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This is the fourth 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 United Nations.

Mitigating food insecurity and the dangerous effects of climate change are the two biggest challenges facing humanity today. Thomas Malthus proposed in 1803 that human population increases exponentially whilst food production grows at an arithmetic rate, and thus predicted widespread food shortages (). Unless 50 per cent more food, 50 per cent more energy and 30 per cent more freshwater are available by 2030, simultaneous shortages of all of these would be on a global, catastrophic scale ( ).

Current forecasts predict that by 2050, the global population will have reached 9.6 billion people, with estimates reaching 11 billion by 2100 (, ). Previously, food demands were met through land extensification and advancing technologies in agriculture. Food security comprises food availability (crop productivity is the key determinant but also includes food waste), food access (reflects income and the ability to purchase food, as well as market factors), stability of access and availability (influenced by climate variability and prevalence of extreme events) and food utilisation (linked to the nutritional quality and safety of food) (). Current and predicted food insecurity are the result of: 1) lack of income in developing regions 2) high levels of loss during harvest, transport and storage especially in less economically developed countries 3) high levels of food spoilage, especially in developing regions and 4) changing dietary preferences ().

Food security is also massively related to a global food imbalance 1.4 billion people worldwide are overweight or obese () yet child mortality is exceedingly high with approximately 10.9 million children under the age of 5 dying from hunger related causes (Lal, 2013). During the green revolution, vast improvements were made to fertilisers, pesticides, irrigation and crop varieties which prevented approximately one billion people from starvation. Since 1950, the population has risen by approximately 5 billion people. To feed the projected population of over 9.6 billion people by 2050 land use change is no longer an option ().

Over 38 per cent of the Earth&rsquos permanent ice free land is used for food production (). The Food and Agricultural Organization (FAO) has projected that cropland and pasture-based food production will see a 60 per cent increase by 2050 calculated in tonnages weighted by crop prices (). projected that food production from cropland production would need to increase by 100 per cent, measured in calories and includes both food and livestock feed. Currently, global agriculture and food production are responsible for over 30 per cent of all total greenhouse gas emissions (Tilman and Clark, 2014). If we are to limit global mean temperature rise by 2¡ãC above pre industrial levels, as agreed at COP21, this goal requires a reduction in total GHG emissions from both energy and industry sectors to 30 to 70 per cent of 2000 levels by 2050, and to zero or negative emissions in the second half of the twenty first century (Lal, 2014).

In providing future food security, the global population faces many challenges with little room for compromise. If food production is to grow by 60 to 100 per cent and we are to limit the anthropogenic impact upon the environment, food production must be achieved without further land expansion or an increase to greenhouse gas emissions. Means to provide future food security must utilise and improve existing resources, including reducing food waste, sustainable intensification (bridging the yield gap), and healthier diets.

The nature of global food demand can strongly influence GHG emissions. To meet the needs of feeding a growing population a reform of food production is needed to provide healthier, nutritional food whilst reducing the environmental impact. There are a number of methods that should be utilised in combination to sustain the growing population whilst reducing the effects of climate change. The global population is increasing rapidly, urbanizing and becoming wealthier. Over half the world&rsquos population lives in cities and by 2050 nearly two-thirds of people will live in urban areas (Godfray et al, 2014).? This in turn has affected dietary patterns with a higher demand for dairy and meat products and subsequently heightening demand for land and resources and, thus increasing GHG emissions (Garnett, 2014). From 1960 to 2010 demand for meat has risen 4-fold, 2.7-fold for cereals and 1.6-fold for roots (). It also impacts human health: diets become dominated by energy, sugar and fat rich foods which are linked to a number of health issues such as obesity and chronic disease in both developed and less developed countries (Godfray et al 2014).

