Scientists say acid rain probably will cause a decline in the Great Lakes region's sugar maple trees.
Sugar maple abundance already has dropped in parts of the northeastern U.S. and southeastern Canada over the past 40 years, primarily because of high acid levels in soils.
The upper Great Lakes region has mostly escaped the damage because its soils are rich in calcium, which provides a buffer against acid.
But in an article published this month in the Journal of Applied Ecology, scientists say they've discovered another way that acid rain harms sugar maple seedlings in upper Great Lakes forests.
Donald Zak of the University of Michigan says it prevents dead maple leaves from decaying on the forest floor, creating a barrier that hampers growth of new trees.