How much carbon can farmers store in their soil? Nobody’s sure.
Advocates say the long-awaited farm bill could help fix that.
Dirt, it turns out, isn’t just worm poop. It’s also a humongous receptacle of carbon, some 2.5 trillion tons of it — three times more than all the carbon in the atmosphere.
That’s why if you ask a climate wonk about the U.S. farm bill — the broad, trillion-dollar spending package Congress is supposed to pass this year (after failing to do so last year) — they’ll probably tell you something about the stuff beneath your feet. The bill to fund agricultural and food programs could put a dent in the country’s greenhouse gas emissions, some environmental advocates say, if it does one thing in particular: Help farmers store carbon in their soil.
The problem is, no one really knows how much carbon farmers can store in their soil.
Research Assistant Colleen Smith crouches low to the ground over a tray of crumbled soil. Using a boxy grey device that looks like a heavy-duty flashlight, she presses the flat glass end against the soil and fires a beam of infrared energy that bounces off the soil and back into the device’s sensor.
In moments, a readout pops up on a tablet screen, showing a spectrum of reflected light. With some analysis, Smith will have data on the chemical makeup of this patch of ground. With enough data points, she could estimate the soil properties of an entire field, pasture, ranch or farm, and how it might be changing over time.
Soil spectroscopy is a newer but fast-growing technique employed by scientists studying soil composition. At Woodwell Climate Research Center, a group led by Carbon Program Director Dr. Jonathan Sanderman has been spearheading its use to help improve the availability and affordability of reliable soil quality information, which is essential if we want to get serious about soil carbon sequestration as a natural climate solution.
Why soil spectroscopy?
“The heart of the technology is essentially getting the fingerprint of the soil, which tells us something about the overall chemical makeup of that sample,” says Dr. Sanderman.
The principles of soil spectroscopy are based in nuclear physics. Elements in the soil react in unique ways to the energy from the electromagnetic spectrum, reflecting some wavelengths and absorbing others. The reflected wavelengths give scientists clues to which minerals and elements are present and in what quantities.
That information can then be related to certain soil properties, like whether it’s suitable for certain crops, or whether it’s effectively sequestering carbon. The former is valuable information for producers like ranchers or farmers who need to make land management decisions. The latter is what climate researchers are most interested in. Soil spectroscopy represents an opportunity to marry the interests of both.
In a single scan, soil spectroscopy can estimate carbon, nitrogen, phosphorus, moisture, pH levels, and more. Traditional methods rely on multi-step chemical analyses to get you the same information— a time consuming and expensive process that could involve grinding, drying, weighing, mixing with reagents, and other steps to extract information on just one or two indicators of soil quality.
“With soil spectroscopy, you can get a pretty large suite of properties from one sixty second scan. A lab needs easily $2 million worth of instruments to be able to make all the same measurements using traditional methods,” says Dr. Sanderman. The most precise soil spectrometers can cost $100,000, but lower resolution and portable ones are substantially cheaper. “The speed and cost of spectroscopy are unmatched.”
Soil Spectroscopy for Global Good
These benefits make soil spectroscopy a method with big potential, but according to Dr. Sanderman there is still work to be done in refining the methodology to get universally accurate data. Alongside collaborators from the University of Florida and OpenGeoHub, he started the Soil Spectroscopy for the Global Good project (SS4GG) to jumpstart that work.
The project focused on two main efforts. The first was an extensive inter-laboratory comparison to understand how much the accuracy of scans varies between different instruments. Twenty laboratories across the globe participated, scanning identical samples which were then compared to the output from a lab widely regarded as the gold-standard in accuracy. The results were published in Geoderma late last year.
“We demonstrated that there is lab-to-lab variability, but also that there are procedures we can use to correct for differences between laboratories and get better integration of data,” says Postdoctoral Researcher, Dr. José Safanelli, who coordinated the study.
The second goal was to pool data from different labs into one accessible and open-source resource that also provides tools to analyze the data. The Open Soil Spectral Library (OSSL) now hosts over 100,000 soil spectra from across the globe that scientists can incorporate into their research and offers an engine for analysis. The idea is that with more people using and contributing soil spectral data, the faster the technology and the information gained from it will advance.
“We hope that the OSSL will be a driver of the soil spectroscopy community, advancing the pace of scientific discovery, and promoting innovation,” says Dr. Safanelli.
Building a community of soil scientists
Throughout the project, SS4GG efforts remained dedicated to transparency.
“We were always available to answer questions. We shared best practices and gave advice on which instruments are better, which manufacturers are the best in the market, and which procedures to use to collect spectra,” says Dr. Safanelli.
According to Dr. Sanderman, that openness fostered trust and collaboration— in both contributing data to the OSSL and participating in the inter-laboratory study— strengthening the community of scientists using soil spectroscopy.
“As we built momentum, more groups began to contribute,” says Dr. Sanderman. “It’s been great to see people realizing the value of collaborative, open science. People are now taking advantage of the foundation we’ve built.”
