The pinyon-juniper woodlands and the sagebrush-grasslands, with a combined area of over 90 million ha, comprise a major portion of the rangelands in western North America. During pristine times fire played an important role in these vegetation types. The role of fire has changed significantly in the historic period. Changes in fire occurrence have resulted from fire suppression, livestock grazing, and the breaking of the fuel continuity with roads and other developments. In general, fire is less common today than it was prior to Euro-American settlement, but in some areas it is more frequent. This alteration of the fire frequency has resulted in major successional changes in the vegetation. Prescribed fire is currently used to counter the successional changes and to achieve a variety of land management objectives both vegetation types. While herbaceous productivity is often increased following fire, there are many problems associated with the use of prescribed fire in these communities. Low amounts of fine fuels, high populations of exotic annual plants, and severe environmental conditions create challenges for the land manager when planning prescribed fires. Source: Canadian Forest Service, Northern Forestry Centre. Abstract reproduced with permission of the Minister of Public Works and Government Services Canada, 1999.