Month: November 2024

Six thousand years ago, the Sahara, now the largest desert in the world, was grassland. The oscillation of the Earth’s axis turned the Sahara from an orchard to a sandy area where almost nothing can grow. This was a natural process of desertization and is in striking contrast to what is happening now as large areas of the planet are being desertified at an accelerated rate.

According to the United Nations, more than 24 billion tons of fertile soil disappear every year. More than 75 percent of Earth’s land area is already degraded. More than 90 percent could be by 2050.

Human-caused desertification is expected to intensify significantly in the near future as a result of climate change and soil degradation, exacerbated by overgrazing and unsustainable agriculture.

Agriculture in arid areas requires nutritional supplements, imported soil and processed water for irrigation purposes, increasing costs and negatively affecting the environment. It’s a feedback loop – the way we’re doing things now is making things even worse.

Soil doesn’t just become sand because the temperatures rise. Centuries of animal grazing strips vegetation, and local populations tend to clear land for monoculture crops and habitation. Where trees and greenery are removed, so is the land’s ability to retain moisture and its structure. Soil is washed or blown away, and what was once fertile land becomes desert.

But it’s almost impossible to turn a desert back into land fit for agriculture. Or is it? There have been plenty of attempts.

  Gobi,China

China has been fighting desertification for decades. The Gobi is the fastest-growing desert on Earth, transforming nearly 10,400 square kilometers of grassland per year into wasteland.

In 1978, the country launched the Great Green Wall of China initiative, the largest afforestation project in the world, which would see 66 billion trees planted in an effort to combat the expanding Gobi. Spanning 4,500 kilometers, this forest was meant to stop the spread of the desert, buffer sand storms and offset the country’s carbon footprint.

Like many reforestation projects, the Great Green Wall uses fast-growing species like aspen, birch and poplar, none of which are native to China and all of which require large quantities of water: perhaps a less-than-wise choice for a desert environment. Such monoculture ecosystems are also fragile. In 2000, a single disease took down 1 billion poplar trees, setting the project back 20 years.

Even worse, the trees that survive damage the environment. As the trees require so much water, hardier native desert plants are stripped of the little water they were getting in the first place. They die off, the top soil no longer anchored by their roots blows away, and the area has even fewer nutrients than before. The soil structure changes, its capacity to retain water is diminished, and the desert’s expansion marches on.

However, there are also success stories and audacious projects both planned and started.

At the end of the 20th century, China’s deserts were expanding at a combined annual rate of 10,400 square kilometers. Despite the failed Great Green Wall of China, by 2018, they were shrinking at a rate of 2,424 square kilometers per year.

Much of this success can be attributed to the teams behind regreening the Kubuqi and Ulan Buh deserts.

Kubuqi, China

After more than three decades of effort and innovation, one-third of the Kubuqi Desert has been returned to green.

According to a 2017 U.N. Environment Programme report, more than 6,250 square kilometers of the Kubuqi have been reclaimed.

Local knowledge and modern technology have stabilized mobile dunes into semi-anchored dunes covered with green engineering developments. An area of more than 5,000 square kilometers has been afforested through planting programs, and a sand barrier of more than 10 million trees and 4,000 hectares of grass was established to protect the plantation. Another shelter belt of forest was planted along the northern margin of the Kubuqi, along the south bank of the Yellow River: 350,000 hectares of shelter forest in a belt of trees, bushes and grass over 242 kilometers long and 5 to 20 kilometers wide.

Other saline- and alkali-tolerant plants are also used to reduce salt content in the soil and improve soil properties: Lycium barbarum L. or the matrimony vine, another shrub native to China, sea buckthorn, wild olive and the Euphrates poplar all help restore saline-alkali soils.

The Kubuqi Desert was not transformed overnight. Almost three decades have passed since the Kubuqi Ecological Restoration Project started in 1988.

Africa’s Great Green Wall

This African initiative shares the same name as China’s afforestation attempt, but trees are only part of the equation in the Great Green Wall Initiative across the Sahel-Sahara region. Djibouti, Eritrea, Ethiopia, Sudan, Chad, Niger, Nigeria, Mali, Burkina Faso, Mauritania and Senegal have joined forces to combat land degradation and restore native plant life.

The African Union in 2007 adopted the project, conceived as a way to combat the expansion of the Sahara. It has expanded to creating a “mosaic of green and productive landscapes” across North Africa and aims to restore 250 million acres by 2030. Despite security issues and political instabilities, 12 million drought-resistant acacia trees have been planted in Senegal, 15 million hectares of degraded land have been restored in Ethiopia and 5 million hectares each were restored in Nigeria and Niger, with a further 3 million rehabilitated in Burkina Faso through local farming practices.

Can we go faster?

Ulan Buh, China

In 2018, Yi Zhijian’s team from Chongqing Jiaotong University turned 650 hectares of the Ulan Buh Desert in Inner Mongolia from sand to soil. Yi isn’t an ecologist or an expert in horticulture: He’s part of a department of mechanics and says a technique called “desert soilization” can make the surface layer of desert sand stick together by changing its mechanical properties.

