I’m a field research scientist. What does this mean? I enjoy being outside, in forests and wetlands, studying the environment up close and personal. One of my favorite places to work and explore over the course of my career has been Howland Research Forest in central Maine.
Dominated by red spruce, eastern hemlock, and red maple, this mature northern forest feels old. There is a 400 year old yellow birch that was already a mature tree during the American revolution. The ground is soft— spongy with a lot of “holes” where past trees have fallen and roots decomposed. My feet often plunge into these holes, which can sometimes be filled with water.
The Howland Forest Research station was established in 1986 by the University of Maine in partnership with a packaging and paper company, International Paper. My first trip to Howland Forest was in 1998 and at the time the research center was just a collection of trailers housing equipment. I had never seen so much mouse poop in a building.
Howland was one of the first sites ever dedicated to measuring the net exchange of carbon between a forest and the atmosphere. Its support comes from the Ameriflux Network, a grass roots, science driven network of research stations spread across North and South America that monitors the flow of carbon and water across ecosystems. In these early years, Howland forest also served as a training site for testing out NASA’s remote sensing capabilities. At one time, Howland Research Forest was the most photographed site on earth from space. Soon the well used trailers were replaced with multiple buildings to accommodate the ever expanding research. The mice were evicted.
Howland forest was selectively harvested over 100 years ago, evidenced by cut stumps, but the forest has remained intact, growing under natural conditions since then. Most trees range between 100-120 years old. In 2007, International Paper was scheduled to harvest these mature trees. Recognising the value of maintaining a continuous long-term record of observations, scientists from Woodwell Climate Research Center, The University of Maine (UMaine Orono), and the U.S. Forest Service (USFS) partnered with the Northeast Wilderness Trust (NEWT) to purchase the forest. The Howland Research forest, now owned by NEWT, was protected in a forever wild state. This science and conservation partnership saved an invaluable mature natural forest and research site. As scientists continued to collect data over the next decades, we would learn just how important this partnership was to our understanding of mature forests.
Long-term measurements of carbon exchange between the forest and the atmosphere are being taken from the top of a tower, as part of the Department of Energy (DOE) supported Ameriflux Network, and paired with measurements on the ground. It’s the measurements on the ground where I come in. Myself and collaborators at UMaine Orono, USFS and a host of other scientists and students over the decades have measured carbon exchange from soils, tracked changes in temperature and moisture, and taken tree inventories.
Mature forests contain large stores of carbon in their tree stems, foliage, roots, and within the soils, accumulated over decades of growth and decomposition. Allowing mature forests to continue to grow, untouched, is beneficial to maintaining carbon stores along with the natural biodiversity and water cycling, often collectively called “ecosystem services”.
Over the last 25 years, Howland Research Forest has seen the warmest, driest, and wettest years. Observations show an increasing trend in the net uptake of atmospheric carbon (as carbon dioxide) into this mature forest, meaning that Howland forest is continuing to take up and store more carbon each passing year.
If the forest had been harvested in 2007, observations spanning that shorter time frame would have indicated a decreasing trend in net net carbon uptake, meaning that Howland Forest was taking up less carbon each passing year.
Although Howland Forest continues to take up carbon, the overall number of live trees has been declining (17% decline since 2001 in live trees, particularly red spruce and northern white cedar) and the number of dead trees has nearly doubled since 2001. Theoretically, fewer live trees would indicate less carbon uptake, but that is not happening. The mature, large diameter trees continue to grow; although there may be fewer in number, they continue to take up significant amounts of carbon.
Tree species can differ in how they respond to environmental changes as well as how carbon is allocated within the tree and across a mature forest ecosystem. Teasing out these complex, multi-scaled, multispecies responses requires long term studies. However, given the challenges to acquiring and sustaining funding for long-term studies, it’s unusual to have this type of paired dataset like we have at the Howland Research forest. This would not have been possible without the forward-looking vision of scientists and NEWT, and the consistent support from the Ameriflux Network.
Thanks to its preserved, forever-wild status, a new generation of scientists has the opportunity to continue this work, building on our understanding of the mechanisms driving climate resilience in this mature northern forest.
