They keep us cool, we cut them down

Standing forests are our best natural climate solution. So why aren’t we treating them that way?

In terms of climate mitigation, forests are like green gold—working overtime to cool the planet, while also supporting a wealth of biodiversity. But we have not been saving them as one would a precious asset. Despite pledges to end deforestation, old growth forests are being cut down at alarming rates. And planting new trees is widely prioritized and incentivized over protecting existing forests. Across the board, standing forests are vastly undervalued. This has to change if we are to stand a chance of limiting warming to internationally agreed targets.

Forests are global air conditioners

According to a recent study from scientists at Woodwell and the University of Virginia, tropical forests alone are holding back approximately 1 degree Celsius of warming. About 75% of that cooling effect is due to carbon sequestration. Forests grow, trees lock away carbon in their trunks and roots and shunt it into the soil. The other 25% comes from the innate properties of forests that work to cool vast regions of the globe.

Through photosynthesis, plants release water vapor into the air in a process called evapotranspiration. The vapor contributes to cooling near the ground, as well as cloud formation higher in the atmosphere that reduces incoming solar radiation. The shape of the tree canopy also contributes. So-called canopy “roughness” disrupts air flow above the forest. The more uneven the canopy, the more turbulent the air, which disperses heat away from the surface. In the tropics, evapotranspiration and canopy roughness are high, which means that surface temperatures remain relatively low, with the heat dispersed throughout the deep atmosphere.

Forests also naturally produce molecules called biogenic volatile organic compounds (BVOC), which can either contribute to cooling by encouraging the formation of clouds, or to warming by creating ozone and methane. In the tropics, the net effect of these chemicals is cooling.

The cumulative result of these properties is that when forests are removed, the land around them begins to heat up even faster, which can increase the frequency of extreme heat and drought events. Without forests, some regions will become a lot less resilient to sudden shocks. And the release of carbon contributes to global warming which further exacerbates hot, dry conditions.

“Forests act like air conditioners,” says Woodwell Assistant Scientist, Dr. Ludmila Rattis, who studies the impacts of deforestation on agriculture in Brazil. “Deforesting in the face of climate change is like getting rid of your air conditioners before an upcoming heatwave.”

Not all forests are created equally

Protecting forests, and maintaining the cooling services they provide, is vital to limiting warming. But, with forests covering 30% of the Earth’s land, prioritizing protection is a massive task. And when it comes to carbon storage, not all forests are equally valuable. Older, healthier forests tend to have a more secure hold on their carbon.

“Mature forests have higher biodiversity and create their own microclimate,” says Woodwell Associate Scientist, Brendan Rogers. “They’re more resistant to drought and other types of disturbance. And because of that, they tend to be more stable in the face of environmental perturbations over time.”

New research from Woodwell and Griffith University has developed a method of identifying high-value forests using satellite imagery. Estimating the metric of “forest stability” through satellite data on the light reflected by vegetation and a water stress index of the tree canopy, researchers were able to determine gradients of stability within forest patches in the Amazon and boreal forests.

Using a gradient of forest stability allows for a better prioritization of forest protection strategies based on their carbon value.

“The first priority is to protect stable forests from further human disturbance,” says paper co-author Dr. Brendan Mackey. “The second priority is to identify forest areas where restoration efforts will be most cost effective.”

Guarding the forests that guard our future

But if the state of existing forests is any indication, forest protection continues to be deprioritized. Many wildfires are left to burn unless they threaten human settlements. Governments continue to incentivize deforestation for development or agricultural expansion. Indigenous and local communities are not compensated for their work stewarding their territories and keeping forests safe. And the warmer the planet gets, the more susceptible even protected forests become to drought, fire, and disease.

Research has shown that stewarding standing primary forests, and reviving degraded ones, represents the greatest opportunity for near-term carbon storage and removal. A study of global land-based carbon storage potential found that improved management of existing forests alone could store approximately 215 billion metric tons more than they currently do.

Protecting forests is cost effective, too. For example, in the United States, investing in fire fighting in Alaska’s boreal forests would require just $13 per ton of CO2 emissions avoided. That’s easily on par with other mitigation strategies like onshore wind or solar energy generation.

