Ecological Drought Across the Country

Historically, drought has been viewed in terms of its agricultural, hydrological, and socioeconomic impacts. How drought affects ecosystems - and the services they provide humans - is often not discussed. In response, the National Climate Adaptation Science Center (NCASC) initiated a national-scale effort that’s addressing this gap in drought research. A  new concept  – ecological drought – was developed to capture this emphasis on how drought impacts ecosystems.

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 and Ramirez, 2017 ).

The concept of ecological drought does not exclude humans from the equation. Rather, it recognizes that the relationship between humans and ecosystems in the context of drought is closely linked, with multiple feedbacks. For example, take an ecosystem that has been significantly altered by human development. This ecosystem is now more vulnerable to drought than it once was and more susceptible to increased competition for water resources. When a drought occurs, the existing pressures on the ecosystem’s natural water supplies are amplified. If the water needs of the ecosystem are not considered in allocation decisions, then this already vulnerable ecosystem may be pushed beyond the threshold at which it can recover. The ecosystem will then begin to function differently, leading to a loss in the critical services it once provided humans -- such as purifying water and air, preventing erosion, and providing recreation opportunities.

Every region of the country is susceptible to some form of drought. In the Northeast, a region which is used to predictable precipitation patterns, small shifts in the timing, type (rain vs. snow), and amount of precipitation can be detrimental. In the Southwest, even the hardiest of desert species can be challenged by prolonged and extremely hot droughts. And in Hawai’i, drought is contributing to the spread of invasive grasses, which now make up a quarter of the state’s land cover. With our eight regional Climate Adaptation Science Centers (CASCs), which cover the entire United States in addition to the U.S. Virgin Islands and U.S.-Affiliated Pacific Islands, our network is well-positioned to examine ecological drought across the country.

The overarching goal of the Ecological Drought initiative is to support the effective management of ecosystems and human communities in the context of drought. To meet this goal, we aim to:

1. Identify drought impacts across the country;
2. Synthesize our knowledge of the ecological impacts of drought, so that we can get a complete picture of what we know and where the gaps are – which will help guide future research;
3. Communicate this knowledge to resource managers and other stakeholders;
4. Support decision-making by ensuring that resource managers have the information they need to prepare for and respond to drought.

To identify and communicate regional drought impacts, NCASC teamed up with the  Integration & Application Network (IAN)  at the University of Maryland Center for Environmental Science. Through this partnership, an Ecological Drought Workshop was held in each CASC region to convene regional experts in drought and discuss the impacts to ecosystems and ways forward for management. Each regional workshop resulted in a fact sheet communicating the story of ecological drought in that region. A national synthesis workshop followed, summarizing emerging drought themes across the country. View the region-specific fact sheets by clicking on the map above.

During these workshops, it became clear that islands such as Puerto Rico, the U.S. Virgin Islands, and the U.S.-Affiliated Pacific Islands experience unique challenges related to drought. To delve further into this topic, the CASCs worked with partners to hold two workshops on island drought.

The National and Regional CASCs funded research to identify what we know about the impacts of ecological drought across the country, where information is lacking, and how managers can plan for these impacts and adapt to changing conditions in the future. These projects examine both documented impacts and potential future impacts of drought, based on projected changes in temperature and precipitation.

The SNAPP Ecological Drought Working Group was launched by NCASC, The Nature Conservancy, and The Wildlife Conservation Society, and is part of the Science for Nature and People Partnership (SNAPP). The group is focused on understanding the natural and human dimensions of ecological drought impacts and promoting the application of solutions that provide mutual benefits to people and nature. The group has developed a framework and definition of ecological drought that is flexible across landscapes and helps communities prepare for the rising risk of drought, and the potential for novel drought conditions, in the 21st century. They are already working closely with natural resource managers in the Upper Missouri Headwaters in Montana to better understand manager needs and test the framework in a  real-world drought preparedness effort .

“It is time for ecosystems to have a seat at the drought decision-making table, with the realization that an investment in water for nature may also be an investment in water for people. A more holistic planning and research approach that includes ecological drought means both people and nature will be better prepared for the rising risk of drought." - Shelley Crausbay, SNAPP Ecological Drought team member

To help get the word out about our ecological drought research projects, NCASC hosted a monthly ecological drought webinar series for the duration of 2017. Each webinar highlights drought research being done at one of the CASCs.

The Climate Adaptation Science Centers (CASCs) partner with natural and cultural resource managers to provide the scientific information needed to help fish, wildlife, ecosystems, and the communities they support adapt to the impacts of a changing climate. Our network is comprised of eight Regional CASCs, managed by the National CASC located at USGS headquarters in Reston, VA. This story map highlights our Ecological Drought Initiative.

Learn more about our network  here 

Contact us: casc@usgs.gov

References Cited:

Crausbay, S.D. and Ramirez, A.R., 2017, Defining ecological drought for the twenty-first century: Bulletin of the American Meteorological Society, v. 98, p.2543-2550.  https://doi.org/10.1175/BAMS-D-16-0292.1 

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