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The term 'tipping point' is currently being used to describe natural systems that are on the brink of significant and potentially catastrophic change (Barnosky et al. 2012). Agricultural food production systems are considered one of the key ecological services that are approaching a tipping point, as climate change increasingly generates new pest and disease risks, extreme weather phenomena and higher global temperatures. Poor land management and soil conservation practices, depletion of soil nutrients and risk of pandemics also threaten world food supplies.
Available arable land for agricultural expansion is limited, and increased agricultural productivity in the past few decades has primarily resulted from increased cropping intensity and better crop yields as opposed to expansion of the agricultural landmass (e.g. 90% of gains in crop production have been a result of increased productivity, but only 10% due to land expansion) (Alexandratos and Bruinsma 2012; Schmidhuber 2010). Global population is estimated to reach 8.3—10.9 billion people by 2050 (Bringezu et al. 2014), and this growing world population, with a corresponding increase in total as well as per capita consumption, poses a wide range of new societal challenges. The United Nations Convention to Combat Desertification (UNCCD) Global Land Outlook Working Paper 2017 report notes worrying trends affecting food production (Thomas et al. 2017) including land degradation, loss of biodiversity and ecosystems, and decreased resilience in response to environmental stresses, as well as a widening gulf between food production and demand. The uneven distribution of food supplies results in inadequate quantities of food, or lack of food of sufficient nutritional quality for part of the global population, while in other parts of the world overconsumption and diseases related to obesity have become increasingly common. This unbalanced juxtaposition of hunger and malnutrition in some parts of the world, with food waste and overconsumption in others, reflects complex interrelated factors that include political will, resource scarcity, land affordability, costs of energy and fertilizer, transportation infrastructure and a host of other socioeconomic factors affecting food production and distribution.
Recent re-examinations of approaches to food security have determined that a 'water-energy-food nexus' approach is required to effectively understand, analyse and manage interactions among global resource systems (Scott et al. 2015). The nexus approach acknowledges the interrelatedness of the resource base — land, water, energy, capital and labour — with its drivers, and encourages inter-sectoral consultations and collaborations in order to balance different resource user goals and interests. It aims to maximize overall benefits while maintaining ecosystem integrity in order to achieve food security. Sustainable food production thus requires reduced utilization of resources, in particular, water, land and fossil fuels that are limited, costly and often poorly distributed in relation to population growth, as well as recycling of existing resources such as water and nutrients within production systems to minimize waste.
In this chapter, we discuss a range of current challenges in relation to food security, focusing on resource limitations and ways that new technologies and interdisciplinary approaches such as aquaponics can help address the water-foodenergy nexus in relation to the UN's goals for sustainable development. We concentrate on the need for increased nutrient recycling, reductions in water consumption and non-renewable energy, as well as increased food production on land that is marginal or unsuitable for agriculture.