Global tree pledge frenzy threatens ancient grasslands


Speed read

  • Grassland experts fear ‘green’ pressures pushing forest agenda
  • Invasive trees threaten global ecosystems, waterways
  • Tree pledge campaigns need to consider what to plant, and where

By: Aisling Irwin

Grassy ecosystems are under fire. Aisling Irwin investigates the world’s booming tree campaigns.

When Madagascans flocked to the country’s barren Central Highlands in January this year to help plant a million trees in a day, botanist Cédrique Solofondranohatra stayed at home.

Vehicles jammed the highway from the capital Antananarivo, the mood was jovial and an estimated 12,000 people turned up in Ankazobe, north-west of the capital. But Solofondranohatra was not in the party mood: she was convinced the tree-planting was destroying an ancient ecosystem. 

Solofondranohatra says that an ancient grassland was being planted – a place whose rich biodiversity is only now being elucidated, and which serves its people best without the disruption of trees. Ancient Madagascan grasslands are, she believes, falling victim to a modern frenzy to afforest the world that has gripped political leaders from Madagascar to Ethiopia and from Turkey to the United States.

“Conservation has moved from ideas of biodiversity to how much carbon can you capture — and then to the idea that forests should be the focus of carbon sequestration.” (Joseph Veldman, ecologist at Texas A&M University, United States)

Solofondranohatra, a PhD student at the University of Antananarivo and Kew Madagascar Conservation Centre, has just published work suggesting that the common view that the grasslands are degraded forest, razed by humankind and in need of replanting, may be wrong.

Instead, at least parts of the grasslands appear to be crammed with species that have evolved over millions of years to live there and nowhere else in the world. That is, it is not somewhere to try and set trees growing, particularly if they are fast-growing alien species such as eucalyptus or pine.

“Knowing that where they were going to put the plantation might have been ancient grasslands, I was not okay with it,” she says.

The robust savannah grass Hyparrhenia variabilis in Ankazobe

As presidents, corporations and billionaires scramble to turn hundreds of millions of hectares globally into forest, ecologists fear that less fashionable ecosystems, and the people who use them, are under threat. They are particularly worried about the open canopy woodlands, savannahs and grasslands that together make up what are known as ancient grassy biomes. Already depleted by agricultural expansion, they may face a second wave of encroachment as the planting of forests gathers pace, with damage to water supplies, long-term social and cultural consequences as grassland ways of life become harder — and even a net loss of carbon.

Forests are seen as “intrinsically more valuable,” says Caroline Lehmann, tropical biologist at the Royal Botanic Garden Edinburgh.

But, they are not the “ultimate ecosystem”, says Guy Midgley, a biologist and grasslands specialist at Stellenbosch University in South Africa.

“There are parts of the world where … they’re not the richest ecosystems in play … In fact, some of these open ecosystems, these grasslands, are incredibly rich with ancient lineages of diversity that have existed for millennia.”

Planting pledges

The number of trees pledged to be planted worldwide can be hard to grasp.

The Trillion Tree Campaign aims to plant a trillion trees; the Trillion Trees initiative aims to conserve or re-grow a trillion.

The Bonn Challenge aims to bring 350 million hectares of the world’s deforested and degraded land into restoration by 2030.  The European Commission is aiming to plant three billion trees.

The organisation 8 billion trees plans to “plant and save” that number; YouTube stunt philanthropist Jimmy MrBeast Donaldson is aiming for 20 million. National presidents are also planting. 

For context, there are thought to be three trillion trees already in the world.

But where are these new trees to be planted? Last year, scientists from the Swiss research institute ETH-Zürich and the Food and Agriculture Organization (FAO) argued there were 900 million hectares of space on the planet where trees could be planted without affecting existing cities or agriculture. A few years earlier, scientists at the World Resources Institute (WRI), in the United States, published an influential digital atlas showing that two billion hectares of degraded land worldwide provided an “opportunity” for restoration.

But critics say vast, empty, plantable spaces mostly do not exist.

Grassland experts have calculated that of the 23 million square kilometres identified in that atlas as  deforested or degraded land that could be restored, nine million square kilometres were actually ancient grassy biomes. These “could be destroyed by misinformed forest restoration projects,” a research group, led by Joseph Veldman, an ecologist at Texas A&M University in the United States, wrote in a 2015 paper. Far from being empty or degraded, these grasslands are supplying the needs of up to one billion people.  

