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Historically, drought has been viewed in terms of its agricultural, hydrological, and socioeconomic impacts. How drought affects ecosystems - and the services they provide human communities - is often not discussed. In response, the U.S. Geological Survey's 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 defined as part of this effort. This geo-narrative explains the concept of ecological drought, and highlights the research and products that were initiated as part of this effort.
Drought is an inescapable reality in many regions, including much of the western United States. With climate change, droughts are predicted to intensify and occur more frequently, making the imperative for drought management even greater. Many diverse actors – including private landowners, business owners, scientists, non-governmental organizations (NGOs), and managers and policymakers within tribal, local, state, and federal government agencies – play multiple, often overlapping roles in preparing for and responding to drought. Managing water is, of course, one of the most important roles that humans play in both mitigating and responding to droughts; but, focusing only on “water managers” or “water management”...
Categories: Publication; Types: Citation
THE RISING RISK OF DROUGHT. Droughts of the twenty-first century are characterized by hotter temperatures, longer duration, and greater spatial extent, and are increasingly exacerbated by human demands for water. This situation increases the vulnerability of ecosystems to drought, including a rise in drought-driven tree mortality globally (Allen et al. 2015) and anticipated ecosystem transformations from one state to another—for example, forest to a shrubland (Jiang et al. 2013). When a drought drives changes within ecosystems, there can be a ripple effect through human communities that depend on those ecosystems for critical goods and services (Millar and Stephenson 2015). For example, the “Millennium Drought”...
Categories: Publication; Types: Citation
Abstract (from Ecosphere): When animals select areas to occupy, decisions involve trade‐offs between the fitness benefits of obtaining critical resources and minimizing costs of biotic and abiotic factors that constrain their use. These processes can be more dynamic and complex for species inhabiting desert environments, where highly variable spatial and temporal distribution of precipitation can create high intra‐ and inter‐annual variability in forage conditions and water availability, and thermal constraints can differ significantly among seasons and diel periods. We examined resource selection in desert bighorn sheep (Ovis canadensis mexicana) in Cabeza Prieta National Wildlife Refuge, Arizona, USA, at multiple...
Categories: Publication; Types: Citation
Abstract (from One Earth): Novel forms of drought are emerging globally, due to climate change, shifting teleconnection patterns, expanding human water use, and a history of human influence on the environment that increases the probability of transformational ecological impacts. These costly ecological impacts cascade to human communities, and understanding this changing drought landscape is one of today’s grand challenges. By using a modified horizon-scanning approach that integrated scientists, managers, and decision-makers, we identified the emerging issues in ecological drought that represent key challenges to timely and effective responses. Here we review the themes that most urgently need attention, including...
Categories: Publication; Types: Citation
Under climate change, ecosystems are experiencing novel drought regimes, often in combination with stressors that reduce resilience and amplify drought’s impacts. Consequently, drought appears increasingly likely to push systems beyond important physiological and ecological thresholds, resulting in substantial changes in ecosystem characteristics persisting long after drought ends (i.e., ecological transformation). In the present article, we clarify how drought can lead to transformation across a wide variety of ecosystems including forests, woodlands, and grasslands. Specifically, we describe how climate change alters drought regimes and how this translates to impacts on plant population growth, either directly...
Categories: Publication; Types: Citation
Drought is a complex challenge experienced in specific locations through diverse impacts, including ecological impacts. Different professionals involved in drought preparedness and response approach the problem from different points of view, which means they may or may not recognize ecological impacts. This study examines the extent to which interviewees perceive ecological drought in the Upper Missouri Headwaters basin in southwestern Montana. Through semistructured interviews, this research investigates individuals’ perceptions of drought by analyzing how they define drought, how they describe their roles related to drought, and the extent to which they emphasize ecological impacts of drought. Results suggest...
