Pontus Lurcock and Fabio Florindo
Antarctic climate changes have been reconstructed from ice and sediment cores and numerical models (which also predict future changes). Major ice sheets first appeared 34 million years ago (Ma) and fluctuated throughout the Oligocene, with an overall cooling trend. Ice volume more than doubled at the Oligocene-Miocene boundary. Fluctuating Miocene temperatures peaked at 17–14 Ma, followed by dramatic cooling. Cooling continued through the Pliocene and Pleistocene, with another major glacial expansion at 3–2 Ma. Several interacting drivers control Antarctic climate. On timescales of 10,000–100,000 years, insolation varies with orbital cycles, causing periodic climate variations. Opening of Southern Ocean gateways produced a circumpolar current that thermally isolated Antarctica. Declining atmospheric CO2 triggered Cenozoic glaciation. Antarctic glaciations affect global climate by lowering sea level, intensifying atmospheric circulation, and increasing planetary albedo. Ice sheets interact with ocean water, forming water masses that play a key role in global ocean circulation.
Eduardo Marone, Ricardo de Camargo, and Julio Salcedo Castro
This article describes the threat costal hazards pose to existing life in light of climate change and natural disaster. It includes an overview of flooding, extreme waves, and other water-related stressors. The article discusses how human-induced risks in the coastal zone, resulting from mismanaged urbanization, persistent pollution, and overexploitation of resources, exacerbate matters and pose extra pressure on the environment, science, and society. Ways of measurement and reaction to these events, as well as best practices for preparedness, are discussed. Businesses, individuals, and ecosystems are under threat of destruction from these circumstances. The article also emphasizes the need to make scientific work in this field accessible and understandable to society and decisión makers.
Anthony J. Reynolds
Conservation agricultural practices have been widely adopted across the world in the past 30 years. Farmers recognized that their soils had been degraded by deep ploughing and by dependence on chemical fertilizers, pesticides, and herbicides. Conservation agriculture, involving the agronomic and technological practices of no-till, cover cropping, and rotation, can be a sustainable alternative to conventional farming both economically and environmentally. While improving soil and crop health, it also has a dramatic and beneficial impact on the soil structure and on organic matter content that in turn can improve drainage and the availability of water. Costs are greatly reduced and crop yields—after an initial decline—return to former levels. Increasing interest and uptake by the global farming community shows that the system can be adapted in a variety of farming situations and significantly aid both the environment and sustainable food production.
Rami Zurayk and Azza Dirar
Since agriculture consumes the largest share of the world’s water, farmers undoubtedly play an instrumental role in the management of this precious resource. As such, various policy approaches have sought to engage farmers in the management of water for irrigation. There is much literature on policy approaches that devolve irrigation management to farmers through organizing them into ‘water user associations’ and mobilizing them into cooperative water resource management. When the implementation experience and success of these approaches are assessed, the results show a great variation in experience with overall limited success. The key challenges stem from various assumptions underlying the policy approaches, namely the way in which farmers are conceptualized as a homogenous group of ‘water users’. Cooperative and participatory approaches to natural resource management cannot be institutionally manufactured without addressing key political ecological realities and the wider contexts in which ‘resource users’ operate.
Mustapha Besbes, Jamel Chahed, and Abdelkader Hamdane
Northwest African countries (NA) consume 70 percent of their renewable water resources, and groundwater overdraft has become a major problem. Blue water irrigation represents 17 percent of overall water resources and is economically significant. Green water represents 83 percent, but is not yet well evaluated, and is not considered in national water strategies, along with virtual water embedded in international food trade. Irrigation enhances local agrifood production but it has not changed the proportion of staple foods. The region remains a major net food importer and, largely due to population increase, water dependency increased from 30 percent to 50 percent between 1970 and 2010. Population forecasts predict that water demand will continue to grow, and could reach more than three times the present level. Given the blue water status, NA must develop approaches to cope with water–food challenges, based on international virtual water flow optimization and better green water valorization.
Peter Johnston and Arthur Chapman
Irrigation is a critical input for raising food production in southern Africa, parts of which are food-insecure, especially as a result of low levels of technology employed, low investments into the sector, small farm sizes, and high levels of exposure to the hazards of climate variability. Most food production (including exports) and irrigation in the region occurs in the arid south—in South Africa by a large margin. Further north, in Angola, Zambia, and the northern parts of Mozambique, water resources are abundant yet irrigation farming is far less developed and inefficient, resulting in water resources being less intensely managed. The region needs to become more tightly integrated economically, with a greater flow of technology, investment, and management capability to the north, allowing the north to produce more food (and other agricultural products) which would flow to the more industrialized south—essentially virtual water flows to that region.
America Lutz Ley, Ryan Lee, Yulia Peralta, and Christopher Scott
The United-States-Mexico food system, and in particular the section located in the Sonoran Desert, is an example of the detrimental effects that result from instensified food production to supply increased demand from regional, transboundary, and global areas. Impacts to freshwater and terrestrial ecosystems in addition to human livelihoods and institutions create serious management and policy challenges. Understanding the region as an integrated water-food system with institutional imbalances reveals the following consequences: (a) an increasing reliance on groundwater resources for the majority of agriculture and livestock production; (b) a net export of nonrenewable water; and (c) a virtual water imbalance that further threatens the region’s water and food security.
Michel Petit and Phillipe Le Grusse
The food and water challenges to be faced in the Mediterranean Basin, particularly those on the southern and eastern shores, are daunting. They form a complex nexus of problems and require policies pursuing several important potentially conflicting goals at the same time: reducing or limiting food import dependency through increased agricultural production in environmentally sustainable ways while protecting the natural resource base and keeping food affordable for poorer populations. The worrisome trends affecting countries on the southern and eastern shores of the common sea can also have seriously negative consequences in the North which explains why the North-South collaboration has a long tradition in the region. But, as the case of water management institutions shows, ineffective advocacy for trade liberalization has led to conflicts and tensions on various issues and has distracted attention from potentially much more fruitful areas of collaboration.
West Asia is one of the most water-scarce regions of the world and one of its foremost importers of virtual water despite sustained efforts at self-sufficiency, especially in cereal production. Technology-oriented policy solutions eye a reorientation of agriculture towards fruit and vegetables that are less water-intensive than cereals and provide more value added per water unit consumed. Turkey is a role model here; the country has an agricultural trade surplus and ranks among the top ten agricultural economies globally in value terms. Yet technology-oriented policy prescriptions overlook the sociopolitical ‘problemsheds’ that emerge (along with new agro-lobbies) and agriculture as the main water consumer has to compete with other economic sectors and sprawling urbanization. This article looks at the different categories of countries and their specific challenges.
Brendan Bromwich, Tony Allan, Anthony Colman, and Martin Keulertz
Society’s greatest use of water is in food production, a fact that puts farmers centre stage in global environmental management. Management of food value chains, however, is not well set up to enable farmers to undertake their dual role of feeding a growing population and stewarding natural resources. This chapter introduces an analytical framework by which food, water, and society can be investigated. Food value chains comprise three market modes: production; trade and process; retail and consumption. The model demonstrates the interfaces between blue water, green water, virtual water, polluted drainage, and evapotranspiration. By categorizing social, cultural, and political influences on the three market modes the framework enables integrated analysis of food, water, and society . The combined management of food and water through redesign of food value chains emerges as a key challenge for the twenty-first century.