"In 1941, conservationists from across the province met in Guelph to address the extensive damage to southern Ontario's environment. Great tracts of land had been ruined through over cutting of the forest and through faulty farming practices. The conference, under the leadership of J.D. Thomas, chose the Ganaraska watershed, one of the most damaged in the province, as its pilot project.  Over the next few years they worked to restore the natural values of the watershed, mostly by planting trees. Its restoration marked the beginning of the conservation authorities of Ontario. The Conservation Authorities Act was passed in 1946. Over the next four decades the Ganaraska watershed had become one of the largest forested areas of southern Ontario with two million trees planted."