The soil spectroscopy community convened this past year for several webinars and presentations, including the Agronomy, Crop, and Soil Science Society meeting, where Drs. Sanderman and Safanelli hosted a training workshop and symposium on spectroscopy, as well as a two-day immersive workshop on the future of the field.
“We all benefit when this technology is more widely used,” says Smith.
Soil carbon as a climate solution
Speeding up the pace of soil science is key for developing climate solutions. Agricultural soils represent a large potential carbon sink; changes in farming and ranching practices can encourage sequestration of carbon in the soils. Soil carbon markets, and other payment for ecosystem services schemes could incentivise producers to make sustainable management decisions and soil spectroscopy could be a useful tool to track their contributions.
“The ultimate goal is to better monitor soils across landscapes to make food production more sustainable,” says Dr. Safanelli.
The handheld device that Smith was using is a test case for the speed and convenience of soil spectroscopy for analyzing soil carbon. If testing the quality of your soils can be as simple as a 60 second measurement with a low-cost piece of portable equipment, and the scan can get you additional information about soil fertility, then why not participate?
“We are trying to verify that we actually are sequestering carbon, and that requires lots and lots of measurements. So this is where we start moving into field-based spectroscopy,” says Dr. Sanderman. “If we can eliminate bringing the sample back to the lab altogether, we’re cutting our costs by another order of magnitude and could potentially scan several hundred points in a field in a day.”
Smith theorizes that cost could be further diffused through farming cooperatives or extension offices offering soil testing using inexpensive spectrometers. “Soil spectroscopy could be an easier way to get answers to big questions,” says Smith. “And that’s exciting.”
With the OSSL now up and running, the team is now focusing efforts on maintaining the growing network of interested soil researchers, pursuing new opportunities for collaboration as they arise.
“The network is getting stronger,” says Dr. Safanelli. “More people are coming and reaching out to us. That’s our biggest contribution: creating a network and sharing information across the community.”
Woodwell Climate Research Scientist, Dr. Taniya RoyChowdhury, has been awarded the inaugural Christiana Figueres Prize for microbiology. The prize, part of the Applied Microbiology International Horizon Awards, recognizes scientists who have used microbiology to make a significant contribution to our understanding of terrestrial life and the preservation of our global ecosystem.
Figueres, for whom the prize is named, has been a leader in climate action for almost three decades, founding the Centre for Sustainable Development in the Americas in 1995 and serving as a negotiator of the United Nations Convention on Climate Change and the Vice President of the Bureau of the Climate Convention representing Latin America and the Caribbean. The prize seeks to honor scientists who have followed in her footsteps as climate leaders, using microbiology to help improve our understanding of climate change and solutions that could help mitigate emissions.
Dr. RoyChowdhury is a first-generation college student who grew up in urban India with a passion for nature and science. With help from her family, she was able to pursue an education in environmental studies.
Her research now focuses on how soil systems are responding to climate change at both the broad ecological scale and the complex microbial one.
“Microbes regulate the rate at which organic carbon inputs from plants are metabolized and stabilized in the soil,” says Dr. RoyChowdhury. “The soil microbiome is also a major driver of carbon loss via greenhouse gasses. My research seeks to quantitatively understand the responses of the soil microbiome to climate change factors.”
According to Dr. RoyChowdhury, a deeper understanding of these dynamics could help inform strategies for improving soil carbon sequestration. She has published more than 25 papers on topics like the impacts of seasonal and tidal wetland drawdowns on methane production, the impacts of drought on prairie grasslands, and the connection between land-use and management change in agroecosystems and microbial processes.
“My goal is to realize the powerful impact that soil microbiology can have towards achieving the sustainable development goals of climate action,” says Dr. RoyChowdury. “Using a multi-dimensional approach and comprehensive understanding of diverse ecosystems, I strive to provide valuable insights into the factors influencing climate vulnerability, soil health and sustainability.”
At Woodwell Climate, Dr. RoyChowdhury is currently leading research on the soil and plant productivity impacts of organic farming in Andhra Pradesh state in southern India. She has trained local volunteers and farmers to collect and analyze soil samples on 300 farms in the region, with the hopes of quantifying how organic farming practices can be used to increase carbon and other nutrients in the soils.
“The farmer is the best scientist here because they know the soils more than we could test in the lab. They have been farming for years and years and inheriting practices over generations,” says Dr. RoyChowdhury. “So when they see the changes in the soil, they’ll know it.”
The Christiana Figueres Prize was announced November 16 at the 2023 Environmental Microbiology Lecture, held at the British Medical Association House in London.
When boreal forests burn in the Far North of the U.S. and Canada, the whole world feels the impact. From communities evacuating from the blazes, to smoke clogging the air thousands of miles to the south, to the release of carbon emissions that accelerate climate change, boreal forest fires are a global issue.
