Canadians rarely consider opossums, magnolias, cacti and sassafras as native to their country – yet all of these species are found in southwestern Ontario. After all, the southernmost parts of the province are at the same latitude as northern California. Where large bodies of water moderate the climate, it is warm enough to support an ecosystem with features typical of the Carolinas. A narrow band of Carolinian forest extends along the north shores of Lake Erie and western Lake Ontario. Although this Carolinian zone comprises less than a quarter of one percent of Canada's land area, it is home to more types of flora and fauna than anywhere else in the country.

When Europeans first arrived in what is now Ontario, forest blanketed much of the southwest. Thousands of hectares of wetlands surrounded Lake Erie and Lake St. Clair, and prairies studded with wildflowers and marshes were found in different parts of the region. Today, some of North America's largest remaining tall grass prairies are on Walpole Island at the north end of Lake St. Clair.

A warm climate and rich soils have made the Carolinian zone attractive both for farming and for urban expansion. As a result, only three per cent of the original forest cover remains. Almost 90 per cent of the wetlands have been lost, and prairies are now among its most threatened ecosystems. The loss of habitat has had a major impact on flora and fauna. For example, the tiny colourful prothonotary warbler is now restricted to a small number of nesting sites. Fish and the "creepy crawlers" on river bottoms have suffered as well. Although it was originally the richest habitat in the country, the Carolinian zone now holds the distinction of containing more rare, threatened and endangered species than any other part of Canada.

Carolinian Canada is a cooperative project set up in 1984 by the Province of Ontario and non-profit conservation groups to preserve the ecological diversity of this zone. In 1987, $3.6 million was pledged by the Government of Ontario, Wildlife Habitat Canada, the Nature Conservancy of Canada and the World Wildlife Fund Canada to protect 38 critical natural areas totalling 40,772 acres (16,500 hectares). The Trust protects over 2,000 acres (over 800 hectares) itself in this zone. Grants to local conservation organizations supported private land stewardship, land acquisition, public education programs, the protection of threatened species and the restoration of endangered ecosystems. The Ontario Heritage Trust assumed a major role as trustee as well as fund and grant administrator (until 1994), and it remains a member of the project’s management committee.

Carolinian Canada has enjoyed success. Two-thirds of the 38 designated areas are now protected by conservation authorities or private landowners. The land stewardship feature of the program was particularly effective. Private landowners who entered into verbal agreements to conserve their land and its features received grants. Over 1,000 landowners have agreed to protect more than 14,826 acres (6,000 hectares) of Carolinian habitat. Another 14,579 acres (5,900 hectares) are owned by conservation organizations. The Trust, for example, owns the Rowanwood Sanctuary and has conservation easements on the Backus Woods, Mill Point and Hanrath properties to ensure the long-term protection of these significant Carolinian Canada sites.

The protection of the Carolinian zone continues to be a challenging conservation issue in southwestern Ontario.