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Globally, land-based crops and pasture occupy approximately 33% of total available land, and expansion for agricultural uses between 2000 and 2050 is estimated to increase by 7—31% (350—1500 Mha, depending on source and underlying assumptions), most often at the expense of forests and wetlands (Bringezu et al. 2014). While there is currently still land classed as 'good' or 'marginal' that is available for rain-fed agriculture, significant portions of it are far from markets, lack infrastructure or have endemic diseases, unsuitable terrain or other conditions that limit development potential. In other cases, remaining lands are already protected, forested or developed for other uses (Alexandratos and Bruinsma 2012). By contrast, dryland ecosystems, defined in the UN's Commission on Sustainable Development as arid, semiarid and dry subhumid areas that typically have low productivity, are threatened by desertification and are therefore unsuitable for agricultural expansion but nevertheless have many millions of people living in close proximity (Economic 2007). These facts point to the need for more sustainable intensification of food production closer to markets, preferably on largely unproductive lands that may never become suitable for soil-based farming.
The two most important factors contributing to agricultural input efficiencies are considered by some experts to be (i) the location of food production in areas where climatic (and soil) conditions naturally increase efficiencies and (ii) reductions in environmental impacts of agricultural production (Michael and David 2017). There must be increases in the supply of cultivated biomass achieved through the intensification of production per hectare, accompanied by a diminished environmental burden (e.g. degradation of soil structure, nutrient losses, toxic pollution). In other words, the footprint of efficient food production must shrink while minimizing negative environmental impacts.
Aquaponic production systems are soilless and attempt to recycle essential nutrients for cultivation of both fish and plants, thereby using nutrients in organic matter from fish feed and wastes to minimize or eliminate the need for plant fertilizers. For instance, in such systems, using land to mine, process, stockpile and transport phosphate or potash-rich fertilizers becomes unnecessary, thus aso eliminating the inherent cost, and cost of application, for these fertilizers.
Aquaponics production contributes not only to water usage efficiency (Sect. 2.5.2) but also to agricultural input efficiency by reducing the land footprint needed for production. Facilities for instance, can be situated on nonarable land and in suburban or urban areas closer to markets, thus reducing the carbon footprint associated with rural farms and transportation of products to city markets. With a smaller footprint, production capacity can be located in otherwise unproductive areas such as on rooftops or old factory sites, which can also reduce land acquisition costs if those areas are deemed unsuitable for housing or retail businesses. A smaller footprint for production of high-quality protein and vegetables in aquaponics can also take pressure away from clearing ecologically valuable natural and semi-natural areas for conventional agriculture.