How to Rewild

Returning Water to the Earth

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Returning Water to the Earth



Over the past century, the sands of the Sahara desert have been creeping ever-southwards, but now we’ve found an ancient method for resisting the spread. 

It’s important to recognise that this desert is a habitat with its own merits, and the dust storms originating here affect air temperatures and deposit minerals across Europe and the Atlantic Ocean. Yet this habitat holds little biodiversity, and its long march south is displacing not only wildlife, but also the human population of the Sahel region.

The dusty Sahel is a transition zone lying between the greener savannah to the south and the dry desert to the north. And it’s here that a huge new project kicked off in recent years – perhaps the most ambitious ecosystem restoration on the planet. The ‘Great Green Wall’ is a sea to sea expanse of forest which will stretch from the Atlantic Ocean in the West to the Red Sea in the East.

Planting Trees in the Desert

You might wonder how it’s possible to plant trees in the desert, and it’s taken many years to develop a system which works effectively. Not only was the planting system a challenge, but everything from terrorism to unstable states and a lack of funds have posed issues for this ambitious project. It has taken longer than expected to reach where we are today, but progress is being made, with an astonishing 20 million hectares of land restored by 2023, according to the UN Convention to Combat Desertification. That’s about the size of the island of Britain.

The mindblowing target of 100 million hectares by 2030 would require $4.3bn per year of investment. But the benefits of this investment are huge – not only is the desert held back, but this massive strip of green land is creating local employment opportunities, which is reducing migration pressure in politically-unstable countries.

Arid sahel zone
Much of the Sahel is a dry and dusty landscape, dominated by Acacia trees, with hard soils

How to Reverse Desertification

So, how are they doing it? One of the systems used is an ancient technique which is now being redeployed in communities across the region. It involves digging crescent-shaped pits into the concrete-hard ground. These crescents run along the contours of the land, so that rainwater pools in them and seeps into the soil rather than running off or evaporating. As the rock-hard soil is broken up, and the rainwater begins to seep into it, underground aquifers are slowly recharged, allowing locals to begin extracting water during the dry season.

The very same pits which allow rainwater to soak in are also ideal for planting crops, trees and native vegetation. And that’s just what the locals are doing, with a bit of expert guidance from the UN. In fact, some of our crop species – wheat and sorghum – evolved in just this kind of dry Mediterranean climate. So they’re perfect for creating productivity, alongside the biodiversity provided by native trees and plants. The cereal crops allow locals to make a living here, while the trees tie the soil together with their root system, and develop a shady canopy which is valuable for livestock and people alike.

Rewilded landscape
In the UK, digging ponds can have a positive impact on the local water table, and recharge the aquifer

The Wider World

The same kind of crescent berm structure is now being used across the world to recover productivity in desert ecosystems. In the U.S., people on low incomes are buying up plots of land in the dry SW and digging these crescents; returning months or years later to plant them out and farm the land. As we’ve already mentioned, there’s important biodiversity to be found in arid, desert ecosystems, but this may be a valuable system of creating productivity in a mosaic landscape.

Even in the UK, digging ponds can recharge aquifers, and create valuable supplies of water for agriculture in dry summer months. However, there’s an important distinction between a pond and a reservoir. A reservoir sits within an existing stream, using a dam to back up the water, while in this context, by a pond, we mean a disconnected body of water, usually dug on a low-lying point in the landscape. Artificial dams can have devastating impacts on local aquatic biodiversity. Which is strange in a way, because beaver dams typically have the opposite effect – they’re more porous, allowing wildlife to slip through.

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