Abstract
Some plants are rare because they naturally occur in very
specialized habitats or in very low numbers; others may be rare because they
have suffered setbacks because of natural processes or pressures from human
activities. The highest number of rare plant species is in southern
Ontario, where human activity is intensive and extensive. Farming, deforestation,
draining of wetlands, and the use of insecticides and herbicides has reduced
the populations and areas of distribution of numerous species.
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