Do chainsaws belong on a forest preserve? Photo: George C. Gress
By Matt Miller, senior science writer
This might seem a tough thing for a forest conservationist to admit: there are times when an invasive forest pest can’t be stopped.
There are times when you know it’s coming, and you can’t do anything about it. It will arrive in the forest, and trees will die.
They will die en masse.
It might seem a hopeless situation, to watch helplessly while the trees you’re trying to protect are dying.
But what if you could sell those trees for lumber before the pest arrived, and use the proceeds to save other trees?
After all, the trees are doomed anyhow, so this is one positive thing that could be done to benefit the forest.
That is the decision made at the Conservancy’s Woodbourne Forest Preserve in the case of the emerald ash borer. The ash borer was coming and the ash trees couldn’t be saved. Some trees were timbered to fund the protection of eastern hemlocks (the subject of yesterday’s blog).
It’s a tough choice made tougher by this important fact: one of the main reasons Woodbourne Preserve was established was to prohibit any logging on the property. When Francis Cope donated the preserve to the Conservancy in 1954, he envisioned a place that would be protected from chainsaws and logging trucks, forever.
But forever does not take into account the wave of invasive forest pests hitting North American forests. It does not account for the devastation wrought by the emerald ash borer.
Welcome to forest management, 2014 edition. Tough choices need to be made if forests are to be conserved. How do conservation scientists and foresters make these decisions? The case of Woodbourne offers a compelling example.
“The Closest Thing to Chestnut Blight”
Waves of forest pests are arriving in eastern forests. Photo: George C. Gress/TNC
With increasing global trade comes increasing global pests. The recent report Fading Forests (co-authored by the Conservancy’s Faith Campbell) found 28 new invasive species devastating forests in the past 12 years.
For conservationists, it can feel like forests are under siege. Always a new pest threatening to devastate trees.
This is not a new threat in eastern forests: after all, chestnut blight rendered the American chestnut functionally extinct.
The emerald ash borer could prove to be an equally devastating pest. “It is the closest thing I’ve seen to chestnut blight,” says Don Eggen, Division Chief of the Forest Pest Management Division for the Pennsylvania Bureau of Forestry. “I don’t think the emerald ash borer will completely eliminate ash trees, but there’s going to be a lot less of it for a very, very long time.”
The emerald ash borer is a green beetle native to Asia and Eastern Russia. It was first documented in the United States in Michigan in 2002, believed to have arrived in wooden shipping crates.
As its name suggests, the ash borer’s larva does bore into the ash tree’s bark, and effectively girdles the tree.
Many forest pests can be treated even after an infestation has occurred. The hemlock woolly adelgid, for instance, can be controlled with pesticides and bio-control after it is found in hemlock trees.
Not so the emerald ash borer. Once it is in a stand of trees, it is very, very difficult to control.
The Pennsylvania Bureau of Forestry is selecting 3400 trees for protection around the state, focusing on areas far from where the ash borer has reached. The agency is also collecting seeds to save until a time comes when the trees can be planted without threat from the emerald ash borer.
“It has to be very targeted,” says Eggen. “We’re focusing on the conservation of genetics of the ash and treating individual trees.”
“We Knew It Was Coming”
Inevitable: the emerald ash borer was coming, and trees would die. Photo: George C. Gress/TNC
But that approach only works in areas free of the ash borer. Woodbourne Forest Preserve was near other infestations. Staff there knew it was only a matter of time before it arrived at the preserve. It was already too late to stop.
“We knew it was coming” says Mike Eckley, conservation forester for The Nature Conservancy in Pennsylvania. “By the time you find emerald ash borer, it’s too late. You can’t put chemicals into the tree, because the tree is girdled and there’s no place for the chemical to go.”
Ash has commercial value. One idea would be to harvest trees that were going to die anyway, and use that funding to save imperiled hemlocks.
“You have multiple forest pests causing major problems, and they’re expensive to control,” says Eckley. “Which problems do you focus on? Where do you put your limited funding? You have to focus on where you can make the most difference. We can make a difference for hemlocks. We can’t for ash trees.”
To some, it might sound defeatist – to essentially write off hopes for protecting a tree species. To others, it’s practical.
But these are tough decisions, especially at a preserve with a strict no logging policy. A policy that could only be undone in an extreme situation.
A Woodbourne preserve committee, consisting of neighboring landowners and committee members, has to decide on any potential management action, and they must determine it is the only option.
“We showed them clearly why we were proposing what we were proposing,” says Eckley. “It was still controversial. One committee member left. But most understood that this was an important decision to make.”
It was a decision based on ecology. Ash provides great habitat but other tree species can serve the same function.
“No other species can take the place of hemlocks,” says Eckley. “It’s foundational to the ecosystem. We would have had very low success in treating ash, and the ecological return would not be as great.”
Why not wait until ash trees are infested and then cut them?
Ash trees quickly lose all value when infested with ash borers. “When you fell trees that were hit with ash borers, they basically split and disintegrate when they hit the ground,” says Scott Sienko, a third-generation logger who conducted the ash harvest on Woodbourne. “If you catch it before the tree starts to deteriorate, you can still get a little value out of the tree. But it is a very narrow window.”
The committee approved the ash harvest, which was completed in March. Not all trees were cut. Conservancy staff established a core area where dead trees would pose a hazard to roads and high recreational use areas.
“A Gut-Wrenching Decision”
Harvesting ash at Woodbourne. Photo: George C. Gress/TNC
Some might consider it a gamble. What if the emerald ash borer never showed up at Woodbourne?
That proved to not be the case. The forest pest was confirmed in two trees that were logged. It was already there – the first found in that county.
“I wasn’t at all surprised,” says Sarah Johnson, GIS conservation specialist for the Conservancy. “We have been searching for it, knowing it was coming. But it can be a very difficult pest to locate.”
“If we had waited five years, the trees may not have any value,” says Scott Sienko.
Still, it was difficult for many conservationists to see the logging trucks at Woodbourne. Even for staff, it was not a tough moment when the ash borer was confirmed there.
“We’re scientists. We’re practical and we understand forest ecology and invasive species,” says Johnson. “Still, it can be very emotional. You know it’s going to get there; you know it’s going to have consequences. But it still hits you in the gut.”
Jerry Skinner has lived at Woodbourne as preserve naturalist for 24 years. He’s led school groups and citizen scientists. He’s documented moths and songbirds and dragonflies.
He knows forest science well – he teaches ecology at a local college. But it was an emotional moment to see the logged forest.
“You’d drive along and see those cut threes, and just have to remind yourself of the reality,” he says. “Those trees were going to die anyway. Still, to make the decision to be proactive was a gut-wrenching decision. It really was.”
Sacrificing one tree to save another: this is the reality that many conservation managers face. They must look at the science, look at the ecology, look at the costs.
Proceeds from the ash harvest will fund hemlock protection. Photo: George C. Gress/TNC
It can seem a harsh accounting, to accept that not everything can be saved. But a savvy conservation scientist can focus on the big picture: to ensure a healthy forest for generations to come.
“Given the circumstances, this was a high-quality outcome,” says Eckley. “We maximized financial return on the situation, while reducing liability to people and enabling us to better fund hemlock conservation. We weren’t giving up on ash trees so much as doing what was best for Woodbourne.”
Editor’s Note: This is the foruth in a five-part series on the challenges of eastern forest conservation in the Anthropocene. Read the previous blogs.
Opinions expressed on Cool Green Science and in any corresponding comments are the personal opinions of the original authors and do not necessarily reflect the views of The Nature Conservancy.
Making the best of a tough situation. Photo: George C. Gress/TNC