lunes, enero 16, 2012
The world can't afford to keep wasting soil
One-third of Earth's soil is degraded because of unsustainable farming methods, which could lead to a major food crisis.
Aljazeera, 12 Jan 2012 12:49 / Stan Cox
Salina, Kansas - Late last year, the United Nations' Food and Agriculture Organisation (FAO) released a hair-raising report on the state of the world's soil and water resources. The bottomline: 25 per cent of the world's food-producing soils are highly degraded or are rapidly being degraded. Add to that other soils which they say are degrading "moderately", and the area under threat amounts to one-third of the Earth's endowment of cropland.
Loss of productive soil, FAO reported, is most severe in the Himalayan and Andean regions; semi-arid tropical regions of Africa and India; rice-growing lands of Southeast Asia and areas of intensive and industrialised farming in Western Europe, North America, eastern China, India, Brazil and New Zealand.
According to the most recent Global Land Degradation Assessment, 18 countries - nine of them in sub-Saharan Africa and four in Southeast Asia - now see more than half of their entire land area going downhill rapidly. Countries whose land is in the worst trouble are often, but not always, countries where large numbers of people live in poverty. In just 10 countries - India, Bangladesh, Brazil, China, Thailand, Mexico, Philippines, Democratic Republic of Congo, Vietnam and Burma - more than 530 million people are feeling the impact of land degradation directly. Worldwide, 1.5bn people are feeling it.
We humans now grow two-and-a-half to three times as much food as we did in 1960 while cultivating only 12 per cent more land area. It's an extraordinary achievement, but the cost has been high. Tilling, fertilising and irrigating year after year damages the soil's native structure, and the water that runs off into streams or percolates into groundwater can be laced with dangerous quantities of nitrates, pesticides or other pollutants.
The fate of the Earth's agricultural lands is closely tied to the fate of its waters. Expansion of irrigation has been the biggest factor in increasing food production over the past half-century, and improving irrigation will be a key to boosting yields between now and 2050. But irrigation can deplete local water resources and disrupt the soil's chemical balance. Furthermore, flooding of reservoirs has already driven tens of millions of people off of perfectly good forest and cropland around the world.
Back to traditional methods
While declining soil health is a global problem, many of the soils in critical condition are in the global South. Tropical soils are especially vulnerable, and when they're farmed, all kinds of problems can be expected: loss of essential nitrogen, phosphorus, potassium and micronutrients; washing away of already-thin topsoil; carbon depletion; crippling of the soil's ability to store water; buildup of salts and aluminum toxicity; acidification and perhaps most importantly, destruction of the many species of microorganisms needed for a robust soil ecosystem.
When that has happened, farmers have still managed to produce harvests by pouring on synthetic fertilisers (if they can afford them.) Instead of restoring the soil, that renders it a more-or-less inert growth medium.
The cost of producing sufficient food between now and 2050, while retaining soil's productive capacity on the global scale, was estimated by FAO at US $1tn for irrigation improvements plus $160bn for soil conservation. Governments of the global North could easily pay for that; such sums are not huge at all when viewed alongside the North's expenditures on, say, armaments or corporate bailouts. But the cheque's decidedly not in the mail.
And many farmers are not waiting to see that cheque before pushing back against erosion and loss of fertility. Using resources at hand, they've built terraces; planted rows of trees and shrubs; built water-breaks with crop residues or brush; interplanted nitrogen-fixing legume crops with cereals, root crops or perennial forage grasses; returned manure or nitrogen-rich leaves and stems to the soil and built field-scale rainwater-harvesting systems.
Researchers who've been working for years to improve food production on tropical soils say it will take more than cash to reverse the damage, and that what farm communities lack in the form of money and labour power they can make up for with "social capital" - their capacity to act collectively to protect their common life-support system, the soil.
Given sufficient social capital, communities have taken on even more ambitious soil-conserving projects that bring long-lived, deep-rooted trees and shrubs into agricultural plots - a group of techniques known as agroforestry. Examples can be seen on every continent.
Farmers are interplanting rows of fodder-producing trees and food crops in Africa's Sahel region; incorporating nitrogen-fixing leguminous trees into crop and grazing lands in Asia and Latin America; popularising a broad array of agroecological techniques through the "campesino-to-campesino" method in Nicaragua and Cuba and establishing "home garden" plots in South Asia that contain a wide diversity of food-producing trees along with traditional crops. (In Bangladesh, where 90 per cent of natural forest cover has been stripped away, more than 20 million home gardens are bringing at least some trees back to the landscape.)
Still, such practices will have to proliferate rapidly if they are to make a difference in holding back soil degradation at the global scale. And room for expansion is limited; farmers are often reluctant to have trees taking up space on the often small plots of land where they must grow all of their staple crops.