Research from Woodwell Climate has recently expanded our understanding of the scope of impact that boreal fires have. A new paper, led by Research Associate Stefano Potter, quantified emissions associated with fires across most of boreal North America, shedding light on the dynamics of boreal fires and climate change. These four graphics explain:
1. Boreal fires threaten an important carbon sink.
Using a new higher-resolution dataset, generated as part of NASA’s Arctic-Boreal Vulnerability Experiment (ABoVE), Potter and his co-authors created a map of burned area across the boreal region. The researchers combined satellite imagery with observations from the largest database of boreal field studies, which allowed them to calculate emissions from both vegetation burned aboveground, and organic matter in the soils that burned belowground.
The results show that the overwhelming majority of carbon emissions from boreal fires—over 80% of total emissions in most places—comes from soils rather than trees. Despite the dramatic imagery of burning forests, most of the real damage is happening below the ground.
2. The true impact of boreal emissions is currently underestimated.
That finding on its own was not surprising to researchers, as the majority of carbon in boreal forests is stored below the ground. However, the fact that the overwhelming contribution of belowground carbon to fire emissions is being left out of existing global fire and climate models, means we’re drastically underestimating carbon emissions from Arctic and Boreal environments.
“A large reason for that is because the [existing] models are not detecting the belowground carbon combustion, which we are modeling directly,” says Potter.
Potter and the team working on the paper were able to accurately model belowground carbon loss because of their machine learning approach and the abundance of available field measurements in their dataset.
Accurately representing these numbers in global fire models is critical, because these models are used to plot climate trajectories and inform carbon budgets, which tell us how much we need to cut emissions to stay below temperature thresholds like 1.5 or 2 degrees C.
3. Boreal fires are becoming more intense.
It is becoming more urgent to get an accurate understanding of boreal emissions, because boreal fires are becoming larger, more frequent and more intense. Burned area has increased as fire seasons stretch longer, return intervals between fires shorten, and single ignitions can result in massive blazes that burn further and deeper and cause greater carbon loss.
In 2023, for example, while the number of ignitions has been lower than most years since the 1990s, burned area as of August has far surpassed any year in the past three decades.
4.Fire suppression can be a cost effective protection against carbon loss.
Ultimately, preventing carbon loss from boreal forest fires will require bringing down emissions from other sources and curbing warming to get fires back within historical levels. But preventing boreal forests from burning in the short term can offer a climate solution that could buy time to reduce other emissions.
A collaborative study between Woodwell Climate and the Union of Concerned Scientists, published in Science Advances, modeled the cost effectiveness of deploying fire suppression in boreal North America and found that actively combatting boreal fires could cost as little as 13 dollars per ton of CO2 emissions avoided—a cost on par with other carbon mitigation solutions like onshore wind or utility-scale solar. Informed by this data, the U.S. Fish and Wildlife Service has decided to start combating fires in Yukon Flats National Wildlife Refuge, not only when they present a threat to human health, but also with the intent of preventing significant carbon losses. Yukon Flats is underlain by large swaths of carbon-rich permafrost soils, at risk of thawing and combusting in deep-burning fires.
Deepening our understanding of the complex boreal system with further research will help inform additional strategies for bringing emissions under control, preventing devastating fires that threaten human health both regionally, and across the globe.
Millions of acres of rangelands managed by the U. S. Bureau of Land Management are not meeting land health standards, according to a recent report from watchdog organization Public Employees for Environmental Responsibility. Range degradation is also happening on U.S. Forest Service and privately held lands. Healthy rangelands are vital to the economic and public health of the communities that depend on them, which includes ranchers, Indigenous nations, and recreationists. Failing rangelands undermine these groups, lead to loss of habitat, and result in landscape degradation, and they also minimize our ability to mitigate climate change through carbon sequestration. Taking policy action to ensure the longevity of rangelands has the potential to increase climate mitigation potential and improve the health of U.S. ecosystems.
What is healthy rangeland?
Covering more than 31 percent of the U.S., rangelands are any wilderness or rural open space grazed by domestic or wild herbivores, including grassland, shrubland, and pasture. Rangelands provide a wide array of ecosystem services, including food for livestock, habitat for wild species, and climate regulation through the uptake of carbon dioxide (CO2) by growing plants and the transfer of this sequestered carbon into the soil (as soil organic carbon). Globally, rangelands store 20 percent of the world’s soil organic carbon and U.S. rangelands may have the capacity to offset 2.5 – 3 percent of U.S. CO2 emissions from fossil fuels, but only if the rangelands are considered in “full health”.
Improving monitoring to foster healthy rangelands
The capacity for rangelands to sequester carbon is increasingly threatened by drought and overgrazing and there is an urgent need for improved land use planning to tackle these issues. However, the lack of an integrated monitoring system makes it difficult to know what changes to land management are needed on the individual ranch scale.
