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What is Drought

Ecological Drought

Healthy ecological systems support every form of life by providing food, water, and energy; regulating pests, floods, and diseases; supporting spiritual, recreational, and cultural activities; and sustaining other critical functions, including soil formation, pollination, and nutrient cycling. Drought can alter or degrade any or all of these functions and services at a local, landscape, or system scale.

What Is Ecological Drought?

Droughts and other natural hazards have been part of Earth’s natural processes since the beginning of time. Plants, animals, and ecological systems have adapted and evolved with these hazards. When driven beyond their capacity to adapt, ecosystems may cross critical thresholds, resulting in temporary or permanent alteration in their composition, structure, and/or functioning at local or landscape scales. The vulnerability of natural systems to withstand or adapt to drought disturbances depends on the sensitivity of the system, its exposure to the hazard, and its capacity to adapt and recover from drought.

Ecological drought is an “episodic deficit in water availability that drives ecosystems beyond thresholds of vulnerability, impacts ecosystem services, and triggers feedbacks in natural and/or human systems” (Crausbay et al. 2017). Examples of drought impacts to ecological systems may include:

  • Reduced plant growth over a season or permanently
  • Local species reduction or extinction
  • Landscape-level transitions, such as forest conversion to non-forested vegetation, which may in turn reduce water retention in soils
  • Freshwater ecosystems may change flow regimes, increase water temperature, and deteriorate water quality, which may result in fish kills, reduced opportunities for recreation, and decreased hydropower production.

Ecological drought may be driven by natural phenomena, such as lack of rainfall or warming temperatures, and it may result in or be exacerbated by multiple competing demands on existing limited water supplies. Thus, land use and water allocation decisions may drive or exacerbate ecological drought; for example, modification of hydrological processes to store water prior to drought may reduce water available to ecosystems.

According to recent research, major large-scale ecological changes “are becoming more commonplace as anthropogenic climate change drives more extreme high temperatures, greater evaporative demand (a ‘thirstier’ atmosphere), faster onset, longer duration, and altered timing of drought conditions that cross ecological thresholds, e.g., Smith [2011a, 2011b] and Allen et al.,” creating “novel forms of drought ... globally, challenging our ability to anticipate and manage drought impacts” (Crausbay et al. 2020). 

Monitoring, Forecasting, and Assessing Impacts of Ecological Drought

Planning for Ecological Drought


Impacts and Related Content

Diminished Ecosystem Services

Drought impacts to ecological systems may diminish, alter, or extinguish the resources and services provided by those systems, including clean water, agricultural production, wildlife habitat, and sufficient water levels for recreation, tourism, and aquatic species.

Human Decisions and Ecological Drought

Water allocations and land-use decisions can drive or exacerbate ecological drought.

By Sector | Ecosystems

Long periods without precipitation can alter the delicate balance of ecosystems. Learn more about how natural resource managers can prepare for and mitigate the effects of drought.

Drought Research | Ecological Drought

NIDIS is funding seven 2-year projects through its FY22 Coping with Drought: Ecological Drought research competition, which focus on research and tools to improve our understanding and management of drought risk in terrestrial and aquatic ecosystems. Explore these projects.


Ecological Drought Webinar Series

NIDIS and the U.S. Geological Survey National Climate Adaptation Science Center (NCASC) co-organized a series of four webinars on ecological drought to raise awareness of ecological drought and share new research and practical actions from across the nation to strengthen ecosystem resilience to drought. Recordings of the webinars are available below:

Low water levels and dry, cracked soil due to drought