St. John River Forest
See animals and cutting-edge satellite images from the St. John River Forest.
Satellite imagery has been used to record fine-scale harvest history across Maine's forests.
Dr. Dan Harrison, wildlife ecologist
By Kate Frazer
Twenty years of change in the way Maine’s vast spruce-fir and hardwood forests are harvested for timber has led to a shift away from clear-cutting and toward “partial harvests,” a practice in which stands of trees are cut in stages rather than all at once.
Intuitively, putting the brakes on large clear cuts made perfect sense. There was just one catch: No one stopped to consult the wildlife.
Turns out the federally threatened Canada lynx (whose only eastern stronghold is in Maine) actually prefers dense, younger forests where it can stalk its favorite prey, the snowshoe hare, among small, re-growing conifers. But the solution isn't simply more clear cuts.
For bounding though the canopy and smack into the center of this quandary is another important forest dweller: the American marten. This small weasel is a treetop specialist who needs large tracts of mature forest and a latticework of tree cover. If the canopy is opened up too much by logging, martens disappear.
Suddenly, forest management in Maine got a lot more complex. But in a wide stretch of forest that envelops 40 miles of the St. John River, The Nature Conservancy found itself with the perfect lab to figure out how lynx, marten and forestry could get along in the same woods.
“We knew that balancing sustainable forestry and habitat for Canada lynx and American marten would be tough, but the potential results for nature are incredible,” says Bill Patterson, director of the Conservancy’s Northern Maine program.
“Lynx and marten are what we call ‘umbrella species.’ If forests are managed to protect these two animals, about 85 percent of other forest vertebrate species — birds, reptiles, amphibians and other mammals — will also benefit.”
But tracking these solitary creatures tests the limits of researchers. A Canada lynx is nearly invisible as it pads along the tree line in the mist. And martens spend much of their time foraging under the snow or racing through their vast home ranges.
So in 2007, the Conservancy partnered with Drs. Dan Harrison, Angela Fuller and Bill Krohn, wildlife ecologists at the University of Maine who have spent a combined 65 years studying how these two species use the North Woods. With your support, we can advance projects like this in Maine and beyond.
Harrison and his colleagues are combining satellite images, land-use data and aerial photography with on-the-ground reconnaissance to build maps and models that reveal a full picture of how lynx and marten use the landscape.
On complex pixilated maps, deciduous, conifer and mixed forests each have unique signatures and appear in hues of green and yellow. Light and heavy timber harvests appear in shades of blue, red and purple.
By “reading” these layers of images and data, researchers can assess the entire landscape from the point of view of a lynx or marten and figure out how these animals make decisions about the habitats they use.
When it comes to selecting habitat, a female lynx has only one chance to make the right choice.
“Winter in the North Woods is harsh,” says Harrison. “Imagine traveling alone in sub-zero temperatures with two kids who are almost as big as you, but who aren’t very good at hunting. Roaming far and wide in search of meals wastes precious energy, so you’d want to set up home in a place with a lot of food in easy reach — for a lynx, that means plenty of snowshoe hares.”
In Maine, snowshoe hares are most concentrated in young conifer stands re-growing from clear-cuts, which offer plenty of dense understory for nibbling.
The American marten sees the forest much differently — often as a green safety net whizzing below as it leaps from treetop to treetop. A marten needs trees to be more than 40 feet tall and close together if it is to outrun its arch enemy, the fisher (another member of the weasel family).
While the 1999 Maine Forest Practices Act curtailed clear cuts, it also stimulated more partial harvests: Within 15 years, such harvests doubled to encompass 500,000 acres annually.
“In effect, we were shooting the landscape full of 20-acre holes,” Harrison adds. “If a marten is darting through treetops pursued by a fisher, he could find himself with nowhere to go. So when we look at the landscape through a marten’s eyes, we’re looking for forests with a continuous canopy of taller trees and few heavy harvests.”
But what’s good lynx or marten habitat today, might not be tomorrow. As science slowly uncovers the full story of lynx and marten habitat here, researchers are discovering that it isn’t just the management of individual patches of forest that they must take into account, but the composition of the entire forest.
“It’s like a medical profile,” explains Harrison. “One aspect alone doesn’t tell you whether or not you’re healthy — you need a wider picture.”
The Conservancy is playing a key role in revealing that big picture. “It once seemed impossible to meet the very different needs of these two species while maintaining sustainable forestry, but that’s exactly what these maps and models are helping us do,” says Patterson.
“Now, foresters can actually see the impact of the past 34 years of cutting practices and predict future gains and losses of habitat across millions of acres," he concludes. "And if we can bring this technology to bear on planning in the St. John, it could open the door to partner with even larger landowners to ensure a healthy future for the North Woods and all of its species.”
Kate Frazer is a Nature Conservancy conservation writer based in Boston, Massachusetts.May 31, 2011