The partnership between science and conservation is a victory for both. Results from the Howland Research Forest demonstrate the need to continue supporting long-term studies to fully understand how natural, mature forests respond to a changing climate. Conservation organizations and land trusts are preserving and restoring critical habitats across the U.S. and the globe. This is an opportunity to build alliances between science and conservation, to inform how natural ecosystems function and the impact of restoration efforts on the ecosystem services that we all benefit from, while preserving natural spaces for future generations.
The last decade has shattered global temperature records, with all 10 of the planet’s warmest years occurring since 2015. Under the Paris Climate Agreement, countries across the world are working to limit global warming to 1.5 degrees Celsius by decreasing their heat-trapping greenhouse gas emissions. But researchers say more action is needed to protect us from the worst impacts of climate change.
“We’re beyond the point where emission cuts alone are going to keep us within a safe climate range. We need to remove carbon from the atmosphere,” Dr. Jonathan Sanderman, carbon program director and senior scientist at Woodwell Climate Research Center, says. “And there’s really two ways of doing that: tech-based solutions, like direct air capture or other engineering-based solutions, or we could try to reverse the last several 100 years of degrading nature and pull more carbon back into the biosphere.”
While both solutions are likely needed, Sanderman and others at Woodwell Climate are focused on using the power of natural environments, such as forests, wetlands, agricultural land, and rangelands, to reduce carbon in the atmosphere. These methods, called nature-based climate solutions, help combat climate change in three major ways: decreasing greenhouse gas emissions from deforestation, capturing and storing carbon from the atmosphere, and building ecosystems more resilient to climate hazards such as flooding and wildfires, according to the International Union for Conservation of Nature (IUCN).
Natural climate solutions could contribute more than 30% of the cost-effective climate solutions needed globally in the next few decades. They could also save countries hardest hit by climate change $393 billion in 2050 and reduce climate hazards by 26%.
Storing carbon on land
Sanderman researches one of Earth’s largest carbon pools: the soil. Plants release carbon they’ve absorbed from the atmosphere back into the ground when they die, which stores a total of about 2,500 gigatons of carbon globally.
“Soils hold four times as much as trees do — about three times as much as the atmosphere,” Sanderman says.
Good land management can stabilize the amount of carbon in soil, but soils across the world have degraded substantially due to cultivation and overgrazing around the turn of the century.
Storing carbon in the ground not only reduces the level of this greenhouse gas in the atmosphere, but carbon is the backbone of soil organic matter, which is a key regulator of soil health and crop yield consistency. It helps reduce erosion, keep soil structure in place and retain water. Carbon is often used as an indication of soil quality, with healthy soils usually containing about 2% organic carbon. Yet, precisely determining how much carbon is stored in soils worldwide — and which land management techniques lead to the most efficient carbon storage — is tricky.
Rangelands as a nature-based climate solution
Sanderman is working with Dr. Jennifer Watts, the Arctic program director and an associate scientist at Woodwell Climate, to understand how much carbon dioxide U.S. rangelands are helping capture. These lands have big potential for sinking carbon: Rangelands make up about 31% of land area across the U.S. and about 54% across the world. Using both field data and satellite data, Sanderman and Watts are creating models of overall rangeland health in the U.S. Using this information, they can then quantify how much carbon is gained or lost over time under different scenarios.
“We are hoping, with our integrated system, to be able to provide the ability to scan all landscapes to determine their carbon status, and then go back in time and look at the trajectories of change,” Watts explains. “And provide that information directly to the land managers so they can make really informed decisions on where they should invest conservation work. At the same time, it’s great for us, because as an output, we get to quantify how much carbon is being gained versus lost in certain places and what the climate benefits are.”
Capturing Methane
While carbon dioxide is one of the most abundant and long-lasting greenhouse gases, methane is far more efficient at trapping heat in the atmosphere. Per molecule, it’s about 80 times more harmful in the atmosphere than carbon dioxide, though it lasts an average of only a decade in the air, whereas carbon dioxide can persist for centuries. Nevertheless, reducing methane emissions by 45% by 2030 could help us reach our goal of limiting global warming to 1.5°C, per the United Nations.
Cutting anthropogenic methane emissions should be prioritized, but using nature-based solutions to increase uptake can also help bring down methane concentrations in the atmosphere. Although forests and soils play a smaller role in methane cycling, “When you start thinking about how much they can do over large areas, the numbers really get big,” Watts says. “And then it makes a huge difference.”
