Just to add some elements that go somewhat counter conventional wisdom in this matter, though not against scientific evidence, let me remark on some often disregarded points:

1. Food security is defined by access to food, and nutrition by access to food, safe water, sanitation and health care; they do not require that everyone produce food on their own plot. Access is chiefly determined by income level and distribution, not by self sufficiency: even subsistence smallholders can only produce a fraction of their food needs, mainly staple food, and most need extra income to purchase more food and other goods and services in the market. They usually procure that extra income through off farm activities, chiefly wage labour. In fact, subsistence producers are, and have been for decades, among the people more affected by food insecurity and malnutrition, especially when they lack complementary sources of income, Urban folk (even poor urban folk) customarily get more food and better nutrition indicators than peasants, in spite of (or due to?) not producing any food themselves. Other than producing food in everybody's plot, economic development brings more income, and also more trade (domestic and international) to bring more food from whatever point of production to whatever point of consumption. Livelihoods diversify, social labour is divided and specialized, and trade plays an ever greater role. This is already happening: Since 1961 to 2012 food production worldwide more than trebled (increasing 50% per capita), but international food trade increased by a factor of nearly nine times, confirming what the World Food Summit found: that "trade is a key element for achieving food security". Increased world output, increased income in developing countries, and increased world trade, will save more people from hunger than scrapping a few more grains or tubers from tiny subsistence plots. More peace and better governance will also help, by eliminating major causes of today's famines and food emergencies (war, refugee camps, internecine strife, corruption).

2. There is no shortage of land at the world level. The world has about 3 billion Ha of prime and good land (according to FAO agro-ecological zones and soils classification) and only about 1.5 bn Ha are actually used for crops. Ample reserves of good arable land exist especially in Africa, Latin America, North America and Eurasia. Moreover, existing projections of future requirements of extra land do not foresee a significant increase in arable land use (which is, moreover, rather stagnant since the mid 1980s). See for instance the FAO report by N. Alexandratos and J. Bruinsma, 2012. World agriculture towards 2030/2050: The 2012 Re¬vi-sion. Rome: FAO. http://www.fao.org/docrep/016/ap106e/ap106e.pdf. (This FAO land classification already accounts for land degradation occurred in the past).

3. Climate change has both beneficial and deleterious implications for agriculture. A warmer climate in temperate regions opens up new lands for cultivation, extends the growing period, and improves land productivity; warming also increases water evaporation and thus rainfall at global level, though changes in convection currents may cause more drought in some areas like Southern Africa and Northern Mexico. On the whole, world arable land is projected to increase. Increases in usable land area and land productivity, due to increased rainfall and milder winters, are already observable in several areas of the world (cf expansion of cultivation into formerly dry non-cultivable areas in the North and West of Argentina). Also, higher concentrations of carbon dioxide in the atmosphere increase crop yields (especially for the C3 type crops like wheat, and also for the C4 type like maize when grown in dry conditions). More availability of atmospheric CO2 also reduces the water needs of C4 crops. Both effects countervail other negative impacts that climate change may have (for instance, maize in Mexico may suffer due to expected drier conditions there, but at the same time maize, a C4 plant, would require significantly less water under increased CO2, partly contributing to offset the former effect).

4. Agricultural productivity is on the rise almost everywhere. Yields, and output value per hectare, are growing faster than ever, including Africa, and also Asia and Latin America (it grows more slowly in Europe and North America). Even if no further technical development or discovery occurs in agriculture (hardly a likely prospect), simply by catching up with existing technology, growth of productivity can continue for decades, especially in developing countries where the technology gap is wider and productivity increase is faster.

5. All indicators of food security and nutrition are improving. The MDG of halving the prevalence of undernourishment is practically on the verge of being achieved globally (see FAO's SOFI reports). Anthropometric indicators of nutritional failure are also decreasing, as reported by the Nutrition division of WHO. Moreover, the rate of improving in both aspects seems to be accelerating. There is an increasing worldwide problem of obesity and overweight, affecting already more people than acute or chronic undernutrition, and this marks a significant nutritional transition never seen before in the history of mankind.

6. It is often mentioned that from 2000 to 2050 food production has to increase by 50-70%, and this is seen as an alarming prospect, but in fact it just requires a growth rate of 0.8-1.0% per year, whilst in the previous past century food output has been increasing at about 2.5% per year on average, and this rate has been accelerating in recent decades compared to previous ones. Note that this includes the period of most rapid climate change and intense emissions of greenhouse gases, especially noticeable since 1970.

7. Studies on the impact of climate change on future levels of food production and prevalence of undernourishment, even under quite pessimistic assumptions, indicate that progress would continue, covering future demand for food and other uses of agricultural products (including biofuels) and reducing undernourishment to non-significant proportions in all major regions by 2050 or thereabouts. See for instance the report of Dr Günther Fischer commissioned by FAO: World Food and Agriculture to 2030/50: How do climate change and bioenergy alter the long-term outlook for food, agriculture and resource availability? Included in FAO 2011, Looking ahead in World Food and Agriculture: Perspectives to 2050. Ed by Piero Conforti. http://www.fao.org/docrep/014/i2280e/i2280e00.htm.

I do not make these rather heretical comments to mean that there is no problem and nothing needs to be done. On the contrary, a lot remains to be done. For the 850 million hungry people existing today, it is little comfort to learn that things will be better by 2050: they need assistance today, every day, both in the form of agricultural development for family agriculture, help to transform their present livelihoods, and social protection to support them in their current predicament and bridge the difficult transition into a better way of life.

Food prices are decreasing since 2010, and the spikes of 2007 and 2010 fortunately did not trigger the dire effects once feared (no famine and very few food riots occurred worldwide in the wake of the price surge), but many people suffered from high food prices, and generating higher incomes to afford food and other necessities are of the very highest priority.

More energetic efforts should also be deployed internationally to stop the many local conflicts, State failures and collapse, and widespread corruption that affect the lives, food security and nutrition of millions in poor countries and cause the most dramatic food crises we see today.

In view of the ongoing migration and urbanization process in the developing world, helping people to enter in a better way into urban and international employment (through education, training, and better domestic and international migration and housing policies) is also a crucial ingredient to help people earn better incomes and improve the food security of themselves and their relatives, including those left in the old country and expecting to receive remittances.

Facts reflected in the above comments suggest some shifts in emphasis are needed: people are moving from subsistence production to into new livelihoods. Livelihood transformation and diversification may perhaps be more important than incremental (and often ineffectual) efforts to improve traditional livelihoods. To accelerate the current rate of progress in access to food and better nutrition a strong emphasis is needed on economic development; agricultural productivity; better supply of water, sanitation and health care; labour training and productivity; and food trade (including cheaper and steadier food supplies for regions in need, and better access of poor countries to world markets for agricultural products). Climate change may make things more difficult in some aspects and places, and may help in others. Humankind will undoubtedly deal with all these challenges (we have dealt with far worse ones in the past), but knowing them in advance surely helps.

I hope this may provide food for thought and make for a more spicy debate.