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Maine's forests: past, present and future . . . 

A talk with the author of "The Changing Nature of the Maine Woods"

Andrew Barton grew up Asheville, in the mountains of North Carolina, and as a boy of 8 or 9 he was fascinated by salamanders, lizards and snakes. “My mom wouldn't let me keep any in the house, which I think just stoked my love of these creatures,” he remembers.

“The first time I remember being awed by forests was when I was about 14. My father loved the woods, loved to hike, loved to read maps. He was really an inspiration to me, a major reason why I became a forest ecologist. We went backpacking with one of my friends in Joyce Kilmer Memorial Forest, an incredibly impressive piece of old growth not far from the Smokies.”

The big trees impressed him, and Barton went on to get degrees in biology and zoology and become a forest ecologist.

Andrew Barton at his farm in Farmington. (Photo: The Rankin File)His new book, “The Changing Nature of the Maine Woods,” written with colleagues Alan White and Charles Cogbill, was published earlier this year by the University of New Hampshire Press. It tells the story of how the state's forests developed, evolved and changed since the last great glacial ice sheet retreated to the north some 12 millennia ago. The book taps into the latest research on everything from the pollen record to “witness” trees referenced by the state's first surveyors. It's a highly readable volume sure to engage the average reader.

Drew got his first taste of New England when he came to Brown University in Providence, R.I. to go to college. He got his undergraduate degree from Brown, a masters in zoology from the University of Florida and in 1991 received a doctorate from the University of Michigan. He came to Maine with his wife, Sarah Sloane, who is also a biologist and UMF professor, and children in 1996. He now teaches biology at the University of Maine at Farmington.

White is a professor of forest ecology at the University of Maine. Cogbill is a plant ecologist and historical ecologist from Vermont.

Joe Rankin, the Forests for Maine's Future writer, sat down with Barton at his farm on Perham Hill in Farmington to talk about the forest and writing.

There are a lot of books about the Maine woods, how and why did you decide to write this one? 

First, I very much admired Alan's work and greatly enjoyed spending time with him, talking about forests and our common discipline, forest ecology. We had also both been teaching a course on forest ecology and conservation at our respective universities that attempted to take a comprehensive look at Maine forests from an ecological point of view. By 2007, Alan and I had decided that we should pull together and extend the material from our courses into a book. A second strong motivator was that, although there are some great books on Maine forests, the book we were imagining did not exist: a book that synthesizes some of what we know about Maine forests not just for our colleagues but mainly for a University of Maine Professor Alan Whitegeneral reader. This suggested to us that there was a place for our book idea. Moreover, we felt that such a book would help those who live in, visit, and love Maine forest understand more about the diversity and dynamics of our forests. Finally -- and I'm speaking very personally here -- I have a strong need for forming a big picture view of whatever I work on; I struggle unless I can clearly see how my own research, teaching, and conservation efforts fit into the whole. So, I've been driven since not long after my arrival in Maine more than 16 years ago to read about and learn about and synthesize the remarkable storehouse of scientific knowledge about Maine forests.

Your book is all about the change in the Maine forest. Give us a time lapse view of how the forest grew and changed following the retreat of the glaciers.

A really important thing to keep in mind is that after the glaciers retreated it's not like the climate remained stable. Temperature continued to change, as did precipitation. Forests kept changing in response. Early on spruces were favored, but then things warmed up and other species like white pine were favored. It's a moving target. After the glaciers' retreat there was a mix of sand, boulders and cobbles, like the bottom of a gravel pit. The earliest vegetation seemed to be primarily tundra-like plants. The first trees were spruces and poplar, species that were adapted to colder climates and an open environment. By 11,000 years ago spruce was largely replaced by white pine, oaks and birches. It was a warmer and drier climate then and there's some evidence that there was more fire. Then about 8,000 years ago things become a little moister and we get more of a beech-hemlock forest. That continues for a while with one major interruption: about 5,400 years ago hemlock largely disappeared. This is one of those mysteries of the paleoecological record in the northeast: it could have been that the climate changed or there was an outbreak of hemlock looper, or a pathogen like chestnut blight. There's evidence for all of these hypotheses, but no one knows for sure. Eventually hemlock recovered after 1,000 to 1,500 years. One of the quite amazing things is that the most common tree in Maine is spruce, but 2,500 years ago it was not common. It wasn't until about 1,500 years ago that spruce became abundant. There's quite good evidence that when the first European explorers came to North America that the forest was still changing, that spruce was still undergoing a renaissance.

