Thumb Description
The Thumb region of the Lower Peninsula of Michigan is a post-glacial
landscape where northern forest blends with central hardwoods, bordered by
Lake Huron, the Saginaw Bay, the Saint Clair River, and Lake Saint Clair. There
are differing opinions about exactly what geographic areas are included in the
Thumb, which is named because the Lower Peninsula is shaped generally like a
large mitten, and the Thumb like the thumb of the mitten. Historically, most
people have probably considered the Thumb to be limited to that area from Port
Huron north, and from the Saginaw Bay east. The Thumb. Land Conservancy
has taken a slightly broader view of what constitutes the Thumb. We basically
drew a straight line from the south end of Saginaw Bay and extended it to the
northwest end of Lake Saint Clair. By this definition, the Thumb includes at least
part of Macomb County in addition to the more traditional Thumb region of Saint
Clair, Sanilac, Huron, Tuscola, and Lapeer Counties. Considering watershed
boundaries, the Thumb could be expanded even further to include parts of Bay,
Saginaw, Shiawassee, Genesee, and Oakland Counties. But sticking to the idea
that the region is a big thumb, the TLC definition is fairly close to an anatomical
thumb, although there is some debate about how much to include as the lower
knuckle or metacarpophalangeal joint. We are pretty sure that when Paul
Bunyan put his hand in the mud in lower Michigan, he didn’t mean for it to be too
complicated.
Overview
The Thumb is a great place with so much worth protecting. For those who know
the Thumb, there really seems to be no end to the fascinating natural areas,
historical sites, points of interest, and cultural history.
The Thumb is actually quite unique on a global basis. Few regions border as
much fresh water as the Thumb, nearly surrounded by the Great Lakes,
including Lake Huron, Saginaw Bay, the Saint Clair River, and Lake Saint Clair.
The south end of the Thumb, where the Saint Clair River flows into Lake Saint
Clair, is one of the largest freshwater deltas in the world, including Harsens
Island, Dickinson Island, and Walpole Island in Ontario.
The Thumb is crossed by many rivers including the Black River, Mill Creek,
Cass River, Flint River, Clinton River, Pine River, Belle River, Salt River,
Sebewaing River, Pigeon River, Pinnebog River, New River, and Willow Creek,
to name the largest. The Black, Belle, and Clinton Rivers are known particularly
for their diverse and resilient fish and mussel communities, with many rare
species.
The Thumb is a post-glacial landscape of rolling glacial till plains where the last
glacier churned out vast piles of sediment; a flat perimeter of lakeplain along the
current Great Lakes where an expanse of glacial meltwater once covered the
land as much as 40 miles inland; a higher interlobate region formed between the
Huron and Saginaw ice sheet lobes, of large hills and scattered pothole lakes
formed by huge chunks of ice left behind by the last melting glacier; the Port
Huron Moraine, a broad ridge paralleling the lakeplain marking the edge of the
last melting glacier as it stalled during a colder climate period; eskers or ridges
of sediment that were deposited in huge drainage channels under the glacier,
such as Deanville Mountain; and other unique features formed or revealed by
the interaction of the glacial melt waters and present-day Great Lakes with the
shoreline area such as the dune and swale complex, Rush Lake, Lake Huron
bluffs and ravines, sandstone outcrops, beaches, dunes, and Sand Point.
The variety of landscapes across the Thumb has resulted in at least as many
unique natural communities including Great Lakes marsh, dune and swale
complex forest, lakeplain prairie, lakeplain oak openings, southern hardwood
swamp forest, hardwood conifer swamp forest, mesic flatwoods, bog, fen, mesic
and dry-mesic southern upland forests, mesic and dry-mesic northern upland
forests, floodplain forest. Some of the Thumb’s largest and most impressive
examples of these natural communities are the Great Lakes marshes along
Saginaw Bay and the Saint Clair River delta, the dune and swale complex of
Port Crescent, lakeplain prairie along Saginaw Bay, the large expanses of forest
in the Verona, Deford, Tuscola, Vassar, Lapeer Deford, and Port Huron State
Game Areas, Minden Bog, one of the southern-most raised bogs in North
America, and the Minden City State Game Area, the high interlobate hills and
lakes region extending from the Kingston area southwest through Lapeer
County, and the vast stretch of mesic northern forest and other forest types and
associated species of the Port Huron State Game Area.
Over 200 rare species have been documented across the six counties of the
Thumb region. Some of the more iconic species include Lake Sturgeon,
Eastern Sand Darter, Northern Riffleshell mussel, Rayed Bean mussel, Eastern
Fox Snake, King Rail, Cerulean Warbler, Prairie White-fringed Orchid, and
Painted Trillium.
Thanks to the foresight of federal and State leaders, decades ago, over 160
square miles of State recreation land in 29 State Game and Wildlife Areas were
established across the Thumb, including the St. Clair Flats SWA, St. John’s
Marsh SWA, Deford SGA, Tuscola SGA, Lapeer SGA, Minden City SGA,
Verona SGA, Port Huron SGA, Fish Point SWA, Wildfowl Bay SWA,
Quanicassee SWA, Vassar SGA, Murphy Lake SGA, Rush Lake SGA,
Sandusky SGA, Sanilac SGA, Gagetown SGA, and Cass City SGA. There are
also over 8 square miles of State recreation land in 6 State Park and Recreation
Areas including Port Crescent SP, Sleeper SP, Lakeport SP, Algonac SP, Wetzel
SRA, Metamora-Hadley SRA, and Sanilac Petroglyphs HSP. Numerous county
parks, township parks, a few nature centers, several nature preserves, camps,
public access sites, and trails are scattered across the Thumb also.
Every plant, animal, woods, field, wetland, creek, … even your yard, now
matters.