‘You Can’t Be a Forester without Understanding Chad’s Work’
The idea that forests are dynamic systems — that disturbance is the norm — might seem obvious now. But that's only because it was demonstrated by Professor Chad Oliver, one of the many ways the retiring professor has impacted forestry and forest education throughout his 45-year career.
A few years ago, visiting the Changbai Mountains on China’s northeastern border, Chad Oliver listened quietly as local forest scientists described the surrounding landscape. They had inherited the old idea of the forest steadily progressing over time, with the bigger trees having arrived first, to prepare the way for the smaller, younger trees around them, which would eventually grow up in their place. It was a Peaceable Kingdom vision of nature, with a stable climax forest as the end result.
The next morning, Oliver woke up early and led a small group back to the site. There, says Xuemei Han ’11 Ph.D., Oliver’s doctoral student at the time, he took a core sample from a big tree and cut down some of the smaller trees nearby.
His listeners joined him in aging the trees by counting tree rings. It turned out, of course, that the bigger trees weren’t any older than their smaller neighbors. In fact, the smaller trees were smaller, as Oliver puts it, in his soft Southern accent, “because the bigger trees had suppressed ’em.”
It was a simple demonstration — and the heart of what he has taught over a 45-year career, first at the University of Washington and more recently as Pinchot Professor of Forestry and Environmental Studies at Yale: There is no such thing as a balance of nature or some imaginary climax state. Forests are dynamic, and disturbance is the norm, whether by fires, droughts, wind storms, disease, insects, logging, or other factors. A mosaic of habitats is the usual result, from grasslands and scrub to dense forest, with each tree stand consisting mostly of even-aged trees, all of them having gotten their start in the aftermath of the same local disturbance. It’s a big idea that can seem obvious now. But that’s only because it has become so widely accepted and influences how people manage forests in so many places.
“It is impossible to imagine the field of forestry without Chad’s contribution,” says Kris Covey ’10 M.F., ’16 Ph.D., a former student now teaching environmental science at Skidmore College. “You can’t be a forester, and you can’t be a forest ecologist, without understanding Chad’s work. It is fundamental to our field in a way that is very rare for a scientist to achieve.”
Chadwick D. Oliver began to work in the woods at 10 or 11, with the land survey crew for his father’s forest management company in Camden, South Carolina. His official title was water boy, he says, “but every chance I got, I’d pick up a bush ax for cutting a line through the trees, so the person with the transit could get a straight shot.” He backed away from forestry for a time as an undergraduate, to separate himself from his father’s influence. But when he revisited forestry in junior year, it took hold hard.
Oliver went on to study with the Yale School of Forestry’s David M. Smith, a legendary figure known for his ability to read a stand of trees from seemingly trivial clues and reveal its secret life. Smith suspected from the history of his own family’s woodlot in Massachusetts that even-aged stands were commonplace. Oliver set out to test the hypothesis on study plots in the Yale-Myers Forest, conducting a kind of archaeological reconstruction of their history back deep into the 19th century and taking samples up the length of living trees to understand recent patterns of growth.
When his findings — the disturbances, the even-aged stands, the single species dominating the others — eventually appeared in the journal Ecology, the celebrated ecologist Robert MacArthur remarked that it might be true for the heavily disturbed forests of New England, “but it’s not true of the rest of the world.” Oliver, his own students, and others then went on to demonstrate the same pattern in the Douglas fir forests of Washington, the Sitka spruce forests of Alaska, the cherrybark oak forests of the American South, and elsewhere until the Harvard forester Peter Ashton half-jokingly remarked, “OK, but not in the tropics.” Then he invited Oliver to send a student to his own study plots in Thailand, and the pattern held true there, too.
Oliver went on to develop this new understanding of forests in his book “Forest Stand Dynamics,” co-authored with Bruce Larson ’78 M.F.S. of the University of British Columbia, a former student. (Another former student, Patrick Baker ’93 M.F., is now preparing a third edition.) Recognizing the even-aged character of most tree stands was of course only a start. It meant that managing any given stand, typically anywhere from 10 to 60 acres in area, needed to happen in relation to other stands in a larger landscape that might cover 1,000 or 100,000 acres. That led Oliver and Jim McCarter, then a data-oriented doctoral student at the University of Washington, to develop a computer platform called the Landscape Management System for taking account of different values — economic output, protection of wildlife, carbon capture and sequestration, recreation — in the context of the larger ecosystem. The U.S. Forest Service now uses its own version of the program, called Suppose, to manage the 294,000-square-mile national forest system.
Chad Oliver (left) helps students measure a cut pine during a field trip to Yale-Myers Forest in 2018.
Oliver’s science has sometimes put him at odds with environmentalists. During the spotted owl fight in the Pacific Northwest in the late 1980s, for instance, he took the side of local communities, pointing out that Douglas fir regeneration occurs only in full, or nearly full, sunlight in the aftermath of major disturbance. Clear cuts fit this natural pattern and also benefit other plant and animal species. He advocated an approach that would prevent further cutting of the old growth on which spotted owls depend but also manage dense younger stands to maximize future old growth and sustain the local logging economy at the same time. Neither that proposal nor another to open up dense young growth for forest fire prevention were implemented at the time.
Oliver’s work has also produced some environmental success stories; for instance, in the aftermath of that demonstration of tree stand dynamics in the Changbai Mountains. It was 2006, and Oliver was just beginning to work with a team led by ecologist Jianping Ge at Beijing Normal University. The focus was on a vast area of northeastern China that had been indiscriminately logged in the 1950s and then left to regrow into a dense, scrubby forest. Ge wanted to know what it would take to make it suitable habitat for the Amur leopard and the Amur tiger, both critically endangered and hanging on just across the border in Siberian Russia. He thought Oliver could help.
Oliver advocated an approach to prevent further cutting of old growth on which spotted owls depend but also manage younger stands to maximize future growth.
“We felt like old friends already at our first meeting,” says Ge, who had read “Forest Stand Dynamics” in the 1990s. “Professor Chad’s profound knowledge and global ecological strategic vision provided key support for us to formulate a scientific protection plan for tigers and leopards in Northeast China.” That plan set out to recover the forest habitat; rebuild the population of deer, wild boar, and other prey species; and encourage some of the tigers and leopards that had been visiting the area from Russia to settle down and call it home. As a result, the Chinese government in 2016 created the Northeast China Tiger and Leopard National Park, protecting an area just north of the Changbai Mountains that is 1.6 times larger than Yellowstone National Park. Together with the surrounding forests, it could eventually support as many as 100 tigers and 200 leopards.
Last October F&ES hosted a “festschrift” during which colleagues, former students, and friends presented readings and lectures about Oliver’s defining research.
Oliver, meanwhile, will retire from Yale this June. He plans to divide his time thereafter between New Haven and Istanbul, where his wife, Fatma Arp Oliver, grew up. He will also certainly continue to be found, in person and in spirit, in forests almost anywhere.
PUBLISHED: July 1, 2020
Note: Yale School of the Environment (YSE) was formerly known as the Yale School of Forestry & Environmental Studies (F&ES). News articles posted prior to July 1, 2020, refer to the School's name at that time.