Endangered ecosystem: Carolinian zone

by Lorraine Johnson

Botanists have wrangled over its proper name for more than a century. Scientists still debate its boundaries. But in the 23 years since Ontario Nature first published a special issue of this magazine (then called Seasons) devoted to Carolinian Canada, the unique nature of this region has been celebrated by naturalists and gained currency in the popular imagination.

An Entomological Gem
It’s a question that sounds more like Zen koan than science: is the Ojibway Prairie Complex a hot spot for insect diversity simply because so many naturalists are looking for insects there? Paul Pratt, City of Windsor’s chief naturalist, acknowledges the notion’s appeal but ultimately rejects it, citing prairie habitat as the key factor that accounts for Ojibway being such an entomological gem. “It’s still pretty easy to find new insect species here,” he says, having made a number of discoveries himself.

Of the estimated 30,000 known insect species in Canada, more than 2,000 have been found in the Ojibway Prairie Complex. Recent records include 16 species new for Canada and six species new for Ontario. One of the rarest insects, a small Psilidae fly, was discovered at Ojibway – the only known site in the world for the species – and is now appropriately named Loxocera ojibwayensis.

Butterflies and Moths
More than 300 species of butterflies and moths have been found at Ojibway, which often has the highest numbers of any area surveyed in the North American Butterfly Association’s annual counts. Three Ojibway butterfly species are considered imperilled in Ontario, seven are rare to uncommon in the province and 17 are rare in the region. One prairie moth new to Ontario was discovered in the Spring Garden Natural Area in 1994.

Grasshoppers, Crickets and Katydids
These jumping insects of the order Orthoptera account for the summer cacophony of song at Ojibway. The snowy tree cricket even tells the temperature – the number of chirps in 13 seconds, plus 40, equals the temperature in Fahrenheit degrees.

“True” Bugs
Distinguished by their piercing and sucking mouthparts, true bugs (of the order Hemiptera, meaning “half wings”) often use their needle-like mouthparts to extract fluids from plants. Predatory ambush bugs hide in flowers such as black-eyed Susan and goldenrod, waiting to catch bees, flies and butterflies – prey much larger than themselves.

Mayflies
Adult mayflies live for just a few hours or days, neither drinking nor eating, simply mating in swarms and then returning to water to lay their eggs. Clouds of mayflies emerge along the shores of Lake Erie and Lake St. Clair in mid-June.

Spiders
From the fierce-looking orb weaver spider, with its prominent jaws, to the camouflaged crab spider, which changes colour to match its surroundings, Ojibway is home to a large variety of arthropods. Spider numbers can reach as high as 100,000 per hectare at the height of summer, when insect prey is likewise abundant.
Lorraine Johnson

The Carolinian zone is tucked into the southwestern corner of Ontario, spreading south from an imaginary line connecting Toronto to Grand Bend and all the way down to the southernmost tip of Canada. Surrounded along all but its northern border by significant bodies of water, the region has the warmest climate in Ontario.

Though small in size, at approximately 22,500 square kilometres, the Carolinian zone is rich in biological diversity. According to Michelle Kanter, executive director of the Carolinian Canada Coalition, “the Carolinian life zone is one of the most diverse landscapes in North America in terms of natural habitat. Still, it is a struggle for Canadians to recognize what is on their doorstep in southwestern Ontario.” Close to 400 bird species have been recorded here, representing more than half of all bird species in Canada. Two-thirds of Ontario’s plant species grow in the region. Unique woodlands, grasslands and wetlands dot the landscape, and southern species find a home at the northernmost edge of their ranges. The region provides habitat for many species of flora and fauna found nowhere else in Canada – from the majestic tulip-tree (for many naturalists, the region’s iconic species) to the pointy-faced opossum, North America’s only marsupial.

The Carolinian zone is perhaps best known for its lush woodlands. In spring, ephemeral groundcovers bright with colour carpet the forest floor, and vernal pools in moist swamps are alive with the chorus of frogs. Trees with unusual and evocative names – Kentucky coffee-tree, cucumber magnolia, black gum and pawpaw – can be found in the region, which has the highest diversity of tree species of any forest region in Canada. And species new to Ontario, such as pumpkin ash and swamp cottonwood, are still being found, amazing discoveries considering that the Carolinian zone is not at all remote and is possibly the most heavily settled region in Canada.

In areas where soil, microclimate and historic fires (either ignited by lightning or intentionally set by Aboriginal Peoples) favoured grasslands rather than forests, prairies and savannahs endure, though many of them are now small, isolated pockets. The tallgrass prairie, more familiar from the midwestern United States, extends into Ontario’s Carolinian zone and slightly beyond, supporting a mix of grasses such as big bluestem and Indian grass and wildflowers such as blazing star and culver’s root. Oak savannah shares many of these grassland herbaceous species but also includes open-grown trees such as black oak and bur oak.

Of the various wetland types found in Carolinian Canada, the coastal marshes along the shores of Lake Erie are some of the best remaining examples of the vast wetland complexes that existed prior to European settlement.

Today, the Carolinian region is home to roughly one-third of the country’s human population, and the natural habitats of Carolinian Canada are under increasing pressure. Development, intensive agriculture, pollution and invasive species have all taken their toll. Though it comprises less than 1 percent of the nation’s total land area, Carolinian Canada is home to one-third of the country’s rare and endangered species.

In 1984, conservation groups including Ontario Nature, World Wildlife Fund Canada and the Natural Heritage League banded together to form the Carolinian Canada Coalition. It works to educate the public about the unique nature of this special region and to implement the Big Picture, a collaborative vision for healthy landscapes in southwestern Ontario. For more information, visit the Carolinian Canada website (www.carolinian.org).

Carolinian Canada curiosities
Southern flying squirrel A small mammal that glides through the air, “flying” from tree to tree.
Swamp rose mallow The largest native flower in Ontario, a member of the tropical hibiscus family.
Eastern prickly pear A native cactus found in the wild in Canada only at Point Pelee National Park and three other locations in southwestern Ontario.
Eastern hog-nosed snake A harmless but fierce-looking snake that raises and inflates its head when alarmed.
Wavy-rayed lampmussel Attaches itself at its larval stage to small-mouth bass.
Eastern sand darter A small, translucent fish that hides in the sand with only its eyes exposed.
Opossum North America’s only marsupial, the female of which raises its young in its small pouch.
Eastern spiny softshell A turtle with a rubbery “pancake” shell and a snorkel-like nose.
Pawpaw A tree that bears Ontario’s largest edible native fruit, which tastes like a tangy cross between banana and apple.

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1 Comment

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