Science & Tech

Peter Ashton: A legacy written in trunk, limb and leaf

long read

Tropical forests fuel Ashton’s intellect

They were in a bind, no doubt about it.

Wearing little but cotton shorts, the four men huddled on a streambank deep in the Bornean rainforest. Water dripped from their soggy clothes, making muddy pools around their feet as they assessed the situation.

They were surrounded by a forest so vast that it would take three days walking just to reach the nearest house. They had no food, no shoes, not even a knife.

Minutes earlier, they had been floating downstream in a rough bark canoe they had made that morning, assured that they would eventually find their way out of the forest, just as the stream did.
They heard the waterfall’s roar too late and despite their best efforts to save the clumsy craft, had been forced to bail out and swim for shore.

From the waterfall’s pool, they retrieved only a small bamboo container holding four matches. Feet bare and stomachs empty, they set out, slogging all day until that evening when, to their horror, they realized they’d marched full circle.

The rainforest was testing Peter Ashton again. Over the years he spent in their humid depths, Ashton, who would go on to become Bullard Professor of Forestry at Harvard, endured many physical hardships. He saw companions die — one in flames, one in water —and had nearly been killed himself by a pit viper’s poison.

But he learned from the forest. Whether from the data that helped him explain tree diversity and distribution, from the local people versed in the forests’ ways, or from hard experience, Ashton made a career out of listening to what the forest had to say.

On that ill-fated trip many years ago, the three men did what the forest required. They rested through the night, climbed a tree to get their bearings, and set out, marching until they couldn’t march anymore. They filled their bellies with a milky clay that satisfied even if it didn’t nourish. And when one of them became too weak to continue, Ashton stayed with him while the others went on.

Ashton and his companion waited by the stream for three days until they heard the sound of an outboard. It was their comrades who had reached the longhouse of a friendly tribe and returned, led by the chief and his son. To this day, Ashton remembers the food – fish and condensed milk — carried in the canoe.

“We poured the condensed milk over the salt fish and it was one of the best meals I ever had. It was absolutely fantastic,” Ashton said, relish evident in his voice even decades later.

After years of listening to the forest, Ashton has shifted tactics. Today he is putting a bullhorn to the forests’ mouth so the whole world can hear its message about climate change. Though retired from teaching, Ashton is still active, using an expanding network of forest plots to find out how trees around the world are responding to changes in the environment. His work has brought him prestigious official honors — the Japan Prize and the Sultan Quaboos Prize from the United Nations Educational, Scientific, and Cultural Organization (UNESCO). It’s also brought him academia’s highest unofficial prize:  the accolades of the scientists whose lives he’s touched.

“I can certainly say my career is all due to him,” said Paul Chai, who worked for Ashton when Ashton was a government forest botanist in the Malaysian state of Sarawak early in his career. Chai came into the job as a young kid just looking to make a living. When Chai left two years later, however, it was not for another job but for school. He eventually earned a doctorate and returned to assume Ashton’s role as government forest botanist.

“When I started work I didn’t know anything about [forest trees]. He introduced me to tropical botany and ecology,” Chai said. “I wouldn’t have gotten into this career without him.”

Savithri Gunatilleke, one of Ashton’s graduate students in the 1970s, said he encouraged the fieldwork that not only led to her doctorate, but also opened the forests of Sri Lanka to women scientists.

“Thirty years ago, a woman did not go into a forest alone,” Gunatilleke said. “At one point a friend told Peter, ‘You’re making a big mistake. That lady is not going to get into the jungle.’ ” 

Gunatilleke, who received her doctorate in 1975, did go into the jungle and is now a professor at Sri Lanka’s University of Peradeniya. She said Ashton infected her with a love of field work that she passes on to her students.

“I think some of it rubbed off on me,” Gunatilleke said. “When I came back after my Ph.D., it was impossible for me to stay in the classroom. Here was this rich outdoor laboratory right on our doorstep that nobody made use of.”

Infected by beauty on the wind

Though Ashton’s career in tropical forests was largely an intellectual pursuit, he was initially drawn to the natural world by its beauty. As a boy growing up in the south of England during World War II, Ashton often wandered forests near his home. The war’s fighting left French fields untended and sparked a mini population explosion of continental insects that drifted over the Channel.

“I had a very strong sense of color in my childhood. I was very interested in patterns, the patterns on insect wings, particularly butterflies and moths,” Ashton said recently. “Butterflies came across the channel that had not been seen in any number of years, perhaps since the beginning of the Industrial Revolution in the 18th Century. It was an incredibly exciting time for a young, beginning naturalist.”

Ashton, who has 10 plant species named after him, has written six books and more than 200 scholarly articles, got his first taste of a tropical forest as an undergraduate at Cambridge University in the 1950s, when he and a friend traveled to the Amazon one summer.

