Water Scarcity

Hoover DamWater scarcity is an enormous challenge in many parts of the world, with many of the world’s most important aquifers being drained much faster than they can be replenished. These trends in water availability will have effects on food production systems, water-borne illness patterns, and other water-related diseases.  For example, the aquifer under the North China Plain, where half of China's wheat is grown, is falling at up to three meters/year, and it is estimated that each year 300 million Indians and Chinese are being fed on fossil water that is not being replenished.  Demographic changes are driving sharp increases in global water demand at a time when climate change promises to increase water scarcity in a variety of ways, including more extreme forms of precipitation, dry areas becoming drier, earlier spring runoff from winter snow pack, loss of glacial contributions to dry-season flow, sea level rise and inundation of coastal aquifers with salt water, and hotter temperatures leading to increased evapotranspiration. 

These complex changes in quantity, quality, and timing of water availability, overlaid on significant existing water scarcity and increasing demand, are likely to impact food production, water-borne disease exposure, and water-related diseases.  Changes in land use (e.g., deforestation) also impact water quality and quantity and exposure to water-borne disease in ways that are inadequately understood.  Research to better characterize these challenges and identify approaches to reducing vulnerability is urgently needed.

Learning Objectives

  • L1: Relate and analyze the linkages between drivers of water scarcity and health implications.
  • L2: Describe how water availability and quality affect economic opportunities and human well-being, and how human activity affects water resources.
  • L3: Understand the natural systems and physical properties of water that contribute to its fundamental role in driving Earth systems.
  • L4: Explore how availability of and demand for water resources is expected to change over the next 50 years and what this means for health.

 

Scheffera M. Anticipating societal collapse; Hints from the Stone Age . PNAS [Internet]. 2016;113 (39) :10733–10735. Publisher's VersionAbstract

Few aspects of human history are as mindboggling as the sudden disintegration of advanced societies. It is tempting to seek common patterns or even draw some lessons for modern times from the many ancient cases of societal disintegration. In PNAS, Downey et al. (1) report that universal warning signals of reduced resilience systematically preceded the collapse of Stone Age societies. Might similar indicators of fragility be relevant in modern times? Of course, the nature of human societies has changed entirely. However, there are at times striking parallels between stories of collapse even if they happened in entirely different periods. Consider the abrupt abandonment of the iconic alcove sites in Mesa Verde by the ancestral Puebloan people: the greatest “vanishing act” in prehistoric America (2). Archaeological evidence now reveals that before Pueblo peoples massively migrated in the mid-to-late 1200s, there had actually been a slow build-up of tension (3, 4). Over a century of drought, violence, and political turmoil drove increasing numbers of people into the Mesa Verde region, which was relatively productive for farming, straining carrying capacity as well as cultural traditions and resulting in destabilizing conflicts. Portions of the northern Southwest began to empty out in the first decades of the 13th century and by the mid-1200s even the favored central Mesa Verde region was starting to lose population, well in advance of the “Great Drought” beginning in the late 1270s that seems to have given the final blow. Now, Syria is the scene of a sudden massive exodus, and some aspects of the complex situation do seem to echo the Pueblo story. The Fertile Crescent has likely been experiencing the worst drought in 900 y, making subsistence farming in the countryside extremely challenging and driving millions in Syria to the cities, where tensions increased …

Putnam AE, Broecker WS. Human-induced changes in the distribution of rainfall. Science Advances [Internet]. 2017;3 (5). Publisher's VersionAbstract

A likely consequence of global warming will be the redistribution of Earth’s rain belts, affecting water availability for many of Earth’s inhabitants. We consider three ways in which planetary warming might influence the global distribution of precipitation. The first possibility is that rainfall in the tropics will increase and that the subtropics and mid-latitudes will become more arid. A second possibility is that Earth’s thermal equator, around which the planet’s rain belts and dry zones are organized, will migrate northward. This northward shift will be a consequence of the Northern Hemisphere, with its large continental area, warming faster than the Southern Hemisphere, with its large oceanic area. A third possibility is that both of these scenarios will play out simultaneously. We review paleoclimate evidence suggesting that (i) the middle latitudes were wetter during the last glacial maximum, (ii) a northward shift of the thermal equator attended the abrupt Bølling-Allerød climatic transition ~14.6 thousand years ago, and (iii) a southward shift occurred during the more recent Little Ice Age. We also inspect trends in seasonal surface heating between the hemispheres over the past several decades. From these clues, we predict that there will be a seasonally dependent response in rainfall patterns to global warming. During boreal summer, in which the rate of recent warming has been relatively uniform between the hemispheres, wet areas will get wetter and dry regions will become drier. During boreal winter, rain belts and drylands will expand northward in response to differential heating between the hemispheres.

Almada AA, Golden CD, Osofsky SA, Myers SS. A case for Planetary Health/Geohealth. GeoHealth [Internet]. 2017;1 (2) :75-78. Publisher's VersionAbstract

Concern has been spreading across scientific disciplines that the pervasive human transformation of Earth's natural systems is an urgent threat to human health. The simultaneous emergence of “GeoHealth” and “Planetary Health” signals recognition that developing a new relationship between humanity and our natural systems is becoming an urgent global health priority—if we are to prevent a backsliding from the past century's great public health gains. Achieving meaningful progress will require collaboration across a broad swath of scientific disciplines as well as with policy makers, natural resource managers, members of faith communities, and movement builders around the world in order to build a rigorous evidence base of scientific understanding as the foundation for more robust policy and resource management decisions that incorporate both environmental and human health outcomes.

McMichael AJ, Patz J, Kovats RS. Impacts of global environmental change on future health and health care in tropical countries. Br Med Bull [Internet]. 1998;54 :475-88. Publisher's VersionAbstract

The aggregate human impact on the environment now exceeds the limits of absorption or regeneration of various major biophysical systems, at global and regional levels. The resultant global environmental changes include altered atmospheric composition, widespread land degradation, depletion of fisheries, freshwater shortages, and biodiversity losses. The drive for further social and economic development, plus an unavoidable substantial increase in population size by 2050--especially in less developed countries--will tend to augment these large-scale environmental problems. Disturbances of the Earth's life-support systems (the source of climatic stability, food, freshwater, and robust ecosystems) will affect disproportionately the resource-poor and geographically vulnerable populations in many tropical countries. Ecological disturbances will alter the pattern of various pests and pathogens in plants, livestock and humans. Overall, these large-scale environmental changes are likely to increase the range and seasonality of various (especially vector-borne) infectious diseases, food insecurity, of water stress, and of population displacement with its various adverse health consequences.

Rosegrant MW, Ringler C, Zhu T. Water for agriculture: maintaining food security under growing scarcity. Annual Review of Environment & Resources [Internet]. 2009;34 :205-22. Publisher's VersionAbstract

Irrigated agriculture is the main source of water withdrawals, accounting for around 70% of all the world's freshwater withdrawals. The development of irrigated agriculture has boosted agricultural yields and contributed to price stability, making it possible to feed the world's growing population. Rapidly increasing nonagricultural demands for water, changing food preferences, global climate change, and new demands for biofuel production place increasing pressure on scarce water resources. Challenges of growing water scarcity for agriculture are heightened by the increasing costs of developing new water, soil degradation, groundwater depletion, increasing water pollution, the degradation of water-related ecosystems, and wasteful use of already developed water supplies. This article discusses the role of water for agriculture and food security, the challenges facing irrigated agriculture, and the range of policies, institutions, and investments needed to secure adequate access to water for food today and in the future.

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