What was the impact of native Americans on the Maine forest, and how did it differ from their impact on the forests of southern New England?

Human populations in Maine were very different than southern New England, where there were much larger populations and they were much more agriculturally oriented. They appear to have used fire a lot more than they used it in Maine. There was much less ecological impact in Maine than in southern New England. Not that there was none, but there was much less. 

In looking at the beginnings of white settlement in Maine, how quickly did colonists begin to have an effect on the forest? 

This was one of the things that surprised me. I know a little Maine history and I had the notion that settlement patterns were more continuous and more gradual. Here again there was a big difference between southern New England and Maine. In southern New England, for instance, hostilities between Indians and Euro-Americans largely ceased with the Pequot Wars in the 1630s. In Maine they continued really all the way to the 1750s. The first big wave of settlement in Maine didn't really happen until after the Revolutionary War. That's more than a century after it happened in southern New England. Until the early 1800s settlement was largely on the coast and tree-cutting and land-clearing were largely confined to the coast. There were a few exceptions. Some towns in the interior were settled in the late 1700s, but the population was still concentrated on the coast.

One of your co-authors' exhaustive research on “witness” trees gave you a detailed glimpse into the pre-settlement forest of Maine. Can you talk a little about that and how it contributed to the book?

One of the key strategies of our book is to provide readers with as clear as picture as possible of what Maine forests were like at different points in time and what they might be like in a century. This is the basis of all of our discussions about how and why the forest has changed over time -- the fundamental theme of the book. A crucial time slice for this approach is the pre-settlement forest, that is, the forest before Euro-Americans settled the land. Charlie's witness tree database, based on detailed notes from land surveyors during settlement across the state, provides an amazingly detailed view of the species composition of that forest, and even substantial information on the extent to which it was influenced by natural disturbances such as fire and insect damage. We were even able to come up with a list of species found not far from my family's house on Perham Hill from these early records. These records are that local! Pretty cool. I hope that readers will also appreciate the immense amount of work Charlie invested in this database, poring over pages and pages of dusty old records in registry of deeds offices, town offices, and more.

You used your farm in Farmington to help illustrate the changes in the forest after white settlement. How did that come about?

As the book came together, we decided to start each chapter with a narrative -- a story -- that would help readers form images of people, places, and ecosystems before diving into the complex science of forests dealt with in the chapter. We needed one for the chapter on how Maine forests changed from pre-settlement to today. I had interviewed a couple of colleagues about their lands, but in the back of my mind, I kept thinking that our place, the Perham farm and Farmington, might be great examples of the trajectory of forests from the late 1700s to today. As the chapter on the pre-settlement forest was coming together, Charlie mentioned to me that one of the original settlers on our land, Lemuel Perham, was an early land surveyor, whose witness trees were part of Charlie's vast database of witness trees that has helped him reconstruct what the pre-settlement Maine woods were like. In fact, Lemuel was already mentioned in the book draft in that context. I love history as well as forest ecology, and this was too good a connection to pass up.

Much of southern and central Maine was cleared for farming and the interior was heavily logged. Later, as agriculture declined, the forest came back. What does that tell us about the Maine woods?

If we look back we see that forests can change and they can change fairly rapidly in terms of hundreds and thousands of years. On the other hand forests have some degree of inertia because trees live a really long time and once individual trees get established they are strongly buffered from change. Even if conditions change and are not ideal for them, they can survive. That's probably one of the reasons why, if we compare what we know about the pre-settlement forest from witness trees to the forest of today, the composition of the forest isn't that different and the regional distribution of the forest is not that different. Having said that, the structure of the forest is very different because of land clearing and logging and the relative abundance of tree species has changed greatly. A good example is that the pre-settlement forest didn't have that much popple and white birch and other species that are light demanding, compared to today.