The team’s success stems from improving soil with poor mechanics – i.e., where soil particles do not show cohesive behavior.

“Our technique is based on two scientific discoveries,” he writes in The Innovation. “One is that granular constraints determine the mechanical states of a granular material. The other is the relationship between the mechanical properties and the ecological attributes of soil. Sand is turned into ‘soil’ by imposing an omni-directional integrative constraint. The single discrete state of sand is converted into two mechanical states of soil — a rheological state when wet and a solid state when dry — simply by mixing sand with a constraining material.”

The team’s “constraining material”? Modified sodium carboxymethyl cellulosic material or cellulose gum, a common food additive used to thicken or stabilize. It gives the sand the ability to switch between two mechanical states in an endless cycle. This switching ability allows the sand to retain water. Add nutrients and you have instant soil.

Soilization is as simple as churning cellulose into the top layer of desert sand, about 15 centimeters thick, and adding fertilizer. It is then ready for planting. Even better – once soilized, that’s it. The sand is soilized permanently.

“The whole process is simple and fast, applicable for large scale use,” Yi says. “A local biodiverse ecological environment has formed in the Ulan Buh desert experiment. In addition to the kinds of plants growing exuberantly there, it also became home to different kinds of bids, mice, wild rabbits, frogs and worms.”
The 650 acres of soilized Ulan Buh Desert now houses 70 species of thriving plants, including sunflowers and tomatoes, and the biomass yield is generally higher than that grown in natural soil nearby with denser and longer roots. Plus, the pilot project showed that the soilized sand has increasingly better soil properties in the second and third year after planting.

Yi’s team has also been experimenting with its technique in the Sahara, Middle East, Tibet and beaches in China.

Sinai, Egypt

Dutch engineering company The Weather Makers, led by Ties van der Hoeven, has a 20-year plan to transform the Sinai Peninsula from the desert that connects Egypt and Asia to a green paradise.

The Sinai Peninsula is a 60,000-square-kilometer mix of desert, mountains and rocky terrain. It wasn’t always this way: Cave paintings in the region depict trees and plants. Geological and archeological research also suggests the Sinai was once covered by grass, trees and lakes.

John D. Liu is a visiting fellow at the Netherlands Institute of Ecology and a consultant on the Sinai team. He says the Sinai Peninsula looks like a beating heart when viewed from space, with arteries and veins flowing to nurture the body that is the surrounding lands:

“Dust has blown over the Sinai’s denuded landscape for so long that it is hard to imagine it as the biblical ‘Land of Milk and Honey,’ but satellite images and other evidence tell another story. Clues from geologic time, evolution and human history are all etched on the exposed soils. It is possible to see that rivers flowed through the Sinai over vast evolutionary time. Even now, there are periodic flash floods when, because of the degraded landscape, rain that would nurture the land flows immediately into the sea.”

Land without vegetation and the mechanical properties of soil can’t hold water. This is most easily seen in areas that experience drought and then heavy rain: Periods of aridity lead to dry and hardened land, affecting the soil’s ability to absorb rain. Just to compound the problem: When water rushes over land that can’t absorb it, it strips more soil away.

For the Sinai, this soil ended up at the bottom of Lake Bardawil. Lake Bardawil sits to the north of the peninsula, connected to the Mediterranean Sea by two inlets and is no longer the “abundant 40-meter-deep aquatic nursery” it used to be, Liu says. Now, its depth registers at under 2 meters, with hyper-saline warm water. But Van der Hoeven says there’s 2.5 billion cubic meters of silt down there, and this “vast reserve of nutrient-rich material is the solution to all the problems.”

Again, the plan is low-tech: Dredge the lake and put that silt to good use as fertilizer. Increasing the amount of organic matter in the soil helps restore its ability to absorb water. This will also provide nutrient-rich soil for the plants that will regreen the desert.

Removing silt and deepening the lake will also make it cooler and less salty, improving the water quality and restoring the fish population. But Lake Bardawil will remain a salt lake, and the new plants in the desert need fresh water. Enter another low-tech innovation: the imaginatively named “eco machine.”

It’s a bunch of connected transparent plastic water barrels, developed and named by John Todd, creator of the New Alchemy Institute, a Massachusetts-based research community dedicated to sustainable living.

“An eco machine is basically a living technology,” Todd tells The Guardian. “They are solar-driven and reflect the aggregate experience of life on Earth over the last 3.5 billion years.”

Each barrel is a self-contained pond with all the algae, fish, salt-tolerant plants and insects a tiny ecosystem needs. The water flows from one barrel to the next, being filtered as it goes. In the system designed for the Sinai, salt water from Lake Bardawil goes in, and fresh water comes out.

It’s a small system but the Sinai team plans to use it in a network and at a much larger scale. The team believes it should take only five years or so for the regreening plants to start impacting the local climate.

“As the landscape of the Sinai regreens and retains more moisture, a stable hydrological cycle is predicted to return, thus improving conditions for further regreening and agriculture, and by, extension, economic and political stability in the face of anticipated population pressure.”

