Can tree-growing campaigns curb climate change without harming grasslands?

Everyone from famous primate scientist Jane Goodall to former President Donald Trump and House Republicans in the United States have endorsed the A trillion trees campaign. This international effort to plant and protect 1,000 billion trees, organized by the World Economic Forum, comes in response to climate and biodiversity crises.

But forests are not the only ecosystems worth conserving. Grasslands – from the African savannah to the North American prairie – are conservation’s neglected stepchildren. In fact, grasslands are among the most threatened ecosystems, according to experts. Several are considered “biodiversity hot spots”, A label that conservationists at Conservation International have assigned to 36 endangered regions that each contain thousands of unique plant species and collectively are home to nearly half of the species of plants, birds, mammals, reptiles and animals. amphibians of the world as endemic species or found nowhere else.

The biggest threats to the grasslands are agriculture and mining, according to the International Union for the Conservation of Nature. And some scientists fear that, if carried out poorly, campaigns such as the Thousand Billion Trees could have unintended consequences for the grasslands.

“Almost all the attention, attention and resources are spent on planting trees,” says Leighton reid, environmentalist at Virginia Tech. “Native grasslands are somewhat ignored in this push. And worse, I think the prairies are being destroyed, or are in danger of being. To an untrained observer, grasslands may look like a good target for tree planting, he says.

Misread the landscape

The tahr Nilgiri of India is only found in the grasslands of the Western Ghats [Credit: A. J. T. Johnsingh | CC BY-SA 4.0]

People have already made this mistake. The mountainous region of the Western Ghats in India, along the country’s west coast, is one of 36 biodiversity hotspots. “This is a classic example of an ecosystem that has been completely misinterpreted by the colonial powers,” says the ecologist. Jayashree ratnam, at the National Center for Biological Sciences in India.

In the 1800s, British foresters came to the area and believed that the local people had burned the forests on top of the mountains to create pasture for cattle. In fact, the alternation of forests and grasslands naturally forms a mosaic in the landscape, with hardy grass growing at high elevations where frost and freezing temperatures would kill most native tree seedlings. Ancient pollen buried in the ground shows this landscape to be at least 14,000 years old, Ratnam says.

The Western Ghats as a whole are home to more than 30% species of plants, fish, birds and mammals of the country. And the high grasslands have their own unique plants and animals, including an endangered mountain goat called the Nilgiri tahr that cannot be found anywhere else. But tree plantations have replaced more than half of the area of ​​the mosaic ecosystem at the top of the mountain, Ratnam says. In a mistaken attempt to ‘reforest’ the landscape, UK authorities introduced acacia and eucalyptus trees from Australia, replacing native plants and reducing the habitats of resident animals.

This colonial error could soon be rectified, at least in part. More than 62,000 acres of the Western Ghats could be suitable for grassland restoration, researchers from the Indian Institute for Scientific Education and Research, and the Ashoka Trust for Ecology and Environment Research. they published their discoveries last December in the Environmental management journal.

Restoring grasslands can require significant resources – people have to travel to remote places, uproot invasive trees, and sometimes actively replant native grasses. The Indian researchers therefore used high-resolution satellite images to identify places where the invasive trees had not completely passed the grass, and where young trees or sparse trees would be easier to remove.

The duality of fire

A maned wolf sits in the grass

South America’s Cerrado grasslands, home to maned wolves and many other species, are fire adapted [Credit: minka2507 | Pixabay license]

For the Brazilian Cerrado – a vast meadow that is home to giant armadillos, maned wolves and more than 800 species of bees – expansion of agriculture is the biggest threat. But a resolute focus on forest conservation can endanger grasslands in subtle ways.

The Cerrado has adapted to withstand periodic forest fires, and some plants even depend on fire to reproduce. Many grasslands have adapted to fire, explains Giselda Durigan, environmentalist in Brazil Florestal Institute. But in response to deforestation in the Amazon rainforest, she says, Brazil’s conservation policy has been to suppress fires across the country. In addition to fighting forest fires in the rainforest, the government has at times issued blanket fire bans that extend to prescribed burns intended to help conserve grasslands.

Forest fires only occur naturally in tropical rainforests every 100 or 200 years, according to Durigan. Rainforest trees are not fire-friendly, and man-made fires to clear land for agriculture are causing obvious devastation in the Amazon. Grasslands, however, can burn naturally every year during the dry season. In the absence of fire, the trees expand from small isolated plots to other areas of the Cerrado region. They literally eclipse shorter grasses and shrubs, outdoing them for sunlight.

“Sometimes the fire is good and sometimes the fire is really bad,” says Durigan. “If it’s difficult for scientists, can you imagine how difficult it is for policy makers and for society as a whole to understand? “

As in the Western Ghats of India, restoring the Cerrado will take some effort, but the Brazilians are trying. Durigan and other scientists are experimenting with prescribed burns, with recent government support. In recent years, a group called Cerrado Restaurant has also built a network of 40 local families in the Cerrado region who can cultivate and provide native grass seeds for restoration projects.

Hope for meadows and forests

An elephant crosses the savannah

Large mammals like elephants help keep South Africa’s grasslands healthy [Credit: Jetiviri | Pixabay license ]

Regions where people understand grasslands better include the iconic African savannas, grassland ecosystems that cross the continent in two distinct bands just north and south of the equator.

“I think Africa deserves a lot of credit for what it has done with small budgets,” says Guillaume Bond, biologist at the University of Cape Town.

In South Africa, for example, the government values ​​grasslands and actively conserves them, Bond says, allowing savannas to periodically burn and protecting elephants and other large herbivores in large nature reserves like the Kruger National Park. Both fires and herbivores limit the amount of trees that grow in the savannah, allowing grasses to thrive in their place.

For their part, the leaders of the Trillion Trees campaign are aware of the concerns about the prairies. The initiative itself does not plant trees, but rather connects local organizations with donors and supporters around the world, explains Justin adams, director of the Tropical Forest Alliance of the World Economic Forum. And the Trillion Trees initiative goes beyond just planting trees, he says. It aims to inspire conversations about reforestation in the right places.

At the same time, efforts to protect and restore grasslands internationally are gaining momentum. Recently, Kew and Botanical Gardens Conservation International published a list of 10 rules to guide responsible reforestation. Trees should not be planted on wetlands and grasslands, they say, noting that these ecosystems also store carbon.

In fact, grasslands are a particularly safe and resilient form of carbon storage, says Reid, the environmentalist at Virginia Tech. Droughts and fires exacerbated by climate change are conditions for which grasslands have evolved, he explains. Grasslands store most of their carbon underground in extensive root systems and soils, safe from forest fires, and grow back quickly after such disturbances. It is estimated that the Cerrado alone stores about 13.7 billion metric tons of carbon, which is roughly equivalent to the emissions a year from more than 12,000 coal-fired power plants.

And on June 5, the United Nations will kick off its 2021-2030 Decade of Ecosystem Restoration, which encompasses both grasslands and forests as well as other ecosystems. Prior to this global campaign, Durigan and Bond published a paper with several co-authors, describing the research needed to effectively restore grasslands.

Given the perilous state of the climate, trees are a powerful symbol for connecting people with nature and offer hope for tackling massive problems on the planet, Adams says. Now, less charismatic but no less natural or important grasses are also starting to do their part. Campaigns like the One Trillion Trees initiative and the Decade of Ecosystem Restoration, he adds, are “restoration of hope in addition to restoration of landscapes”.

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