2017-12-09 / Top News

Wildfires Unlikely in Island Forest

The Humidity, Organic Material Help Protect It, Says Dykehouse
By Jacob A. Ball

Jeff Dykehouse, curator of Natural History for Mackinac State Historic Parks, says Mackinac Island’s forest is not as susceptible to wildfires as those in the Pacific Northwest. Jeff Dykehouse, curator of Natural History for Mackinac State Historic Parks, says Mackinac Island’s forest is not as susceptible to wildfires as those in the Pacific Northwest. The untrimmed forest that covers much of Mackinac Island has built-in protections from the kind of wildfire that in the last two years has devastated the warmer, drier woodlands of the Pacific Northwest. High humidity and a healthy layer of dead organic material covering the ground beneath the trees make the woods here much less likely to burn out of control.

Removing brush to improve their appearance and eliminate kindling – recommended by some forestry leaders to reduce the fire danger on America’s vast public lands – would threaten the Island’s natural defenses, said Jeff Dykehouse, curator of natural history for Mackinac State Historic Parks. Mr. Dykehouse said the layer of brush along the forest floor stores moisture and acts as a buffer during dry periods.

Visitors sometimes are disappointed at the Island’s seemingly unkempt woods, he explained, but mature plants must decompose naturally to allow new ones to grow. The mission of park personnel in the management of the Island’s forests is not to create a manicured garden, he said, but to maintain a natural ecosystem that behaves similarly to the way it did centuries ago and will continue to do for centuries more.

Forest fire igniter such as lightning, arson, and negligence, are hard to anticipate and prevent, but of greater concern to Mr. Dykehouse is the management of invasive species and the prevention of diseases that can harm the biodiversity of the Island’s forests.

Whenever wildfires erupt in California and the Pacific Northwest, of course, new concerns are raised about the possibility of an out-of-control forest fire decimating Mackinac Island. Fortunately, the Island’s ecosystem differs from that of western forests populated overwhelmingly by evergreens that retain far less moisture and more often are subject to drought conditions. On Mackinac, there are humid winds throughout the year.

Given the historically-significant structures on the Island and its compactness, less than four square miles, the State Parks and the Mackinac Island Fire Depart- ment, of course, take fire safety, education, and prevention very seriously. Their strict policies include a ban on overnight camping and bonfires within the park. The fire department, responsible for battling fires throughout the Island, provides its volunteers with extensive training and upto date equipment.

Mackinac Island’s natural fire protection is a result of the way it was formed more than 10,000 years ago as glacial ice melted and gradually left a huge rock jutting from a new-formed lake. Over millennia, erosion would create a soil bed atop the rocky surface, which would serve as the foundation for the Island’s forests and wildlife. Mr. Dykehouse said deep, healthy soil is crucial to maintaining a vibrant ecosystem that also happens to be fire-resilient. The deepest and healthiest soil on the Island is in the wooded center, while the shoreline, exposed for a much shorter time, has thinner and more fragile soil.

Island soil has expanded and regenerated countless times over its geological lifespan, Mr. Dykehouse said. Maintaining healthy soil and a healthy forest is possible owing to the constant introduction of additional dead organic material such as fallen trees, leaves, and branches. As the dead vegetation decomposes, it provides nutrients that feed the soil microorganisms. If a policy were enacted to remove all fallen trees, he said, it not only would increase the risk of forest fire, but noticeably degrade the forest. Mr. Dykehouse said fertilizer could be used as a substitute to maintain the soil, but this would cost significantly more and still would do nothing to insulate the Island’s forests from fire.

“To have a healthy forest, you need healthy soil,” he said.

Mackinac Island’s forests are mature, which means they contain a mix of young and old trees. This assures that new dead material is added every season. Some logs and larger branches will decompose for more than a decade, while leaves and twigs will be absorbed within a few years. Together, they form a productive and sustainable carbon cycle that provides additional nutrients to grow new vegetation, according to Mr. Dykehouse. The presence of decomposing logs and tree trunks serves as a valuable buffer to maintain moisture levels on the forest floor, even when humidity declines. Mr. Dykehouse said having a reserve of moisture further reduces the probability that dryness caused by climate change can build up to cause a wildfire.

Research has shown that roughly 1,000 hours of dryness are needed to raise the risk of a wildfire to extreme, he said, adding that this is an unlikely scenario, even during the winter when the air is dry, on an Island surrounded by water. Dry Arctic air does regularly travel across Michigan, but the Great Lakes add moisture before it passes over Mackinac Island.

The interweaving roads and trails that cut through Mackinac’s forests create an added benefit: they’re natural barriers that would otherwise need to be built in the event of a wildfire. Mr. Dykehouse said every part of Mackinac Island is within a quarter-mile of a road or trail. This contrasts with nearby Round Island, which is preserved as a National Wilderness Area by the U.S. Forest Service and has no such barriers against the spread of fire. Mr. Dykehouse said considering Round Island’s wilderness designation, a forest fire there might be left to burn — something that would never be the case on Mackinac Island.

The Island is home to three distinct types of forests. Along the shoreline, there is a traditional northern forest of coniferous trees. Upland, there is a hardwood forest primarily of beech, maple, and oak. Swampier areas of the Island are predominantly populated with cedars, spruces, and balsam firs. This biological diversity protects against other types of devastation. The arrival of oak wilt, for example, would be greatly concerning, said Mr. Dykehouse, but if the forests were composed only of oak trees it would be catastrophic. A monoculture forest is far more susceptible to the impacts of disease and invasive species. Of current concern are invasive Norway maples, which have the ability to take over a forest. In fact, Norway maples have overrun some New England forests.

While Mr. Dykehouse is most concerned about that kind of a threat, Mackinac State Historic Parks do encourage employees who work and live on Mackinac Island to become part of the volunteer Mackinac Island Fire Department. He said several of the members of the fire department work at the park. A past example is retiree Dennis Bradley, who once served both as the city’s fire chief and manager for the state park-owned airport. Such partnership between the park and the city ensures quick firefighting response times anywhere on the Island.

Additional measures that would bolster the Island’s security, said Mr. Dykehouse, include improved education about its fire regulations and encouraging proper disposal of cigarettes.

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