Large parts of the world are becoming more arid. In the past 30 years, more than three-quarters of all land on Earth has experienced a drier climate, according to the United Nations.
When dry land is degraded by factors including unsustainable land use and prolonged drought, desertification can occur, leading to loss of biodiversity, water scarcity and food insecurity.
Land degradation affects 3 billion people around the world, with this figure set to climb as the climate crisis continues.
But what if there was a way to turn back the clock? ‘Regreening’ projects are taking place on every continent except Antarctica, from the Sahara to the Atacama and the Gobi to the Mojave.
The Great Green Wall
The scale of some of them is mind-blowing. The Great Green Wall initiative, for example, launched by the African Union in 2007, involves restoring 156 million hectares of degraded land across 22 countries spanning the width of Africa.
Originally designed to be a continuous ‘wall’ of forest, it has evolved into a project covering a much larger area. Millions of trees and shrubs have been planted, agricultural terraces and gardens have been restored and thousands of local people have received training to help ensure the project’s long-term success.
Engagement with communities is key and goes both ways, according to Shaun Fitzgerald, director of the Centre for Climate Repair at the University of Cambridge.
“You’ve got to understand the needs of the community, and what they’d be interested in,” he says. “They have a huge amount of knowledge about what it takes to live in some of these areas.”
Restoring biodiversity
While the focus of such work is landscape change, studies are beginning to show there are benefits for biodiversity too. Researchers found more bird species than expected in Koyli Alpha, an area of Senegal restored as part of the Great Green Wall.
Their tally of 198 included rare and vulnerable species such as Rüppell’s vulture and the Abyssinian ground hornbill.
Planting and terrace restoration were also used on the Loess Plateau in western China as part of a programme called Grain for Green, which saw farmers paid subsidies to convert cropland to forest or grassland.
Some 5.6 million hectares of land were restored on the plateau between 1999 and 2020, with startling results: more vegetation meant less soil erosion, better habitats for wildlife and more water held by the land.
But what happened on the Loess Plateau also goes to show some of the risks inherent in this type of intervention. In the early years of the programme, local authorities planted non-native trees chosen for drought tolerance.
These species thrived at the expense of their native counterparts and the wider ecosystem, as they took up more water than was sustainable for the soil.
In the years since, as awareness has grown globally about the impacts of non-native species, it’s less likely that those designing regreening projects would make the same mistake – but there is nevertheless a lesson about how the best of intentions can have unintended consequences.
Regreening can also affect how much solar energy is reflected or absorbed, a phenomenon known as ‘albedo’.
Given that vegetation is darker than bare, sandy desert soils, regreening can result in more sunlight being absorbed, which can create a local warming effect and therefore potentially reduce the associated climate benefits of such projects.
You could argue that, given the complexity of these landscape-scale interventions, it might be better to focus our energies instead on preventing the process of desertification where it’s currently occurring, such as in the Amazon rainforest.
Top image: aerial view of the Danxia landform at the Wave Valley in Yulin, Shaanxi Province of China. Credit: Yang Ena/VCG via Getty Images
