Climate change has had no direct role in Brazil`s worst-ever environmental disaster, but its effects could make a bad situation even worse.
Scientists believe the soil may take centuries to recover from the accident, which released millions of tons of iron ore waste into the River Doce in Brazil´s south-eastern state of Minas Gerais. Many plant and animal species have been wiped out locally.
Some fear that the drought which affects most of Brazil and has already reduced river volumes – and which many attribute to the changing climate – could prevent the river from fully dispersing the toxic matter.
Minas Gerais means General Mines – the mountainous region was once famous for its goldmines, worked by slaves. Today most mines produce iron ore for export to China.
On 5 November an earthen dam at the Samarco mine containing tailings, waste from the ore, collapsed, sending a tidal wave of mud and water roaring through the nearby village of Bento Rodrigues, sweeping away men, women and children. At least 11 people were killed, and 12 are still missing.
The mining company had rejected a recommendation to install a warning siren, saying it was unnecessary, because they could call or text people on their mobile phones.
Over fifty million cubic metres of toxic sludge then swept down the valley and into the Doce. The river, whose name means Sweet, became instead a lethal expanse of stinking orange-brown water, instantly killing every living organism in it and contaminating the water supply of a dozen towns along its course, one of them with over 200,000 inhabitants.
As the sludge made its way slowly downstream, leaving behind a desolate landscape of dead fish and animals, uprooted trees, and a thick layer of solidified mud, scientists said this was Brazil’s worst-ever environmental disaster.
“The loss of habitat is enormous, and the damage to the ecosystem is irreversible”, said Marcus Vinicius Polignano, an environmental health lecturer at UFMG, theFederal University of Minas Gerais.
“Besides iron ore and other metals, the mud, which invaded houses and fields, brought sewage, pesticides and dead animals, which accelerate the production of algae and bacteria.“
So far the government has fined Samarco, administrator of the dam, which is joint-owned by two of the world’s mining giants, the Brazilian Vale and the Anglo-Australian BHP-Billiton, about US$60 million for environmental damage. The company has agreed to pay a further US$300 m to repair damage to the ecosystem.
But the true cost of revitalising the river and the basin´s biodiversity is expected to run into billions of dollars. The company has not yet provided a complete list of the minerals in the mud, apart from iron ore and manganese.
As inquiries into the cause of the dam burst continue, scientists say there could also be lead, cadmium, zinc and mercury, but nobody knows for sure. They fear the Doce’s low volume means a lot of the mud will end up as silt on the riverbed, instead of being carried downstream and dispersed into the ocean.
In August the river fell so low it did not reach the sea, but ended up trickling into a sandbank; in some places it was only three cm deep.
Polignano believes the quantity of tailings in the water is so great that local ecosystems will be unable to recover.
“It is irreversible. They talk of remedying the situation, but in the case of this mud in the rivers, it is impossible, there is no way of removing it from there”.
Marcos Freitas is from the International Virtual Institute of Global Change at COPPE, the centre for engineering research at Rio de Janeiro´s Federal University.
He describes the layer of mud which covers a 30-km radius around the dam as a sterile “floor of iron, a no man’s land”, covering the fields where animals grazed and crops grew.
Biologist Andre Ruschi , director of an environmental research centre in the river basin, says: “There are animal and plant species there that we can consider extinct as from today. It is the biggest environmental disaster in the history of the country.”
For the Krenak indians, who live on the banks of the contaminated river and now have to rely on deliveries of drinking water and food, it is much worse than that. Chief Leomir Cecilio de Souza says: “The river was everything for us, not just water, and fish, but a source of survival and culture.
“Since the time of our ancestors, the river maintained our people. It was sacred. But now it is dead”.
As the tide of mud makes its slow way downstream, the environmental authorities have begun urgent efforts to prevent major damage to the rich marine life in the mouth of the Doce.
The Brazilian navy has joined teams of specialists from Ibama, the government environment agency (in Portuguese only), to try to install the type of barriers used to contain oil spills so as to protect the mangrove swamps. Volunteers have been digging up hundreds of sea turtle eggs buried in the sand to help them hatch and move them to safe beaches.
The disaster has prompted desperate plans to try to save the region´s biodiversity, much of it unique. Local fishermen have been scooping up fish and moving them to lakes before the toxic tide kills them.
World-famous photographer Sebastião Salgado, who was already involved in an ambitious project to restore the now deforested region he grew up in, has proposed a plan to revitalise the area.
Local authorities are talking about a special fund, with money from the mining companies. A group of scientists are raising their own funds to carry out independent studies of the situation and work out how they can restore the Doce basin.
But there is concern about nearly 200 similar earthen dams holding mine waste that could also be at risk, two of them next to the dam that ruptured. NGOs and environmentalists are calling for a tightening-up of mining regulations, instead of present efforts to relax them.
For this they blame the close relationship between mining companies and politicians. Last year the companies were reported to have spent over US$7 m funding politicians’ election campaigns.
There is concern that, despite the River Doce disaster, the result of their lobbying could be a new mining code that benefits rather than regulates the sector.