Categories: Publication; Types: Citation
Abstract (from Ecological Applications): Increasing aridity is a challenge for forest managers and reducing stand density to minimize competition is a recognized strategy to mitigate drought impacts on growth. In many dry forests, the most widespread and common forest management programs currently being implemented focus on restoration of historical stand structures, primarily to minimize fire risk and enhance watershed function. The implications of these restoration projects for drought vulnerability are not well understood. Here, we examined how planned restoration treatments in the Four Forests Restoration Initiative, the largest forest restoration project in the United States, would alter landscape‐scale patterns...
Categories: Publication; Types: Citation
Abstract (from Journal of Applied Ecology): Increasing heat and aridity in coming decades is expected to negatively impact tree growth and threaten forest sustainability in dry areas. Maintaining low stand density has the potential to mitigate the negative effects of increasingly severe droughts by minimizing competitive intensity. However, the direct impact of stand density on the growing environment (i.e. soil moisture), and the specific drought metrics that best quantify that environment, are not well explored for any forest ecosystem. We examined the relationship of varying stand density (i.e. basal area) on soil moisture and stand‐level growth in a long‐term (multi‐decadal), ponderosa pine Pinus ponderosa,...
Categories: Publication; Types: Citation
We studied the impacts of drought and invasive trout on survival and productivity on Rio Grande cutthroat trout (Oncorhynchus clarkii virginalis, RGCT) populations. Rio Grande cutthroat trout is the southernmost subspecies of cutthroat trout and endemic to the Rio Grande, Canadian, and Pecos River basins of Colorado and New Mexico. The subspecies is reduced to less than 11% of its historic range with most populations occupying isolated high elevation headwater streams. One of the greatest threats to its survival is the effect that low stream flow due to drought will have on this coldwater trout living at the edge of its range. Our work will provide insight into the current and future threats of RGCT populations...
Categories: Publication; Types: Citation
Abstract (from Science Advances): Heterogeneity is a central feature of ecosystem resilience, but how this translates to socioeconomic resilience depends on people’s ability to track shifting resources in space and time. Here, we quantify how climatic extremes have influenced how people (fishers) track economically valuable ecosystem services (fishing opportunities) across a range of spatial scales in rivers of the northern Rocky Mountains, USA, over the past three decades. Fishers opportunistically shifted from drought-sensitive to drought-resistant rivers during periods of low streamflows and warm temperatures. This adaptive behavior stabilized fishing pressure and expenditures by a factor of 2.6 at the scale...
Categories: Publication; Types: Citation
Fire in Southern California chaparral communities is a historically common occurrence [1]. Hot, dry summers interact with strong “Santa Ana” winds and large human interfaces to create extreme risks of devastating wildfires [6], [11]. These plant communities also feedback into wildfire probabilities, producing drought-resistance mechanisms – such as volatile oils and woody stems - that can increase the spread and intensity of wildfire [1], [13]. Understanding the main drivers of wildfire is a priority in the wake of recent drought conditions, which are likely to worsen. California experienced its most extreme drought of the last millennia during the 2012-2016 period [5]. These extreme conditions interact with an...
Categories: Publication; Types: Citation
In this study, scientists with the U.S. Geological Survey, Montana Fish, Wildlife & Parks, and the University of Montana studied how climate change affected world-renown trout fisheries across 3,100 miles rivers in Montana from 1983 to 2017. Extreme droughts reduced streamflows and increased water temperatures, causing stressful conditions for trout and numerous fishing site closures. This resulted in anglers moving to find fishing locations that were more favorable to trout during extreme drought conditions. By moving to fishing locations that were more favorable during drought, visitors kept trout fishing revenue in the state rather than choosing to travel elsewhere. This flexibility revealed surprising resiliency...
