Southern Great Lakes forests

This ecoregion covers much of the industrial heartland of North America, including southern Michigan, much of Ohio and Indiana, extreme southwestern Ontario, including the lowlands of the south of Lake Ontario in Ontario and western New York State. The area is so heavily populated and developed that essentially no large blocks of natural habitat remains.

Most of this ecoregion is rolling, but some parts are nearly flat. The northern but not the southern parts were glaciated. The climate shows strong annual temperature cycles: summers are hot with frequent tornadoes, and winters are cold. In Ontario, the Lake Erie Lowlands are marked by humid, warm to hot summers and mild, snowy winters. The mean annual temperature is 8°C, the mean summer temperature is 18°C, and in winter it is -2.5°C. Mean annual precipitation ranges from 750-900 mm and is distributed evenly throughout the year (ESWG 1995).

Much of the ecoregion is underlain by carbonate-rich, Palaeozoic bedrock. Most of the region lies southwest of the Niagara Escarpment, where the land surface slopes gradually toward the southwest through rolling topography. Bedrock outcrops are limited to only small areas (ESWG 1995).

The Southern Great Lakes Forests are dominated by deciduous forests which are distinct from the mixed forests in other parts of the St. Lawrence lowlands to the north and contain lower species diversity than ecoregions to the east and south. Historically, the ecoregion consisted of sugar maple (Acer saccharum) and beech (Fagus grandifolia), which together comprised 80 percent of the canopy in the region. Beech reaches its western limit in the transition zones between forest and grasslands and savannas (ecoregions 9 and 65), and basswood (Tilia americana) becomes a more important species. Other forest types, dominated by oaks (Quercus spp.) and hickories (Carya spp.), occur on drier sites, whereas mixed swamp forest, especially elms (Ulmus spp.), ashes (Fraxinus spp.), and red maple (Acer rubrum), occupy the wettest soils. A tightly closed canopy and a thick layer of humus and leaf litter characterize these forests, encouraging the growth of spring perennial herbs and discouraging bryophytes (Greller 1988). Forest species assemblages are highly influenced by surficial materials (sands or clays). Fire and water table depth are important ecological processes in maintaining relict prairie grasslands and oak savannas. Forested areas on moist and wet sites are characteristically renewed largely through tree falls from wind and/or ice storms.

  • Scientific Code
  • Ecoregion Category
  • Size
    94,400 square miles
  • Status
  • Habitats

Biological Distinctiveness
Some characteristic mammals include white-tailed deer (Odocoileus virginianus), red fox (Vulpes vulpes), eastern chipmunk (Tamias striatus), grey (Sciurus carolinensis) and red squirrel (Tamiasciurus hudsonicus). Breeding birds include northern cardinal (Cardinalis cardinalis), wood thrush (Hylocichla mustelina), screech owl (Otus asio), mourning dove (Zenaida macroura), green heron (Butorides virescens), pileated (Dryocopus pileatus) and red-bellied woodpecker (Melanerpes carolinus), and wild turkey (Meleagris gallopavo) (re-introduced through parts of the ecoregion) (ESWG 1995).

Although little forest habitat remains, the Southern Great Lakes ecoregion contains some rare ecological phenomena. The Great Lakes include extensive interior wetlands, and freshwater bodies with dune systems, such as Long Point, Presqu’ile, and Lake Erie’s Rondeau and Point Pelee, which have large sand pits supporting unique plant communities. These are major staging areas for migrating birds. They are also of international significance as peninsular sand and dune complexes in a freshwater system. The sand dune complex on the shores of Lake Michigan is another important site. The southern extent of the Niagara Escarpment has numerous ancient trees of varied species.

The ecoregion is the most northward distribution of many ‘Carolinian’ species in North America. As well, it is the eastern extension of the Niagara Escarpment and Niagara Gorge. There is an archipelago of islands in western Lake Erie, including several endemic sub-species and varieties. This is the most eastern extension of mid-western prairies and savannas in North America.

Conservation Status

Habitat loss
Agriculture and industrial and urban development are the predominant land uses in much of this ecoregion. Thus, the ecoregion is one of the most heavily impacted by human activities on the continent. Habitat loss is nearly complete in this ecoregion. Nearly 100 percent of the region was ranked as heavily altered. Wetland losses have been particularly severe; Ohio, for example, has lost 90 percent of its wetlands, and 80 percent of the southern tamarack swamp in Michigan has been destroyed (Noss and Peter 1995). Major urbans centers include: Toronto, Hamilton, Buffalo, Rochester, Syracuse, Detroit-Windsor, Erie, Cleveland, Cincinnati, Columbus, and Indianapolis.

Remaining Blocks of Intact Habitat
No habitat blocks of significant size remain, but the Long Point area of Ontario has approximately 40 km2 of semi-natural lands in various ownerships, much of it public.

Degree of Fragmentation
Remaining patches are tiny, with effectively no connectivity in most areas and little core habitat due to edge effects. The individual fragments and clusters that remain are highly isolated, and the intervening landscape precludes dispersal for most taxa.

Degree of Protection
This region has no protected areas larger than 500 km2.

Types and Severity of Threats
The remaining tiny fragments of natural habitat in the Southern Great Lakes face intense conversion pressure from development and agricultural expansion. Agricultural conversion for corn, soybeans, tobacco, grains, canola, and tender fruit has occurred. Urban sprawl threatens this region. Agricultural land and woodlots are being severed to accommodate country homes. Habitat not being converted is being degraded by pollution and exotic species. Wildlife exploitation continues and the elimination of most target species is imminent or complete.

Suite of Priority Activities to Enhance Biodiversity Conservation
Given the parlous state of natural habitats in this ecoregion, conservation requires:

•urgent protection of the remaining fragments
•planning for restoration of those degraded areas that have not been irreversibly altered.
Conservation Partners

•Carolinian Canada ProgramPeninsula Field Naturalists
•Essex County Field NaturalistsPeninsula Field Naturalists
•Federation of Ontario NaturalistsSouth Peel Naturalists
•Friends of Point PeleeSydenham Field Naturalists
•Hamilton Naturalists ClubThe Wildlands League
•McIlwraith Field Naturalists of LondonWorld Wildlife Fund Canada
•Norfolk Field Naturalists
Relationship to other classification schemes
The Southern Great Lakes Forests ecoregion includes parts of Bailey’s Laurentian Mixed Forest Province and Eastern Broadleaf Forest (Continental) Province. Omernik finds four distinct ecoregions here: the eastern corn belt plains, S. Michigan/N. Indiana till plains, Huron/Erie Plain, and Erie/Ontario Lake Plain. We believe that the forest types found in the Southern Great Lakes are sufficiently closely related to warrant a single ecoregion.

In Canada, the southern Great Lakes Forests cover the Lake Erie Lowland in southern Ontario and northern States (ESWG 1995). In southern Ontario, this ecoregion overlies the Niagara Deciduous forest region (Rowe 1972).

Prepared by: K. Kavanagh, S. Buttrick, M. Davis, J. Adams, M. Sims, G. Mann.