Issue At Hand

During the past 150 years, forest harvesting, alteration of historical fire regimes, land conversion to agriculture, herbivory, and changing land ownership have greatly altered forests across the US Great Lakes region. Extensive harvesting early in the century, often followed by fire, decreased mature forests dominated by sugar maple, yellow birch, hemlock, and white pine, and increased the abundance of early successional species dominated by aspen . This “second forest” has matured, and natural succession along with a host of other factors is creating different forests at local and regional scales. The implications of these changes are poorly understood.

What We Hope to Accomplish

Our goal is to quantitatively understand forest change across the northern Great Lakes region. To achieve this goal, we examine the extent to which forests across the region been restored and resemble historical extent, species diversity, structure, and function. In doing so we compare land cover and forest conditions from the period just prior to intensive Euro-American settlement in the region (mid-1800s) with those of the present (1990s).

What We Found

We reveal a distinct and rapid trajectory of forest change toward historically unprecedented and simplified conditions. In addition to overall loss of forestland, current forests are marked by lower species diversity, functional diversity, and structural complexity compared to pre-Euro-American forests. Today’s forest is marked by dominance of broadleaf deciduous species in comparison to the pre-Euro-American period. Aspen and maple species comprise the primary deciduous species that have replaced the historically-dominant conifers. These changes reflect the cumulative effects of local forest alterations over the region. They also affect future forests and the goods and services these forests can provide.