In northern forests across the U.S., Woodwell Climate researchers have set up methane monitoring systems, including specialized towers that measure the exchange of greenhouse gases, energy, and water between the ecosystem and the atmosphere. The team also analyzes soil samples from the forest to see exactly where methane-consuming and methane-producing microbes are thriving.
The team has discovered a unique feature of the Howland Research Forest in Maine: It is an overall methane sink — though exactly why remains unknown. But by understanding more about how and under which conditions these methane-consuming microbes live, forest managers can change their strategies to harness the creatures’ natural power to reduce the effects of climate change.
To combat the climate crisis, we must do “a lot of things simultaneously,” Watts says, including using good land management practices to capture and store greenhouse gases.
“Working with nature has a lot of advantages, because you’re optimizing the health of ecosystems, at the same time providing ecosystem services, not just for climate but also for local communities,” Watts says. “If we identify how to do this effectively, we’re really unleashing the power of something that’s already there, and then trying to work with it instead of against it.”
A Permafrost Pathways study informed one of the biggest headlines in the National Oceanic and Atmospheric Administration’s (NOAA) 2024 Arctic Report Card, sending a clear but alarming message to the world: more than one-third of Arctic-boreal region has shifted to a source of carbon. The sobering results, mentioned in over 700 news stories from 42 countries, shed light on the urgency of Arctic research.
Read more on Permafrost Pathways.
A new study, published today in the peer-reviewed journal Biological Conservation and co-authored by scientists from Woodwell Climate Research Center and Wild Heritage, finds that greater protections of mature and old-growth forests in the United States are critical to meeting global commitments to forestall the climate and biodiversity crisis. The research underscores why safeguarding the nation’s carbon stockpile in older forests needs to be a focus of U.S. policy to reduce emissions from commercial logging and burning of fossil fuels.
Using a new approach combining remote sensing of forest structure with ground data from the federal Forest Inventory and Analysis (FIA) program, the research team analyzed younger, mature, and old-growth forests across the contiguous U.S., looking at their size and carbon stocks, as well as ownership (public or private) and protection status, to examine how much additional carbon could be protected if stricter regulations were in place to curb commercial timber harvesting.
According to the study, contiguous U.S. forests currently hold 54.3 billion tonnes of carbon. However, 83% of that carbon stock remains unprotected, revealing the critical role that policy action to prevent increased logging of federal forests can play in promoting ecosystem benefits and enabling U.S. forests to reach their full carbon storage potential. This is especially true for mature and old-growth forests, which provide the greatest climate and biodiversity benefits.
“Mature and old-growth forests are made up of our oldest and typically largest trees, that not only store massive amounts of carbon right now, but can continue to accumulate carbon for centuries if protected. These forests also play an irreplaceable role in maintaining biodiversity, fostering ecosystem resilience, promoting human health, and much more,” said Dr. Rich Birdsey, Senior Scientist at Woodwell Climate and lead author of the study. “As communities everywhere feel the real time consequences of the climate crisis, our policies must reflect the urgent and unparalleled importance of preserving these forests to reduce emissions and bring global temperatures back down.”
With stepped-up protection measures that avoid logging of mature and old-growth forests and large trees, and allow mature forests to develop into old growth over time, researchers found that the total carbon stored in these forests could increase by 10.8 billion tonnes within decades, locking away the equivalent of eight full years of fossil fuel emissions in the United States.
“Our study points to the urgency of protecting the nation’s best natural climate solution, especially as the current administration begins to ramp up logging on public lands under the President’s executive orders,” said Dr. Dominick A. DellaSala, Chief Scientist at Wild Heritage and study co-author. “This is the worst possible time for backpedaling on forest protections and our international commitments for a safe climate.”
The study can be found here.
Passed in 1970, the National Environmental Policy Act (NEPA) requires U.S. federal agencies to assess the environmental impacts of their proposed actions prior to implementing them. To facilitate this, and to ensure decisionmaking is uniform across government agencies, the law stipulates regulations around the process for conducting these impact assessments. A March ruling from the Council of Environmental Quality (CEQ) removes these regulations, opening up the possibility for regulatory confusion and inconsistency between agencies that ultimately lessens the effectiveness of environmental protections.
