Fall
In the fall, our colorful trees draw visitors from distant places. You might ask yourself, "How did we get so lucky? Why do these trees grow here, and not in Miami or Alaska?"
Of course, climate has a lot to do with where trees grow. Trees prefer certain climates - a palm tree wouldn't last long in Burlington!
If the climate changes, what will happen to Vermont's trees?
Past Forest Changes
When Vermont's climate changed in the past, the trees moved, too.
You can find local evidence that the average global temperature was once much lower. Glaciers rampaged across the land, scratching up the bedrock and blanketing the ground with broken rocks. During this cold period, our familiar trees grew farther south, where temperatures were closer to Vermont's temperatures today.
The last glacier left Vermont about 13,000 years ago. As the climate warmed, plants returned, following the warmer temperatures northward. First there was tundra in Vermont (just like in the Arctic!), and then came the trees. Each tree species came back to Vermont at its own speed.
After the rampaging glaciers had melted away, the climate became more stable. Still, temperatures rose and fell. Trees kept adjusting their ranges to fit regional climate differences.
Visit this quick look at post-glacial New England from UMass Amherst, and explore our natural history in the book The Nature of Vermont by Charles Johnson.
Future Forest Changes
A Warmth-loving Pest
The hemlock wooly adelgid is an insect that attacks hemlock trees. Recently, it's been causing trouble in Vermont. In years past, our cold winters kept this pest from moving north.
In the long term, tree species will probably change their ranges - just like they did before. Some scientists predict, for example, that Vermont will become much less favorable for colorful sugar maples, and they may move right out of the state.
But how fast will these changes happen?
That's a complicated question. Trees need time to change their ranges - they can't just get up and walk! Trees "travel" by sprouting up to fill gaps when old trees die. Storms, droughts, and pests can kill old trees faster, and climate change will affect these threats in unpredictable ways.
Many scientists are concerned about the high speed of recent climate change. They wonder what will happen to the trees as they struggle to keep up.
It's important to remember that trees are just one part of our forests, and climate change will affect the many parts the forest in ways we can't predict. Healthy forests are an important part of Vermont's identity and economy - but climate change is a rapid, large-scale experiment with our forests.
Use the Climate Change Tree Atlas from the USDA Forest Service to see one projection of future tree ranges, and read University of Vermont researcher Dr. Timothy Perkins' testimony to Congress about maples at the bottom of this page.
Clues from Mountain Forests
To get an idea of how trees are responding to recent climate change, scientists are climbing mountains.
Mountains are good places to study climate and forests, because hiking uphill is in some ways like travelling north very quickly. Imagine you're climbing Camel's Hump mountain. The air gets colder, and at the top you'll find arctic plants.
As temperatures rise, trees should begin to "move" higher up our mountains, chasing after their favorite climate conditions. Has this started happening already?
In the fall, our tallest mountains have a strange color pattern. On the lower parts you'll see the bright colors of autumn. Near the top, the mountains are dark green; evergreens that prefer a cool climate are thriving here. Scientists at the University of Vermont study this pattern on Camel's Hump. They are finding that the trees from the lower, more colorful forest are moving upward at a fast pace.
Other factors related to human activity, like acid rain and introduced diseases, can combine with climate change to kill those cold-loving mountain evergreens more quickly.
Click here to read a University of Vermont paper about the shifting place where the two forest types meet.
Will Leaf Color Change?
Some years, the fall colors around Burlington are brighter than others. You might have heard someone say, "The leaves aren't as colorful these days!". Is this true, and can we blame recent climate change?
Scientists suspect that temperature might affect the timing of leaf color changes. They even think that it might influence color brightness. Therefore, changes in climate might mean changes in fall colors.
However, research into the link between leaf color and climate is very new, and it's ongoing, so we can't make conclusions yet.
Scientists are studying temperature and fall colors right here in Vermont, at the Proctor Maple Research Center in Underhill Center. Over the next few years we should learn whether leaf peepers can expect climate-related changes in leaf color.
Learn more about the Proctor Maple Research Center over at their web site.
