An invasive insect that has hurt forests in eastern states for more than 50 years is spreading to northern forests. Richie Duchon reports officials think it came by way of out-of-state nurseries:
An invasive insect that has hurt forests in eastern states for more than 50 years is spreading to
northern forests. Richie Duchon reports officials think it came by way of out of state nurseries:
The tiny bug kills hemlock trees. The Hemlock Wooly Adelgid makes the trees weak and
vulnerable to droughts. Most of them die within ten years.
Mike Phillip is with the Michigan Department of Agriculture. He says this is an important time
of year for finding the adelgid.
“It begins to become active and will develop a white cottony, fluffy surrounding for its body. It’s
called an ova sac. And that is where it gets its name Wooly Adelgid. And that is an important
stage for us, because that’s where it becomes visible to us, and we can really get an idea of the
size of an infestation and what we’re really facing.”
Hemlocks are an important tree in forests, because they make good habitat for birds and animals.
Largeflower bellwort (Uvularia grandiflora) is one of the wildflowers declining at many of the sites studied by University of Wisconsin researchers. (Photo courtesy of Dave Rogers, UW Herbarium)
Don Reiter manages wildlife at the Menominee Tribal Forest in northeastern Wisconsin. The forest retains a healthy diversity of plant life, and has a low deer population. (MPR photo/Stephanie Hemphill)
University of Wisconsin researcher Tom Rooney says forest and wildlife managers should try to maintain a diversity of forest types, and not favor deer or any other particular species. (Photo courtesy of Tom Rooney)
Most of us think of the white-tailed deer as a graceful and cherished part of the natural scene. But it turns out when there are too many deer, it’s bad for some of the plants in the forest. New research suggests deer may be a prime culprit in a worrisome loss of rare plants in the woods. The Great Lakes Radio Consortium’s Stephanie Hemphill reports:
Most of us think of the white-tailed deer as a graceful and cherished
part of the natural scene. But it turns out when there are too many
deer, it’s bad for some of the plants in the forest. New research
suggests deer may be a prime culprit in a worrisome loss of rare
plants in the woods. The Great Lakes Radio Consortium’s Stephanie
Gardeners in many suburbs and rural areas know deer are good at
mowing down hosta, tulips and other favorite plants. In the woods,
deer munch on the small plants that live on the forest floor… plants
such as orchids, lilies, and other wildflowers.
Fifty years ago, researchers at the University of Wisconsin surveyed
hundreds of acres in the state, and made careful records of the plants
on those sites. In those days, the deer population was a lot lower
than it is now. In the last couple of years, two biologists went back to
many of those same sites and counted the plants living there now.
Tom Rooney says at most sites they found fewer different kinds of
“It tends to be the same species occurring over and again on the site.
You’re losing the rare species and picking up more and more
He says they tried to link the decline in rare species to the fact that
the forest is getting older. But they found no evidence for that.
Instead, lead researcher Don Waller says the evidence points to
deer, which have increased dramatically over the last fifty years.
“The worst changes we’ve seen, ironically were in a couple of state
parks and a protected natural area, that showed losses of half or
more of species in 50 years. However, in these sites there was no
deer hunting, implying high densities of deer may be causing a lot of
the effects we see in the woods.”
Plants that rely on insects for pollination declined more than other
types of plants. Waller thinks it might be because the insect-
pollinated plants have showy flowers, which could catch the eye of a
wandering deer. As the flowering plants decline, the insects and
birds that rely on them for food could decline as well – bees, moths,
butterflies, and hummingbirds.
Waller says it’s worrisome because scientists don’t know how
particular insects and plants work together to support each other.
“As we’re losing parts of the ecosystem, we’re really not sure what
their full function is, they might play some crucial role we’re not aware
of and only too late might we become aware of the fact that this loss
led to an unraveling or threats to other species.”
Waller says the only places they studied that still have a healthy
diversity of plants are on Indian reservations. The Menominee Tribal
Forest in northeastern Wisconsin is pretty much like it used to be fifty
(forest sounds under)
In this forest, there are only about ten deer per square mile. That’s
about as low as the deer population gets in Wisconsin. It’s not that
the tribe is hunting more deer; it’s the way the forest is grown.
Deer find lots to eat in young aspen woods; there’s less for them to
eat where pines and oaks and maples grow. Don Reiter is the wildlife
manager here. He says in the 360 square miles of the Menominee
forest, there’s really four different types of woods.
“We have pulpwood, we have northern hardwoods, white pine, red
pine, and again, the forest ecosystem as a whole, there’s plenty of
food out there for the deer.”
And because there aren’t too many deer, young pines and hemlocks
– and orchids and lilies – have a chance to grow.
In the upper Great Lakes states, wildlife officials have been trying to
thin the deer herd for several years. That’s because state officials
have been aware deer were causing problems by eating too many
plants. The recent study provides dramatic evidence.
In Minnesota, for instance, hunters are shooting four times the
number of deer they shot fifty years ago.
Steve Merchant is forest wildlife program consultant for the
Minnesota DNR. Merchant says the agency has liberalized its rules,
to encourage hunters to kill even more deer. But the number of
hunters hasn’t gone up in recent years. And lots of private
landowners post no-hunting signs.
“We need to have some help from people, people still need to get out
and hunt deer, and landowners need to provide that access for
people to harvest deer.”
Merchant says Minnesota is gradually trying to restore pine forests,
which were cut down for lumber and replaced with fast-growing
aspen. More pine forests could cut down on the deer population…
“But as long as we still have the strong demand for the aspen
markets that we do, and we manage those aspen forests in a
productive manner for wood fiber, we’re going to create a lot of good
white-tailed deer habitat.”
Merchant says it would take decades to change the woods enough to
reduce the deer population. And in the meantime, we’re losing more
and more of the rare flowers.
For the Great Lakes Radio Consortium, I’m Stephanie Hemphill.