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Wetlands in the polar desert environment of the High Arctic provide a special ecological niche for the tundra plants, insects, birds, and animals. Non-tidal patchy wetlands exhibit a hydrologic regime that includes a high water table and extensive flooding in the snowmelt period, followed by a gradual summer drying that is interrupted by rainfall events that raise water levels. These wetlands are also prone to inter-annual variations in wetness. Given sufficient local water supply, they are self-sustaining entities in which soil saturation favors ground ice formation, but the ice-rich permafrost prevents deep percolation while vegetation growth and peat development further insulate the ground. Several processes can alter this balance: a change in drainage can reduce inflow; excessive melting of ground ice leading to thermokarst can modify wetland morphology and flow pattern. On a regional scale, projected climatic warming of the Arctic may extend the thawed season, enhance evaporation, and eliminate the late-lying snowbanks that feed some patchy wetlands. Under such a scenario, patchy wetlands in the High Arctic are considered to be highly vulnerable.