A few related points
Current projections indicate that world population will increase from 6.9 billion people today to 9.1 billion in 2050. By this time, another one billion tonnes of cereals and 200 million extra tonnes of livestock products will need to be produced every year.
In addition, economic progress, notably in the emerging countries, translates into increased demand for food and diversified diets. World food demand will surge as a result, and it is projected that food production will increase by 70 percent in the world and by 100 percent in the developing countries. Yet both land and water resources, the basis of our food production, are finite and already under heavy stress. Some further land and water resources could be diverted to crop production, but in most cases they already serve important environmental and economic functions
Land and water resources and the way they are used are central to the challenge of improving food security across the world.Today almost 1 billion people are undernourished, particularly in Sub-Saharan Africa (239 million) and Asia (578 million).
Deeper structural problems have also become apparent in the natural resource base. Water scarcity is growing. Salinization and pollution of water courses and bodies, and degradation of water-related ecosystems are rising.
In many large rivers, only 5 percent of former water volumes remain in-stream, and some rivers such as the Huang He no longer reach the sea year-round. Large lakes and inland seas have shrunk, and half the wetlands of Europe and North America no longer exist. Runoff from eroding soils is filling reservoirs, reducing hydropower and water supply. Groundwater is being pumped intensively overpumped and aquifers are becoming increasingly polluted and salinized in some coastal areas. Large parts of all continents are experiencing high rates of ecosystem impairment, particularly reduced soil quality, biodiversity loss, and harm to amenity and cultural heritage values.
Overall, increasing water scarcity constrains irrigated production, particularly in the most highly stressed countries and areas. In low- to medium-income countries with fast population growth, the demand for water is outstripping supply. Rising demand from both agriculture and other sectors is leading to competition for water, resulting in environmental stress and socio-economic tension. Where rainfall is inadequate and new water development is not feasible, agricultural production is expected to be constrained more by water scarcity than land availability.
The global land area is 13.2 billion ha. Of this, 12 percent (1.6 billion ha) is currently in use for cultivation of agricultural crops, 28 percent (3.7 billion ha) is under forest, and 35 percent (4.6 billion ha) comprises grasslands and woodland ecosystems.
A series of land and water systems now face the risk of progressive breakdown of their productive capacity under a combination of excessive demographic pressure and unsustainable agricultural practices. The physical limits to land and water availability within these systems may be further exacerbated in places by external drivers, including climate change, competition with other sectors and socioeconomic changes. These systems at risk warrant priority attention for remedial action simply because there are no substitutes.
The world's net cultivated area has grown by 12 percent over the last 50 years, mostly at the expense of forest, wetland and grassland habitats. Although only a small proportion of the world's land and water is used for crop production, most of the easily accessible and (thus economic) resources are under cultivation or have other ecologically and economically valuable uses. Thus the scope for further expansion of cultivated land is limited.
By their nature, rangelands are fragile ecosystems and when mismanaged readily result in degradation, loss of biodiversity and water retention capacity, carbon emissions and reduced productivity. Grasslands (including rangelands, shrubland, pasture land, and cropland sown with pasture trees and fodder crops) occupy almost 30 percent of the emerged icefree land areas. Fodders and pastures cover over 60 percent of the world's agricultural land (FAO, 2010b).
Worldwide, land suitable for cropping (prime and good categories combined) is about 4.4 billion ha (4.0 billion ha if areas with protected status are excluded). This is considerably more than the 1.6 billion ha currently cultivated (Table 1.16). There is thus a large area of currently uncultivated land that could theoretically be brought into production. However, much of this land is effectively not available for crop production.
In addition, it is generally of lower food potential than existing cultivated land: much of the presently agriculturally unused land suffers from constraints such as ecological fragility, low fertility, toxicity, high incidence of disease or lack of infrastructure. cher et al. (2002) show that over 70 percent of the land with rainfed crop production potential in sub-Saharan Africa and Latin America suffers from one or more of these constraints.
Thus, much of the land would be capable of producing only at low to medium average yields. A large fraction may not available for crop production due to its protected status, its carbon sequestration and biodiversity value (including forests), and its current use for feeding the world's 3.5 billion ruminant livestock.