Woodwell Climate Research Center submitted a public comment on the ruling, criticizing the move for its potential to hinder coherent decisionmaking based on rigorous science. The comment states:
“NEPA reviews are not an impediment to “major federal actions” but provide an essential, science-based safeguard for ensuring that decisionmaking adequately balances a myriad of interests. This balance is especially critical in areas of the United States where increasingly frequent natural disturbances and extreme events threaten to derail the durability of a proposed federal action.”
The comment speaks to the effectiveness of the existing environmental review process, especially for decisionmaking in Alaska, where construction projects were guided to consider the impacts of permafrost thaw and erosion as part of hydrological and ground assessments, and in forest management plans, where the NEPA review process ensures management strategies are scrutinized with empirical data.
The ruling is considered “interim final” which means it can be put into effect before comments have been considered and is not dependent on public input. Despite this, engaging in the rulemaking process is one critical way Woodwell Climate contributes to environmental policy. It ensures that technical expertise is part of the public record, and provides evidence that can be used in court cases should the ruling or any action based on it be challenged in the future.
The full comment can be read here.
In the Arctic, permafrost plays a crucial role in building infrastructure. However, as the region warms and permafrost thaws, infrastructure is threatened as the ground shifts beneath the built environment. Unfortunately, the full extent of the risks associated with this process is not yet realized, but researchers are working to address this knowledge gap.
Woodwell Climate Associate Scientist, Dr. Anna Liljedahl, along with UConn Department of Natural Resources and the Environment researchers Elias Manos and Assistant Professor Dr. Chandi Witharana developed a method that uses high-resolution satellite imagery and deep machine learning to map Alaskan infrastructure and more accurately project economic risks associated with permafrost thaw. Their findings published in Nature Communications Earth and Environment estimated that the costs of permafrost damage to infrastructure will double under low and medium emissions scenarios by 2050.
“Damages to infrastructure caused by permafrost thaw is on par with the average yearly cost of all natural disasters in the country, yet permafrost thaw is not recognized by the federal government as a natural hazard making it harder for people in Alaska to obtain disaster relief funding,” says Liljedahl.
This study is the latest from Witharana’s research group, which examines the ways satellites can help monitor changes in the Arctic landscape over time. According to Manos, in order to understand the hazards of a changing climate, we need a clear understanding of what’s at risk—in this case, vital structures like buildings and roads.
Permafrost serves as a structural foundation; piles are secured through it and buildings are often designed specifically to help the thermal integrity of this anchor layer. But the structural integrity of the layer, and consequently the structures above, is compromised as the permafrost thaws.
“When the temperature of permafrost starts to increase, piles start to shift out of place, and that’s what we call bearing capacity loss, or decrease in bearing capacity. That was the main hazard that we looked at which impacts buildings,” says Manos. “Then there’s also transportation infrastructure that’s primarily impacted by ground subsidence. When ice-rich permafrost thaws, the ground will cave in and that was the hazard we used to assess the disaster risk for roads.”
Previous studies have made risk estimates based on data from OpenStreetMap (OSM), which is one of the most widely used geospatial data sets available, says Manos. OSM is available for every nation across the globe, and information is updated by volunteers who manually input local data, like buildings, trails, roads, or other kinds of infrastructure, from high-resolution imagery on a global scale. For some regions, like Europe and parts of the United States, the data is accurate, says Manos, but that is not true for all locations. Unfortunately for the Arctic, OSM data is lacking.
“There are several previous risk studies that relied on this incomplete infrastructure data. It all goes back to the fact that infrastructure across the Arctic is not completely mapped, and that’s problematic if you want to understand disasters because you must have the full picture to understand the scale of what is or could potentially be exposed,” says Manos.
To fill in that picture, Witharana’s group developed a method to accurately map infrastructure and permafrost thaw risk called High-resolution Arctic Built Infrastructure and Terrain Analysis Tool (HABITAT). The model uses machine learning and AI to extract road and building information from high-resolution satellite images from the years 2018-2023. They compared the HABITAT data with OSM data to evaluate the new model’s quality and to look for potential misclassifications. Then they added the new information to OSM, nearly doubling the amount of information available for Alaska.
“The sheer amount of infrastructure and buildings that were missing from Open Street Map was, really shocking to me, 47% missing,” says Manos. “Though OpenStreetMap is a powerful volunteer-based resource, it has limitations and that is not a surprise.”
