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Climatic extremes taking a toll on Michigan’s forests

Photo courtesy of MDEGLE: High water levels have impacted shorelines statewide, including on Lake St. Clair, above.

By Jim Bloch

While humankind is facing the ongoing crisis with the coronavirus pandemic, forests are locked into their battles for survival, including Michigan’s plentiful woodlands.

The dangers to Michigan’s forests are many.

Forest fires come to mind.

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The dangers presented by insects are another. Gypsy moths, introduced to the state in the 1950s, defoliated about a million acres of Michigan’s forests in the Lower Peninsula in 2020.

Less familiar insects, such as the Hemlock woolly adelgid, introduced to the state in 2006, pose a threat to the state’s 176,000 hemlock trees

In the central UP especially, spruce budworms, which are native to the state, have been defoliating spruce and fir trees.

Fungi such as oak wilt, first found in Michigan in 1944, kills thousands of oaks, especially red oaks, across the state each year. Heterobasidion root disease, identified in the state in 1963, attacks conifers.

A less well known threat to forests is climate change. Among the consequences of a warming planet are more extreme weather events. High temperatures result in higher rates of evaporation from the land and lakes; more water in the atmosphere tends to mean that storms will drop more precipitation in the form of intense rain and snow, which can damage forests.

Storms intensify

” Climatic extremes are taking a toll on Michigan’s trees,” according to Michigan Forest Health Highlights 2020, released by the Michigan Department of Natural Resources on March 12.

A lot is at stake. Michigan has nearly 20 million acres of forests, most of it Up North. Nearly 13 million acres of forestland is privately owned. The federal government controls nearly three million acres. The state of Michigan manages more the four million acres.

“The eastern Upper Peninsula experienced a heavy snow and ice storm at the end of December 2019, which left downed trees across roads and trails and created extensive power outages,” the report said. “Long-term impacts to damaged trees depend on the extent of the damage. Younger, more vigorous deciduous trees will be able to replace lost crown area quickly and wall off damaged areas, preventing diseases and insects from taking advantage of open wounds. Stressed trees may struggle.”

In Chippewa and Luce counties, the damage to young pines proved long-lasting.

“Some trees lost central leaders, the important vertical stem at the top of the trunk, permanently altering their form,” the report said. “Small trees were pressed toward the ground under the snow, creating small wounds that resulted in infection and subsequent dieback or death due to a fungal disease called Diplodia.”

“Over the last half century, average annual precipitation in most of the Midwest has increased by 5 to 10 percent,” according to the EPA.

Windstorms, which often drive rain and snow events, can also damage forests. According to Scientific American, wind speeds have increased worldwide since 2010.

All of this is happening as the pandemic drives more people outside and into the woods.

“(People) grew more interested in local surroundings as they spent an increasing amount of time outdoors and sent record numbers of questions about backyard trees to Michigan Department of Natural Resources staff,” said Jeff Stampfly, DNR Forest Resources Division Chief and State Forester, in the report. Forests help clean the air and filter the water. “(Forests) even boost our physical and mental health when people visit them to hike, hunt, bike, fish, ski or bird watch.”

Other climate impacts on forests

Climate change also appears to be disrupting the jet stream which generally keeps the polar vortex circling in the Arctic regions. When the jet streams dips southward, unusually cold temperatures may result.

In late May last year, a deep frost descended over the state and temperatures fell into the low 20s across for up to three straight nights.

“Trees appeared ragged, with thin crowns, as leaves struggled to emerge from the damage,” the report said. “Heavily impacted trees tapped into stored resources and produced a second flush of leaves. In many cases in southern Michigan, these leaves appeared to be yellow in color and not the normal deep green typical in oaks. While frost damage alone is not enough to kill trees, the stress can predispose older oak trees to crown and branch dieback or severe nutrient deficiency, particularly when combined with other stressors like defoliation by insects or drought.”

High water tables are having a negative impact on forests around the state

“Many waterfront property owners reported dying trees that had previously appeared to be perfectly healthy,” the report said. “Upon further investigation, it was discovered that most of these trees were near the lakeshore. Rising water tables were effectively drowning the trees’ root systems. In other lowland areas of the state, large numbers of trees have died or are dying as well, either as a direct result of the high water or in combination with insects and diseases taking advantage of stressed trees.”

According to the EPA, temperatures in the state have risen two to three degrees Fahrenheit over the past century.

Warmer temperatures appear to be contributing to insect infestation in trees. Larch case bearer and eastern larch beetle, for example, have caused periodic defoliations of Michigan tamaracks, especially in the eastern Upper Peninsula last spring.

“(R)ecent research in Minnesota suggests that warmer autumn temperatures may be suppressing the beneficial parasitoids and favoring larch casebearer survival,” the report said. “Studies in Minnesota also suggest warmer temperatures and extended growing seasons may increase eastern larch beetle populations, further contributing to tamarack damage.”

Jim Bloch is a freelance writer based in St. Clair, Michigan. Contact him at bloch.jim@gmail.com.

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