Defining Ecological Drought for the Twenty-First Century

Abstract

Made available through Montana State University's ScholarWorks 2543 DECEMBER 2017 AMERICAN METEOROLOGICAL SOCIETY | 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" in Australia caused unanticipated losses to key services provided by hydrological ecosystems in the Murray-Darling basin-including air quality regulation, waste treatment, erosion prevention, and recreation. The costs of these losses exceeded AUD $800 million, as resources were spent to replace these services and adapt to new drought-impacted ecosystems (Banerjee et al. 2013). Despite the high costs to both nature and people, current drought research, management, and policy perspectives often fail to evaluate how drought affects ecosystems and the "natural capital" they provide to human communities. Integrating these human and natural dimensions of drought is an essential step toward addressing the rising risk of drought in the twenty-first century.Part of the problem is that existing drought definitions describing meteorological drought impacts (agricultural, hydrological, and socioeconomic) view drought through a human-centric lens and do not fully address the ecological dimensions of drought.

Drought: Progress in broadening its understanding

“…Drought has been recognized as one of the most widespread and expensive of natural disasters (Crausbay et al, ; Sheffield et al, ; Stagge et al, ) that requires precautionary actions. When drought occurs, huge losses of socio‐economic resources occur due to lack of timely response strategies via accurate drought early warning information (Zhang, Tang, et al, ; Zhang, You, et al, ).…”

Extensive drought‐associated plant mortality as an agent of type‐conversion in chaparral shrublands

“…Ecological drought refers to droughts that lead to water deficits that drive ecosystems beyond thresholds of vulnerability, impair ecosystem services, and trigger feedbacks in natural and human systems (Crausbay et al, 2017). One manifestation that ecosystem thresholds have been surpassed is when a system converts from one vegetation type to another in what has been called vegetation typeconversion, as illustrated in Fig.…”

Experimental droughts with rainout shelters: a methodological review

“…While we recognize the limitation of focusing solely on precipitation inputs, given the lack of other common metrics across drought experiments (e.g., soil water potential; Vicca et al 2012), we believe this is a justified approach. Furthermore, it is important to note that drought conditions can develop due to factors other than precipitation deficits, such as increased temperatures, altered precipitation patterns, and human modifications of hydrological processes (Dai 2012, Trenberth et al 2014, Knapp et al 2015b, Crausbay et al 2017).…”