Drought in the Anthropocene Authors: Anne F. Van Loon et al (Nature, Feb 2016) Kimberly Duong March 1, 2016

Background This paper describes: – human influences on drought – potential feedbacks between drought and society Land use changes by humans alter hydrologic processes (evapotranspiration, infiltration, surface runoff, etc) In order to cope with future drought, we must consider human influence as much as we do natural climate variability (yes, it’s that significant!)

Redefining Drought Drought is traditionally considered a natural phenomenon only – This way of thinking hinders effective drought monitoring and management Authors suggest including human-caused water shortages in definition of drought – New definition = exceptional lack of water compared with normal conditions Drought is an episodic phenomenon, which is different from water scarcity (a long-term imbalance between supply and demand)

Classifications 1.Soil moisture drought: below-normal soil moisture levels 2.Hydrological drought: below-normal river discharge, groundwater, lake, reservoir levels In regions without heavy anthropogenic modification of the water cycle, these droughts are caused by meteorological anomalies. However, in most places, significant human development results in changes in surface/subsurface water abstraction and land use change Therefore, we should distinguish between climate induced, human induced, and human modified droughts

Shift between different types of drought Climatic drivers Human drivers Hydrological catchment processes Alterations by human activities Changes to human influence on drought & climate variability

Authors show simulated water supply that considers only natural drivers will underpredict (or not predict at all) the presence of a drought. This type of drought (middle example) would be purely human-induced Drought that has both natural and human influences (on right side) will have underestimated severity if simulations only consider natural drivers

Drought Research Properly attributing drought to both human and natural drivers is essential Why? Because it informs drought management on whether to focus on adaptation (in response to natural drought) or on prevention of human-induced drought Researchers can use virtual models to assess groundwater levels and streamflow in the absence of human influences Research gap: feedbacks on soil moisture, streamflow and aquifer water levels are rarely quantified – In California, near-future groundwater legislation will impact California water resources, but it is unclear how it affects droughts Societal adaptation to drought results in a new “normal” water level for that society

Conclusion We need to consider drought as an interaction of both natural and human influences! We need to integrate natural and social sciences when doing drought research so that we can better predict, manage, and prevent future droughts. (Shout out to Australia for combining technology, education, and pricing during the Millennium drought)

References Van Loon et al. “Drought in the Anthropocene.” Nature Geoscience, Vol 9, pg 89 – 91, Published online: 02 February Web link: l/ngeo2646.html l/ngeo2646.html

Hi Stan!