“I actually went as an entomologist. I got overcome with the excitement of the forest itself,” Ashton said.

When he graduated in 1956, Ashton wanted to do his graduate studies with John Corner, the professor who had encouraged him on the Amazon trip. But Corner didn’t think school was the right place for him.

“He actually declined and said, ‘If you stay here, your knowledge will be based on the knowledge of others. If you’re interested in tropical forests, what you really need to do is go out and get your own personal experience and decide what you think about these things,’ ” Ashton said. “That was really good advice.”

With Corner’s help, Ashton landed a job as a government forest botanist in Brunei, with orders to catalog the nation’s timber resources. Ashton spent the next 10 years on the island of Borneo, first in Brunei and later in the Malaysian state of Sarawak.  He also continued his studies at Cambridge, earning a doctorate in 1962.

In 1966, Ashton and his wife Mary – to whom Ashton credits much of his success — decided it was time to return to the U.K. with their three children. Ashton took a job at Aberdeen University in Scotland, where he was a lecturer and then senior lecturer in botany.

Ashton’s oldest son, Mark, who became a forester and now is a forestry professor at Yale University, said he remembers Ashton taking him, his brother and sister into the forest, where they’d swim in freshwater streams among the trees. He also remembers his father being gone for months at a time conducting fieldwork. Mark credits his father’s influence on his going into forestry – a more practical field than tropical botany – and today the two sometimes collaborate on projects.

Though Ashton began his career studying the extraordinary diversity of tropical forest trees – a single plot can hold as many tree species as exist in the entire U.S. and Canada – he wasn’t content with that.

“He didn’t stop there. He wanted to ask big questions about how various species coexist in the landscape. This is where his enthusiasm bubbles out,” said Cambridge University Professor Emeritus Peter Grubb, who attended Cambridge with Ashton and has kept in touch with him over the years.

Ashton expanded his studies to examine why different trees exist in different places, focusing on tree communities living in different soil types. Unlike temperate forests that may be dominated by two or three tree species, the tropical forest is characterized by a far more complex mosaic spread across the forest floor and arranged in multiple layers rising hundreds of feet above. In this jigsaw puzzle community, tree species can be represented by single individuals, separated by large distances from other members of the same species.

Ashton examined how tree distribution is related to their reproductive habits. He looked at how the trees pollinate each other over such large distances and whether, given the relatively constant conditions day to day and year to year, there was much genetic variability among the trees, an important consideration in the operation of natural selection.

“If in a community you can get 800 tree species in 100 acres, more than all of North America north of the Mexican border, the key question is how do they fit together? Is it completely random or are they specialists in some way?” Ashton said.

As he puzzled over these questions, he realized that the answers lay hundreds of feet above the ground in the rainforest canopy. He also realized that somehow, someone had to get out to where reproduction happens: the flowers growing on the flimsy tips of the trees’ branches.

Though he was studying tropical forests, Ashton said he was lucky at the time to be based in Aberdeen, where the oil industry was booming.

“We got engineers to design a kind of tree prosthetic, an aluminum alloy boom that was extensible with ropes, so you can actually manipulate the twigs and flowers in the canopy,” Ashton said, then adding with his typical humor. “On the other end you don’t suspend yourself, of course, you suspend one of your graduate students. All this is happening at night — to make it extra exciting — while I’m down below barking out commands.”

What they found in those hard-to-reach flowers was considerable genetic variability among the trees as well as specific insects that carried pollen from one tree to another, fertilizing the flowers despite the distances between them and producing the next generation.

Colleagues describe Ashton as friendly and enthusiastic but tough, both physically and mentally. Sitting in a room with Ashton, it’s difficult to go 30 minutes without him breaking into laughter at least once, one colleague said. Another described him as friendly, but also very firm about how things needed to be done. The local tree-climbers in Sarawak gave him the nickname “Taji Buloh,” or “bamboo spur” in the local tongue, a reference to the spurs attached to roosters during cockfights.

“What he did was physically immensely challenging,” Grubb said. “He’s a very, very tough man.”

When asked about his life and career, Ashton talks about the science, the forests, and the people he’s known. When questioned more closely about a life lived in the forest, Ashton switches into the storytelling mode that friends say help even arduous trips pass quickly.

“He has so many stories, even on long, rough trips, you don’t even feel the journey,” Gunatilleke said.

One particular story is recounted even by his friends when asked about Ashton. During a visit to the field by Ashton’s Cambridge University mentor, John Corner, Ashton led a hike into the forest. They were accompanied by several local tree climbers when, at about noon, the tree climbers stopped and announced that they’d reached a good camp site.

After talking to the men, Ashton realized they’d seen a bird fly across their path that they took as an omen that they shouldn’t go forward. In an effort to keep the expedition moving for a few more hours, Ashton offered to take the lead, so anything bad that happened would happen to him first.

