Drought can have severe impacts on rangeland ecosystems in North America. For the purposes of this chapter, rangelands include natural grasslands, savannas, shrublands, many deserts, tundras, alpine communities, marshes, meadows, and woodlands. Drought impacts vary depending on the severity, frequency, duration, and aerial extent of the drought(s); how the land is managed; and whether plans are in place and implemented to respond to drought. Drought can be simply defined as "a lack of water" characteristic of time, not of place; or it can be defined in a climatic context, as "precipitation levels that are much lower than the annual average” (chapter 2). Chapter 2 identifies four drought classifications: (1) meteorological drought which focuses on water in the atmosphere, (2) hydrologic drought which focuses on available surface water, (3) agricultural or soil moisture drought which emphasizes crop response to declining moisture in soils, and (4) socioeconomic drought which emphasizes the social and economic impacts of drought. These classifications emphasize the harmful impacts of drought, particularly on managed systems and people.