Acid Rain Still Impacting Adirondack Lakes and Forest

By Richard Gast, CCE Program Assistant: Horticulture and Natural Resources, Master Gardener

In a recent newsletter from Congresswoman Elise Stefanik, she mentioned visiting the facilities of the Adirondack Lakes Survey Corporation to discuss strategies for measuring and combating acid rain in the Adirondacks. Although acid rain remains an important topic of study and discussion, the once commonplace phrase has become somewhat obscure in recent years and the problems associated with acid rain have taken a back seat to other, more widely discussed environment-impacting issues.

Like global warming, acid rain results from burning fossil fuels, either to generate electricity at large power plants or to run vehicles and heavy equipment. As the resulting ‘acid gasses’ are released into the air, they combine with water vapor, producing sulfuric and nitric acids, which fall to earth in acidified rain, snow, sleet, fog, mist, or hail.

One of the most significant impacts of acid rain is the acidification of lakes and streams, which has been a serious environmental problem in many areas of the world for more than a half-century. Scientists in our region first became alarmed about acid precipitation in the 1970s, when small lakes in the Adirondack Park were found to be so abnormally acidic that fish were no longer able to live in them. Recovery in some Adirondack lakes has been very slow since then, even with a decline in acid precipitation. U.S. emissions of sulfur and nitrogen decreased by 51 and 43 percent between 2000 and 2010, after regulations targeted power plant emissions and vehicle exhaust.

The problem is one of balance. Nature depends upon balance. Normal precipitation reacts, for example, with anhydrous (or water-free) ammonia and other alkaline chemicals found naturally in the air and in alkaline bedrock and soils (limestone, for example) which help to neutralize the effects of acid rain and snow. In many regions of the world, the soil within lake watersheds provides ample acid-neutralizing-capacity to mitigate the effects of acid deposition. (Nonetheless, if precipitation remains highly acidic, it can eventually deplete available acid-buffering chemicals, in which case, the buffering effect will no longer occur and nature’s ability to maintain balance will have been destroyed.)

The surrounding soils and underlying bedrock of the majority of lakes within the Adirondack Park are comprised of minerals which are slow to weather and, as such, have little capacity to neutralize or buffer acidic water. Consequently, as acid precipitation falls (or thaws) into Adirondack lakes and the streams that feed them, these bodies of water gradually become more and more toxic. At one time, 409 Adirondack lakes supported brook trout. Many are known to have lost their trout populations because of acid rain.

In the 1970s, people also began to see dead and dying trees in many areas of the Adirondack forest and suspected that the cause was acid rain. Today, scientists almost unanimously agree that acid rain threatens the well-being of some native tree species and that harm to trees is compounded when acid rain is present with other stress factors (i.e. abnormal weather conditions, insect damage; both of which are also often tied to global warming associated with the burning of fossil fuels).

One of those threatened species, the sugar maple, which gets its Latin name, Acer saccharum (sweet maple), from its remarkably sweet sap, is quite possibly the most economically valuable tree species in the eastern United States and Canada, because of its role in the multi-million dollar maple syrup industry, the value of its in-demand, high-quality, hardwood lumber (used in making furniture, cabinets, and floors, including bowling alley floors and basketball courts), and regional tourism generated by the magnificence of its fall foliage. It’s one of the region’s most ecologically important trees as well, and the official state tree of both New York and Vermont. It’s the national tree of Canada, too. And the sugar maple leaf is the Canadian national emblem.

Research conducted in recent years by State University of New York (SUNY) College of Environmental Science and Forestry (ESF) scientists involved analyzing growth rings from hundreds of sugar maples from across the Adirondacks. The results of the study, which were published on Oct. 21, 2015, in the open-access journal ‘Ecosphere,’ showed that a decline in the growth rate for a majority of sugar maples began after 1970, although the study concluded that the reasons for the decline are unclear.

An earlier study of acid rain impacts on sugar maple forests in the Adirondacks, led by Dr. Timothy Sullivan at E&S Environmental Chemistry of Corvallis, Oregon, and Dr. Gregory Lawrence of the U.S. Geological Survey, whose ongoing research includes study of recovery processes in an Adirondack watershed where acid deposition has acidified soils and stream water, and assessing acid deposition effects throughout the Adirondack ecoregion through the use of stream surveys and soil sampling, showed lower regeneration and poor health of sugar maple in forests heavily impacted by acid rain.

Prior research by U.S. Forest Service Northern Research Station scientists suggests similar growth declines might be occurring widely across the northeast, but further study is needed to verify their observations.