Just Planting Trees Won’t Stop March of Deserts
On the World Day to Combat Desertification and Drought, we look at two pioneering ways to stave off the loss of fertile land by challenging the conventional wisdom of merely planting more trees.
Attendance was sparse at a press conference following last fall’s first ever U.N. General Assembly devoted to desertification, as the loss of fertile land in dry areas is known. “If this were about climate change, the room would be full,” Luc Gnacadja of Benin, executive secretary of the United Nations Convention to Combat Desertification, began his remarks to the press.
On the 20th anniversary of the 1992 United Nations Conference on Environment and Development, where the desertification convention was established, it remains a poor cousin to other groundbreaking treaties set up at that same Rio Summit: the Convention on Biological Diversity and the Framework Convention on Climate Change.
Despite the lack of ink, desertification is not a fringe problem. Some facts provided by the U.N. offer a sobering understanding: Drylands—arid, semi-arid, and sub-humid areas with seasonal, often unpredictable rains—account for 41.3 percent of the world’s land mass, including 44 percent of cultivated land. Drylands are complex ecosystems whose utility to humans is vulnerable when land and water are not sustainably managed. Each year more than 30 million acres of productive land degrade into desert. Perhaps surprising to those who see desertification and think Third World, the continent with the highest proportion of its dryland areas termed severely or moderately desertified is North America, at 74 percent.
Desertification is not a “natural” development. It’s driven by human action, such as over-cultivation, deforestation, and poor livestock management. Today 1.5 billion people depend for their food and livelihoods on land that is losing its capacity to sustain vegetation. It’s been estimated that half of today’s armed conflicts can be partly attributed to environmental strains associated with dryland degradation. A number of scholars cite desertification as a key factor in the fall of some civilizations: think Carthage, Mesopotamia, ancient Greece and Rome.
To combat the advance of deserts, most governments and NGOs say planting trees is the best way to halt encroaching sands. As the NGO The Eden Projects (“Plant Trees/Save Lives”) writes on its website, “The world needs to find a way to plant 30 BILLION trees each year, for the next ten years.”
Two field scientists addressing the problem from very different directions, Allan Savory and Chris Reij, say that planting trees will not stop encroaching sands.
“Planting trees cannot reverse desertification in most places because the desertifying land generally has too low a rainfall for full soil cover from tree leaf fall litter,” Savory says, “and exposed soil leads to less effective rainfall.” His solution relies not on trees, but on animals.
Savory was a wildlife ranger in the 1950s and 60s in his home of Rhodesia (now Zimbabwe) and noticed that land set aside for parks was deteriorating. Once-healthy land where herds of grazers (antelope, zebra, wildebeest and the like) and their predators (lions, cheetah, etc.) no longer roamed in large numbers began to degrade upon being “protected” as parkland. He concluded that grasslands, herbivores and pack-hunting predators evolved together, and that the land needed animals in the same way that animals needed the land.
Savory developed a land management process, holistic management, that challenged the conventional belief that grazing can only harm land. The key, said Savory, was to manage livestock to mimic the behavior of wild herds, intensively grazing (and defecating on and trampling upon the ground) and then moving on (as if driven by predators) so that no plants are overgrazed. This rejuvenates the soil so that it retains water and supports a diversity of plant species.
The centerpiece of Savory’s work is Dimbangombe Ranch near Zimbabwe’s Victoria Falls. While the people in neighboring areas depend on international aid, this ranch has used holistic planned grazing and seen a 400 percent increase in livestock (which have been integrated with Africa’s wildlife). There’s now open water, fish and water lilies even after the long dry season. Using the same planning process involving livestock on crop fields, the yields are three to five times higher than neighboring farms with no plowing or fertilizing.
“All we’ve done really is make the rainfall more effective,” Savory says. Holistic planned grazing is now being practiced on more than 40 million acres around the globe. And trees—naturally occurring trees—do have a role.
“As we’re learning at Dimbangombe, as soon as we use properly managed livestock to reverse desertification, trees don’t need planting [by humans] since everything begins growing better—trees, shrubs, forbs and grass.”
Trees bring several benefits to farming: decreasing wind-speed; protecting soil against water and wind erosion; controlling temperature; providing food for livestock. That’s what Chris Reij, a Dutch geographer, explains to people about agroforestry: integrating trees and croplands by relying on the trees to generate naturally, as opposed to planting them. “Agroforestry is the major tool for farmers to adapt to climate change as well as improve food security,” he says, noting that while the sub-Saharan country of Niger suffered a series of crop failures in 2011, the areas with the highest number of on-farm trees did much better.
Reij admires the work of Yacouba Sawadogo of Burkina Faso, featured in the film “The Man Who Stopped the Desert.” “Yacouba had a lot of land that was degraded. Nothing was growing,” Reij recounts. “He took a traditional technique, digging basins, or zai pits. He made the pits deeper, to collect more rainwater, and added manure, to nourish plants, and used these to grow crops and trees. He started a 15-hectare forest this way.”
These trees, he notes, weren’t intentionally planted: “We’re talking about protecting and managing trees that grow spontaneously on farmers’ fields. A lot of tree planting has not been very successful. The survival rate of trees planted in drylands is only about 20 percent. Yet it’s continued year after year despite not such a good track record.”
Savory’s work focuses on areas with low population and low rainfall; Reij’s at the margin of the deserts, with more rainfall, higher population and wall-to-wall agriculture. Between the two approaches, we could cover—and re-cover—a lot of ground.