While any regreening program can proceed only as fast as a plant can grow, there are quicker ways to make deserts fertile again.

While the Kubuqi team used plants to reintroduce nutrients to the soil, a more direct route is possible.

Dubai, UAE

The International Center for Biosaline Agriculture, headquartered in Dubai, has spent nearly two decades researching how plants survive in the type of ecosystems where water and soil quality are low. It has developed techniques that build on ancient farming practices in the desert.

One such technique is turning date palm waste into biochar. There are plenty of date palm plantations in the UAE, and the residual product can be burned into a charcoal to add to the soil. This introduces carbon, a critical element for plant life.

Desert Control is a Dubai-based start-up looking to take the process of regreening from years to hours. The team says its liquid nano-clay (LNC) can turn desert sand into fertile soil ready for seeding and planting in about seven hours. The process is constrained by the rate of crop growth, but the treatment is applied directly on top of the sand and lasts up to five years.

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“Our invention is a new way of mixing clay and water so when it is distributed to the soil, it envelops each sand grain perfectly and spreads in the sand – in one go,” according to the company’s website. “When LNC is applied, the sand turns into a sponge-like fabric that retains moisture and holds the nutrients in the soil much better. You need less water for irrigation and the crop gets more nutrients and grows better.”

Adding clay to the sand creates micropores and increases surface tension. The soil then acts like a net, preventing water and nutrients from seeping away from roots.

Dubai company Dake Rechsand has a technique that works in a similar way, using “breathable sand” that helps desert sand retain water around the roots but still allow air to flow freely. The change in surface tension creates a pool of water on the surface that can slowly be absorbed by plant roots rather than disappearing as water does when poured onto normal sand.

Adding bacteria and fungi into desert sediments also helps create a stronger network of water and nutrients to sustain plants.

We can regreen the desert – but should we?

Afforestation programs in India introduced the invasive Prosopis juliflora shrub to regreen the Thar Desert, and so many Populus and Salix trees were planted in the Ladakh region that a Guinness World Record was achieved. These rapid changes come at a cost, however. In 2019, millions of locusts devastated the greenery across the African and Asian deserts. In India, 170,000 hectares of farms were infested. Pakistan declared a national emergency. The U.N. Food and Agriculture Organization called it a calamity.

Ninad Mungi, research scholar with the Wildlife Institute of India, squarely blames “prolonged rainfall in the deserts.”
“We know that locust outbreaks follow years when plentiful rains brought greenery to the deserts,” says Mungi, who completed his Ph.D. at the Wildlife Institute of India and works at Aarhus University, Denmark, focusing on environmental-management strategies for controlling invasive plants and restoring native ecosystems.

“This species remains dormant in the hot years and swarms only when the deserts turn green. Now imagine if the rains and productions are higher every year. Not just higher but spatially contiguous with farming and plantations,” he says. “It provides a homogenous bountiful resource for locusts to recur more frequently. Did we cook the perfect recipe for this green tragedy?”

Regreening deserts will have profound effects on the planet. Functional, biodiverse ecosystems sequester carbon. In a world looking to transition to a zero-carbon future, locking the atmospheric carbon dioxide into plant life seems the ultimate carbon-capture proposal. But deserts also play a crucial role in balancing the planet’s climate, reflecting up to 30 percent of solar radiation back into space in a process known as albedo. The 70 percent that isn’t reflected sticks around for a short while as heat, but two-thirds of that is emitted back into space as the dry air and clear skies can’t hold it in. This is another key mechanism for cooling the planet that could be affected by increasing vegetation in desert areas.

The team behind the audacious plan to regreen the Sinai says a regreened Sinai Peninsula could significantly alter weather patterns across the wider region: “At present, in summer, the hot, dry Sinai draws moisture-laden north-westerly winds from the Mediterranean out into the Indian Ocean, where it fuels extreme weather events. A cooler, moister Sinai would reverse the direction of these winds, distributing this moist Mediterranean air more locally. This would result in dramatically increased precipitation to surrounding areas such as eastern Egypt, western Saudi Arabia, Jordan, and beyond.”

The team recognizes that any restoration action “must assess the feasibility of intentionally inducing ecological regime shifts and the associated (regional and global) impacts of doing so.”

The question is: If we regreen the Sinai, the Kubuqi, the Rub’ al Khali, what implications will that have for other areas of the world? And can we make those choices without input from the people who will be unintentionally affected? In the Sinai plan, for example, moisture that would have been funneled toward the Indian Ocean should fall as rain across the Middle East and North Africa, but how much would the ecosystems and communities used to getting this rain miss it?

The Sinai team has an answer:

“Like no other, we are aware of the unorthodoxy of regreening desert regions, but rather than be paralyzed by uncertainty, we have joined forces with academics, ecologists and engineers all over the globe to conceive a science-informed, holistic and long-term approach for restabilizing the local ecosystem to its old state – one that is fully biofunctional and regenerative.”

As you might expect, Liu, consultant on the Sinai project, has a similar outlook: “What if this capacity to create change at enormous scale tempered by consciousness and mutual benefit is exactly what [is] needed?”