This includes the development of irrigation systems, application of fertilizers, and use of bio-engineered crops and other bio-technologies , as well as the implementation of new farming systems .Although the use of fertilizers and irrigation can reduce the gap between actual yields and the maximum potential yields of existing crops, new advances in biotechnology can increase the maximum potential yields by engineering crop varieties with improved “harvest index” , water use efficiency, photosynthetic efficiency, or drought tolerance. Between the 1960s and 2005 the green revolution has allowed for a 135% increase in crop yields worldwide by intensifying production through irrigation, fertilizers, and improvements in the harvest index. In the next few decades crop yields will have to keep increasing in order to meet the increasing demand for agricultural products . This is a major challenge because, recently, crop yields have been stagnating after decades of growth . The analysis of factors limiting the increase of crop yields shows that so far technological improvements aiming at the enhancement of photosynthetic efficiency have played only a marginal role in the increase of crop yields, and for most crop plants, the photosynthetic efficiency is far below the biological limits . The next stage of the green revolution could use modern technologies from genetic engineering and synthetic biology to improve the mechanisms of light capture, sunlight energy conversion,ebb and flow and carbon uptake and conversion . For instance, in full sunlight conditions, most plants absorb more light than they can use. To avoid damaging photo oxidation from excess light, plants typically dissipate excess light as heat .
To improve efficiency, plants could capture less light or improve the way they respond to changes in light availability resulting from variations in cloudiness . Additional gains can be obtained by developing crop varieties with improved water use efficiency, pest resistance, or temperature stress tolerance . Genetic engineering technology is commonly used to develop genetically modified organisms, including new crop varieties. Unlike traditional breeding techniques and artificial selection for desired traits, transgenic methods allow for more precise genetic modifications by inserting specific genes from other species to improve crop performance . The use of transgenic crops in agriculture has been and still is at the center of a heated debate because of possible risks and unintended consequences, including possible gene mutation, accidental activation of “sleeper” genes, interactions with native plant and animal populations, and gene transfer . Other controversial points deal with intellectual property rights and the control of the biotechnology corporations on the agricultural sector. A detailed analysis of this debate is beyond the scope of this review.Transgenic methods, which have been extensively used to improve crop varieties , can be adopted to induce genetic modifications in livestock species by inserting specific genes in organisms that do not have a copy of those genes .Other studies have investigated mammary gland-specific transgenic livestock to change the fat content in goat’s milk, reduce saturated fats in dairy products, and improve disease resistance in lactating cows .As noted in section 2, the ongoing increase in meat consumption worldwide is challenging the agricultural system. Livestock production uses roughly 30% of global ice-free terrestrial land and contributes to 18% of global GHG emissions associated with deforestation, methane emission, and manure management . It has been argued that the increasing demand for meat could be met by culturing animal tissues in vitro in the lab, without having to raise livestock.
These methods could strongly reduce the carbon, land, and water footprints, as well as exposure to food borne pathogens , and cardiovascular diseases by making healthier meat products. Moreover, in vitro meat production would address ethical concerns on animal welfare. In his book “Thoughts and Adventures,” Winston Churchill predicted that “… Fifty years hence, we shall escape the absurdity of growing a whole chicken in order to eat the breast or wing, by growing these parts separately under a suitable medium…” . Churchill’s prophecy is now about to become true. In the last few decades scientists have developed methods to produce muscle tissue ex vivo . Meat culture technology was initially developed for medical applications to produce insulin and implants. Three different approaches have been used, namely, stem cell isolation and identification , ex vivo culture of cells taken from a live animal and put in vitro, or tissue engineering . Applications to the meat industry are facing some major challenges because, to be marketable, cultured meat needs to look and taste like real meat. Thus, research on in vitro meat production is working on appearance, texture, and taste to improve the resemblance to real meat. Today, only small amounts of meat have been produced in vitro and served in a handful of restaurants in the United States. It has been estimated that, compared to meat from livestock production, cultured meat allows for substantial savings in land and water resources, emits less GHGs, and uses less energy than ruminants .It is commonly believed that crop plants need soil, in addition to water, nutrients, and light, for their growth. However, it is possible to grow plants without soil but in water with adequate mineral additions. Known as hydroponics, this technique can be used indoors and outdoors, in recirculating, as well as in flow-through, systems. The main advantages of hydroponics with respect to soil cultivation is that plants do not need to invest much in root growth to find nutrients; they grow faster and take less space.
