- Scientists say that climate change and high deforestation rates will worsen the severity of landslides across Colombia.
- Regular landslides in the country already have a huge human and economic toll; a disaster in Dosquebradas municipality in February killed 14 people after a heavy rainstorm hit the coffee-growing region.
- Yet scientists say that targeted forest restoration and protection offers an inexpensive way to mitigate landslides, with one study in the Colombian Andes showing that it would be 16 times cheaper to invest in forests than to pay the high costs of repairing destroyed roads, power lines and pipelines after landslides.
- Scientists say that using forests to fight landslides would also have major biodiversity benefits in Earth’s second-most biodiverse nation.
Only aerial footage captures the true scale of the horror: Houses have been flattened, roads ruined, and everything looks like it’s been covered in a film of dark-brown syrup. A sludgy scar down the mountainside shows the trail that a hunk of dislodged rock and earth took in the moments before it upturned the lives of dozens of homeowners in the Dosquebradas municipality of Colombia.
“It felt like the whole world was coming down,” Maria Juliet Lugo, a survivor of the landslide that killed 14 people and left dozens of others hospitalized, told Al Jazeera after a rainstorm hit central Colombia this past February.
Such scenes are becoming all too familiar across the country. Colombia’s undulating, rain-soaked topography makes it a landslide hotspot. Each year, hundreds of landslides wrack the nation; some 30,730 hit between 1900 and 2018. Not all leave untold destruction in their wake, but many do.
In 2017, a downpour in Mocoa, capital of the department of Putumayo, triggered hundreds of landslides and kicked off a debris flow through the city streets, killing 333 people. And in May 2019, a series of mudslides that barreled into the Vía al Llano, Colombia’s major highway, cut the country in two, according to reporting by The Economist. For months, mud and rocks severed supply chains and cut off 1.7 million people living in Colombia’s farming heartland, causing food shortages and rocketing prices.
But to call these purely natural disasters would be wrong; the country’s landslide vulnerability has a man-made twist. Poor urban, land-use and development planning intertwine with geomorphological factors and heavy rainfall to create a hazardous cocktail. But growing evidence points to two other forces adding to the danger: deforestation and climate change.
Fifty-two percent of Colombia’s landmass is covered in forest. Like big, green umbrellas, when standing, the forest canopy provides natural protection from the wind and rain. The underground architecture of deep roots acts like living avalanche barriers, locking loose soil in place and providing a lifesaving service to people downslope.
“The scientific evidence for forests reducing the occurrence and impacts of landslides has a solid base,” Nelson Grima, a researcher at the International Union of Forest Research Organizations (IUFRO), told Mongabay.
But when forests disappear, so does this natural buffer. After illegal ranchers or industrial farmers hack down forests or burn natural vegetation, they leave behind an unstable landscape primed for mass movement. According to one study led by Grima, landslides in Colombia are six times more likely to happen on non-forested than on forested land.
So it’s bad news for landslide risk that between 2001 and 2020, Colombia lost 5.7% of its tree cover, an area of 4.66 million hectares (11.52 million acres). And it’s more worrying still that these high deforestation rates show little sign of relenting in recent peacetime years.
Meanwhile, scientists warn that matters are likely to worsen as climate change turbocharges rainstorms and interacts with deforestation in unpredictable ways. Many paint grim forecasts of intensified deluges battering into naked mountainsides that have been stripped of their natural landslide-mitigation systems. A recent global map pinpoints where more extreme precipitation will slam into unprotected mountains, vulnerable to deforestation, and large swaths of the Colombian Andes lose their green cover.
There may be a way out. Scientists and policymakers are increasingly arguing that targeted forest protection, and in some cases restoration, could provide communities and infrastructure with resilience against climate-worsening landslide risk. And it could also help stanch Colombia’s biodiversity loss.
Forests as a cost-effective landslide prevention system
The idea that forests provide an effective nature-based solution against landslides is not a new one. China’s massive state-sponsored tree-planting program, Grain for Green, has for decades incentivized the revegetation of bare slopes to reduce the risks of soil erosion, flooding and landslides. But the idea is attracting renewed interest under the auspices of the U.N. Decade on Ecosystem Restoration. In a flagship project in the Peruvian Andes, Indigenous communities are restoring Earth’s highest-altitude forests — gnarled fairy-tale forests of Polylepis trees — to capture glacial meltwater and reduce the risk of landslides downslope.