An important first step, then, to fostering healthy rangelands is establishing an open-access region-wide range monitoring platform that ranchers can use to verify and track changes in rangeland ecosystem condition and carbon storage across entire land units. Large-scale monitoring for these indicators will make it clearer where land is being effectively managed, and where it is not.
Dr. Jennifer Watts focuses on how climate change and human disturbance are affecting vegetation, soils, and the carbon cycle. She and her colleagues are currently working to develop a monitoring platform to provide stakeholders access to land health information.
“Having free, easy access to long-term information about lands will empower us to become fully aware of how our land use is impacting the health and future of rangeland ecosystems,” Dr. Watts explains. “This gives us the ability to invest in alternative management approaches that provide a more sustainable future for our lands while protecting our communities and ecosystems in the face of climate change.”
Building a system of rewards and incentives
Reward systems can then be established across different scales to incentivize land use that improves ecosystem services. Monitoring platforms can be used in conjunction with clear land management directives to ensure rangelands are managed in a way conducive to ecosystem health.
Overgrazing is one of the biggest drivers of rangeland carbon loss and land degradation. It not only undermines the carbon storage potential of rangelands but also compromises other ecosystem services and limits future grazing capacity for livestock and wildlife. Consequently, it is in the best interest of everyone–ranchers, conservationists, Indigenous groups, and recreationists–to ensure that grazing on rangelands is managed in a way that increases vegetation cover, diversity, and rooting depth, while minimizing bare ground. Grazing practices can be addressed through process-oriented approaches.
Practicing management intensive grazing could help limit overgrazing. This adaptive technique involves concentrating grazing animals in one place for a very short period of time and then moving them to a different location. This ensures that the ecosystem has a chance to recover and regrow following a concentrated period of grazing. Ranchers will need technical assistance to develop grazing and management plans. Given that this is a practice under the Environmental Qualities Incentive Program (EQIP) it is likely to receive a boost in funding from the 2022 Inflation Reduction Act. Building more programs, at the federal, state, and county level, that reward ranchers for shifting grazing techniques to those that support the sustainability of ecosystem services and provide equipment needed to support fencing and water distribution could be a way to incentivize more effective land management.
Manipulating grazing fees to more accurately represent the costs associated with maintaining the integrity of rangelands is another option for fostering healthier rangelands given the current low fees and stagnant pricing of grazing fees. Furthermore, revenue generated from increasing grazing fees on public lands could be used to support a monitoring system for all U.S. rangelands.
Most stakeholders agree that better rangeland monitoring, soil health, and payment for land improvements are important, but a big question is how to actually pay for these services across multiple levels of governance. Exploring how to leverage different options for funding, then, will be the necessary next step in supporting thriving rangeland ecosystems and reaping the potential climate benefits.
At age 12, Woodwell Assistant Scientist, Dr. Jennifer Watts was accustomed to black dirt—the rich, wet, crumbling, fertile stuff she dug through on her family’s hobby farm in Oregon. But after moving with her parents and siblings to a roughly 224-acre dairy farm in Minnesota, all she saw around her was light brown, dry earth.
“A lot of the farms around us were a mix of dairy farms and really intense cropping rotations of corn and soybean,” Dr. Watts says. “And I started to notice, where there was tillage, how depleted the soil looked.”
In the United States, farmland covers more than 895 million acres (an area larger than the size of India), and it has a proportionately massive footprint on the environment. Intensive agriculture pulls nutrients out of the soil and doesn’t always return them, converting natural grasslands into monocultures and releasing large amounts of stored carbon in the process.
But what Dr. Watts saw throughout a childhood spent tending to her family’s farm, was that changing the way agricultural land is managed can sometimes reverse those impacts. In converting their cropland to pasture, to support an organic, grass-based dairy farm, Dr. Watts and her family stumbled upon the principles of regenerative agriculture. A practice that can produce food in a way that works with the ecosystem, rather than against it, and has implications for climate mitigation as well.
“It became, for me, an unintentional transformative experiment that my family conducted on our farm,” Dr. Watts says. “By the time I graduated high school, our lands were so lush and green. It was a healthy, productive, diverse ecosystem again.”
Going rogue on the range
When Dr. Watts talks about her father’s idea to move to central Minnesota and start a dairy farm, she calls him a “rogue.” Originally from Alaska, he intended to work in fisheries, but had to change course after a cannery accident. Searching for something that would allow him to still spend his days outside, he settled on farming.
From the beginning, the Watts’ farming practices were considered unconventional in their rural Minnesota community. Firstly, they planted wild grasses and legumes like clover and alfalfa. Then, they left it alone. No tilling in the springtime alongside their neighbors; they simply let the plants establish themselves and moved the cattle frequently (with the help of a cow dog named Annie) to avoid overgrazing.
“After the first couple of years, I started noticing we had a lot more biological diversity in our fields, relative to our neighbors. We had a lot more bees buzzing, and butterflies, and we were popular with the deer and ducks,” Dr. Watts says. A few more years, and the soil started becoming dark and earthy-smelling again, like the soil she remembered from Oregon.
