But it does mean a drastically different agricultural system— one where hard decisions have to be made about land use.
“Increasing crop failures doesn’t mean that these crops won’t ever be able to grow in these areas again, or that they should be abandoned, just that it’s going to be much harder for them to be as productive,” Capraras says. “There might be a certain threshold of losses that would lead people to leave these croplands.”
There is some potential for migration of the most productive lands as northern latitudes begin to warm. Caparas’s projections showed the greatest likelihood of breadbasket migration from the United States into Canada.
However, just because the climate suitability is migrating, doesn’t mean agricultural production will shift along with it. Other factors including soil fertility or existing land uses could limit the practicality of moving to new regions, especially if it jeopardizes existing climate solutions as the case in Brazil has shown. Clearing forests is only accelerating warming, drought and declining productivity.
Shoring up food security in a changing climate will require system-wide changes to our current agricultural system. Part of that starts with adjusting farming strategies to mitigate the effects of the warming that’s already unavoidable. Dr. Rattis has begun outreach to the farmers whose land she collected data on, giving them a picture of what their farms will look like if nothing changes.
“We need to make them feel that they’re part of the research, because they are. If we do, once we get the results, the probability of them using those results to adapt the way that they produce food will increase,” Dr. Rattis says. “They can see themselves in the historic part of the graphic and then I show them where, climatically speaking, their farm is going,”
She’s hoping these conversations will open Brazil’s farmers up to practices that leave more native vegetation on the landscape, which would help stabilize the local climate and keep the natural watershed intact.
Caparas takes hope from the fact that the outcomes of her models are not set in stone. In the planet-wide experiment of climate change, we can affect the results.
“These projections are due to changes in climate. They don’t account for adaptation strategies. The agricultural technology industry is fast-growing and so I think that there is hope, as long as adaptation techniques are implemented equitably,” Caparas says.
Much of the innovation, Caparas says, will have to involve developing drought resistant crop varieties and less water intensive agricultural processes. In the long term however, securing a productive agricultural future for the Earth’s nearly 10 billion people by 2050 will depend on securing a stable climate.
“First and foremost it always has to be getting climate change in check,” says Caparas.