Grima says Colombia, too, has a lot to gain from better managing its natural forests. His research evaluates the costs of paying farmers to protect or restore vegetation alongside key infrastructure. All told, his models demonstrate that it’s up to 16 times cheaper for the public to fork out for landslide-mitigating forests than to pay the high costs of repairing destroyed roads, power lines and pipelines — not to mention the risk to lives. And, according to Grima, even this figure is likely an underestimate.
“[Our] considered costs of ‘repairing infrastructure’ do not consider the economic losses due to the infrastructure not being operative during the reconstruction time,” Grima told Mongabay.
Such expenses can reach into tens of millions of dollars. The Chamber of Commerce in Villavicencio, capital of the department of Meta, estimates that the blocking of the Vía al Llano cost $15 million a day in lost economic activity.
Other researchers have highlighted the tremendous complimentary benefits of using forests to fight landslides in Colombia, especially in the ashy-soiled, landslide-vulnerable Andes, home to much of the country’s human and endemic wildlife populations.
Natalia Ocampo-Peñuela, a conservation ecologist and assistant professor at the University of California, Santa Cruz, started investigating how forests could better protect both people and nature after a landslide shattered a water pipe in 2011, cutting off the water to Manizales, capital of the department of Caldas.
“The town is home to over 400,000 people and most of them were left with no running water for over 10 days, forcing evacuation and total chaos, plus several millions in damages,” Ocampo-Peñuela told Mongabay.
Ocampo-Peñuela and colleague Stuart Pimm knew that cleverly targeted efforts to foil future landslides in the region could also benefit biodiversity, since the world-renowned bird-watching hotspot of Río Blanco Nature Reserve was right on Manizales’s doorstep.
Working with water utility Aguas de Manizales, the two scientists used information on endemic bird ranges and landslide risk to prioritize where landslide-buffering forests could simultaneously prevent future human devastation while safeguarding rare bird life.
According to Ocampo-Peñuela, one of the major advantages of investing in forests is the flexibility they offer as a nature-based solution.
“Actions can take place at very local scales, or they can happen as large efforts to reforest large regions and increase regional connectivity for biodiversity,” she says.
In all, Ocampo-Peñuela’s research identified 154 hectares (381 acres) of restoration sweet spots in the Río Blanco Nature Reserve and 88,600 hectares (218,900 acres) in the wider Central Andes region where focused reforestation could slash landslide risk, protect people and water supplies, and bolster populations of iconic species.
“Conservation and restoration actions that benefit both biodiversity and people are win-win. Resources invested have a double benefit and so you get ‘more bang for your buck,’” Ocampo-Peñuela says.
She adds that policies recognizing these vital connections can have powerful outcomes in a country where biodiverse ecosystems form one of the first lines of defense against landslides.
But as community members in Dosquebradas municipality struggle in the aftershock of Colombia’s latest landslide-driven tragedy, it’s a race to get the potential role of forests in diverting future disasters recognized more widely.
Banner image: A landslide near Manizales in the Central Andes. In 2011, a landslide broke a pipe supplying water from the cloud forests and paramos into city, leaving hundreds of thousands of people without access to water for 10 days. Image courtesy of Natalia Ocampo-Peñuela.
Aristizábal, E., Sánchez, O. (2020). Spatial and temporal patterns and the socioeconomic impacts of landslides in the tropical and mountainous Colombian Andes. Disasters, 44(3), 596-618. doi:10.1111/disa.12391
De Jesús Arce-Mojica, T., Nehren, U., Sudmeier-Rieux, K., Miranda, P. J., & Anhuf, D. (2019). Nature-based solutions (NbS) for reducing the risk of shallow landslides: Where do we stand? International Journal of Disaster Risk Reduction, 41, 101293. doi:10.1016/j.ijdrr.2019.101293
Grima, N., Edwards, D., Edwards, F., Petley, D., & Fisher, B. (2020). Landslides in the Andes: Forests can provide cost-effective landslide regulation services. Science of the Total Environment, 745, 141128. doi:10.1016/j.scitotenv.2020.141128
Li, B. V., Jenkins, C. N., & Xu, W. (2022). Strategic protection of landslide vulnerable mountains for biodiversity conservation under land-cover and climate change impacts. Proceedings of the National Academy of Sciences, 119(2), e2113416118. doi:10.1073/pnas.2113416118
Ocampo-Peñuela, N., & Pimm, S. L. (2015). Bird conservation would complement landslide prevention in the Central Andes of Colombia. PeerJ, 3, e779. doi:10.7717/peerj.779