What was happening on their “rogue” dairy farm, was a gradual, partial reclamation of a lost grassland ecosystem— one that used to stretch across the midwest United States and was tended by native grazing species like bison or elk. Grazing plays a major role in cycling nutrients back into the soil, building up important elements like carbon and nitrogen. The near extinction of bison and the proliferation of monoculture cropping have broken this cycle—but cows have the potential to fill the gap left by ancient grazers, re-starting that process. Simple adjustments to management techniques, like lengthening time between grazing a pasture, can give the land time to recover.
Storing carbon in the soil
This also has implications for how we combat climate change—a term Dr. Watts wasn’t familiar with until later in high school, when family trips back to Alaska revealed the glaciers she loved to visit were shrinking.
“Seeing the glaciers was our favorite thing to do with my grandma, but they were beginning to disappear. And one year, suddenly, I noticed these informational panels along the walk exiting the National Park talking about this thing called climate change,” says Dr. Watts.
Dr. Watts was also seeing another pattern emerge on the farms in her midwest community. Water was becoming a little scarcer. Many of the farms around her family’s had begun investing in irrigation—something that was previously unnecessary, and remained so for the Watts’ farm. Their rich, black soil held onto the water for longer.
As she grew up and (with the help of a pre-Google web search over dial-up internet) charted a course for her career as an ecologist, Dr. Watts began to study the science underlying these patterns she was noticing, and connected them to climate change.
Growing plants draw carbon from the atmosphere. When plants die and decay, some of that carbon is released to the air to be drawn back down again by a new season of growth, while some is stored away as organic matter in the soil. Over centuries, this process forms a stable sink of carbon on the land. Regenerative grazing—the way the Watts family did it—stimulates more plant growth to keep this cycle turning, while overgrazing or removing grazers entirely can halt the process, allowing for erosion, less healthy root systems, and the degradation of the carbon sink. In the U.S., rangelands have historically contributed more to the depletion of soil carbon, but Dr. Watts’ research with Woodwell has demonstrated that, with proper management, rangelands and other agricultural lands have the potential to contribute positively to the climate equation again.
Seeing patterns from a new perspective
For the past two summers, Dr. Watts, alongside the Woodwell Rangelands team and collaborators, has driven across the western U.S. to collect biomass and soil samples and measure carbon flux from working ranches and federal grazing leases in Montana, Colorado, and Utah. These measurements will help calibrate a new satellite remote sensing-informed model that can track how much carbon is being stored on grazing lands. The model will be hosted on the Rangeland Carbon Management Tool(RCMT) platform—a new web application she and researchers at both Woodwell and Colorado State University are developing to give land managers access to carbon and other ecosystem data for their lands.
The idea is that, with a tool like this in hand, ranchers can account for carbon dioxide flowing into and out of the rangeland ecosystem, and track how this changes over time in response to land management adjustments. It will also show changes in correlating ecosystem metrics like plant diversity and productivity, as well as soil moisture—two things that are crucial to maintaining a healthy and economically viable range. With this information, Dr. Watts and colleagues hope to encourage a regional shift in ranch management strategies that protect and rebuild stores of soil carbon, while providing ranchers with essential co-benefits.
Dr. Watts has been working with Jim Howell, owner of sustainable land management company Grasslands LLC, to connect with individual ranchers and discuss how a tool like this could help their operations. Though ranchers can be a tradition-bound group, Dr. Watts says seeing data that confirms their anecdotal experiences of hotter winters, drier summers, longer droughts, and other climate-related changes has opened them up to making changes.
“There are so many times when we just see the ‘aha moment’ in the manager or the land owner’s face, because they’re suddenly able to see these patterns from a very different perspective,” says Dr. Watts. “Most people, we have strong memories, we know that something’s different, but to be able to show that through data and not only memories—it’s so powerful.”
Building climate solutions on the ground
In addition to ecosystem co-benefits, storing carbon on rangelands could have direct economic benefits for ranchers as well. The RCMT will provide baseline data that could be used to verify credits within a voluntary soil carbon market. Rangelands historically haven’t been included in carbon markets because of gaps in monitoring data that the RCMT will help fill. The data could also be useful for local or state governments setting up payments for ecosystem services schemes in their region that would provide money directly to ranchers in exchange for storing carbon on their lands.
Of course, cattle aren’t without their complications, and ranching practices are just one element of a global meat and dairy industry that contributes to 15 percent of global emissions. But Dr. Watts’ roots as a dairy farmer make her enthusiastic about the possibilities this solution holds to both mitigate emissions and keep an important American livelihood resilient as climate conditions change.
“It’s just one aspect in this really complicated global system,” says Dr. Watts. “But if we manage our ecosystems better, building more intact environments where we can, this can sequester more carbon while restoring ecosystem health and productivity. It’s not the solution, but it is a solution that can benefit our planet while supporting rural communities.”
“Talk to Jim. Jim knows everything.”
