This is the second article of the UNAI 'Food Security and Climate Change' series. Schools and departments which specialise in climate change and food security at UNAI member institutions were asked to submit articles highlighting research and work encompassing the newly adopted Sustainable Development Goals and to showcase the importance of sustainable agriculture to mitigate the dangerous effects of climate change, whilst ensuring present and future food security. Please note that the articles are for discussion, and do not necessarily reflect the views of the 51勛圖.
Most of our food is grown on the land, so there has always been a close link between the delivery of food security and land use. In the era before industrial fertilisers, improved crop cultivars and modern livestock breeds, producing more food largely meant converting more land to agriculture. Historically, the expansion of agriculture into forests and natural ecosystems has contributed significantly to the loss of ecosystem services. Much of this loss of forest and other natural systems 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.
, in 1999, 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 1900, agricultural expansion was the most prominent way to increase food production, but after the advent of industrial agriculture, using improved cultivars and mineral fertilisers, 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 from1900 to the1940s, in the former Soviet Union between 1940 and1960 and South East Asia from 1980 to 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 United States in the 1940s followed in developing countries in subsequent decades. Cereal production (wheat, maize and rice) has increased from 877 million tonnes in 1961 to 2,342 million tonnes in 2007, the world average cereal yield has increased from 1.35 tonnes per hectare in 1961 to 3.35 tonnes per hectare in 2007, and is projected to be about 4.8 tonnes per hectare in 2040. Simultaneously, per-capita arable land area has decreased from 0.415 hectares in 1961 to 0.214 hectares in 2007. Had the increases in yield of the last 60 to70 years not been achieved, almost three times more land would have been required to produce crops to sustain the present population 每 this is land that simply does not exist or that is unsuitable for agriculture.
Therefore intensification has been essential, but has resulted in many undesirable outcomes, including air, water and soil pollution with agro-chemicals and surplus nutrients, increased climate forcing (the amount of sunlight that is absorbed by the planet versus the energy radiated back to space), resource depletion, high fossil energy inputs and habitat / biodiversity loss. During the last century, whilst agricultural area expansion has continued, the emphasis for increasing food production has shifted toward 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 therefore future intensification needs to be sustainable.
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). , in 2003, estimated that 78 per cent of the increase in crop production between 1961 and 1999 was attributable to yield increases, and 22 per cent to expansion of harvested area. Of the world's 13.4 billion hectares land surface, about 3 billion hectares are suitable for crop production 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. Expansion of agricultural area will still contribute significantly to crop production in Sub-Saharan Africa (27 per cent) and Latin America and the Caribbean (33 per cent), but there is practically no land available for expansion of agriculture in South and East Asia and the Near East/North Africa, so sustainable intensification is expected to be the main means of increasing production in these regions.
, in 2013, 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 and therefore perhaps some demand-side measures such as changing diets and reduced waste are also needed. It is clear that we need to use land more effectively to produce our food, and we have choices to make regarding so-called land sharing versus land-sparing: do we practice less intensive agriculture on a larger area; do we sustainably intensify production on existing agricultural land and leave some areas outside of production to preserve other ecosystem services; or do we take a step back and examine the food system as a whole and think more about producing the food that we need for a healthy life, rather than the food we are projected to want in the future?
To help address some of these questions, a team from University of Aberdeen, The James Hutton Institute and University of Dundee, and world leading partners from 7 other countries including the University of Minnesota (USA), CSIRO (Australia), University of Witwatersrand (South Africa), The Brazilian Space Agency (INPE; Brazil), the National Rice Research Institute (India), INRA (France) and ETH Zurich (Switzerland) have come together under an project called Delivering Food Security on Limited Land (DEVIL), funded by the Belmont Forum / FACCE-JPI. Together they aim to shed more light on the intimate links between food and land and to devise options to deliver food more sustainably in the future.
Professor Pete Smith is a Chair in Plant and Soil Science and a Professor in Soils and Global Change at the University of Aberdeen, Scotland. His main areas of expertise are in modelling greenhouse gas/carbon mitigation, bioenergy for fossil fuel offsets, and biological carbon sequestration. He is Science Director of Scotland's Climate Change Centre of Expertise, Director of Food Systems of the Scottish Food Security Alliance-Crops and is theme leader for the University-wide theme, Environment and Food Security. He is the editor for Global Change Biology and Global Change Biology Bioenergy. He is the convening lead author for Agriculture and Forestry of Intergovernmental Panel on Climate Change, Fifth Assessment Report and he is Expert Advisor on bioenergy issues to the UK Committee on Climate Change. ?
Further reading:
Bruinsma J (editor) (2003) . London: Earthscan Publications.
Ramankutty N, Foley JA (1999) . Global Biogeochemical Cycles 13, 997-1027.
Smith P (2013) . Global Food Security 2, 18-23.
Smith P (2015) . Proceedings of the Nutrition Society 74, 187每190.