Agricultural production will have to be intensified, rather than expanded, says a UN report
"It is now estimated that more than 40 percent of the world's rural population lives in river basins that are physically water scarce," said the UN Food and Agriculture Organization (FAO) report, which looked at land and water from a food security perspective. That is a lot, considering 75 percent of the population in developing countries is poor, lives in rural areas and depends on agriculture for income and food.
The report, the most comprehensive take on the health of the planet's land and water resources, contains plenty of bad news.
To feed a burgeoning global population, estimated to hit nine billion by 2050, we will have to produce another one billion tonnes of cereals and 200 million extra tonnes of livestock products every year. "The imperative for such agricultural growth is strongest in developing countries, where the challenge is not just to produce food but to ensure that families have access that will bring them food security," the report noted.
To do that we will need to increase agricultural water consumption by 10 percent until 2050. This might not sound like much, but it is "incredibly difficult" for water-stressed countries like South Africa, which can only dream of another one percent increase in the water channelled to agriculture, said Jean-Marc Faures, a water specialist with FAO.
A growing population will also put a squeeze on the per capita amount of land available in developing countries, which is expected to halve (to 0.12 hectare) by 2050.
But there is some light amid the gloom. Globally we may not have run out of food or land by 2050, said Hubert George, the editorial coordinator of the report.
There is agricultural land that can be used for expansion in sub-Saharan Africa, South America and parts of Europe, Russia, northern America and Australia.
But half of it is concentrated in just seven countries - Brazil, Democratic Republic of Congo, Angola, Sudan, Argentina, Colombia and Bolivia. About 70 percent of that land suffers from constraints such as ecological fragility, low fertility, toxicity, high incidence of disease or lack of infrastructure.
There is no spare land for expansion in south Asia, east Asia, the Middle East and northern Africa, which are home to the largest portion of the world's population.
Currently, 25 percent of the earth's land is highly degraded, another 8 percent is moderately degraded, 36 percent is stable or slightly degraded, and 10 percent is ranked as "improving" in quality. The remainder is either bare (around 18 percent) or covered by inland water bodies (around 2 percent)
The land used to grow crops - about 1.6 billion hectares of the world's best - falls into the "improving" category, but some parts are being degraded by farming practices that result in water and wind erosion, the loss of organic matter, topsoil compaction, salinization and soil pollution, and nutrient loss.
Doing more with less
Various trade-offs will be required to help countries feed themselves: intensification of agriculture rather than expansion, and irrigation systems rather than depending on rainfall.
More than four-fifths of production gains will have to occur largely on existing agricultural land, but all will involve policy decisions that need to be grounded in an agricultural approach that is not only friendly to land and water resources, but also to the ecosystem at large, says the report.
Unsustainable approaches - present and past - have played a big role in putting world food security in a precarious position.
For instance, in countries like Bangladesh and China, where fertilizer is heavily subsidized, application rates tend to be higher than recommended, resulting in overuse. In 2008, Chinese farmers received a fertilizer subsidy of US$84 per hectare. In 2008-09, Bangladesh spent $758 million on urea support. Large adverse impacts on groundwater quality have been reported in both countries.
In Brazil, until the economic crisis of the early 1990s, credit subsidies and tax exemptions tipped in favour of clearing land in the Amazon region for often unsustainable crop production. The distorted incentive framework contributed to the permanent loss of forest ecosystems, but failed to encourage efficient, equitable or sustainable agriculture.
Worldwide, almost one billion people are undernourished today, particularly in sub-Saharan Africa (239 million) and Asia (578 million). "In developing countries, even if agricultural production doubles by 2050, one person in twenty still risks being undernourished - equivalent to 370 million hungry people, most of whom will again be in Africa and Asia," the report said.
Climate change, which will affect the patterns of rainfall, temperature, and evaporation rates from rivers, is another risk driver of shrinking food output.
The world has not agreed on an integrated international framework within which major initiatives for sustainable land and water management can be formulated. Recent studies and programmes by UN agencies, among others, place agricultural production and land and water management in an ecosystems framework.
"But countries need to start taking action now, otherwise we will not have the resources we need," said editorial coordinator George.
Here is a brief look at the main categories of land, water and agriculture systems identified in the report, and the risks they face.