That’s what everyone told Woodwell Assistant Scientist, Dr. Jennifer Watts, when she started writing up a research plan to study soil carbon on U.S. rangelands. “And indeed, he does,” Dr. Watts says. “He knows everything about the region, about grazing management, species management, anything having to do with land management on these ranches.”
With his felt Stetson, dusty jeans, and perennial tan, ranch manager Jim Howell looks a bit like the kind of cowboy Hollywood might dream up. And in a way he is—despite looking at home on the range, Howell grew up in Southern California. But he spent his summers out in Colorado’s Cimarron mountains, working on his grandfather’s cattle ranch.
Those summers were Howell’s introduction to the idea that the way livestock are managed can change their impact on the land—a thread that would pull him through a college degree in animal production, towards a career “knowing everything” about holistic ranch management. He was first clued into this concept while walking the fence line separating his family’s property from a patch of public land being used to graze sheep.
“I noticed there were lots of very healthy, perennial, bunch grasses on the sheep side, while our side of the fence had degraded to mostly silver sagebrush, Kentucky bluegrass, and dandelions,” says Howell. “And I just didn’t understand why the differences were so stark.”
Howell’s cattle were stocked continuously on the land, low in number but able to graze year round, while the sheep grazing permit required rotation. There might be a great flock of sheep up there one day and nothing but grass for the remainder of the year. That difference, it turned out, dramatically altered the kinds of plants that could flourish on the land.
“I became aware then that the way that we’d been managing our cows in our country up there was leading to its slow, long-term, ecological degradation. And I didn’t know what to do about it,” says Howell.
The grazer makes the range
There have always been animals grazing the American West—before colonizers, even before native peoples. On the Great Plains there were bison; in the mountains and high altitude deserts of Southwestern Colorado, it was bighorn sheep and pronghorn antelope, as well as elk and mule deer. All three are rare sights now, with populations decimated by overhunting and habitat degradation.
Now, if you see any animal grazing on these ranges, it’ll probably be cattle.
Despite displacing native species, cows can still fill a natural niche in the rangeland ecosystem. Antelope, bison, sheep, and cows all belong to a group of animals called ruminants—animals that can digest grass. Many grasslands have co-evolved with ruminant species; their roaming feasts influence plant growth the same way pruning might affect the shape of a tree. Occasional shearing by a hungry cow stimulates new grass growth. It also creates a more competitive environment that supports a diverse array of plant species.
Grazing also plays a part in cycling nutrients and storing carbon in the soil. In a frequently dry climate like this one, digestion breaks down plant matter much faster than it would decay in the environment. Manure fertilizes new plant growth and returns carbon to the soil. Let this process continue unencumbered for a couple hundred thousand years, and you can build up a valuable carbon sink. And as long as the number of cattle isn’t rising, the oft-cited methane emissions from cow burps are minimal and cycled back down into the plants that grow up after grazing.
Since settlers arrived, however, the land has been put through centuries of abuse. Public lands were, for a long time, left open to unregulated grazing. Many rangelands have been over-stocked and grazed too frequently in order to make a profit and meet growing global beef demand. Land has been ecologically degraded, valuable topsoil was lost, and carbon stores declined as a result.
Let the cow do the work
It would be easy to blame cows for this. But really, they’re not behaving much differently than pronghorn or bison would. They eat what’s in front of them. And they eat the tastier plants first. Howell likens it to a salad bar.
“If you go into a salad bar and there’s some lettuce that has been sitting there for three months, and some of it that’s just been replaced that morning, you take the new stuff. So that’s exactly what the cow does,” Howell says. “If she’s not made to move anywhere new, she’s just going to keep coming back and grazing the regrowth of the good stuff as long as it’s there.”
Pretty soon, perennial grass species, important for their deep roots that help prevent erosion and store carbon and water longer, are grazed into nothing. All that’s left are the sagebrush, dandelions, and other less desirable plants that Howell noticed dotting his family ranch.
“So the whole thing is about how the cows are managed, it’s not the cow itself that is a problem,” says Howell.
But if bad management can degrade the land, then good management should be able to restore it. While studying animal science in college, Howell encountered the concepts of “holistic management”, a term that began to decode this relationship between management practices and the health of the land. Controversial at its introduction a half century ago, holistic ranching has been gaining traction, and Howell and his ranch management company, Grasslands LLC, have helped urge its uptake.
The core principle is to make management decisions that restore lands and keep cattle in balance with the rest of the ecosystem—helping them fill the niche of the ancient grazers. This comes with a host of co-benefits, including water retention and higher plant productivity, that actually end up improving economic profitability for ranches in the long run. Simple adjustments, like lengthening the time between grazing a pasture again and wintering cows on native ranges instead of hay, can turn cattle from an ecosystem destroyer to an ecosystem helper.
“The trick is to let the cows do all the hard work,” says Howell.
