Land, water, and energy are the main inputs for food production. Land and water are essential local resources, and their availability determines the potential of food production and, therefore, the potential for the food supply of that region. On the contrary, energy inputs (such as fuel for machinery, fertilizers/indirect energy, etc.) could be brought from other regions.
The amount of land and water needed to fulfil food demand in a certain region depends on the number of people that need to be fed (more people need more food), on their type of diet (affluent diets rich in animal products generally need more land and water), and on the type of production systems (in general, intensive systems need less land but more water and energy than extensive systems).
These three factors (population, diets, and production systems) are strongly different throughout the world and have been and will change differently due to the socioeconomic development of each country.
In this study, we assess whether the available land and water in each country are enough to fulfill the national food demand and changes from 1960 to 2050. We call this the Land-Water-Food Nexus.
The availability of land and water for food have and will strongly decrease due to population growth. To discuss it, we use the availability of cropland (FAO 2013a) and total renewable water per capita (FAO, 2013b) of each country. Countries in Asia, with the largest population density nowadays, have the lowest availability of land and water per capita. In 2050, countries in Africa will face similar population densities as Asia which will result in strong land and water constraints.
We calculate the Land-Water-Food Nexus using the data of land and water demanded per capita per country (Kastner et al., 2012; Hoekstra and Mekonnen, 2012) and the availability of cropland and water per capita (FAO, 2013a; FAO, 2013b). The figure in the article shows, for 2010, whether each country has enough cropland and/or water for food supply.
A large share of the global population (57%) did not have enough cropland but did have enough water (yellow countries): countries with large population density in wet climates. The number of shortfalls is different throughout the regions; it is stronger in Asia where the amount of shortfall is 30% of the cropland demanded by the population.
The future of the Land-Water-Food Nexus will highly depend on changes in both diets and on population growth, and the latter will determine the availability of land and water per capita. These two factors will be driven by changes in GDP per capita of each country. To assess future LWF nexus, we use projections of GDP per capita from the literature for each country with an intermediate socioeconomic pathway (IIASA, 2015). With these values, we can assume future change of diet.
A study (Nonhebel and Kastner, 2011) has shown that countries with a GDP lower than $2,000 per capita have basic diets rich in staple food (cereals, pulses, and roots). Countries in economic transition (with GDP between $2000-$10,000) have transition diets (for which the consumption of animal products, sugars, and vegetable oils increase). And countries with GDP higher than $10,000 have affluent diets rich in animal products, fruits, and vegetables. The basic diets require the least use of land and water followed by transition diets and affluent diets require the largest amount of land and water.
We assess 4 scenarios with a different change in the main driver: diets, population growth and agricultural expansion (availability of cropland). A “Business-As-Usual” scenario, in which all of a population have basic diets, a scenario with no agricultural expansion, and a scenario with low population growth. In this way, it is possible to identify the individual role of each variable. The results show that the scenario in which more people can be feed by their own country will be the one assuming basic diets.
Though, we show strong challenges for all scenarios. Land constraints will be stronger than water constraints. Regions with the strongest challenges will be in South, East, and Southeast Asia, and in Sub-Sahara Africa, for which changes in both population and diets will be taking place.
It is important to point out that in our study, water availability is an overestimation since we consider all water available in the country: the total renewable water which includes underground water, rivers, lakes, rain, etc. All water cannot be used for agriculture; it should be accessible and timely for croplands. In contrast, land availability in our study is an underestimation since we only consider cropland (arable land) and not pasture land which is relevant for food supply.
This study shows the strong impact of the future changes in diets and population numbers on the potential of food production of each country. The stronger challenges for food supply will be in densely populated countries which will be mainly in Asia and Africa. These countries will need to feed their population with a limited amount of land and water per capita to achieve food self-sufficiency. The challenge of the future food system should be a mix of solutions including the demand factors (lower population, less affluent diets) and production factors (efficient use of resources: land and water).
These findings are described in the article entitled, Is the available cropland and water enough for food demand? A global perspective of the Land-Water-Food nexus, recently published in the journal Advances in Water Resources. This work was conducted by Maria Jose Ibarrola-Rivas and R. Granados-RamĂrez from the Instituto de GeografĂa, UNAM, and S. Nonhebel from the University of Groningen.
References:
- FAO. FAOSTAT Statistical Database. Inputs. 2013a; Last access: April 2016. http://www.fao.org/faostat/en/
- FAO. Aquastat. 2013b; Last access: April 2016. www.fao.org/nr/water/aquastat/main/index.stm
- Hoekstra, A.Y., Mekonnen, M.M., 2012. The water footprint of humanity. PNAS 109, 3232–3237
- IIASA SSP Database. IIASA Energy Program. 2015. Last Access: May 2016. https://tntcat.iiasa.ac.at/SspDb/dsd?Action=htmlpage&page=about
- Kastner, T., Ibarrola Rivas, M.J., Koch, W., Nonhebel, S., 2012. Global changes in diets and the consequences for land requirements for food. PNAS 109, 6868–6872
- Nonhebel, S., Kastner, T., 2011. Changing demand for food, livestock feed and biofuels in the past and in the near future. Livestock Sci. 139, 3–10.