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Nearly 300 people are thought to have died when part of Mocoa, a town in south-west Colombia, was swept away by a torrent of water, mud and debris on 1 April. The trigger for the landslide was a night of extreme rainfall, leading the nation’s president, Juan Manuel Santos, to blame climate change for the catastrophe.

But while the rain, this seems to have been a disaster waiting to happen.

Deforestation in the surrounding mountains, driven by cattle ranchers and by farmers growing coca, the source of cocaine, degraded the environment and helped create the conditions that led to the disaster, says of Kean University, New Jersey.

“The interplay of those factors over the last three decades damaged the soil, making it susceptible to flooding,” Richani says.

The town’s position near a river in a steep-sided valley also put it more at risk. “The lack of urban planning made the population more vulnerable and exposed,” Richani says.

Tragedy predicted

What’s more, the town ignored specific warnings as far back as 2012 about the risk of a major landslide. “This vulnerability was known for at least a few years,” says ecologist Liliana Dávalos of Stony Brook University, New York, whose work first revealed how the drug trade drives deforestation in Colombia.

A 2014 , for example, described how small landslips in the mountains around Mocoa had blocked river channels, leading to a build-up of water in both surrounding soil and fallen debris. It warned of “a tragedy of unimaginable proportions”.

Dávalos is more cautious about blaming coca growing for the disaster. “There is no concrete evidence of coca deforestation contributing to these events,” she says.

But other reports make it clear that the loss of trees related to the cocaine trade is widespread. “There’s been a lot of deforestation in and around Mocoa by farmers, some of them growing coca, which is the raw material for cocaine,” .

Studies by researchers including Dávalos and Richani have shown that the growing of coca and opium poppies is a in some countries.

Coca growers clear paths and roads to their plantations, opening up remote areas for exploitation by conventional farmers, for example. Drug gangs are often involved in illegal mining and logging, too. And they brook no opposition from local people who may want to preserve forests. This process has been dubbed “narco-deforestation”.