Carbon modeling: The rancher’s secret weapon
Dr. Watts and Woodwell Senior Scientist Dr. Jonathan Sanderman, along with Dr. Megan Machmuller of Colorado State University, are interested in quantifying those co-benefits. Especially carbon storage.
“In the western US on our rangelands, just like in our croplands, we can change how we manage in a way that potentially could become a natural climate solution,” says Dr. Watts. “One where we’re bringing in more carbon than we’re emitting and we’re creating ecosystems that not only are beneficial for carbon sequestration, but also have more biodiversity, offer more habitat for wildlife, and more water conservation.”
In order to prove that value however, scientists need a baseline understanding of how much carbon is currently stored across both traditionally-and holistically-managed rangelands. It’s hard to get an estimate for such a large area (roughly 30% of the U.S. is covered with rangelands), so they are using a remote sensing model, which they verify with strategic on-the-ground sampling.
Howell’s work also created the perfect conditions for the research team to study the long term carbon benefits of altered ranching practices, which is a tricky thing to test empirically. Ranchers must constantly adjust their management techniques to stay profitable.
“In a classical research setting, you try to control all the variables but one, but in real life that’s not what happens,” says Howell. “Nothing is controlled. Day to day, you have to adapt to constantly changing conditions.”
But the ranches Howell’s company works with make those day-to-day decisions based on the principles of holistic management, so tracking carbon on those ranches over time offers the opportunity to generate baseline data on how they differ from more traditionally managed ones.
Howell also brought the expertise of a life spent on the range. He can identify just about any plant growing in the pasture, tell you which are native, which are invasive, and which used to be the preferred food of prehistoric ground sloths. His eye is trained to see diversity even in martian-esque deserts and read the history of the land in the structure of the soil. In May of 2022, Howell guided Drs. Sanderman, Watts, and Machmuller and their teams on a sample collection trip through Southwest Colorado and Utah. The researchers took soil cores, plant samples, moisture and temperature readings, and analyzed carbon fluxing in and out of the pasture.
The ultimate goal is to create a rangeland carbon management tool that will make the soil carbon data model accessible directly to ranch managers. Dr. Watts hopes having that data in hand will enable more ranchers to make management decisions with climate in mind. Dr. Sanderman also notes that it could be useful in eventually helping ranchers get paid for sustainable practices.
“Rangelands haven’t been included in voluntary carbon credit markets like cropping systems have,” says Dr. Sanderman. “Monitoring is a big problem because there’s so much land—How do you keep track of all that? That’s what our tool will be able to offer.”
Growing a resilient ranch
There are limits to what grazing can accomplish, though. The lands out west aren’t suitable for large-scale cropping, being too dry or too mountainous, which makes them perfect for cattle. But when the animals take up space on land that would otherwise be used to produce crops—or worse, penned into feedlots—their benefits are compromised. Howell also notes that some grazing lands are already as saturated with carbon as they can be. And there remains the fact that ranching will get more complicated as the climate changes.
At the Valdez ranch in Delta, Colorado, Dr. Sanderman and research assistant Colleen Smith unfold a collapsible table in a field of cracking mud, dotted with the brittle stick skeletons of dead grass. Nearby, Dr. Machmuller is assisting Howell in extracting a long metal cylinder from the ground. It was plunged into the soil by a hydraulic corer attached to a pickup truck that’s idling in the field. Howell and Dr. Machmuller lay it out horizontally on the table and slide out the soil core—a 50 centimeter long history of the land beneath their feet.
Howell breaks open a section of the core with his fingers, revealing clusters of white crystals. This is a pasture that has been abused; over-irrigation by previous owners brought salts to the surface. Now nothing will grow here and wind gusts threaten to blow away loose topsoil. It’s a sacrifice zone. The current owners are considering installing solar panels instead.
Water is a big issue for ranchers and it’s threatening to get bigger. The region is constantly dipping in and out of severe drought, and in a place that depends heavily on winter snows for its groundwater and rivers, a warmer, drier climate is a threat.
Agriculture will depend more on irrigation as the climate warms and precipitation patterns change. But this empty pasture is proof that it’s not always a viable solution, and will become less so as climate change advances.
It enforces the urgency of the work Howell and team are doing. The faster we can draw carbon out of the atmosphere, the more successful these ranches are likely to be in the long term. The better managed the ranch, the more resilient it will be in the face of tough conditions.
In the end, Dr. Watts says, the outcome rests in the hands of ranch managers—people like Howell.
“Land managers are the ones that ultimately are going to make or break this country.”
It’s a windy morning in May and the Valdez ranch in Delta County, Colorado is alive with the sounds of lowing cattle, chattering sparrows, and the whirrs and clanks of scientific equipment. This particular field is not being grazed at the moment, so Woodwell’s soil carbon team has free rein over the rows of alfalfa and sweetgrass.
