When it comes to reversing climate change, trees are a big deal. Globally, forests absorb nearly 16 billion metric tonnes of carbon dioxide per year, and currently hold 861 gigatonnes of carbon in their branches, leaves, roots, and soils. This makes them a valuable global carbon sink, and makes preserving and maintaining healthy forests a vital strategy in combating climate change.

But not every forest absorbs and stores carbon in the same way, and the threats facing each are complex. A nuanced understanding of how carbon moves through forest ecosystems helps us build better strategies to protect them. Here’s how the world’s different forests help keep the world cool, and how we can help keep them standing.

Tropical forest carbon

Tropical rainforests are models of forest productivity. Trees use carbon in the process of photosynthesis, integrating it into their trunks, branches, leaves, and roots. When part or all of a tree dies and falls to the ground, it is consumed by microorganisms and carbon is released in the process of decay. In the heat and humidity of the tropics, vegetation grows so rapidly that decaying organic matter is almost immediately re-incorporated into new growth. Nearly all the carbon stored in tropical forests exists within the plants growing aboveground. 

Studies estimate that tropical forests alone are responsible for holding back more than 1 degree C of atmospheric warming. 75% of that is due simply to the amount of carbon they store. The other 25% comes from the cooling effects of shading, pumping water into the atmosphere and creating clouds, and disrupting airflow.  

In many tropical forest regions, there is a tension between forests and agricultural expansion. In the Amazon rainforest, land grabbing for commodity uses like cattle ranching or soy farming has advanced deforestation. Increasing protected forest areas and strengthening the rights of Indigenous communities to manage their own territories has proven effective at reducing deforestation and its associated emissions in Brazil. “Undesignated lands” have the highest levels of land grabbing and deforestation.

Fire has also become a growing threat to the Amazon in recent years, used as a tool to clear land by people illegally deforesting. When rainforests have been fragmented and degraded, their edges become drier and more susceptible to out-of-control burning, which weakens the forest even further. Enforcing and strengthening existing anti-deforestation laws are crucial to reduce carbon losses.

In Africa’s Congo rainforest, clearing is usually for small subsistence farms which, in aggregate, have a large effect on forest loss and degradation. Mobilizing finance to scale up agricultural intensification efforts and rural enterprise within communities, while implementing protection measures, can help decrease the rate of forest destruction. Forests and other intact natural landscapes such as wetlands and peatlands could be the focus of climate finance mechanisms that encourage sustainable landscape management initiatives. 

Temperate forest carbon

Much of the forest carbon in the temperate zone is stored in the trees as well— particularly in areas where high rainfall supports the growth of dense forests that are resilient against disturbances like drought or disease. The temperate rainforests of the Northwestern United States, Chile, Australia, and New Zealand contain some of the largest and oldest trees in the world. 

Two thirds of the total carbon sink in temperate forests can be attributed to the annual increase in “live biomass”, or the yearly growth of living trees within the forest. This makes the protection of mature and old-growth temperate forests paramount, since older forests add more carbon per year than younger ones and have much larger carbon stocks. Timber harvesting represents one of the most significant risks to the carbon stocks in temperate forests, particularly in the United States where 76% of mature and old growth forests go unprotected from logging. Fire and insects are also significant threats to temperate forests particularly in areas of low rainfall or periodic drought.  

Maintaining the temperate forest sink means reducing the area of logging, by both removing the incentive to manage public forests for economic uses and by providing private forest owners with incentives to protect their land. Low-impact harvesting practices and better recycling of wood products can also help bring down carbon losses from temperate forests. In areas threatened by increasingly severe wildfires, reducing fuel loads especially near settlements can help protect lives and property. 

Boreal forest carbon

In boreal forests, the real wealth of carbon is below the ground. In colder climates, the processes of decay that result in emissions tend to lag behind the process of photosynthesis which locks away carbon in organic matter. Over millennia, that imbalance has slowly built up a massive carbon pool in boreal soils. Decay is even further slowed in areas of permafrost, where the ground stays frozen nearly year round. It estimated that 80 to 90% of all carbon in boreal forests is stored belowground. The aboveground forest helps to protect belowground carbon from warming, thaw, decay, and erosion.

