Elsevier

Global Environmental Change

Volume 41, November 2016, Pages 88-98
Global Environmental Change

Human appropriation of land for food: The role of diet

https://doi.org/10.1016/j.gloenvcha.2016.09.005Get rights and content

Highlights

  • New index (HALF) quantifying the effects of diet on agricultural land use area.

  • 14-fold range assuming global adoption of current country-level average diets.

  • Half current area if average Indian diet adopted, but nearly 3-time for diet in USA.

  • Types of food commodities in diets more important factor than the quantity.

  • Area for waste with USA consumption patterns twice that for complete Indian diet.

Abstract

Human appropriation of land for food production has fundamentally altered the Earth system, with impacts on water, soil, air quality, and the climate system. Changes in population, dietary preferences, technology and crop productivity have all played important roles in shaping today’s land use. In this paper, we explore how past and present developments in diets impact on global agricultural land use. We introduce an index for the Human Appropriation of Land for Food (HALF), and use it to isolate the effects of diets on agricultural land areas, including the potential consequences of shifts in consumer food preferences. We find that if the global population adopted consumption patterns equivalent to particular current national per capita rates, agricultural land use area requirements could vary over a 14-fold range. Within these variations, the types of food commodities consumed are more important than the quantity of per-capita consumption in determining the agricultural land requirement, largely due to the impact of animal products and in particular ruminant species. Exploration of the average diets in the USA and India (which lie towards but not at global consumption extremes) provides a framework for understanding land use impacts arising from different food consumption habits. Hypothetically, if the world were to adopt the average Indian diet, 55% less agricultural land would be needed to satisfy demand, while global consumption of the average USA diet would necessitate 178% more land. Waste and over-eating are also shown to be important. The area associated with food waste, including over-consumption, given global adoption of the consumption patterns of the average person in the USA, was found to be twice that required for all food production given an average Indian per capita consumption. Therefore, measures to influence future diets and reduce food waste could substantially contribute towards global food security, as well as providing climate change mitigation options.

Introduction

Human appropriation of global net primary production (NPP) of vegetation is increasing, and has doubled since 1910 (Krausmann et al., 2013). This is due to rising populations, as well as changes in diets. Diet is linked with wealth (Tilman et al., 2011), urbanisation (Huang and Bouis, 2001, Seto and Ramankutty, 2016, Wu and Wu, 1997), and globalising food commodity markets (Pingali, 2007, Popkin, 2006, Yu et al., 2013). These changes, including rising incomes, have seen a concomitant increase in food consumption and shift towards higher rates of consumption of commodities that are more land-intensive to supply; in particular meat and milk (Godfray et al., 2010, Tilman and Clark, 2014, Weinzettel et al., 2013).

Shifts in diets have become an increasingly important driver for land use change over time (Alexander et al., 2015, Kastner et al., 2012), a process that is likely to continue even as the rate of population growth slows (van Vuuren and Carter, 2014). Although increases in yields and production efficiencies have offset additional demand for food commodities, agricultural land areas have been expanding (FAOSTAT, 2015a). Environmental impacts can occur either through the expansion of agricultural production and consequent loss of a previous land cover, or through the intensification of production, e.g. eutrophication or biodiversity loss (Smith et al., 2013). Land use and the environmental impacts associated with agricultural production are also increasingly displaced from the country of consumption, through international trade of food commodities (Erb et al., 2009, Weinzettel et al., 2013, Yu et al., 2013). Agriculture accounts for around a third of global anthropogenic greenhouse gas (GHG) emissions, and land-use change alone presently accounts for 10% of anthropogenic CO2 emissions (Le Quéré et al., 2015). As well as causing environmental issues, dietary transitions have contributed to rising global rates of obesity and increases in associated diseases, e.g. diabetes and heart disease (Hu, 2011, Tilman and Clark, 2014).

Animal products contribute disproportionately low amounts of energy and protein to human diets (respectively 18 and 39% globally in 2011), relative to their land-use footprint (pasture accounts for approximately 68% of agricultural land, plus around one third of cropland is used for the production of animal feeds (Alexander et al., 2015, FAO, 2006). However, grassland is a broad category that covers a diverse range of intensities, from intensively managed pasture to extensively used savannahs with little or no inputs of fertiliser or other management, meaning that direct comparisons between different land use areas are difficult. Nonetheless, the expansion of pasture (62% of the expansion in agricultural area from 1961 to 2011 (FAOSTAT, 2015a), as well as the increasing use of crops for feed, demonstrates the critical importance of animal products as a driver of land use change. Animal products also play a role in water consumption (Jalava et al., 2014), and agricultural GHG emissions not associated with land use change (Tilman and Clark, 2014). The impacts from food production, both of animal products and crops, are exacerbated by losses or inefficiencies that exist at each stage in the production system, from harvesting, through transport and storage, to processing and finally at the consumer (Gustavsson et al., 2011, Parfitt et al., 2010).

