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One of our growing concerns is
the effect climate change will have on Sylvania's forest, lakes, and wildlife.
Nearly every climate scientist agrees that the temperature of the surface of the earth has increased in the last century and that much of that increase occurred during the last few decades. The issue at the heart of the greenhouse debate is therefore not so much the magnitude of that warming as how much of it has been caused by human activities versus natural climate variability (solar output).
There is good evidence that the concentration of carbon dioxide and other greenhouse gases in the atmosphere has been building up during the past century because of human activities. Greenhouse gases absorb long-wave but not short-wave electromagnetic radiation. Much of the solar radiation, having a short wavelength, therefore passes through the atmosphere and is absorbed by the land and ocean. The land and ocean surfaces, having been heated by absorption of solar radiation, radiate energy back into the atmosphere. But the earth and ocean surfaces, having a lower temperature than the sun, emit their electromagnetic radiation over longer wavelengths. Almost all of the long-wave terrestrial radiation is therefore absorbed by the greenhouse gases in the lower layers of the atmosphere which, in turn, radiate about half of it back to earth (the other half into space). Because of this ‘back-radiation or returning’ of energy (the greenhouse effect) the temperature at the surface of the earth is above freezing and life as we know it is possible. An increase in greenhouse gases clearly increases this effect and results in an increase in surface temperatures.
Solar output, on the other hand, has changed only slightly. Climate models that include solar radiation changes cannot reproduce last century’s observed global temperature trend without including a rise in greenhouse gases. Furthermore, the warming is occurring only at the surface and the lower parts of the atmosphere, which is in agreement with an increased greenhouse effect.
Most climate scientists therefore agree that our burning of fossil fuels, which generates atmospheric carbon dioxide, is the main cause of the observed global warming; and that we can estimate the magnitude of the future warming based on estimates of future fossil fuel consumption.
Climate models are now capable of closely simulating past changes in the global mean temperature based on known changes in key factors such as carbon dioxide, volcanic eruptions, and solar output. Simulations of major circulation patterns have also been successful. Simulations of regional temperature and particularly regional precipitation patterns are, however, more difficult because of the great complexity of the interactions between the atmosphere, earth surface, and ocean systems. Projected regional changes are therefore more uncertain than projected global means and projected changes in precipitation are more uncertain than projected changes in temperature.
In the coming decades, the climate of the Upper Great Lakes Region, including Sylvania, is projected to become warmer and probably drier, especially in summer. Average temperatures may rise by 6-10oF (3.5-5.5oC) in winter and 7-13oF (4-7oC) in summer. That may not seem like much until you realize that a 10oF increase in summer would push average daytime highs in July and August from a pleasant 75oF to a less pleasant 85oF and nudge them above freezing during much of the winter. Average precipitation may not change much but soil moisture is likely to decrease in summer because the higher summer temperatures will result in an increase in evaporation.
The increased greenhouse effect over the past century has already had a noticeable effect in the Upper Great Lakes Region: The mean temperature has gone up nearly 4oF (2oC). The period of ice cover on inland lakes near Sylvania has decreased by an average of 5-6 days per decade. Wild turkeys are far more frequently seen around Sylvania. There has also been some change in forest composition but that has largely been due to elevated deer populations (Salk et al. 2011).
It is not known for certain how the combination of projected changes in temperature, soil moisture, atmospheric nitrogen (which is increasing because of air pollution and which tends to stimulate vegetation growth), etc. will affect Sylvania’s forest and lakes in the long-term. However, some possible implications include:
Forest composition: Higher temperatures will likely cause boreal forests to shrink, while other forest species will likely move northward, where possible. Tree species such as hemlock and even sugar maple may have difficulty persisting in the warmer and drier climate, while species such as red oak may be favored.
Forest pests: The northern limit of some devastating forest pests such as the gypsy moth and mountain pine beetle is currently determined by low winter temperatures. Pests such as these, and others, will almost certainly become more widely established in the forests of the Upper Great Lakes Region in a warmer climate.
Forest health: Increased atmospheric carbon dioxide and nitrogen may spur forest growth in the short-term. However, other changes, such as more frequent droughts and forest fires, and more severe outbreaks of insect pests, may counteract and outweigh these gains.
Wildlife diversity: While some wildlife species will benefit from a warmer and drier climate, others will suffer. Boreal species of birds and mammals (such as blackburnian warbler, boreal chickadee, spruce grouse, red-back vole, moose) will likely decline or move northward as the habits they prefer no longer exist in Sylvania. Species such as wild turkey, raccoons, skunks, and the already prolific white-tailed deer, stand to benefit from the expected milder winters, and may increase their population in and around Sylvania. Cold-water species of fish, such as lake trout (which occur in two Sylvania lakes) may decline, as lakes warm beyond their range of tolerance. Largemouth bass, a warm-water species now found in some Sylvania lakes, may increase in abundance, while smallmouth bass, a cool-water species now found in many Sylvania lakes, may decrease in abundance.
Lake levels and water quality: The period of ice cover will continue to decline. This means water surfaces will be exposed to evaporation for longer periods of time, leading to lower lake levels. Less ice cover will also increase water temperature which not only further increases evaporation but adds to the temperature effect on cold and cool-water fish species. Lower lake levels could result in higher concentrations of contaminants and a decrease in water quality.
Wetlands: The increased evaporation will result in a shrinking and disappearance of the many wetlands in Sylvania. This, in turn, will decrease the presently very abundant European Swamp Thistle (a non-native plant) but may support another non-native: the Canada Thistle.
[R. Evans contributed to this article]