And no matter how soil-friendly the cropping system, each year's harvest pulls essential nutrients off the land. Even back in the nineteenth century, it was becoming clear that the way food systems worked - harvesting food grains rich in essential elements, carting them away to villages and cities and then failing to return human and animal wastes to the land - could not be sustained indefinitely. The soil would gradually be depleted of nutrients, and crop yields would drop.
Justus von Liebeg, who first figured out the chemistry of soil fertility, referred to such removal of nutrients through crop harvest as "robbery". Karl Marx viewed it as a stark example of the "metabolic rift" between humans and nature that had come with industrialisation and urbanisation.
One effort to heal that rift is being carried out in Haiti, home to some of the most badly deforested and degraded soils on Earth. An organisation known as SOIL (Sustainable Organic Integrated Livelihoods) is building networks that connect growing numbers of community toilets (ones that segregate liquid and solid wastes) with eco-sanitary composting facilities and fertiliser production and distribution. SOIL now operates the largest waste-treatment operation of any kind in Haiti while helping restore the country's ravaged farmland and increase food production.
Achieving ecological strength
Still, a big hindrance to creating agricultural systems that maintain or improve soil health is humanity's dependence on weak-rooted annual plants for most of our food. Given that dependence, the strategies of nutrient recycling, agroforestry and agroecology will not be sufficient. Therefore, groups of plant breeders in several countries are working to develop soil-conserving perennial cereal and grain-legume crops.
"Ecological benefits... were lost when natural landscapes were converted into croplands growing chiefly annual monocultures."
That work will take time, so "semi-perennial" systems are being pursued as interim measures. For example, a wide array of bean and pea species are typically treated as single-season crops in the tropics, but they can also be maintained for several years as nitrogen-fixing perennial shrubs or vines. In trials on hundreds of farms across the nation of Malawi over the past dozen years, a shrubby edible legume called pigeon pea and a viny one, velvet bean, have been intercropped with maize as multi-year semi-perennials. The intercropped plots were superior in maintaining soil fertility and stabilising food production while providing a combination of high-energy maize and high-protein legume grain.
Intercropping, tree-planting, managing water and restoring nutrients to the land are all efforts to recover ecological benefits that were lost when natural landscapes (mostly mixtures of perennial species) were converted into croplands growing chiefly annual monocultures. But it's not just this component or that characteristic of a natural ecosystem that makes it erosion-proof, watertight and frugal with nutrients. Natural ecosystems came to be that way over evolutionary time thanks to vast networks of interdependent microbes, plants, animals and mineral substances.
Simply adjusting the way soils are farmed can slow soil loss, but it cannot achieve that kind of ecological strength - just as installation of new, efficient air-conditioning in a thousand-square-metre mansion may save some energy, but can't make the house "green". If we are to have a global soil base that can sustain human civilisation over the long term, we will have to create entirely new ways of farming that emulate natural ecosystems to achieve their degree of resilience.
A 'global priority'
That transformation will become especially important as the world's farming communities, especially those in the tropics, face the unpredictable risks that will come with greenhouse warming. But in tackling climate disruption, it will also be essential not to conflate those looming risks with agriculture's widely promoted potential for burying carbon safely in the soil.
In particular, we must not take the quest for soil-conserving food production and reduce it to a matter of "carbon farming" to produce emissions credits. Certainly, the practices for curbing soil degradation outlined above can, to varying degrees, keep carbon dioxide out of the atmosphere. But the world needs to spend whatever is required to get all of those measures in place anyway, for the sake of the landscapes where the food is grown and the communities who grow it. Soil-saving by some should not provide others with a licence to pollute.
To value everything in terms of carbon and treat the myriad benefits of ecologically sound agriculture as mere byproducts of climate protection is to invite all kinds of threats to soil and food. Perhaps the most menacing threats are those posed by connecting food and soil more tightly to global capital markets through carbon-trading schemes and tying them more closely to volatile energy markets by putting already fragile soils to work growing biofuels.
In countries with ample land, it should be possible for farmers to produce just enough biofuel to fill the needs of agriculture, and it makes thoroughly good sense to have farming become energy self-sufficient in that way. But to grow energy crops or strip plant residues from the soil in order to fill the fuel tanks of the world's much larger non-farm transport systems would impose an impossible burden. There is not enough good soil on the whole planet to satisfy humanity's vast and growing car-and-cargo cult.
As fossil fuels become more deeply depleted and (perhaps) their use becomes more restricted, we will become more and more dependent once again on soil, water and sunshine for our lives and livelihoods. And we should be ready for the more modest way of life they are able to provide.
We still have the means and the ability to ensure that as the decades pass, there will still be enough good soils and good farmers to keep civilisation going. But if that's to happen, healthy soils and intact ecosystems must be shifted into the top tier of global priorities, and fast.
Stan Cox is research coordinator at The Land Institute in Salina, Kansas, USA. His most recent book is Losing Our Cool: Uncomfortable Truths About Our Air-Conditioned World
The views expressed in this article are the author's own and do not necessarily reflect Al Jazeera's editorial policy.