“I walked 50 yards and trod on a pit viper,” Ashton recounted. “It bit me on the ankle. They had to carry me out on their backs.”

By the time Ashton reached a local hospital, he was seriously ill and a short time later began having seizures. He eventually recovered, but not before being given four pints of blood. There was no blood bank in the area, Ashton said, just a list of willing donors. To this day, one local man who donated blood always greets him and asks how his blood brother is.

Ashton came to Harvard in 1978, attracted by the Arnold Arboretum’s herbarium and library, which he called one of the world’s best for research on Asian plants and forests. He served as the Arnold Arboretum’s director and the Arnold Professor of Botany. In 1991, he became the Charles Bullard Professor of Forestry, a post he held until his retirement in 2005. Today he is Charles Bullard Professor of Forestry, Emeritus.

The Arboretum’s current Director and Arnold Professor Robert Cook called Ashton a naturalist and scientist in the tradition of Pellegrino University Professor, Emeritus, E.O. Wilson and famed evolutionary biologist Ernst Mayer, whose scientific work was informed by a personal understanding of their subjects born from years in the field.

Cook said Ashton’s nine years as Arboretum director, which ended in 1987, created a vision for the institution as a comparative research facility that endures today, in the construction of a $42 million research laboratory dedicated to fundamental studies of plant biology enabled by the genomics revolution.

“The truth is, the real vision belongs to Peter; I’ve merely been the mid-wife,” Cook said. “As a consequence, our new Weld Hill research facility, and its immense promise for our future scientific reputation, ensures that the Arnold Arboretum will continue to be a unique source of pleasure and intellectual inspiration for all the people for many generations to come.”

A forest chain to measure climate change

In the early 1980s, Ashton had an encounter with scientist Stephen Hubbell that sowed the seeds for what would become the major accomplishment of the second half of his career: the establishment of a unique, global network of forest plots. The plots not only allow scientists to study trees within individual forests, but also allow comparative studies of exhaustively documented forests around the world.

At the time of their meeting, Hubbell had mapped all trees over one centimeter in diameter on a 50 hectare plot on Barro Colorado Island, in the Panama Canal’s Gatun Lake.

Ashton, who had been working with much smaller plots in southeast Asia, convinced Hubbell that the two should work together to set up plots there similar in size to those on Barro Colorado.
The effort led to the founding of the Center for Tropical Forest Science, a collaboration between the Arnold Arboretum and the Smithsonian Tropical Research Institute. The Center would expand on Ashton’s and Hubbell’s ideas and create a network of 18 forest plots in Southeast Asia, Africa, and South America. The plots hold 6,000 species and 3 million individual trees, censused every five years.

Exhaustively documented, the plots have proven invaluable resources to scientists around the world studying a variety of aspects of tropical forest dynamics, including their response to climate change. His “significant contributions towards solving the conflict between human beings and the tropical forest ecosystem” was cited by the Science and Technology Foundation of Japan in awarding Ashton the 2007 Japan Prize. Grubb said that it was Ashton’s people skills, as well as his knowledge of the area and the local governments that were key to establishing the plots.

“He knew where to put the plots in Southeast Asia. He knew the plants and he knew the people,” Grubb said. “When you go to a developing country, it’s easy to put people’s backs up. That’s what he didn’t do.”

Today, the plots are an increasingly valuable tool with which to document the impact of climate change. The Smithsonian Tropical Research Institute recently received an $8 million grant from HSBC Bank to expand the plots around the world, adding temperate forest tracts, including the Harvard Forest in Petersham, Mass.

Ashton also continues his work on tropical forest conservation. He compares the rainforests’ vast array of species to a precious library of information, holding genetic codes, the formulas for defensive chemicals, and unique ways of life. Rainforest trees, he said, are not only numerous, but they provide the framework for the forests’ broader diversity. In addition, he said, the trees drive evolution forward, as their chemical defenses against insect and animal browsers force those species to develop countermeasures that allow them to continue to feed on the trees.

In a talk at Harvard in October 2007, Ashton called for a new approach to conservation, because many of today’s programs are designed around large animals, under the rationale that if the animals are preserved, their forest homes will be too. The problem, he said, is the most diverse parts of the forest are not necessarily the same ones most often frequented by these target animal species. If the extraordinary diversity of tropical forests is to be conserved, programs must be designed specifically for the forests.

Ashton recognizes that in order for the forests to survive, the relationship of the forests to the people who live near them must be understood and the people’s needs taken into account. Ashton decries deforestation not just because of the loss of biodiversity, but also because it turns forests from resources for the people who live nearby into cash in the pockets of logging company owners.

“He was [sure] that unless the local people in the home countries were convinced that the rainforest had to be conserved it wouldn’t get done,” Gunatilleke said. “He has a deep respect for the people.”