Witharana adds that by combining OSM data with the thousands of sub-meter resolution satellite images provided by the National Science Foundation, along with access to NSF supercomputing infrastructure, it was possible for the researchers to enhance the completeness of these datasets.
“We can see that impact and do better assessments of economic disturbances and risk so we can prepare for whatever policy actions or downstream efforts that are needed,” says Witharana “That’s a major outcome. Overall, the integration of AI and big data sets within our application has helped make useful, actionable products that researchers and communities can use right now.”
Witharana, Liljedahl, and Manos have plans to expand this analysis to account for the entire Arctic region to assess economic losses using a comprehensive infrastructure map.
“Alaska is decades behind the rest of the country in terms of geospatial data readiness. Maps are key for assessments and planning and I think the research community can help with some of that,” says Liljedahl.
Associate Scientist, Dr. Brendan Rogers has walked in many forests, but primary forests, he says, “just feel different.”
Rogers’ work often takes him to the cool, dark understories of black spruce and pine boreal forests, where he’s learned the subtle markers of a truly old, healthy, stable forest ecosystem.
“Generally cooler, often wetter, the trees are bigger but sparser and more likely to be conifers than shrubs or deciduous broadleaf trees,” says Rogers. “The ground is squishy to walk on, from the build-up of peat-like soils, mosses, and lichens.”
Primary forests are also a critical piece in the climate puzzle. They represent centuries of sequestered carbon, and every year they remain standing these forests continue to pull carbon from the atmosphere and lock it away in their trees and soils. They are also the subject of intense debates in forest management circles because, according to Rogers, despite knowing intuitively when you are standing in a primary forest, quantitatively identifying one is a tricky task.
That fact hasn’t deterred Rogers and his collaborator Dr. Brendan Mackey at Griffith University, from their work to identify and map metrics indicative of primary forests. In a joint project launched in 2018, Rogers and Mackey created an index of one such metric— forest stability.
Measuring forest stability
Forest stability is a measure of a forest’s resistance to disturbances, both manmade and natural. A stable forest has a high level of ecosystem integrity—a holistic term referring to the combination of ecosystem structure, function, species composition, and adaptive capacity. Stability reflects the ability of a forest to maintain all of those elements in the face of disturbance.
To quantify stability, Rogers and Mackey isolated two metrics that correlate heavily with integrity in forests— “greenness” and water stress. Greenness, also known as the fraction of photosynthetically active radiation (fPAR), indicates the amount of thriving, photosynthesizing plants. Water stress is an index of anomalies in vegetation moisture, indicating an area is dryer than usual. Both of these metrics can be remotely derived from satellites and, when combined with additional data, form an index of overall stability level.
This index was first tested by a postdoctoral scientist at Woodwell Climate, Dr. Tatiana Shestakova, who pulled data from NASA’s MODIS satellite sensor to map stability in sample regions in the Kayapo Indigenous Territory in the Brazilian Amazon and southern Taiga region of Siberia. After testing the model, Rogers, Mackey, and Shestakova expanded it to map stability across the entirety of Ontario, Quebec, boreal Siberia, and the Amazon rainforest.
The studies used a method called a time series analysis, which compares satellite data stretching back to 2002 to determine whether a forest had experienced a large-scale disturbance, reducing vegetation greenness and increasing water stress and thus lowering overall stability. These insights were only possible due to the long, consistent dataset produced by MODIS.
“It can be a little bit dicey to assess stability on shorter time scales,” says Rogers. “Because when you work with remote sensing data, forests can fluctuate year to year and sometimes you can’t completely eliminate things like cloud contamination or other errors from the data, so a longer time series helps smooth the data and lets you see the true patterns.”
Prioritizing protection for primary forests
These maps of stability have a crucial role to play in informing forest management policy.
“We’re trying to analyze and spatially map the ecological condition of forests,” says Mackey. “Because this information is needed to help guide where investments for forest protection and restoration go and how they should be prioritized.”
For a long time, Mackey says, management conversations did not distinguish between types of forests, lumping monoculture tree plantations into the same category as ancient natural forests, despite the vast differences in their carbon storage, biodiversity, ecosystem benefits, and overall resistance against disturbances.
