How much more land is there for agriculture?
Over the next 30 years, the world’s population will likely grow to more than 9 billion. Supporting 2 billion more people will require more agricultural production to satisfy demands for food, but also to meet the need for fibre, biofuels and chemicals to sustain the global economy. However, increasing food production will be one of humanity’s greatest challenges since global agriculture is at the nexus of many complex and interconnected issues, including food production, preservation of biodiversity, energy and water systems, climate change, declining water resources, land and air pollution, floods and land and soil degradation.
There are three ways to increase crop production: expansion of the physical area (arable land) allocated to crops, increased cropping intensity (e.g. multiple cropping, shorter fallow periods) and improvement of crop yields. Based on past trends, it is estimated that a doubling of global food production would require approximately a threefold increase in nitrogen and phosphorus fertilisation rates, a doubling of the irrigated land area and an 18 % increase in cropland.
Expansion of arable land may appear to be the most expedient solution, but this is unsustainable. Cropland expansion has adverse environmental impacts on natural ecosystems. Not only will it contribute to the accumulation of greenhouse gases in the atmosphere, it undermines the ability of natural ecosystems to produce food products, ameliorate infectious diseases, maintain freshwater and forest resources, regulate air quality, provide cultural services that provide recreational, aesthetic and spiritual benefits and supporting services such as soil formation, photosynthesis and nutrient cycling. In fact, since 1960 there has been a continuous decline worldwide of arable land when expressed on a per capita basis (ha in use per person).
Globally, most cropland expansion and intensification in the future will likely occur in the tropics, especially in sub-Saharan Africa and South America. These tropical regions are likely to experience accelerated losses of old-growth forests, woodlands and semi-arid environments. In its timing and extent, most conversion of tropical lands has been driven by export market pressures. For example, the recent crop expansion in the tropics has been driven by the demand for soybeans, and the spike in deforestation of the Amazon since 2015 has been driven by the increase in international demand for beef.
Lands put into agriculture are often those locally best-suited for biological productivity – lands that have a favourable climate, are well-watered and drained and have fertile soils to nurture diverse populations of plants and animals. When these lands are appropriated for agriculture, the multitude of ecosystem services they provide that benefit humans are diminished or eliminated. These include provisioning services such as water, timber and fibre; regulating services that affect climate, floods, disease, wastes and water quality; cultural services that provide recreational, aesthetic and spiritual benefits; and supporting services such as soil formation, photosynthesis and nutrient cycling services.
Inevitably, efficiencies of use have been pursued in response to increasing population density, social evolution and technological innovations. Rather than expansion alone, agriculture has intensified, seeking to produce more per unit area of cropland. Despite continuous and accelerating improvements in agricultural efficiency, agricultural expansion on a vast scale has continued over the past two generations.
Reviving “old” lands
While recent attention has focused on new lands in the tropics, large-scale development has pushed into the mid-latitude drylands over the past three generations, much of it in the former Soviet Union in what is now Russia, Ukraine and Kazakhstan. As the political structure of this region began to unravel in the early 1990s, many of these new croplands were abandoned. Recently, the potential for “reviving” these lands for agriculture has been viewed as an investment opportunity because of their previous agricultural use, their availability at relatively low cost and the proximity of an under-utilised local workforce.
In addition to local economic potential, attention has been focused on the role that revived lands might play in a global context. First, they could contribute to meeting global food demand, particularly with respect to wheat production. However, as might be expected, the productive capacity of these lands is highly variable, as is their conservation value. Taking these factors into consideration, of more than 40 Mha of abandoned land, only less than 9 Mha were judged to be suitable for renewed cultivation. These lands could represent a production potential of about 14 Mt up to 20 Mt of wheat.
Second, the revival of lands that were converted to agriculture in the past would incur far lower development costs and also lower global environmental costs in terms of biodiversity and carbon stocks than would the development of new lands in the tropics.
While the notion of reviving abandoned lands is attractive on a number of levels, caution is appropriate. The quality of land is highly variable, the dryland climate is unreliable for rain-fed production and the capacity of the resident workforce may be problematic.
Although it is generally agreed that agricultural intensification on existing global croplands is not insufficient to satisfy humanity’s future food demands, one modelling study estimates that it would be possible to achieve a 30-39 % increase in attainable yields for wheat, rice and maize under local climatic conditions of suboptimal water and nutrient availability. The approach involves a mixture of strategies that involve multiple cropping and profit-maximising reallocation of crops on existing croplands.
Expansion in the future
Agriculture will continue to expand in extent but more slowly than during the past century. Much expansion will continue to take place in the tropics. Some expansion will occur in the drylands where new lands may be irrigated with the development of new water resources. However, dryland development will be challenged by inherent climate variability that likely will be exacerbated by climate change. Another important issue is that cropland expansion will most likely occur on lands less suitable for cultivation, such as highly erodible lands (e.g. steep slopes), as illustrated in recent studies in the United States and Africa.
The economic, political and social environment for expansion in the future will be much different than the latter half of the past century. First, are global telecouplings in which, to varying degrees, land-use decisions are driven by global, rather than local economic considerations. Telecouplings also have social, institutional and environmental dimensions that can affect not only the locations where they are implemented but other dimensions that are socially or economically linked.
Second, global policy frameworks in which land-use decisions must be made will be increasingly important: the magnitude of trade-offs in developing one area over another are becoming both more apparent and more pressing. For example, for each unit of land cleared, the tropics lose nearly twice as much carbon and produce less than half the annual crop yield compared with comparable development in temperate regions. Therefore, newly cleared land in the tropics releases nearly three tonnes of carbon for every tonne of annual crop yield, compared with a similar area cleared in the mid latitudes.
Third, although development may be guided by national and international policy, it is implemented at a landscape or community scale. At these scales, development efforts can be tailored collectively to tap some resource opportunities and conserve others to meet community goals of securing the resource base and ensuring stable economic opportunities. At the household or farm level, sustainable land management practices can be promoted that conserve and enhance soil and water resources. Ultimately, success is dependent on the willingness and active participation of all stakeholders, the transparency of the development process, how resources are allocated and monitored and a system of governance that is recognised as being fair and inclusive.
Arable land per capita (ha in use per person).
Source: Alexandratos N. and Bruinsma J., FAO, 20123.
Farmers in Rwanda have increased their productivity and their income after they implemented a number of agricultural processes such as these terraces in rural Rwanda.
Source: A'Melody Lee, World Bank [flickr CC BY-NC-ND].