Aitkin and Carlton county foresters have come up with a habitat plan for endangered bats that could become a blueprint for the future of logging in Minnesota and the Upper Midwest.
In the last five years, a foreign fungus causing a deadly condition called white-nose syndrome has killed upwards of 95% of Minnesota's northern long-eared bats, which were placed on the endangered species list in November.
Two other species of Minnesota hibernating bats — tri-colored and little brown — also are on the brink of extinction and under consideration for the endangered list. Bat populations have declined in 38 states and eight Canadian provinces where the fungus has spread since it arrived in New York in the mid-2000s.
The endangered species list will give northern long-eared bats some new federal protections starting in February — the most significant being the requirement that loggers get permits if their cutting could result in death or injury to the bats.
Aitkin and Carlton counties, which manage a total of about 300,000 acres of forest just west of Duluth, are the first in the state to get the permits. They plan to create permanent conservation zones around any trees that are known to be roost sites for pregnant bats, which hunker down in the spring inside tree cavities to give birth. It will allow them to log the usual amount each year, ranging from 1% to just under 3% of their public forest.
Bats can use just about any species of tree to give birth, including trees as young as five years old. They remain there through July as the pup learns to fly, with the mother carrying her young on her back at night as she flies off to devour mosquitoes and other insects.
Under their plan, the counties will periodically survey the forests looking for roost trees. No logging will be allowed within 150 feet of a tree used by a pregnant bat, until that tree is no longer "suitable" for habitat and dies a natural death.
"We'll protect that site for as long as the roost tree is there — from age 5 until it falls over at 150 years old," said Greg Bernu, Carlton County's land commissioner.
The plan, which also bans logging within a quarter-mile of any hibernation sites, requires the vast majority of logging to occur in the late fall and winter, when bats leave the forest to hibernate underground in caves and mines. It further limits logging during the critical pupping months of June and July to less than 10% of that year's total harvest.
The bulk of Minnesota logging already takes place in winter, because that's when the ground is solid enough to enable heavy equipment to easily move through the forests. Even without the restrictions, just 5% of the timber harvest in the two counties typically occurs in June and July.
A deadly fungus
As the fungus spread in 2014, county leaders knew that hibernating bats were likely going to wind up on the endangered species list. They started conducting acoustic surveys that year, finding northern long-eared bats in just about every corner of the woods they looked.
The populations for northern long-eareds, tri-coloreds and little brown bats crashed in 2017, and sightings became rare. By 2020, surveys by Aitkin and Carlton didn't find any northern long-eared bats at all, Bernu said.
The permits allow the counties to continue logging for the next 25 years. That's critical, as the money raised by selling logging rights cover virtually all costs for the upkeep of the land. Without that revenue, the counties would likely sell the forests they manage, Bernu said. Based on population estimates, the U.S. Fish and Wildlife Service guesses that the logging will accidentally kill a total of nine bats over that 25 year period.
While logging did not cause the population crash, any hope for the future of bats depends on their being able to give birth inside those trees. They prefer older ones that get exposed to a lot of sunlight to keep them warm, and their favorites in Minnesota are aspen and elm, according to the Department of Natural Resources.
It's taken the fungus only a few years to kill nearly all of the state's northern long-eared bats. It sprouts when bats slow their immune systems to save energy during the winter, and grows into a fuzzy, white moss-like substance that spreads to the tips of their wings and across their faces. The hibernating bats wake up and try to lick themselves clean, like a dog or cat. But in doing so they burn through the energy and fat they need to survive winter, and starve.
The fungal growth also blocks the release of carbon dioxide, which is done through the bat's wings during hibernation. That forces bats to wake up in order to exhale, expending precious energy. Sometimes bats die in the cave; other times, they fly off in a hopeless search for bugs to eat in the dead of winter.
The fungus has killed millions of northern long-eared bats, wiping out some populations and destroying an estimated 97% in many of their biggest hibernating grounds, such as the Soudan Underground Mine near Ely, Minn.
Life without bats would be hard for Minnesotans. Hibernating bats eat at least nine mosquito species that carry West Nile virus. A U.S. Fish and Wildlife Service study found that they save American farmers at least $3 billion a year by pollinating crops and eating moths, beetles and other pests.
States have largely given up trying to keep the fungus out of the caves where bats hibernate. They're now focusing on making sure the few that have survived can reproduce. The hope is that the survivors have some physical or genetic traits they can pass down to their young that will make them better able to fight off white-nose syndrome.
The Minnesota DNR is working with Wisconsin and Michigan to develop a conservation plan that would cover all their state-run forests. The plan, which is under review by the Fish and Wildlife Service, would be similar to the one approved for Aitkin and Carlton counties, said Lacy Levine, DNR conservation management and rare resources unit supervisor.
Like the counties' plan, the joint state plan would ban logging within 150 feet of roost trees and a quarter-mile of hibernation sites. It would also place new limits on logging, road and ATV trail construction, and prescribed burns during June and July. Similar restrictions were built into plans approved for Missouri and Pennsylvania.
Levine expects the Fish and Wildlife Service to make a decision on the joint state plan by the end of the month.
"A common theme is this desire to protect maternity roost trees," Levine said. "That's so important because [bats] tend to come back to the same stand every summer."
