A Northwoods Almanac for March 1 – 14, 2024 by John Bates
Record Low Great Lakes Ice Cover
As one would expect given this exceptionally warm winter, researchers at NOAA’s Great Lakes Environmental Research Laboratory report that ice coverage across the Great Lakes has reached a historic low. As of February 11, Great Lakes ice coverage was measured at 2.7%. Maximum ice cover for the year usually peaks in late February or early March and, on average, the Great Lakes experience a basin-wide maximum in annual ice coverage of about 53%.
“We’ve crossed a threshold in which we are at a historic low for ice cover for the Great Lakes as a whole,” says GLERL’s Bryan Mroczka, a physical scientist. “We have never seen ice levels this low in mid-February on the lakes since our records began in 1973.”
Coverage on each of the lakes was measured as follows:
Lake Superior 1.7 %
Lake Michigan 2.6 %
Lake Huron 5.9 %
Lake Erie 0.05 %
Lake Ontario 1.7 %
Too Little Snow
Folks talk about the need for “white gold” up here – the positive economics associated with snow cover. And that’s very true for many businesses that rely on snow, and lots of it, for long periods. While we had exceptional snow cover last winter, this winter has been just the opposite, and it’s not just a phenomena specific to this winter.
According to a Dartmouth College study published in the journal Nature in January, during the past 40 years the seasonal snowpack has decreased by 10 to 20 percent per decade in the northeastern and southwestern US and in other regions worldwide.
Another study, this one from Salem State University in Massachusetts, found that from 2000 to 2022, North America’s annual snow coverage decreased by an area nearly the size of Texas.
This doesn’t bode well for many species of plants and wildlife, particularly here in the North Country where winter defines so much of our character. Here’s a sampling of some of the species impacted:
Snowshoe hares and weasels molt into white coats to better hide in a snowy landscape. But without snow, the hare’s intended camouflage transforms them instead into an obvious target for predators. In northern Wisconsin, the snowshoe hare’s range is drifting north, with cottontail rabbits, who don’t turn white in winter, filling the void.
Our three species of weasels are predators, and their story is a bit different – without snowcover, they can no longer easily approach a prey species without being seen.
Canada jays are really in trouble when winters occur like this one, because they’re “scatter-hoarders.” In the autumn, they mix food with their super sticky saliva and tuck it into the bark of trees at randomly selected spots in their territory, creating thousands of food caches. They do this because they nest during late February and early March in cold, snowy, and usually foodless conditions, incubating their eggs at temperatures as low as -30°F. Nestlings are being fed when lakes are still frozen and the ground still snow-covered, and fledging occurs before 80% of migratory birds have even returned.
The problem is that their caches have to remain frozen or they’ll spoil, and then the jays won’t be able to feed their nestlings. So, Canada jays are being forced further north where constant freezing temperatures still occur.
Wood frogs, chorus frogs, and spring peepers all hibernate a few inches into the forest duff, and essentially freeze the entire winter. They need to stay primarily frozen until they are ready to emerge late in April when the weather is warm enough for them to lay eggs. But frequent thaws force them in and out of dormancy, which requires significant energy and potential death.
Most of our rodent population, from mice to voles to shrews, live under the insulating snowpack throughout the winter in what is called the subnivean zone. They store food under the snow, create tunnels through which they can travel, stay relatively hidden from predators, and most importantly, don’t freeze to death. One winter snow study found that, with two feet of new snow on the ground and an air temperature of 9°F, the temperature at the top of the snow surface is 11°F. Eight inches into the snow, the temperature jumps to 25°F. At the soil surface, the temperature rises higher yet to 34°F. Four inches into the soil, the temperature climbs to 36°F. This variance spells the difference between life and death for thinly furred rodents.
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| subnivean zone, diagram courtesy of Trees for Tomorrow |
In the plant world, deep snow protects plants from dry winter winds and protects roots from frost. Researchers from the Hubbard Brook Experimental Forest in New Hampshire found that with no snowpack, sugar maple roots are exposed to extreme cold, resulting in increased damage and die-off – a 40 to 55 percent reduction in growth that lingered for three years. This is not good news for maple syrup producers, nor for those of us addicted to said syrup.
I vividly recall my favorite ecology professor telling us that white pines didn’t survive as well in southern Wisconsin during the winter as they do in the North Country because it’s colder for the pines down there. We all looked at him quizzically until he explained the obvious – the white pine roots weren’t insulated by heavy snow cover in southern counties, and the freeze-thaw vacillations often injured the trees.