“In order to get to the numbers [in the atlas] you have got to afforest the Serengeti,” says Midgley.

Veldman Map
Overlay of a commonly used biome map with the WRI restoration potential map indicates grasslands and savannahs at risk of being turned into forest. Map co-author Veldman says that although some important savannah regions are missing from the biome map, it offers points of comparison based on the same geographical data used by WRI.

Research such as the WRI atlas has heightened ambition. In Africa, for example, the New Partnership for African Development, NEPAD, has worked with the WRI, the World Bank and the German government to create the African Forest Landscape Initiative (AFR100), committed to restoring 100 million hectares by 2030. Since its creation in 2015 it has been over-pledged by 26 million hectares.

Among some spectacular commitments, Cameroon has pledged to restore one quarter of its land, some 12 million hectares. Madagascar, meanwhile, has committed to four million hectares. This year is a special year for tree-planting in Madagascar with a goal of 60 million trees — a million for each year of independence — of which the 1.2 million seeds and seedlings folded into its red soils on January 19 were part.

Tree hunger

While there are many reasons to restore ecosystems, mostly to do with bringing back their ability to supply human needs such as wood, fish or water, one new imperative stands out: to absorb more carbon.

As the effects of climate change become more tangible by the day, leaders are turning to nature in the hope that it can be enticed to absorb some of the excess carbon dioxide. The ETH-Zürich and FAO scientists controversially calculated that such efforts could absorb the equivalent of two-thirds of the carbon dioxide we need to remove from the atmosphere in order to keep global temperature rises below 2 degrees Celsius. They have now admitted this figure is too high, but it remains a seductive offer for all of us, including companies with budgets targeted at offsetting their production or use of fossil fuels.

“Conservation has moved from ideas of biodiversity to how much carbon can you capture — and then to the idea that forests should be the focus of carbon sequestration,” says Veldman.

“Every new minister wants to do something big and giant especially when Ethiopia announced that they had been planting 350 million trees in a day,” says Lucienne Wilmé, national coordinator for WRI in Madagascar.

In the face of this hunger for more trees, there is a massive search going on for the land on which to plant them. Grasslands can seem the obvious choice. To many, they look like they once held forest and are thus a symbol of humanity’s environmental destruction, says Lehmann.

“They are perceived as trashed ecosystems,” says Midgley. “People say, ‘Oh, there’s enough rainfall here to plant a forest let’s put a forest here!’.”

But grasslands are important in their own right, say their advocates.

Grassland vs tree land

Grassy biomes are shaped by the sun. Where life on the forest floor craves the dim and the moist, life within grasslands thrive on drought, fire or herbivory — depending on latitude.

Just like forests, they vary richly across latitudes. In Africa’s south they can be empty, arid savannahs, pocked by the occasional, fire-hardy tree. Further north, towards the wetter forest boundaries in places such as Zambia and Cameroon, trees are more common, increasing to as much as 60 per cent canopy cover. Crucially, there is always grass — by definition — and there are always gaps between the trees.

And below the height of the grass live tiny plants with miniature flowers whose differences can only be distinguished with a magnifying glass.

Vigna pygmaea, in Mwekera, Zambia. This species flowers after fires fuelled by grasses.

Grasslands are not as charismatic as forests, Lehmann concedes.

“Trees are bigger and have big flowers and they often have animals sitting up in them. In grasslands it’s very hard, if you’re not actually a little bit short-sighted, to differentiate one species of grass from another.”

Put together the search for somewhere to plant trees with the perception of grasslands as being degraded land and you have a powerful agenda. Madagascar President Andry Rajoelina says he wants to turn his country from the so-called “Red Island” into a “green island” — covering it with forest being the symbol of environmental good, says Veldman. But, grassy biomes offer important ecosystem services to those who live in and around them — estimated to be hundreds of millions of people worldwide — and use them for grazing, fuel, medicines and water. “I’m not sure our modern civilisations would be here without grasses, as they underpin global food security,” says Lehmann.


Author: Willem Van Cotthem

Honorary Professor of Botany, University of Ghent (Belgium). Scientific Consultant for Desertification and Sustainable Development.