Categories: Publication; Types: Citation
Abstract (from Ecological Society of America): Species that are primarily seral may form stable (self‐sustaining) communities under certain disturbance regimes or environmental conditions, yet such populations may also be particularly vulnerable to ecological change. Aspen (Populus spp.) are generally considered seral throughout the Northern Hemisphere, including P. tremuloides, the most widely distributed tree species in North America. Recent declines in aspen populations have occurred, especially along drought‐sensitive margins of its range and where fire exclusion and herbivory have promoted community transition. However, aspen also forms stable stands, and examination of the mechanisms that influence persistence...
Abstract: Population persistence across broad spatial scales (e.g., watersheds) can depend on asynchronous dynamics among populations at finer scales (e.g., streams or habitats). We applied a von Bertalanffy growth model and closed N‐mixture abundance model in a hierarchical Bayesian framework to examine effects of fine‐scale variability in temperature and density dependence on growth and abundance as well as within‐ versus among‐stream variability in growth and abundance of Rio Grande Cutthroat Trout Oncorhynchus clarkii virginalis (RGCT) in northern New Mexico streams. An accumulation of degree‐days positively influenced instantaneous growth rates and, to a lesser extent, negatively affected asymptotic body length....
Grassland birds in North America have declined sharply over the last 60 years, driven by the widespread loss and degradation of grassland habitats. Climate change is occurring more rapidly in grasslands relative to some other ecosystems, and exposure to extreme and novel climate conditions may affect grassland bird ecology and demographics. To determine the potential effects of weather and climate variability on grassland birds, we conducted a systematic review of relationships between temperature and precipitation and demographic responses in grassland bird species of North America. Based on 124 independent studies, we used a vote-counting approach to quantify the frequency and direction of significant effects...
Categories: Publication; Types: Citation
Abstract (from Environmental Evidence): Background Climate is an important driver of ungulate life-histories, population dynamics, and migratory behaviors, and can affect the growth, development, fecundity, dispersal, and demographic trends of populations. Changes in temperature and precipitation, and resulting shifts in plant phenology, winter severity, drought and wildfire conditions, invasive species distribution and abundance, predation, and disease have the potential to directly or indirectly affect ungulates. However, ungulate responses to climate variability and change are not uniform and vary by species and geography. Here, we present a systematic map protocol aiming to describe the abundance and distribution...
Categories: Publication; Types: Citation
Climate change is already affecting ecosystems, with the potential to trigger significant and permanent state changes in both natural and human systems. Ecological transformations may stem from gradual changes, or may occur rapidly; for an example, an extensive drought-related mortality event may be coupled with regeneration conditions that are no longer able to support the re-establishment of the historic ecosystem. In addition to climate change, patterns of land use and human water use, and site-scale management history may be important contributors to the degree or pace of change. This project focuses on climate-related risks in the Great Plains of the U.S., a grassland dominated region with a complex history...
Categories: Publication; Types: Citation
Executive Summary (from USGS Publications Warehouse): Migratory behavior among ungulates in the Western United States occurs in response to changing forage quality and quantity, weather patterns, and predation risk. As snow melts and vegetation green-up begins in late spring and early summer, many migratory ungulates leave their winter range and move to higher elevation summer ranges to access high-quality forage and areas with vegetative cover for protection during fawning. Ungulates remain on these ranges until the fall when increasing snowfall and decreasing temperatures trigger them to migrate back to their lower elevation winter ranges. While researchers have begun to assess the effects of physical barriers...
Categories: Publication; Types: Citation
Abstract (from ScienceDirect): Rarity and life history traits inform multiple dimensions of intrinsic risk to climate and environmental change and can help systematically identify at-risk species. We quantified relative geographic rarity (area of occupancy), climate niche breadth, and life history traits for 114 freshwater fishes, amphibians, and reptiles in the U.S. Pacific Northwest. Our approach leveraged presence-only, publicly available data and traits-based inference to evaluate area of occupancy, climate sensitivity (i.e., climate niche breadth), and a Rarity and Climate Sensitivity (RCS) index of all species across multiple geographic extents, grain sizes, and data types. The RCS index was relatively stable...