Wildfire— although a natural element in boreal forests— represents one of the greatest threats to boreal forest carbon. With increased temperatures, rising more than twice as fast in boreal forests compared to lower latitudes, and more frequent and long-lasting droughts, boreal forests are now experiencing more frequent and intense wildfires. The hotter and more often a stand of boreal forest catches fire, the deeper into the soil carbon pool the fire will burn, sending centuries-old carbon up in smoke in an instant. Logging of high-carbon primary forests is also a big issue in the boreal.

The number one protection for boreal forest carbon is reducing fossil fuel emissions. Only reversing climate change will bring boreal fires back to the historical levels these forests evolved with. In the meantime, active fire management in boreal forests offers a cost effective strategy to reduce emissions— studies found it could cost less than 13 dollars per ton of carbon dioxide emissions avoided. Strategies for fire management included both putting out fires that threaten large emissions, and controlled and cultural burning outside of the fire season to reduce the flammability of the landscape.

Drought, driven by a combination of El Niño and climate change, has disrupted shipping through the Panama Canal in recent months. Dropping water levels in Lake Gatun forced Panama Canal authorities to pose restrictions on the number of ships that can pass the canal, dropping from the normal 38 down to 24 transits a day by November 2023, causing long queues at nearby ports as ships wait their turn to pass. If the restrictions remain in place through 2024, there could be up to 4,000 fewer ships—with cargo ranging from children’s toys, to solar panel components, to life-saving insulin—passing the canal in 2024. Delay and disruption along shipping routes will only become a more common occurrence in a warmer world. These 7 graphics show how drought threatens serious disruptions to the global supply chain.

1. Panama in Drought

Panama is currently suffering a prolonged drought that began in early 2023 and has not let up. In October, rainfall was 43% lower than average levels, making it the driest October since the 1950s. For the area around the canal, 2023 was one of the driest two years since record keeping began in the country.

2. El Niño-driven dryness exacerbated by climate

Panama’s severe drought is being exacerbated by the double-whammy of a strong El Niño and record-breaking global warming— exceeding the pre-industrial temperature average by 1.35 C. El Niño is a natural climate fluctuation that brings warmer-than-average air and ocean waters to the West coast of the Americas. That influx of warmth can vary in strength and last between nine and twelve months, and the National Oceanic and Atmospheric Administration (NOAA) predicts it will continue into at least April of 2024.

The severity of El Niño fluctuations is linked to climate change. Climate modeling shows swings between El niño and its counterpart La niña have been growing more extreme, resulting in the more frequent and intense events seen in the past few decades Under high emission scenarios, in which we don’t get warming in check, El Niño events could become 15-20% stronger.

3. Gatún Lake levels continue to drop

The drought has had a particularly profound effect on the man-made Gatún Lake, which holds the water supply that operates the Panama Canal. On January 1, 2024 water levels in Gatún Lake were lower than in any other January on record, almost 6 ft lower than January 1, 2023. Millions of gallons of water from Gatún, along with other regional lakes, are used to fill the locks that raise ships above sea level for the passage over Panama’s terrain. Insufficient water supply jeopardizes ship passage

Not only does Gatún Lake feed the locks that power the Canal, it also supplies drinking water to millions of residents in the central region of the country, including two major cities: Panama City and Colón. As both Panama’s population and the scale of global shipping has grown, there has been greater demand on the lake for freshwater.

4. Less water means fewer, smaller ships

In response to dropping water levels, Panama Canal Authorities have been forced to institute restrictions on ship passages. Ship transits are currently limited to 24 per day until April of 2024, when the authorities will re-evaluate at the start of the rainy season. The number of ship passages was 30% lower than usual by the end of 2023. The unreliability of transit through Panama has already prompted some ships to re-route

Lower water levels also restrict the size of ships that can pass through the canal, as larger, heavier vessels sit lower in the water, putting them at higher risk of running aground in shallower waters. Large ships also require more lake water to lift them in the locks. As global shipping volume has grown, many shipping fleets have, too— relying on massive vessels that can carry more goods, but are harder to navigate through shallow waterways like the Panama Canal.

5. Disruptions in Panama affect global trade

The Panama Canal accounts for 5% of global shipping, so disruptions here affect the worldwide supply chain, resulting in delayed shipments, more fuel usage, and GDP losses.

The impacts of shipping disruptions in the Panama Canal are also being compounded by political events in the Red Sea. The Suez Canal, an alternative route for ships bound between Europe and Asia, has also had shipping disrupted by attacks from the Houthis, a Yemeni military group targeting Israel-bound ships. With both the Panama and Suez Canals becoming less reliable routes, more ships will be forced to take the long way around— traveling down to the southern points of Africa and South America.

