Scottish woodland specialist speaks on widespread tree extinction

by Molly Duerig

Eco-friendly Carr Hall was a fitting location for Tuesday’s presentation by Duncan Stone, senior woodland specialist at Scottish Natural Heritage, the Scottish government’s conservation agency.

Stone is visiting the U.S. for nine months to conduct a study comparing European and North American experiences of woodland ecology, and exploring the viability of replacing dying tree species with non-native species. He is one of Harvard Forest’s seven Charles Bullard Fellows in Forest Research for the 2012-13 year.

Before arriving at Allegheny, Stone was at the Harvard Forest in Petersham, Mass., Harvard University’s 3,500-acre forest and laboratory. There, Stone is developing the basis for new policies on native plants in conserved forests.

Stone said forest conservationists are faced with “unpalatable options” to solve the problem of widespread, native tree extinction. This problem is occurring in the U.S. as well as in the U.K.

Widespread extinction of tree species is the combined result of climate change and infestations of non-native fungal and insect pests and pathogens, or tree diseases.

Quickly-increasing temperatures are causing drought, storminess, waterlogging and lack of snow, which freezes roots, insulating them during the winter.

Stone said a common strategy is to replace old trees that are dying with new, young trees of the same species. He said that in 2012, Scotland’s forestry commission stated that native tree and shrub gene pools are perfectly adequate for adaptation to climate change as long as they are given the chance. This statement runs contrary to the truth: that native species are dying at a rapid rate, making them ultimately irreplaceable.

“The option to have the native species is going,” Stone said. “We all learned non-native genotypes are bad. But we don’t know where we are going with native species.”

Stone argues that planting traditionally non-native species is not necessarily a bad practice and in fact it could be supremely beneficial to preservation of forest ecosystems.

He offered an example, saying that it may be possible to replace the whitebark pine that grows in the western U.S. with the Arolla or Swiss pine that grows in the Swiss Alps.

“Not every function of native species is unique. Every combination is,” Stone said.

It is vitally important to consider the effect a particular species has on its ecosystem. Many tree species, like the whitebark and Arolla pines, have overlapping functions within ecosystems.

“Yes, [the Arolla pine] is non-native, but it gives us some of what we need,” Stone said.

One particularly valuable function of the ashwood tree is its luxuriant growth of epiphytes (plants that grow upon other plants). But the ashwood is not the only species with this function.

Stone showed slides picturing vast, mountainous areas in the western United States which had previously been covered by the whitebark pine. Whitebark pine has been disappearing rapidly during the last 20 years due to climate change.

The tree’s disappearance is a problem in large part because grizzly bears depend on whitebark pine nuts as a source of food. Bears also help plant more trees by spreading the seeds.

Assistant Professor of Environmental Science Mark Neff said that the area surrounding Yellowstone National Park is an ideal example of the importance of preventing further tree species extinction.

“Now the grizzlies are going into towns because they’re not getting their natural food source,” Neff said. “They’re attacking people, they’re getting into houses. That really puts the spotlight on this issue.”

Stone reflected on the grizzly bears searching for food in towns and homes in the western U.S. as a result of the diminishing whitebark pine.

“I guess you could feed the grizzlies, but I’m not sure that’s any more unnatural than growing a different tree,” Stone said.

Current projection charts only show estimations of climate change until the year 2100. Especially in terms of tree life, this is not a very large time frame. Stone said the charts do not account for the increasing magnitude of climate change’s harmful effects on the environment and on forest ecosystems.

“We have to grow the next big old trees for our descendants,” Stone said.

He warned about the dangers “do-it-yourself” solutions could yield if forestry experts do not take control of the situation by implementing non-native species. As people notice more and more trees being lost, they may ask friends to bring up tropical plants from other parts of the country, which could cause further problems.

“If we don’t resolve [this] as forest conservationists, then someone else does, and that’s where it gets scary,” Stone said.

Stone emphasized that humans must both acknowledge and grieve their love for “big, old trees.”

“Losing big, old trees hurts. I don’t think we will get anywhere until we admit that this is a crap situation and we hate it,” Stone said. “The reason we’re here is not a happy one.”

Stone shared the picture of the Pontfadog Oak, a 1,200-year-old tree which toppled over in Wrexham, Wales, a week ago. According to’s article about the tree it was one of the oldest and largest in the United Kingdom. Villagers gathered around the tree after its collapse in a type of funeral.

This funeral is just one example of the cultural significance trees have for humans.

“People do care about big trees,” Neff said. “[They’re] the charismatic megafauna of the flora world.”

State trees in the U.S. are another example of trees’ cultural importance.

William Chappel, ’14, asked about the current condition of Pennsylvania’s state tree, the Eastern hemlock.

Stone said that although there is time until the hemlock becomes extinct in Pennsylvania, the damage caused by the adelgid, an invasive pest of the hemlock, has approached an irreversible point.

“You might want to think about another state tree,” Stone said to Chappel.