Habitat Loss and Fragmentation

As with most of the world’s species at risk, the biggest threat to Canadian reptile and amphibian species is habitat loss, primarily resulting from urban development, agriculture, and forestry. Wetland ecosystems, which are depended on by a large diversity of amphibians and reptiles, are being lost at alarming rates. For example, it is estimated that 1.4 million ha or 72 per cent of all wetlands in southern Ontario have been destroyed following European settlement. Wetlands near large urban centres are particularly at risk, and it is estimated that 80-98 per cent of wetlands in or adjacent to Canada’s urban centres have been converted to agricultural fields or filled in to build subdivisions. Areas of high reptile and amphibian diversity are often at greater risk because the habitats (e.g., shorelines, mountain valleys, south-facing slopes) preferred by these animals are also in high demand for development. In the bunchgrass-black sage desert of B.C.’s southern Okanagan Valley, for instance, virtually all natural wetlands and much of the hillsides have been converted to housing developments and vineyards. This extensive habitat loss has isolated denning areas for Pacific Rattlesnake, Gophersnake, Yellow-bellied Racer and Rubber Boa from valley-bottom foraging areas in over 85 per cent of the valley.

A further issue is that amphibians and reptiles rely on different habitat types at different times of year or during different life stages. Loss of one of these habitats, or the fragmentation of the landscapes that prevents movement between them, can doom a population. Fragmentation of foraging, nesting and hibernating habitats by roads also increases the vulnerability of these populations to road mortality (see below).

Further reading:

Cushman, S.A. 2006. Effects of habitat loss and fragmentation on amphibians: A review and prospectus. Biological Conservation 128: 231–240.