The Flip Side
Conversely, sometimes less is more.
Predator species probably cheer for a thin snow layer. They lose far less energy when they're not forced to wallow through deep snow. Foxes, coyotes, wolves, and martens ordinarily have to stay on trails or travel across the compacted snow that covers lakes, because the energy lost by floundering through deep snow seldom justifies the potential gain. Red foxes can bound through six inches of snow, but deeper snows usually restrict them to trails.
Larger herbivores like deer appreciate minimal snow cover, too. Deer can easily access woody browse in shallow snow without an excessive loss of energy. In such conditions, they can avoid the need to yard up and the possibility of starvation that accompanies overbrowsing in a limited area.
Most birds are also among the creatures that are delighted with minimal snow. Heavy snow generally covers cones, buds, insect eggs, seeds of low shrubs, and other food sources.
Even the fish appreciate light snow cover, because it allows sunlight to penetrate the ice layer more extensively, which in turn triggers photosynthesis and the creation of life-giving oxygen.
As with most environmental change, the cost-benefit ratio of snow depth doesn't exactly tip; instead it merely swings, offering advantages to some, disadvantages to others.
Factors Limiting Deer Abundance in the U.P.
Yet another study confirms that wolves are not, I repeat NOT, the reason for lower deer harvests (google the 26 page summary “Factors Limiting Deer Abundance in the Upper Peninsula,” Michigan DNR, 2021). I’ve cherry-picked a few summary statements, but I encourage you to access the report for yourself and draw your own conclusions based on actual data:
· Buck harvest across the northern portion of the state [MI] has been declining in the last
35 years. This decline is due in part to a decrease in the number of deer hunters (nearly 40% over the last 20 years) as well as more restrictive changes to regulations.
· Quantity of fat reserves and seasonal variation in energy demands play an important role in survival of deer during winter. Critical shelter components (hemlock and cedar) are especially important in aiding deer winter survival, particularly in Deer Wintering Complexes. Hemlock has declined drastically and is essentially absent from state forests, while cedar loss has also occurred, but to a lesser extent.
· In the last 11 years there have been six severe winters that have impacted buck harvest. During this time the wolf population has remained stable, emphasizing that winter weather has a much greater impact on the deer numbers than wolves.
· The abundance of each predator is important in determining how many fawns are killed across the landscape. In the Upper Peninsula, each coyote kills about 1.5 fawns per year, on average. However, coyotes are so numerous that the overall impact from coyotes is the greatest for all predators. Black bears are also effective predators on fawns, killing 1.4 fawns per bear each year. Bears are also abundant and therefore, have a large impact on fawn mortality. Bobcat and wolf populations are much lower, so even though they kill more fawns per year (6.6 per year for each bobcat and 5.6 per year for each wolf), their overall impact on fawn mortality is reduced.
· Wolf abundance has remained relatively stable in the Upper Peninsula for the last 12 years with an estimated 557–695 animals while buck harvest has varied substantially. Predation, winter conditions, and habitat quality all interact to play a role in deer abundance in the Upper Peninsula. Wolves are the least abundant predator with the lowest impact on fawn mortality. Wolves prey upon deer, yet annual adult deer survival is high. Wolves are simply one part of the complex predator-prey relationship and are not a primary limiting factor on deer in the Upper Peninsula.
Celestial Events
For planet watching in March, look after sunset for Jupiter low in the southwest. For early birds up before dawn, look for Venus brilliant but extremely low in the southeast, and Mars also very low in the southeast.
The first three days of March ordinarily mark the period when our average high temperature reaches 32° for the first time since late November. But, of course, this average high has already been met in this exceptionally warm winter of 2024.
As of 3/7, we now are the recipients of 11 hours and 30 minutes of sunlight, as we continue racing toward spring equinox on 3/19.
Before dawn on 3/8, look for Mars north of the waning sliver of a moon. The next morning, 3/9, look for Venus in nearly the same place above the moon.
The new moon occurs on 3/10, as does daylight savings time. The moon also happens to be at its perigee this day, the closest it will be to the Earth this year. This means big tides for those who live along ocean coastlines.
Thought for the Week
“To see takes time, like to have a friend takes time.” - Georgia O'Keeffe
Please share your outdoor sightings and thoughts: e-mail me at manitowish@centurytel.net, call 715-476-2828, snail-mail at 4245N State Highway 47, Mercer, WI, or see my blog at www.manitowishriver.blogspot.com
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