6. Arctic ship travel does not offer an alternative route

Far to the north, another waterway is being rapidly altered by climate change. As the Arctic warms faster than any other place on the planet, summer sea ice has been disappearing at a rate of almost 13% per decade. This has opened up new lanes of ice-free water that some countries are eying as potential new routes. But navigating through a melting Arctic is still dangerous, and the majority of new ship traffic in the Arctic is comprised of smaller military or fishing boats, rather than the large shipping vessels used to carry commercial cargo.

Furthermore, increased ship traffic in the Arctic has the potential to further emissions, as melting ice could open up access to new sources of oil and natural gas— perpetuating climate warming.

7. Temperatures are still rising

Though December rains saved Panama Canal officials from instituting further restrictions on ship passage, the region is still experiencing El Niño, and sea surface temperatures in early 2024 have continued to climb higher than 2023. Each day in 2024 has recorded the highest temperatures on record for that calendar date. The only path to stabilizing global shipping lies in stabilizing the global climate.


     It was when you became sick that I truly realized how much you mean to me. How long I have loved you, needed you, learned from you. My entire life I have tried to be self sufficient,  but now I realize how dependent I am, and always have been, on you.

    It is funny to think that I have known you my entire life. Even though I spent most of my earlier years with your cousin Big Blue, I recall seeing you from afar. You were always drifting by our house each day to visit the cranberry bogs. You ran alongside the trails that I walked with the dogs. They swam with you afterwards to cool off, but I never joined. You always seemed busy, hosting pool parties with the swans and snapping turtles. I did not think much of you then. Honestly you were a little too intimidating for my younger self.

Read more on Science on the Fly.

Six months ago, Woodwell Climate Research Center received a $5 million grant from Google.org to put advanced computing to work to track permafrost thaw in near-real time. Now, the Permafrost Discovery Gateway (PDG) project has begun convening experts in remote sensing, machine learning, process modeling, artificial intelligence, software engineering, design, and computing to build upon the existing PDG platform and create a resource hub for Arctic landscape data. 

The Arctic is warming fast— up to four times faster than the global average— and as a result, the ground upon which many Northern communities are built has begun to thaw. 3.3 million Arctic residents live in settlements where models suggest permafrost could degrade and ultimately disappear by 2050, presenting an urgent need for accurate and reliable information to inform community adaptation and preparedness.

PDG was designed to use remote sensing data to identify and map permafrost-related hazards, like erosion and abrupt thaw events. Previously generated data on these features had either been coarse resolution or spanned only small areas within the Arctic. Collaborators on PDG from nine organizations improved and expanded on available data, mapping over a billion ice-wedge features across the Arctic landscape. Now, with the new Google.org funding, the team has goals to develop additional datasets, and make the resource accessible for communities. 

“I feel like we have a pretty good grasp of how the PDG can help researchers working on permafrost-related topics, both in creating and in doing their science,” says Dr. Anna Liljedahl, Woodwell Associate Scientist and PDG project lead. “Now it’s time to dive deeper into the needs of the public— specifically, people living and working in the Arctic and that are dealing with ice-rich permafrost thaw hazards.”

As part of the award, Woodwell Climate also received the support of 15 Google.org Fellows— talented software engineers, user-interface designers, and product managers— most of whom are dedicated full-time to the project between January and June of 2024. The fellows’ expertise will bolster the project’s activities gathering geospatial data, refining machine learning models to detect permafrost thaw features, and designing the platform’s user interface to meet the needs of communities and decision makers.

“The Fellow support from Google.org is an award in itself,” says Dr. Liljedahl. “In addition to all the skills the Fellows bring, we’ll have a large team of people who will work full-time on just this project, which is very rare in academia. So this fellowship is a huge boost to the project, and also an opportunity for the Fellows to gain and grow from the collaboration.”

To inform this new phase of work, the PDG team hosted a workshop in November, 2023. The event convened developers of the PDG and end-users including GIS consultants, permafrost and road engineers for a conversation about what data and tools are needed to support communities affected by permafrost thaw. 

The workshop highlighted basic information needs for the project— the value of detailed datasets that show the expanse of ice-rich permafrost, alongside the importance of including land ownership information and detailed descriptions of each dataset to provide a more complete understanding of the data. For Dr. Liljedahl, these insights were invaluable.