Effective strategies for protecting forests already exist, they’ve just been suffering from a lack of force—and often funding—behind their implementation. For example, forest carbon markets—where landowners and forest stewards are paid to protect standing forests that are otherwise vulnerable to deforestation—have the potential to keep forests safe while offsetting emissions from other sectors. But nascent carbon markets are inefficient, with weak standards for verifying the quality of credits being sold, and lacking the transparency needed to ensure credits are actually reducing overall emissions, rather than greenwashing carbon-intensive business practices.

Credits are also priced incorrectly for their relative climate value—the market currently values reforestation credits more highly, reducing incentive for landowners to conserve standing, old-growth forests when there is a better livelihood to be made in legally deforesting land for  other uses. A truly effective carbon markets system would require large investments in science that can verify credit standards.

Forests are like our global carbon savings accounts—when we cut them down, we’re drawing out money and limiting our ability to collect interest and keep growing our funds. Successful mitigation can’t be accomplished without taking the full value of forests into account and strengthening policies to reflect that. If they aren’t, the planet will pay a far greater price for it as temperatures rise.

“We can’t afford to keep cutting forests. We need to reduce emissions now, and protecting forests is one of our best available solutions. Despite the obstacles, it’s worth the investment,” says Dr. Rogers.

Despite centuries of successful Indigenous management, the Xingu’s fire regimes are changing

Indigenous community in the Xingu reserve

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What’s new?

The first designated Indigenous land in Brazil, Território Indígena do Xingu (TIX), has been cited by studies for decades as a successful buffer against the deforestation, degradation, and fires that plague other parts of the Amazon. A recent study, co-authored by Dr. Divino Silvério, Professor at the Universidade Federal Rural da Amazônia, and Dr. Marcia Macedo, Woodwell Water Program Director, shows that fire regimes are changing in the Xingu region, leading to more forest loss and degradation.

The paper shows roughly 7 percent of the TIX has been degraded by drought and fire. Degradation is part of a feedback loop wherein damaged forests become drier and more susceptible to burning in future fires.

“I remember when I started my Ph.D., a 2006 paper showed that Indigenous lands were extremely effective fire breaks—the Xingu just never saw fire. Climate change has completely changed that story,” said Dr. Marcia Macedo.

Understanding: Changing fire regimes

Indigenous communities in the TIX have been managing the rainforest for centuries with finely adapted slash and burn cycles that create space for agriculture and promote the growth of natural species used in construction, medicine, and cooking. These cycles can last three to four decades before an area is burned again. Traditionally, burns were well controlled and the rainforests surrounding burned areas were healthy enough to prevent flames from escaping.

But over the past two decades, the paper observed, escaped fires have occurred more often within the reserve and the likelihood that forest is lost post-fire is rising, particularly in seasonally flooded forests. Indigenous management practices have not changed significantly, the paper explains, so why the increased prevalence of fire and degradation?

Climate change is drying out forests, making them more susceptible to escaped burning from management practices. The other factor driving degradation within the territory is growing population. Indigenous communities are becoming less nomadic, and village populations are rising, increasing the area of forest used for subsistence. Degradation was higher in areas surrounding villages.

“The way Indigenous people manage fire has stayed the same, but we now have a different climate,” said Dr. Divino Silvério. “Indigenous people have been in these regions for many decades or centuries. And all this time they have had their own fire management to produce food that usually doesn’t end in these huge forest fires.”

What this means for Indigenous fire management

Climate change will force Indigenous communities within the reserve to adapt traditional practices to protect the forest against more frequent, intensifying fires—despite these communities not contributing to global emissions.

Previous attempts to manage increasing fires through prescribed burning have clashed with the needs of residents of the TIX. Burning at a different time of year does not cultivate the same species, and residents were concerned it was jeopardizing the growth of plants used for medicine.

Dr. Silvério is working with residents of the Xingu to understand how to integrate changes to fire management practices with traditional strategies in a way that supports community needs. One example, he said, could be shifting the primary construction material from grasses (that grow after fire) to palms.

“Indigenous people will probably need to learn how to live in this new reality, an environment with more drought and more fires. We are trying to work in a participative way to construct solutions with them.”

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.

Farms beginning to feel the impacts of climate change in Brazil

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.

Ideal climate for agriculture migrating north

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.

Future of food depends on drought resilience

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.