Moreover, hydroponics allows for more efficient nutrient/fertilizer regulation. This technique, however, can be expensive when considering the cost of the system, its maintenance, and energy requirements. A more effective use of resources can be attained with a multi-trophic system, known as aquaponics, that combines hydroponics with aquaculture. In other words, nutrient-rich water from fish tanks is used for plant growth . This system is inspired by old agricultural practices, such as the introduction of fish in rice paddies or the use of nutrient-rich fish-tank water for irrigation . In aquaponic systems, fish produce nitrogen-rich waste that is mineralized by bacteria and taken up by plants . Thus, bacterial biomass and vegetation filter the water in the fish tank, thereby allowing for a recycling of water and minerals and P; this system turns waste products from aquaculture into nutrients for hydroponic production. In this sense, aquaponic is a good example of circular economy, as described in section 11.4.1. The main limitation of this system is that it requires relatively large capital investment and skilled maintenance, and is therefore more suitable for commercial farming than for subsistence agriculture in the developing world.The use of modern technology and the intensification of agricultural production are often invoked as the desired approach to meeting the increasing demand for crops without causing additional land use change . As noted repeatedly in the previous sections, the downside of this approach is that it typically requires investments that rural communities in the developing world cannot afford . Therefore, in many cases agricultural intensification might entail a transition from small-holder semi-subsistence farming to large-scale commercial agriculture.An alternative approach to achieve food, water, and energy security is offered by agroecology. Small-scale farming can capitalize on local knowledge to attain relatively high yields without having to resort to agribusinesses and their technology . In recent years, there has been a renewed interest in peasant agriculture and its use of poly cultures , agroforestry, green manure,greenhouse benches compost turfing, and high-residue farming , without adopting soil tillage or agrochemicals. These traditional practices conserve soils, water, biodiversity, and ecological integrity, while favoring resilience. It would be impossible to review here this rich body of literature but we will instead focus on the significance of these methods in the context of meeting the growing food demand. It has been argued that a shift to agroecology can substantially increase crop production in a sustainable way and that small-scale peasant agriculture is not condemned to achieve low yields as often assumed in the literature. Rather, there is evidence that small family farms can be much more productive and resilient than larger ones . The use of poly cultures in agroecology allows for the attainment of higher and more stable yields, enhances economic returns, and favors diet diversity, while making more efficient use of land, water, and light resources . Thus, small-scale farming with agroecological methods could contribute to meeting the growing demand for agricultural products. Recent estimates indicate that about 525 million small-scale farms exist around the world and provide a livelihood for about 40% of the global population . However, the ongoing changes in the agrarian landscape worldwide entail the replacement of small-holder agriculture with large-scale commercial farms. This transition can be related to a number of factors, such as the globalization of agriculture through trade, LSLAs, better access to credit by commercial farmers, differences in land tenure, use of agricultural subsidies in economically more developed countries, and lack of protection of domestic production against subsidized foreign agricultural products .
This transition has the effect of reducing the opportunities to use small-scale agroecological methods as an approach to increase food availability.A continuation of current trends in production, consumption, and resource use is wholly unsustainable. There is an urgent need to enhance food security without increasing the human pressure on the environment . A current push in the literature is to identify solutions that minimize trade-offs across multiple agricultural, environmental, and economic dimensions . Some of this work has shown the potential to maintain or reduce current levels of resource use while increasing crop production, thereby eliminating large inefficiencies in production systems. One such study found that if nitrogen fertilizer was spatially distributed more efficiently, it would be possible to increase cereal production by ~30% while maintaining current levels of nitrogen application . Likewise, it is possible to use different irrigation and soil management strategies to close the crop yield gap by one half without increasing cropland area or irrigation use . Other work showed that, by redistributing crops on the basis of their suitability, it is possible for the United States to realize a modest water savings and improve calorie and protein production without adversely impacting feed production, crop diversity, or economic value . Similarly, recent research investigating global scenarios of crop redistribution to minimize irrigation water consumption has shown that it is possible to increase food production and feed an additional 825 million people while reducing irrigation water consumption by 12% without losing crop diversity or expanding the cultivated area .Collectively, these results show the benefits of a more efficient use of natural resources for food or energy production. There could be, however, some unwanted effects. Highly optimized systems are not necessarily more resilient . They often lack important redundancies that play an important role in providing resilience to the FEW system . When resources are used more efficiently their consumption can increase rather than decrease. Known as Jevon’s paradox , this rebound effect has been observed for irrigation systems and has been termed the irrigation paradox . Indeed investments in water-saving irrigation technology may result in a decrease in groundwater levels and environmental flows . Unless policies limit the extent of the irrigated land, what typically happens is that more land is irrigated and water-resource availability decreases, which may exacerbate water scarcity and soil salinity problems . Of course, these changes also have some positive effects, such as increased crop production. Approaches aiming at an increase in agricultural efficiency need to first clarify which resource needs to be used more efficiently . If irrigation water is applied to close the yield gap , the land is used very efficiently but not necessarily the water. But, if water is scarce and large expanses of land are available, it makes more sense to use the land less efficiently and the water more efficiently by irrigating a larger area but with smaller water applications. This practice is known as deficit irrigation in that it leaves crops in a water deficit state . These caveats stress the need to account for food demand, livelihoods, and the environment when developing more effective strategies for achieving a sustainable food system.The population factor has been somewhat more marginal in the recent food security debate, but is starting to resurface in the analysis of sustainable food systems.