The massive forest fires that recently swept through Brazil have not spared the vast tropical savannah, but green shoots are already emerging from the ashes there, a testament to the vast grasslands’ rare gift of fire resistance.
The Cerrado, the most species-rich savanna in the world, covers about two million square kilometers of land in central Brazil – almost a fifth of the country’s entire area.
In Brasilia National Park, on the outskirts of the country’s capital, blackened ground and charred tree trunks testify to the ferocity of a fire that destroyed 1,470 hectares of land in September.
Brazil was then in the grip of a record drought – the city of Brasilia had gone 169 days without a drop of rain – which ignited the worst wildfire season in more than a decade, which experts blamed at least partly on climate change. .
But the Cerrado, less known than the neighboring wetlands of the Amazon and the Pantanal, has a superpower: over millions of years it has developed a certain resistance to flames and high temperatures.
– Inverted Forest –
“The Cerrado is an upside-down forest. We only see a fraction of it because the forest is all under our feet,” said Keiko Pellizzaro, an environmental analyst at the Chico Mendes Institute for Biodiversity Conservation, a government agency.
The Cerrado’s deep root system acts like a “pump” that sucks up groundwater “even during extreme drought,” she said.
Meanwhile, above ground, the trees’ thick bark and fruit peel act as “thermal insulators,” says Isabel Schmidt, professor of ecology at the University of Brasilia.
Even when temperatures reach 800 degrees Celsius (1,470 Fahrenheit), vegetation can survive “as if it were just another hot day,” she said.
A month after the recent fires, the first rains caused grass and small plants to grow rapidly, and new leaves sprouted from charred trees in Brasilia National Park.
“Even if it hadn’t rained, we would have seen some resilience,” Pellizzaro said.
“I am amazed at the capacity for regeneration,” said Priscila Erthal Risi, a 48-year-old volunteer who took part in an operation by the Chico Mendes Institute to replant the reserve with native species such as donkey tail and Magonia pubescens trees. .
– Tested to the limit –
Brazilian police are still investigating the cause of the fire in Brasilia National Park.
Most forest fires in Brazil are started by farmers or agricultural industry workers to clear land for grazing livestock or crops.
Schmidt said the Cerrado’s vegetation had always survived sporadic fires caused by lightning strikes during the rainy season.
But she warned that if extreme droughts become more common, the biome’s resilience could be tested.
“The resistance that plants and animals have to any type of fire has evolved over millions of years, but climate change has occurred over decades. No organism can adapt so quickly,” she said.
– ‘Cradle of the waters’ in danger –
The Cerrado is critical not only to the survival of the thousands of species that live there, but also to the water supply of much of South America.
The so-called “Cradle of the Waters” is home to the sources of some of the continent’s largest rivers and aquifers.
But its role as a continental resource is in danger.
With the rainy season starting later and later each year and the amount of rainfall having decreased by an average of eight percent over the past thirty years, the flow of the Cerrado rivers has decreased by 15 percent.
If wildfires become more common, Schmidt warned, “many ecosystems that are more vulnerable to fire,” including in the Cerrado, “simply will not survive.”
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