“We have mapped a billion ice-wedge polygons across the entire Arctic, but we have no map of Alaska trails, which are such an important infrastructure for Alaska’s communities as most are located off the road system. This kind of information will help us build a platform capable of serving community needs,” said Dr. Liljedahl.

Starting February 15, PDG will host a public webinar series that will continue the dialogue started in the workshop and hopefully inform not only this project, but data science research in other fields as well.

“This project addresses a need that goes beyond just permafrost— the need for accessible, public, geospatial data,” says Dr. Liljedahl. “And the need for a dedicated community to work on these difficult issues.”

As part of a new partnership between Permafrost Pathways and the International Centre for Reindeer Husbandry (ICR), the Arctic Initiative at Harvard Kennedy School (Arctic Initiative) and Woodwell Climate Research Center (Woodwell Climate) hosted 18 Indigenous youth from across the circumpolar North for a day of science, mapping, storytelling, and policy programming. Woodwell Climate Senior Scientist and Permafrost Pathways Lead Dr. Sue Natali signed a formal Memorandum of Understanding (MOU) with ICR Executive Director Anders Oskal and Woodwell Climate President Dr. Max Holmes establishing a new relationship focused on climate change and Arctic resilience.

Read more on Permafrost Pathways.

The way science is funded is hampering Earth System Models and may be skewing important climate predictions, according to a comment published in Nature Climate Change by Permafrost Pathways scientists at Woodwell Climate Research Center and an international team of modeling experts.

Emissions from thawing permafrost, frozen ground in the North that contains twice as much carbon as the atmosphere does and is thawing due to human-caused climate warming, are one of the largest uncertainties in future climate projections. But accurate representation of permafrost dynamics are missing from the major models that project future carbon emissions.

Read more on Permafrost Pathways.

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.”

Two new Polaris Project Alumni have been named John Schade Memorial Scholarship recipients. The fund, established in the memory of Dr. John Schade, who founded Polaris and was integral to its success, is dedicated to supporting the higher education goals of students that reflect Dr. Schade’s values of mentorship, education, leadership, equity, and the advancement of Arctic science. 

Mandala Pham

Mandala Pham studies geophysics and history at the University of Texas at Austin. As an undergraduate researcher, she has explored the caves of central Texas, studied marine geophysics in Corpus Christi Bay, and peered back in time to past climates through geology. Her experience in different lab groups spurred her interest in field work, driving her to pursue graduate opportunities to continue getting up close with geology. 

During her Polaris experience, however, Pham’s research focused less on geology and more on ecology. Inspired by her father’s affinity for beautiful, rare, and sometimes poisonous mushrooms, Pham studied the response of Arctic mushroom species to wildfire, comparing biodiversity between burned and unburned areas of land. 

As part of Polaris, Pham saw a glacier in person for the first time, which reinforced her commitment to dedicate her career to studying and fighting climate change. 

“From childhood anxieties to professional aspirations, I’ve taken tackling climate change as my personal direction in life,” says Pham. “I want to be part of the solution rather than spending my time ruminating on the worst-case scenarios.”

She hopes to get her Ph.D. in geophysics, studying glaciology. After that she has aspirations for either full time research or a career in the National Parks Services. Pham is also interested in screenwriting, pig farming, and perhaps one day, becoming a lighthouse keeper.

Aaron MacDonald

Aaron MacDonald’s passion for ecology began during his childhood spent on long family camping trips. Through his studies at University of Toronto, MacDonald has gained experience in oceanography and fisheries science through the Woods Hole Partnership Education Program (PEP) and the National Oceanic and Atmospheric Administration (NOAA) Inclusive Fisheries Internship. His field experience bolstered his confidence to pursue a scientific career.

With Polaris, MacDonald studied the role of willow ptarmigan, a common Arctic ground bird, as drivers of ecosystem dynamics on the tundra. For his career, he hopes to pursue a graduate degree and get involved with mentorship programs like Polaris. MacDonald firmly believes everyone should have the opportunity to study science, and is grateful for the support he received that has allowed him to pursue this career.

“Everyone who wants to is capable of scientific research and everyone has a place in STEM,” says MacDonald. “I have questioned many times if there is a place for me in STEM, but with the support of those around me I am determined to make it.”

In his spare time, MacDonald enjoys running and video games with friends.

Both recipients will receive funding to continue their education and pursuit of science, mentorship, and equity, encouraging a new generation of Arctic scientists working to change the world.