“We weren’t seeing the forest for the wood,” Mackey jokes.
Quantifying a characteristic like stability makes it easier for managers to see the difference between the two, identify the forests best able to provide myriad ecological benefits, and ideally, prioritize those for protection.
Mackey uses the example of woodland caribou in Canada, which are considered a threatened species. These animals require large areas of intact primary forest to support successful populations. Overlaying forest stability on top of caribou habitat maps can help decisionmakers narrow in on the largest, highest-stability tracts of forest as top priority for conservation.
According to Rogers, a future goal would be to eventually link maps of forest stability with carbon estimates in order to create forest protection plans with climate mitigation in mind. Research in primary forests has shown they continue to sequester carbon year over year, even though tree growth has tapered off. With primary forests in many places under intense political and economic pressures, it will become even more important to demonstrate the many co-benefits of protecting the earth’s stable forests.
“There’s no forest anywhere that isn’t threatened,” says Mackey. “Development, infrastructure, roading, damming, logging, clearing for agriculture. It’s happening everywhere.”
Stable forests are resilient forests
Tracking stability of forests also allows us to approach a much harder-to-define characteristic of primary forests—resilience.
Stability and resilience go hand in hand, though they are not the same thing. While resilience speaks to an ecosystem’s adaptive capacity or its ability to recover to its original state after some disturbance, stability is a measure of resistance, which is why it correlates so highly to primary forests that haven’t experienced any recent large-scale disturbance.
“If the stability index is showing recovery, then there’s obviously some resilience happening, but beyond that, primary forests tend to be more resistant to certain disturbances,” says Mackey. “Sometimes resistance is better even than being resilient. You’re not destroyed in the first place.”
Highly stable forests do tend to have better adaptive capacities as well, which is why they are so critical to protect.
“By and large,” says Rogers, “forests are resilient.” The stable ones can handle disruptions, and if you leave them to recover they will do just that, as he and Mackey have seen in the data.
But resilience is not infinite. If you hit too hard too fast—overlapping disturbances on an already unstable forest—you can overwhelm its resilience. Fires, larger and more frequent as a result of climate change, have already begun to override boreal forests’ adaptation. And there are more changes coming as the planet continues heating up.
For now, at least, Rogers says, “resilience is still largely what we see out there.”
Despite thorough preparations, flying the drone is still nervewracking.
Dr. Manoela Machado, a Research Scientist at Woodwell Climate, has double- and triple- checked her calculated flight path over a study plot in the Cerrado, Brazil’s natural savanna. The drone can essentially fly itself, and she’ll be monitoring its speed, altitude, and battery life from her handheld controller on the ground, but many things could still go wrong. High winds, an unforeseen obstruction, loss of connectivity— all could jeopardize the mission, potentially dropping the expensive equipment 40 meters into the woodland canopy below.
Aboard Machado’s drone sits a powerful piece of technology – a LiDAR sensor. Developed originally for use in meteorology, this remote sensing technique now has widespread applications across scientific fields, from archaeology, to urban planning, to climate science. At Woodwell Climate, Machado and others employ LiDAR to create detailed three dimensional models of landscapes, which provide valuable insight into the structure of ecosystems and the amount of carbon stored in them— all with just a few (million) pulses of light.
What is LiDAR?
LiDAR stands for Light Detection and Ranging. Put simply, it is a sensor that uses laser light to measure distance.
Similar to other technologies like sonar and radar, which use sound and radio waves, respectively, LiDAR is an example of an “active” sensor. “Passive” sensors like cameras collect ambient light, while LiDAR actively pings the environment with beams of laser light and records the time those beams take to bounce back. The longer the return time, the further away an object is. That distance measurement is then used to calculate the precise location in three-dimensional space for each reflection.
This process is repeated millions of times during a single scan, resulting in a dense cloud of point locations. With some advanced computing, the data can be assembled into a 3D picture of the landscape.
“It’s effectively three dimensional pointillism,” says Woodwell Climate Chief Scientific Officer, Dr. Wayne Walker, who has been using LiDAR in his studies for 25 years.
Far more detailed than an oil painting however, a LiDAR model can reconstruct nearly every leaf, twig, and anthill on a landscape.
“Once you construct that cloud of millions of points, you get to walk inside the forest again,” says Machado. “When you finish processing the data and see the cloud you go, ‘I remember that tree! I remember standing there!’ It’s mesmerizing.”