In collaboration with Dr. Megan Machmuller at Colorado State University, Assistant scientist Dr. Jennifer Watts and senior scientist Dr. Jon Sanderman have brought their teams here to collect field observations that will help inform a comprehensive model of carbon storage on rangelands across the United States. Grazing lands have the potential to be a valuable carbon sink, provided the livestock on them are being sustainably managed, but the true magnitude of that value is not yet well understood. Developing a regional model of the way carbon moves through rangelands will deepen our understanding of the role they play as a natural climate solution.
Ensuring the model’s accuracy requires the team to collect an array of field data from different ranch types—from irrigated and planted pasture, to the natural vegetation of high mountain and desert grazing lands. Here’s how climate scientists study carbon in the field:
Carbon flux: What’s moving in and out of the atmosphere?
Soil carbon storage begins where plants interact with the air. As they grow, plants draw carbon out of the atmosphere through photosynthesis. When they decay, microbes in the soil digest plant matter and breathe carbon dioxide and methane back out. Measuring the difference between these two processes gives us “net ecosystem flux”—a measure of whether a patch of land is sequestering or emitting carbon overall.
Measuring carbon flux requires a specially made chamber. Dr. Watts and Seasonal Field Technician Jonas Noomah employed a plexiglass contraption that Noomah constructed himself. The chamber is placed over a patch of ground, connected by clear tubes to a machine that can analyze the volume of CO2 within the cube. A handheld fan dangles inside the box to keep the air circulating. The transparent plexiglass allows photosynthesis to continue unhindered. After a few minutes, the box is covered to block out the light and the analysis is run again to capture emissions without the photosynthesis component. The numbers can be compared to assess the rate and overall carbon sink or source status of flux within the ecosystem.
Plant productivity: What’s growing under-hoof?
While plants are growing, they lock away carbon as part of their leaves, stems, and roots, so another important metric in the carbon model is plant productivity—more productive plants with established root systems are more likely to store more carbon belowground.
Productivity can be estimated with satellite imagery, but needs to be validated with on-the-ground measurements. Postdoctoral researcher Dr. Yushu Xia and research assistant Haydée Hernández-Yañez walked transects of pasture to collect data on a variety of indicators that could influence aboveground (and belowground) biomass, including height of vegetation, soil moisture, and temperature. Then the scissors come out and all the plants in a plot are cut and put into a labeled paper bag to be weighed and analyzed later in a lab to determine the total mass of plant matter.
Rangelands managed for better carbon storage also come with a host of co-benefits, including higher levels of plant diversity. Different plants cycle carbon and other nutrients at different rates, so Hernández-Yañez sifts through the vegetation before it’s snipped, identifying and recording the species to provide more detail in productivity estimates.
Soil carbon: What’s locked deep in the ground?
Over time, carbon passes out of the cycle of growth and decay, becoming locked underground as soil organic carbon. Accessing and analyzing soil organic carbon requires coring deep into the earth and pulling out a stratified cylinder of dirt. Dr. Machmuller led the team’s soil coring effort along with Dr. Sanderman and research assistant Colleen Smith.
With a hydraulic soil coring machine attached to the back of a pickup truck, the team rambled through muddy pasture and over sharp bushes to collect 50 centimeter cores. When the terrain was too steep, they pulled out a handheld corer that had to be driven into the soil with a sledgehammer.
The soil cores are separated into three sections and crumbled up. Smith then uses a handheld scanner that employs the same technology used by astronomers to determine the chemical makeup of distant star systems to read the carbon content of each section. The scanner bounces light off the soil particles and the pattern of reflection gives clues to what molecules are present at different depths. Abundance of carbon is sometimes obvious to the naked eye in the cores, showing up as darker, wet sticky soil.
Putting data in the hands of land managers
Drs. Watts and Sanderman and their team are in the process of creating a rangeland carbon management tool that will make the soil carbon data model accessible directly to ranch managers. The website, developed by Dr. Xia, will generate data on carbon and plant productivity, for any geographic area down to the size of a single pasture. The hope is that the tool could be integrated into land managers long-term decision making, and show the results of adapting to more holistic, sustainable management practices over time.
“In the western US on our rangelands, just like in our croplands, we can change how we manage in a way that potentially could become a natural climate solution,” says Dr. Watts. “One where we’re bringing in more carbon than we’re emitting and we’re creating ecosystems that not only are beneficial for carbon sequestration, but also have more biodiversity, offer more habitat for wildlife, and more water conservation.”
Demonstrating the co-benefits of managing rangelands for carbon will also help expand conversations about whether ranching can be done sustainably, from the ground up.
“It allows for transfer of climate solutions into the hands of practitioners who may not otherwise think about climate change. It opens the conversation.” says Dr. Watts.
Ultimately, having that data could be useful for rangeland managers taking part in carbon credit markets, which could help them get paid for sustainable management.
“Rangelands haven’t been included in voluntary carbon credit markets like cropping systems have,” says Dr. Sanderman. “Their monitoring is a big problem because there’s so much land. How do you keep track of all that? That’s what our tool will be able to offer.”