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Questo articolo è stato pubblicato il 17 luglio 2013 alle ore 17:58.


AMSTERDAM – In the Mekong Delta, farmers obtain 6-7 tons of rice per hectare in dry seasons and 4-5 tons per hectare in wet seasons, using fast-maturing rice varieties that allow up to three consecutive yields annually. By contrast, West African rice farmers harvest only 1.5 tons per hectare of traditional upland rice annually, while other cereals yield no more than one ton – a figure comparable to yields in medieval Europe.

Such disparities are unnecessary. Indeed, the proliferation of agricultural technology – from more efficient machinery to higher-yielding or more robust crop varieties – has the potential to narrow the productivity gap considerably, even if differences between climates and producers remain.

For example, a new variety of African upland rice, Nerica, triples annual yields. Likewise, over the last four decades, improved breeding methods, higher-quality feed, and better veterinary care have more than doubled average milk production worldwide. Nevertheless, regional discrepancies remain massive: cows in the Netherlands can produce roughly 9,000 liters of milk annually, while Zebu cattle in the tropics produce only about 300 liters.

The need to increase agricultural output becomes more urgent every day. The global population is set to reach nine billion by 2050, while people in the developing world – where nearly all of the population growth will occur – are seeking more varied diets. By 2030, demand for animal products will double, with overall food demand rising by 40%.

Science has much to contribute to global food security. While genetic modification is not essential to feed the world, it does provide significant advantages, enabling scientists to introduce or enhance traits – virus resistance in cassava, for example, or improved digestibility of feed – that cannot be realized with conventional breeding.

To be sure, raising yields is not the same as feeding the world. If a vast swath of the population cannot afford the food that is produced, the size of the yield is irrelevant. While nearly one billion people have been lifted out of poverty (defined by the World Bank as an income of less than $1.25 per day, in purchasing-power-parity terms) in the last 20 years, such progress will prove more difficult for the next billion.

Given this, policymakers should redouble their efforts to reduce poverty by supporting sustainable and inclusive economic growth. They should commit to advancing sound agricultural management, maintaining well-functioning markets, and increasing investment in agriculture. At the same time, these objectives, while pressing, should not obscure the need to focus on yields – increases in which have accounted for three-quarters of food-production growth in recent decades.

Fortunately, the most significant potential limitations – land, water, and nutrients – seem unlikely to constrain global output excessively in the foreseeable future. But, while none is in short supply globally, local shortages may occur.

Although crop land per capita will continue to decline, more arable land is available worldwide than previously thought. The example of the use of the Brazilian cerrado, once considered useless, augurs well for the African savannas. Underused land reserves also exist elsewhere in South America, Central Asia, and Eastern Europe.

A more immediate challenge is ensuring that crops receive sufficient water, which requires building and maintaining efficient irrigation systems to stabilize yields and enable farmers to harvest an additional crop each year. As it stands, only. While the Middle East will face serious water shortages, Africa, where most population growth is set to occur, contains numerous unexploited water sources.

Fertilizer use has become significantly more efficient in recent years, a trend that will continue. Reserves of minerals like phosphate will remain plentiful in the next decades, and nitrogen is not limited. Technology to extract nutrients from waste already exists, reducing dependency on mining. Moreover, pigs and poultry are ideal food-waste processors, and their effluents can serve again as nutrient and energy sources, turning future food chains into interconnected production cycles.

Perhaps the most pressing constraint on agricultural production is the impending labor shortage, as rural young people, who traditionally comprise the agricultural labor force, flock to cities. With small farmers unable to provide sufficient surpluses, agricultural production will become increasingly consolidated and mechanized, raising fossil-fuel consumption, which will have to be offset by the introduction of more efficient technologies.

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