The New Yorker ran a cartoon in 1989 of a guru sitting cross-legged on a large pillow while men in suits stand in line, waiting to meet him. One businessman is turned to another and appears to be explaining something with excitement. The caption reads, “It’s great! You just tell him how much pollution your company is responsible for and he tells you how many trees you have to plant to atone for it.”

The accompanying article is excerpted and adapted from “Treekeepers: The Race for a Forested Future,” by Lauren E. Oakes (Basic Books, 336 pages).
When I first came across the cartoon, I couldn’t believe it had been published that long ago. It seemed apropos of the media flurry that came decades later surrounding “The global tree restoration potential” study in Science and the booming interest in tree planting. (“We Can’t Just Plant Billions of Trees to Stop Climate Change,” Discover Magazine, July 10, 2019, or “Massive Reforestation Could Greatly Slow Global Warming,” Scientific American, July 4, 2019, among many, many others.)
“We got poked fun of even back then,” Sheryl Sturges told me over a call. I’d come across her name in a short NPR story from 2015 about whether carbon offsets work. The reporter had called her the inventor of carbon offsets, a bold claim but one indicative of her role in putting the idea into practice. (The British-American physicist and mathematician Freeman Dyson had published a paper in 1977 that first proposed controlling carbon emissions through tree planting.)
I reached out to inquire about Sheryl with Gretchen Daily, a mentor at Stanford who is widely recognized as one of the pioneers of ecosystem services and the field of natural capital, the economic valuation of natural stocks such as trees or minerals. I figured Gretchen would know the history of early efforts to offset emissions before Costa Rica made the first certified carbon trade in 1997. She connected me with Roger Sant, cofounder of AES Corporation, the global energy company that Sheryl Sturges was working for when the question of how to address the greenhouse gas emissions from power plants arose.
“I thought, ‘We’re part of the problem.’ Here we are a little company, but we’re building plants that are adding to the problem.”
Roger had started the company in 1981, and from the beginning, he aimed to supply energy by not only meeting the U.S. Clean Air Act but “doing better.” He was also on the board of the then fledgling World Resources Institute, or WRI, which would later become a renowned research-based organization that aims to meet people’s essential needs, protect and restore nature, and stabilize climate. Decades later in 2014, for example, WRI would launch Global Forest Watch, the online platform that still offers the best publicly available data on the state of the world’s forests. Today, anyone can click anywhere on the globe to track the latest on both tree cover loss and gain. With the world in full view, it’s difficult to see the blue pixels that indicate forest gain amid all the magenta-colored loss. But zoom in close, and you can see polygons of emerging forest sprinkled like fairy dust across our plant-covered continents.
Roger was in a boardroom in 1986 with the founder of WRI, who was talking about climate change. “It was one of those moments in your life when you realize, ‘This is a big deal,’” Roger told me over Zoom.
“I thought, ‘We’re part of the problem.’ Here we are a little company, but we’re building plants that are adding to the problem. Here we are hoping we can make the environment better, but we are missing a whole class of pollutants that we’d never focused on.’” Feeling distraught, he didn’t know what to do. He gathered his team at AES and told them what was bothering him.
“We’ve got to find a way to be a part of the solution, or not do what we’re doing,” he told me. He didn’t want to abandon the business, which was just gaining steam and beginning to have an impact in the energy industry. Roger identified a coal-fired power plant that the company was building in Connecticut; he was concerned it would contribute to the problem.

Roger wanted a solution. Sheryl was the staff member who came back with an idea. Sheryl had come to AES with research experience in industrial energy use in the United States and the cost-effectiveness of conserving energy versus constructing nuclear power plants. In her early days with the company, she worked on ways to conserve energy to reduce dependency on foreign oil and approaches for making energy production more efficient.
Roger thought there might be a technological solution to the CO2 issue; perhaps the waste could be used in the enhanced oil-recovery process. Sheryl had read a lot about environmental issues, and she knew that deforestation was contributing to the climate problem. “So, I thought, ‘Let’s look at that,’” she told me.
“My sister worked at the Library of Congress so she was able to send me books and other resources,” Sheryl recounted. “I came across one paper that said if you planted the Big Island of Hawaiʻi with acacia trees, it would absorb the excess global carbon emissions at that time.” She couldn’t recall the study, and I couldn’t find it either. That didn’t matter; I knew the calculations and result wouldn’t hold anymore. But the idea had stuck.