At present, non CO₂ greenhouse gases contribute approximately a third of total anthropogenic CO₂ equivalent. A third of global human protein consumption comes from animal products (). The increase in demand for livestock production for both meat and dairy has raised the ruminant population, with an onslaught of negative effects. Ruminant production is the largest source of anthropogenic methane emissions and also globally occupies more area than any other land use, accounting for 26 per cent of total terrestrial area. Methane has a higher global warming potential of 21 times compared with carbon dioxide, traps up to 100 times more heat in the atmosphere than carbon dioxide within a five year period, and 72 times more within a 20 year period (). On average, in the past 50 years 25 million ruminants have been added to the planet annually (). Ruminant meats (beef and lamb) have emissions per gram of protein that are 250 times those of legumes (Tilman and Clark, 2014) and the livestock sector is responsible for 14.5 per cent of all anthropogenic emissions. Livestock production accounts for 70 per cent of the total agricultural land and the area dedicated to feed-crop production represents 33 per cent of total arable land (Ripple et al, 2014). With over 800 million people chronically hungry, it could be argued that the use of highly productive agricultural croplands to produce animal feed is questionable on moral grounds because it contributes to exhausting the world&rsquos food supply. Although policy makers strive to reduce greenhouse gas emissions, the livestock sector generally has been exempt from climate policies and little is being done to alter the production and consumption of ruminant meat products. Annual meat production is growing rapidly, and without policy changes is expected to more than double from 229 million tonnes in 2000 to 465 million tonnes in 2050 (Ripple et al, 2014). On average, the greenhouse gas footprint of consuming ruminant meat is between 19and 48 times higher than that of high-protein foods obtained from plants (Ripple et al, 2014).

Globally, it is estimated that between 30 and 40 per cent of all food produced is lost in the food supply chain from harvest to final consumers, or ?approximately 1.3 billion tonnes of food (Smith et al, 2013 , 2015). In developing countries, food losses occur on farm or during distribution from the effects of inadequate storage, distribution and conservation technologies. In developed countries, losses occur in the service sector and at the consumer level (Godfray et al, 2010). The energy that goes into production, harvesting, transporting, and packaging of the wasted food generates approximately 3.3 billion metric tonnes of carbon dioxide National Geographic, 2015). The later the food product is lost along the food supply chain, the greater the environmental consequences, since the environmental costs incurred during processing, transport, storage and cooking must be added to the initial production costs. In terms of food wastage, the squandering of meat and dairy products is especially harmful because the production of such items requires increased land occupation and has a larger carbon footprint. High income countries and Latin America account for 80 per cent of all meat wasted. Fruit wastage contributes significantly to water waste in Asia, Latin America, and Europe, and large volumes of vegetable waste in industrialised parts of Asia and Europe. Wastage of cereals is a significant issue in Asia affecting carbon, water and land use. Rice is a particular problem, accounting for 20 per cent of anthropogenic methane emissions, and a significant proportion is wasted (FAO, 2013).

In terms of demand side mitigation measures for ensuring future food security and the alleviation of the effects of climate change upon the environment, there are numerous actions on an individual level that one can take. In reducing food waste, individuals can shop wisely, prepare shopping lists in advance to avoid buying excess food, maintain a healthy fridge to optimise food storage conditions, practice the &lsquofirst in, first out&rsquo method, learn to understand food expiration dates, utilise leftovers, compost, and donate unwanted food. Reflecting changing dietary trends, individuals should buy local produce, eat a healthy more balanced diet through reducing their red meat intake, contemplate pescetarian, vegetarian or vegan diets, limit their meat and dairy intake, and buy organic produce. There have been revisions on recommended &lsquohealthy diets&rsquo with concerns that the consumption of beef and pork increase the risks of intestinal cancer, and the consumption of fatty meat increasing the risks of coronary diseases (). Stehfest et al examined a range of future dietary scenarios and assessed the impact on greenhouse gas emissions from land use change. Each scenario that reduced meat and or dairy intake resulted in fewer emissions compared with the business as usual scenario. The diets considered were no ruminant (red) meat, no meat consumption at all (vegetarian), no animal products at all (vegan) and the recommended healthy diet as proposed by . Compared with the business as usual scenario, if the population were to eat no ruminant meat, land use emissions could be reduced by 48 per cent, a fully vegetarian diet by 55 per cent, a vegan diet by 67 per cent and a &lsquohealthy diet&rsquo by 36 per cent.

With agriculture accounting for over 30 per cent of global greenhouse gas emissions, demand side mitigation options hold the greatest potential in reducing our anthropogenic impact upon the environment, ecosystem services, and climate change, and should be implemented in conjunction with supply side mitigation measures which include sustainable intensification, optimising redistribution and trade, and closing the yield gap (IPCC, 2014 Smith et al, 2013).

Laura Phillips is a PhD student at the University of Aberdeen with the thesis title 'What are the environmental consequences of delivering food security?'?Laura is an intern with United Nations Academic Impact with research interests in climate change, food security, sustainable development, renewable energies and soils.