Fires in Brazil and Bolivia trigger 'black rain' across the region

Large swathes of forests, fields, and meadows in Brazil and Bolivia are being ravaged by fires. Smoke carried by the wind is reaching other countries on the continent, such as Uruguay and Paraguay, creating a phenomenon known as "black rain," according to the Spanish-language station BBC.

The threat of "black rain" was highlighted by 44-year-old Brazilian farmer Tiago Klug, who decided to conduct an experiment. He placed a clean white bucket in his yard, away from buildings, to collect rainwater falling "directly from the clouds". The next day, the water in the bucket had a darker than usual tint.

I have never seen anything like this. It was very sad – he told BBC News Brasil journalists.

The "black rain" phenomenon arises when water mixes with soot carried by fire smoke. Meteorologist Estael Sias from MetSul explained that when soot is exposed to moisture, it can become condensation nuclei around which rain droplets gather.

"With the onset of rain, the atmosphere begins the cleaning process. The result is black rain," added Sias. Experts reassure that rain contaminated with soot has a dark colour and can cause staining but is not generally considered toxic.

Black rain can cause damage, but it is believed that the smoke resulted from burning organic matter, such as forests and grasses – said Gilberto Collares, professor of water engineering at the Federal University of Pelotas (UFPEL).

Professor Collares also added, "If, in addition to these components, there were also potentially toxic industrial waste, it would result in what we call acid rain, which is potentially much more dangerous".

According to estimates from the National Institute for Space Research (INPE), fires have destroyed over 21,600 square miles of forest and meadowland in Brazil since August. In Bolivia, over the past three months, more than 14,700 square miles of forests and meadows have burned, prompting local authorities to declare a state of emergency last week.