For a project like Machado’s, scanning a few dozen hectares, the sensor is usually placed on a drone. Larger study areas require sensors mounted on low-flying airplanes or even satellites, but for small ground-based applications there are sensors one can carry, mount on a tripod, or attach to a backpack. Some newer phone models even have LIDAR apps built in. Regardless of how LIDAR is deployed, it remains a straightforward method of data collection. Just point the sensor at what you want to scan and within minutes, you’ve captured the data for a detailed three-dimensional model of your area of interest.
Estimating the weight of a forest
What Machado and Walker are often after from a LiDAR scan is a measurement of biomass, or the total weight of the organic matter present in an ecosystem. Plants store carbon in the form of organic matter, so biomass measurements are an easy way to estimate an area’s carbon storage.
However, measuring a forest’s biomass directly would require cutting down all the trees, drying them out, and weighing what’s left — impractical and needlessly destructive— so scientists use proxy measurements. Walker likens the process to trying to estimate the weight of a human without access to a scale.
“What are the measurements you might use if you couldn’t actually physically measure weight? You might record height, waist size, inseam, and if you obtain enough of these measurements you can start to build a model that relates them to weight,” says Walker. “That’s what we’re trying to do when we estimate the biomass of an entire forest.”
Raw LiDAR data is only a measurement of distance, but by classifying each point based on its location relative to the cloud, researchers are able to extract the proxy measurements needed to model biomass across the ecosystem. Before LiDAR, these proxy measurements— things like trunk diameter, height, and tree species— had to be recorded entirely by hand, which limits data collection based on human time and resources. The time-saving addition of LiDAR has vastly expanded the possible scale of study plots. While field measurements are still essential to calibrate models, LiDAR is one of the only technologies that can give scientists enough detail and scope to assess carbon stocks over entire ecosystems.
“There is no other kind of sensor that even comes close to LiDAR,” says Walker.
The power and potential of LiDAR
At Woodwell Climate, researchers have employed the power of LiDAR to map biomass and carbon from Brazilian forests, to the Arctic tundra. Outside of the Center, the technology has found applications in archaeological surveys, lane detection for self-driving cars, and topographical mapping down to a resolution of half a meter.
But the detail that makes LiDAR so powerful can also make the data a challenge to work with. A single scan produces millions of data points. According to Geospatial Analyst and Research Associate, Emily Sturdivant, who analyzed LiDAR data for Woodwell’s Climate Smart Martha’s Vineyard project, that wealth of data often overwhelms our ability to extract the full potential of information available in one point cloud.
“LiDAR creates so much data that when you look at it, it’s hard not to be blown away imagining all the different things you could do with it. But then reality kicks in,” says Sturdivant. “It’s challenging to take full advantage of all those points with our current processing power. It’s a matter of the analysis technology catching up with the data.”
Processing LiDAR data requires large amounts of computing time and storage space, especially when performing more complex analyses like segmenting the data on the scale of individual trees. As machine learning and cloud computing technologies advance however, this becomes less of an obstacle, and the potential insights from LiDAR datasets will advance along with them.
LiDAR can be an expensive endeavor, too. Drones with the right equipment can cost tens of thousands of dollars, as can hiring a plane and pilot and paying for jet fuel, so data sharing has been important in making the method more cost effective. U.S. government agencies like NASA and the USGS have facilitated the collection of LiDAR data through satellites and plane flights, making the data available for public use. Woodwell Climate research has benefitted from these public datasets, using them to inform landscape studies and carbon flux models.
According to Sturdivant, the reliable production of public data has been greatly beneficial to advancing LiDAR-based studies, though it now faces risks from federal cuts to science agency funding.
“One of the greatest advantages of having publicly supported data is the consistency, but that’s exactly what’s now at risk,” says Sturdivant. “Public accessibility has been so important in allowing new scientists to learn and experiment and then help everyone else learn.”
Each new LiDAR scan represents a trove of information that could be used to better understand our changing planet, making it critical to continue supporting and collecting LiDAR data. Its intensely visual and highly detailed nature has made it one of the most powerful tools we have for understanding something as complex as a forest.
“And on top of that,” says Machado “It’s just visually beautiful.”