“I just needed to know that for our little power plant, I didn’t have to plant the whole world!” Sheryl told me. “My scale was going to be so much smaller than the Big Island of Hawaiʻi. So, I felt like maybe we could actually do it — or some version of this. We didn’t have connections to foresters, so I was trying to figure out how many trees we’d need. There were some basic numbers I could find about how much one tree absorbs. But then, what species would you use? Where would we plant?” She thought maybe they could reforest in areas with coal-fired power plants, then learned that any emissions released would be circulating in the atmosphere within a couple weeks.
Planting anywhere was fair game. Sheryl came back to Roger and said, “Well, here’s a crazy idea. Trees sequester carbon. Why couldn’t we plant some trees?” They didn’t know how many trees that might require. About a week later, she came back again and told him, “Well, it’s about 50 million trees.”
The estimate turned out to be high; it would be more like 18 million today, according to Roger, given advances in estimation methods. Fifty million seemed like a lot of trees to him for offsetting the emissions from just one power plant, but he was willing to give it a go.
Sheryl came back to Roger and said, “Well, here’s a crazy idea. Trees sequester carbon. Why couldn’t we plant some trees?”
There was also evidence from strategies to address other pollutants that showed an offset system could work. In the 1980s, California was developing an offset market for sulfur oxides and nitrogen oxides (SOx and NOx, or what sounds like “socks and knocks” among experts who enjoy a little word play).
Around that time, John Kerry helped put together a response to emissions from coal plants that were contributing to acid rain. The program later became a model for the world’s first large-scale pollutant cap-and-trade system, and Kerry helped develop the regulatory approach when he was in the Senate. The goal of the Acid Rain Program under the 1990 Clean Air Act Amendments was to reduce annual sulfur dioxide emissions in the United States by “ten million tons from 1980 emission levels.” Coal-burning power plants could buy and sell emissions permits, which were limited in quantity by policy regulation.
The value of those permits rose incredibly high and then effectively went to zero, Roger recalled, still holding a sense of amazement decades later. “People were so creative that they figured out how to stop emitting sulfur dioxide,” he told me.
“I can see how that would make for the perfect mindset,” I said to Roger, as we talked about the SOx and NOx success. “As in, ‘Okay, here’s a new pollutant problem. Why wouldn’t the same thing work?” The key, I later learned, was sourcing low-sulfur coal from the West and shipping it for use — another example of how solving one problem can exacerbate another.
At the time of the tree-planting decision, Roger wasn’t thinking about a global cap-and-trade system for carbon. He wanted to feel that AES was doing its best to reduce or eliminate its own impact.
The team chose a project in Guatemala, and it soon became known as the world’s first effort to offset carbon emissions in one place with removals in another.
Paul Faeth, who was trained in international development and had experience in agroforestry, ultimately led the team that designed the first offset at WRI. “AES asked us to find a project,” Paul recalled, noting that they hadn’t used the term carbon sequestration in the early conversations. They called it carbon fixation, and WRI convened a group of climate modelers and experts to discuss if using trees was even a legitimate strategy to reduce what was accumulating in the atmosphere. “Very quickly, the answer was yes,” he told me.
Among the AES criteria was that the selected project would be a no regret initiative, meaning it had to have additional benefits like supporting farmers through agroforestry activities or preserving biodiversity in case the mounting climate concerns didn’t play out.
The team chose a project in Guatemala, and it soon became known as the world’s first effort to offset carbon emissions in one place with removals in another. It wasn’t a trade for certified credits; that system later evolved with various accreditation programs. The project plan supported 52 million trees by establishing agroforestry systems with local farmers, planting community woodlots and reforesting, fostering natural regeneration of native forests, and reducing fires in existing forests. But over the years, the effort also had issues, as one might expect. Nevertheless, it brought a lot of lessons to the world that are still relevant today in terms of the potential benefits, risks, and failures of forest carbon offsets.
The New Yorker cartoon had highlighted the mockery that persists — this sense that planting trees for carbon might absolve anyone of their pollution sins. Time magazine, on the other hand, published a short article calling the initiative “a healthy environmental equation.” The truth is probably somewhere in between.
Lauren E. Oakes is a conservation scientist and science writer based in Bozeman, Montana. She has held various appointments at Stanford University over many years, as a researcher, a lecturer, and an adjunct assistant professor in the Department of Earth System Science. She is the author of “In Search of the Canary Tree.”