Future food requirements could be met through a combination of increasing production and reducing demand. However, substantial attention has been given to supply-side responses, including expanding land in agricultural use and increasing food yields, especially crops (e.g. closing the ‘yield gap’ or ‘sustainable intensification’) (Foley et al., 2011, Kastner et al., 2014, Mueller et al., 2012, West et al., 2014); or the potential benefits and trade-offs associated with increasing livestock intensities (Davis et al., 2015, Herrero et al., 2016). Such analyses tend to consider dietary change as an exogenous wealth-based factor, and anticipate continuations of current dietary trends (Engström et al., 2016, Schmitz et al., 2014). However, diets and the food preferences that shape them do not necessarily follow fixed trends. Instead, they alter over time influenced by technology, policies and changes in social norms, e.g. (Hollands et al., 2015). Modelling work has been done to project the impact of alternative assumptions regarding future diets (Bajželj et al., 2014, Haberl et al., 2011, Popp et al., 2010, Stehfest et al., 2009), and the ability of the agricultural system to supply the global population with a diet containing adequate calories has also been considered (Cassidy et al., 2013, Davis et al., 2014). Further studies in this area have taken a life-cycle analysis (LCA) approach that typically consider either GHG emissions, energy or water requirements for individual commodities (Carlsson-Kanyama and González, 2009, González et al., 2011, Marlow et al., 2009, Pelletier et al., 2011). However, few studies have quantified the impact of variations in existing diets. Erb et al. (2009) considered the impact of current variations in food consumption patterns on agricultural land use, by quantifying trade in the embodied human appropriation of biomass net primary production. But, despite the potential significance of consumer behaviours on land use, no attempt appears to have been made to quantify the land use impacts of existing diets, dissociated from the complicating effect of domestic production and international trade.

Here, we address this gap by proposing a new index and using it to quantify the land use requirements of diets by country and over time (from 1961 to 2011). The Human Appropriation of Land for Food (HALF) index expresses the land area required for the global population to consume a particular diet, as a percentage of the world land surface. HALF therefore provides a relative measure of the scale of the impacts of alternative diets on land use. Diet here is assumed to include the quantities of commodities lost and wasted after reaching the consumer. The index is calculated from global average production intensities and yields from a baseline year, primarily 2011. HALF is accordingly not predictive, as adaptive responses in production systems that may result from changes in demand are excluded. Rather, the HALF index is a metric that characterises the land use impact of alternative scenarios of dietary patterns. The results can be interpreted in terms of both methods and areas of production, with a given increase in the HALF index implying the same increase in agricultural areas, an equivalent increase in productive efficiency, or some combination of the two.

Section snippets

Method

FAO country-level panel data for crop areas, production quantities, commodity uses and nutrient values were used to construct the HALF index (FAOSTAT, 2015a, FAOSTAT, 2015b, FAOSTAT, 2015c, FAOSTAT, 2015d, FAOSTAT, 2015e, FAOSTAT, 2015f). Global average production values and efficiencies for primary crops, processed commodities and livestock products were used to calculate the agricultural areas needed to meet per capita consumption for each country. The index is expressed as the percentage of

Global and country-level HALF

The total agricultural area used for human food production was 4484 Mha in 2011, of which 871 Mha was used for cropland for human consumption, and 3700 Mha for animal products (497 Mha of cropland for feed and 3203 Mha of pasture). The remaining cropland was used for biofuels (140 Mha), fibre (33 Mha), feed for non-food uses of animal products (9 Mha), and net variations in stock levels (7 Mha). Expressed as a percentage of the global land surface (13,009 Mha (FAOSTAT, 2015a) the Human Appropriation of

Comparisons to previous studies

The results show that global adoption of diets already consumed by hundreds of millions of people could lead to a magnitude of change greater than a doubling or halving of current agricultural land area. There have been few previous studies that have quantified the impact of such substantial shifts in diets on agricultural land areas. Stehfest et al. (2009) is one example, where dietary scenarios for 2050 are considered, including a ‘healthy diet’ (low rates of ruminant meat and pork and

Conclusions

Dramatically different requirements for land for food production could arise depending on the course of dietary change – both in terms of quantity of food consumed per person, but more importantly in terms of the mix of food commodities. A wide range of human appropriation of land for food was found based on global adoption of current country-level average diets, far wider than the divergence in energy or protein in-takes, with the difference due to the types of commodities in each diet, and in

Acknowledgments

The research was supported by the European Union’s Seventh Framework Programme project LUC4C (grant no. 603542). We acknowledge the support of the Scottish Government’s Rural and Environment Science and Analytical Services Division funding to SRUC.

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