When discussing deserts, it's important to keep in the mind the distinction between deserts as a specific ecosystem and desertification as a specific process.
Deserts are beguiling and wondrous: Atacama in Chile, the Sonora in Mexico, the Sahara in Africa.
Desertification is the rapid, human-induced creation of deserts — the sudden, accelerated conversion of arid or semi-arid land, usually by over-grazing, deforestation, over-extraction of groundwater, drought, over-planting, or some nasty combination of the five.
Deserts, we're stuck with. Desertification, we can hopefully stop and, if we catch it early, reverse at a reasonable cost — and in the process, do a good bit to stop climate change and global warming.
That's the idea behind a recent congress on the United Nations Convention on Desertification, which wrapped up this month in Argentina. The Convention is an off-spring of the 1992 United Nations Conference on Environment and Development (UNCED), better known as the Rio Conference.
Its executive secretary, Luc Gnacadja, warned that action is urgent.
"If we cannot find a solution to this problem ... in 2025, close to 70 percent [of the planet's soil] could be affected," Gnacadja said. "There will not be global security without food security."
The process by which desertification occurs is pretty straightforward. When land covered with vegetation loses its vegetation, it heats up more rapidly, worsening climate change. Hotter soil leaks carbon into the atmosphere faster than non-overheated soil, thereby contributing to the world's CO2 count.
Furthermore, as vegetation is eaten up during over-grazing or destroyed, its root structure disappears. Massive amounts of plant-based carbon go directly into the atmosphere from the land, where it had formerly been securely stashed away. Furthermore, the humus that had been stored in the soil also migrates into the atmosphere, contributing to the overload of CO2 already there.
Processes of desertification are world-wide and worsening. Even in 2000, nearly 40 percent of the world's agricultural land was considered seriously degraded, according to the World Resources Institute.
In Central America, the figure was 70 percent. In Africa, 20 percent. There, the situation is deteriorating sharply. UN officials claimed in 2006 that if current trends continue, 75 percent of the continent's people will rely on some kind of food aid by 2025.
Dry-land — which can include forests but primarily means grasslands — is particularly susceptible to desertification.
Dry-lands are 40 percent of the earth's surface and technically refer to lands where the prevailing climate is classified as dry sub-humid, semi-arid, arid or hyper-arid. Although they have a lower per-meter amount of plant biomass, roughly 6 kg/m2, compared to other vegetation-covered ecosystems, which have between 10 and 18 kg/m2 of biomass, they are estimated to contain 27 percent of total global soil carbon.
Many of these regions are also degraded, due to rampant over-grazing compounded by drought. As researchers from the United Nations Environment Program point out, such soils are not remotely close to being saturated with carbon and may have enormous potential for carbon sequestration.
Indeed, according to the Millennium Ecosystem Assessment (MEA), 10 to 20 percent of drylands are already degraded. Between 1 and 6 percent of the people living in drylands live in totally desertified areas. For that reason,
"Desertification ranks among the greatest environmental challenges today and is a major impediment to meeting basic human needs in drylands."
Tragically, dryland populations are already some of the planet's most vulnerable. About 90 percent of dryland populations are in developing countries, and infant mortality rates for countries dominated by drylands tower over the others. Likewise, gross national product is far lower for dryland-countries than for those countries with more diverse and moist bio-regions.
Another issue is the over-use of intensive agriculture in places ecologically unsuited for it. As the MEA researchers note,
"Transformation of rangelands and sylvo-pastoral dryland systems to croplands increases the risk of desertification." Such risks are worsened by the use of input-intensive and heavily mechanized cultivation practices, especially in lands that are utterly unsuited for such intensive agriculture.
A different source of degradation is the forced shift from grassland to shrub-land, as large-scale unsustainable ranching or pasturing practices increasingly prevail throughout the world (although properly-practiced ranching can increase the amount of carbon stores in soil).
As grass-land transitions to shrub-land leads to more naked and exposed soil, accelerating run-off and heightening erosion. In savannas, the carbon flux into the atmosphere may be at least as large as that from deforestation.
Is this fixable? Maybe. For example, in a northern province of Argentina, Santiago del Estero, a team led by Italian soil expert Massimo Candelori reversed desertification in Colonia El Simbolar.
There, his team worked with native plant species to restore the micro-region's bio-diversity and soil quality through a slow, deliberate process of re-vegetation. The plants are still growing and the project is still on-going, but it appears that the process of degradation has been stopped, at least for the time being.
More broadly, agro-ecological practices, making sure cultivation techniques are ecologically appropriate, is the best weapon against desertification: preventing it before it starts.
Rattan Lal, the world's leading soil authority, recognizes the challenges, particularly in poor regions that are also prone to soil degradation. Practices that contribute to soil degradating include removing crop residue for cheap fodder, fuel and fencing; removing top soil for making bricks; and using animal waste for household cooking rather than working it into the soil as natural fertilizer. These are long-held practices, but they can be changed through education. The key, Lal writes, is that "long-term sustainable management of soil must be given priority over the short-term gains."
Desertification is stoppable, if action begins now.