The challenge of feeding 9–10 billion people by 2050

Feeding 9 billion people by 2050 presents an enormous challenge⁽ Reference Godfray, Beddington and Crute ^{4 )}. A number of options have been proposed, making the difference between the attainable yield and that actually realised smaller (i.e. including closing the yield gap), increasing the production potential of crops through investment in research and the use of new technologies), expanding aquaculture, reducing waste or changing diets, all of which would need to be coordinated globally⁽ Reference Godfray, Beddington and Crute ^{4 )}.

As outlined by Smith & Gregory⁽ Reference Smith and Gregory ^{5 )}, at the same time as delivering food security, there is a pressing need to decrease the climate impact of food production⁽ Reference Smith, Martino and Cai ^{6 )}, and to improve the resilience of food production to future environmental change⁽ Reference Smith, Haberl and Popp ^{7 )}. Non-climate-related needs include the need to protect our freshwater resource⁽ Reference Frenken and Kiersch ^{8 )}, protect biodiversity^{( 9 )}, move towards healthier diets^{( 10 )}, and to reduce the adverse impacts of food production on a whole range of ecosystem services⁽ Reference Firbank, Bradbury and Jenkins ^{11 )}. In the following sections, I briefly outline how food production has increased to meet demand in the past, before examining how this might be achieved in the future.

How food production has increased to meet increasing demand in the past

Historically, in the era before industrial fertilisers, producing more food largely meant converting more land to agriculture. Historically, the expansion of agriculture into forests and natural ecosystems⁽ Reference Bruinsma ^{12 )} has contributed significantly to the loss of ecosystem services. Much of this loss of forest and other natural systems had occurred many centuries ago in Europe, East Asia, South Asia and parts of Africa, but has occurred more recently in North America and the populated parts of Oceania. Ramankutty & Foley⁽ Reference Ramankutty and Foley ^{13 )} produced maps showing the expansion of cropland area from 1700 to 1992, showing both the spread of cropland (the spread from east to west in North America is particularly apparent) and its intensification in all regions. Before about 1900, agricultural expansion was the most prominent way to increase food production, but after the advent of industrial mineral fertilisers⁽ Reference Erisman, Sutton and Galloway ^{14 )}, it was possible to also dramatically increase productivity on the same land. Even with productivity (output per unit area) increasing, the spread of agricultural land onto native ecosystems was still clearly visible across North America and South America in 1900–1940, in the former Soviet Union 1940–1960 and South East Asia 1980–1990. Expansion in some regions, particularly South East Asia continues to this day. Despite this expansion of agricultural land, the main increase in production since 1960 has been through increased yields per unit area, characterised by the ‘Green Revolution’ in the USA in the 1940s followed in developing countries over the following decades⁽ Reference Brown ^{15 )}. Cereal production (wheat, maize and rice) has increased from 877 million t in 1961 to 2342 million t in 2007, the world average cereal yield has increased from 1·35 t/ha in 1961 to 3·35 t/ha in 2007, and is projected to be about 4·8 t/ha in 2040. Simultaneously, per-capita arable land area has decreased from 0·415 ha in 1961 to 0·214 ha in 2007⁽ Reference Smith, Gregory and van Vuuren ^{16 )}. Had the increases in yield of the last 60–70 years not been achieved, almost three times more land would have been required to produce crops to sustain the present population; this is land that simply does not exist or that is unsuitable for cropping⁽ Reference Smith and Gregory ^{5 )}.

So intensification has been essential, but has resulted in many undesirable outcomes, including air, water and soil pollution⁽ Reference Smith, Ashmore and Black ^{17 )} with agrochemicals and surplus nutrients, increased climate forcing⁽ Reference Reay, Davidson and Smith ^{18 )}, resources depletion⁽ Reference Cordell, Drangert and White ^{19 )}, high fossil energy inputs⁽ Reference Erisman, Sutton and Galloway ^{14 )} and habitat/biodiversity loss⁽ Reference Firbank, Bradbury and Jenkins ^{11 )}.

During the past century, then, while agricultural area expansion has continued, the emphasis for increasing food production has shifted towards intensification, i.e. the increased production of agricultural products per unit area, but this intensification has come at a cost to the environment. The environmental costs of future intensification, if implemented in the same way, would be too great, meaning that future intensification needs to be sustainable⁽ Reference Garnett, Appleby and Balmford ^{20 ,} Reference Smith ^{21 )}. In the next section, I examine if sustainable intensification could, by itself, again prove Malthus wrong, as agricultural expansion has done over centuries, and intensification did over the past 7–8 decades.

Can sustainable intensification deliver food security by 2050?

As noted in the section ‘Can sustainable intensification deliver food security by 2050?’, increased income and changes in diet have been accompanied by substantial increases in crop and animal production (2·7-fold for cereals, 1·6-fold for roots and tubers and 4·0-fold for meat^{( 22 )}). Bruinsma⁽ Reference Bruinsma ^{12 )} estimated that 78 % of the increase in crop production between 1961 and 1999 was attributable to yield increases, and 22 % to expansion of harvested area. Of the world's 13·4 billion ha land surface, about 3 billion ha is suitable for crop production⁽ Reference Bruinsma ^{12 )} and about one-half of this is already cultivated (1·4 billion ha in 2008). The remaining, potentially cultivatable, land is currently beneath tropical forests, so conversion to agriculture is highly undesirable because of the effects on biodiversity conservation, greenhouse gas emissions, regional climate and hydrological changes, and because of the high costs of providing the requisite infrastructure⁽ Reference Smith, Gregory and van Vuuren ^{16 ,} Reference Gregory and George ^{23 )}. According to these projections⁽ Reference Bruinsma ^{12 )}, expansion of agricultural area will still contribute significantly to crop production in Sub-Saharan Africa (27 %) and Latin America and the Caribbean (33 %), but there is practically no land available for expansion of agriculture in South and East Asia and the Near East/North Africa sustainable intensification is expected to be the main means of increasing production in these regions⁽ Reference Smith and Gregory ^{5 )}. Smith⁽ Reference Smith ^{21 )} provided an overview of the options for sustainable intensification, and concluded that it had an essential role to play, but speculated that alone, it could not deliver food security by 2050. Studies have shown the importance of demand-side measures⁽ Reference Stehfest, Bouwmann and van Vuuren ^{24 –} Reference Popp, Lotze-Campen and Bodirsky ^{26 )}. Recently, a new study has quantified the potential role of sustainable intensification in meeting global food requirements, and it showed that sustainable intensification alone cannot deliver food security; demand management appears to be essential⁽ Reference Bajželj, Richards and Allwood ^{27 )}. Bajželj et al.⁽ Reference Bajželj, Richards and Allwood ^{27 )} found that delivering more food for 2050 by sustainable intensification, through yield gap closure, could reduce baseline cropland area, forest area loss, total greenhouse gas emissions and water use relative to a baseline of current yield trend, but would still lead to expanded agricultural area. The addition of demand-side options (healthy diet, plus waste reduction by 50 %) could deliver enough food but also allowed a decrease of cropland and pasture area, an increase in forest area and a reduction in greenhouse gas emissions, not just relative to the baseline, but also in absolute terms compared with the present. The addition of demand-side options provided better environmental outcomes across all indicators (except for a light increase in fertiliser use) relative to the current yield trend baseline. They concluded that improved diets and decreases in food waste are essential to deliver emissions reductions and to provide enough food for the global population of 2050⁽ Reference Bajželj, Richards and Allwood ^{27 )}.