Given that changes in climate over the past 12,000 plus years have led to substantive changes in the forest, how do you see things playing out as climate change ramps up?

The evidence is pretty indisputable that the climate is changing, that we're causing it and it will continue to change. If projections of the amount of change for Maine in the 21st century come to be true then we know this: that the forest will change dramatically. What we don't know is the exact nature of the change: which species will lose, which will gain, how far they'll move, how much their abundance will change, which combination of species we will have. I think it makes sense that we will lose some of the northern character of the forest and gain some southern character of the forest. That means less spruce and fir, two species that characterize large parts of our state now. We're probably going to get more oaks, probably new oaks. I will guess white oak will become much more abundant and widespread, and we will probably get more white pine. Climates never repeat, communities never repeat. The idea that we will just go back to some type of climate or forest community of the past is probably not true. The idea that we will simply get what is south of here probably isn't true either. A new combination of temperature, seasonality and precipitation will lead to new combinations of species, probably something we've never seen before in the past or in areas to the south of us. I think the Maine forest of two centuries from now will be really, really different.

You also do forest research in the southwestern U.S. Right now the forests in that region are under great stress because of drought and other factors and there's an indication that in some areas forests might disappear altogether. Is there any possibility that Maine could lose its forests, even temporarily?

There is evidence that a large part of the western U.S. is experiencing forest dieback because of drought, heat, insects and fire. In some places we're replacing forests with shrublands. The idea of dieback is scary. Is that something that's in Maine's future? Well, there are a couple of alternatives: gradual change, a plant-by-plant replacement over time, versus an abrupt change where you have no forest for a period of time. Bill Livingston at the University of Maine, the person who knows more about this than anyone, doesn't think that the forests will change in that way, though he does think they'll change. I agree with him. I think Maine is more buffered than a lot of other places to that kind of catastrophic change. We are moist enough, and cool enough, that that type of change probably . . . hopefully, won't occur here.

What do you consider the greatest threats to the Maine forest?

Development, climate change and insect pests are the triple threat. Those would be my top three. As David Foster, the director of the Harvard Forest, said in comments on a draft of the book, development is the most certain enemy of forestland. As far as pests go I'm most worried about the Asian long-horned beetle. From looking at the maps I can't say whether they'll get here or not. They're perhaps the most unpredictable of all because they just seem to be popping up here and there. But that is a species that attacks a range of trees, including maples and birches. Number two is emerald ash borer. Ash doesn't rank as high in Maine in terms of numbers, but there are a lot of ashes. We probably have 20 to 30 acres here on our land that is dominated by ashes. We would be really nailed by the emerald ash borer.

Hemlocks and pines in a managed forest near Farmington (Photo: The Rankin File)What was the most surprising thing you found in your research?

The witness tree data and what Alan White and his students at the University of Maine have put together in terms of Big Reed Forest Preserve have given us a pretty remarkable detail about regional details of the pre-settlement forest. The surprise was how little the distribution of forest types and species has changed. That doesn't mean the forest hasn't changed. It's changed a lot. In terms of relative abundance of species and in terms of structure of forest, how many big trees, little trees, and coarse woody debris, but in terms of where tree species are things seem pretty similar today to what they were like a few centuries ago.

Talk a little about the experience of doing this book?

I loved writing this. I've written a lot of science journal articles. But I love writing for the general reader. I have done that in my teaching for a long time, make complex information accessible without dumbing it down. It is a real creative process that I really, really loved. And I had so much fun working with Alan and Charlie. And learned a tremendous amount in doing that. I've been teaching a course in forest ecology of Maine here at UMF every other year for 16 years. So I thought I knew a lot, but I learned so much more by doing this. That was terrific.