Partially self-inflicted environmental disasters and extreme weather events are becoming far more prevalent around the world. Climate change is leading to higher atmospheric temperatures, which allows the atmosphere to hold more water. Extreme weather events and ensuing damage to ecosystems and human populations are projected to worsen with advancing climate change.

The saturation vapor pressure of water in the air is directly related to temperature. This means that even small increases in atmospheric temperature can lead to a substantial increase of moisture in the air. This moisture can then be released in extreme precipitation events. Though seemingly paradoxical, global warming is actually leading to more severe storms, floods and landslides, while also prolonging droughts.

Conversion of Amazon forest into cow pasture

Unsustainable land use exacerbates these disasters, with deforestation driven by cow pastures, industrial monocultures and extractive industries in particular, causing localized soil erosion and degradation that limits the soil’s ability to store water. An intact forest absorbs water in the vegetation and soil, while a degraded forest sends the water away as storm runoff, or some combination of the water with the loose soil. Deforestation has been strongly correlated to increased and more severe flooding events, especially in the developing world. Droughts further degrade the soil through increased evaporation, while torrential rains can wash them away, causing devastating flash floods and landslides.

Mass-scale deforestation also changes regional precipitation patterns, and further enhances global climate change and rising temperatures by emitting carbon dioxide. Cleared lands also no longer sequester large quantities of carbon from the atmosphere within the vegetation and rich soils of the forests.

The Mocoa Flash Flood and Landslide Disaster

In the early morning of April 1st, a landslide swept through the highly deforested municipality of Mocoa, Putumayo in southern Colombia. The destructive partnership of climate change and unsustainable land use was on full display as torrential rains caused vast amounts of water, mud, boulders, trees and everything else in the way, to sweep through entire neighborhoods of Mocoa. With at least 329 confirmed deaths, 70 missing individuals, and another 332 injured, the flash floods and landslides that struck in those early morning hours created the largest “natural” disaster in Mocoa’s history, and the third largest documented natural disaster in Colombian history.

Making this event even more tragic is the knowledge that it was preventable. Globally, events like this are becoming more common because of rising atmospheric temperatures, so mitigating climate change by reducing emissions and capturing more greenhouse gasses from the atmosphere, would reduce the likelihood of these extreme events occuring. Locally and regionally, terrible decisions involving land-use, city planning and the ignoring of alerts and reports in the months leading up to April 1st, allowed the Mocoa disaster to happen.

The high levels of deforestation and land degradation around Mocoa, which lies along an important ecological corridor between the steep lower slopes of the Andes mountains and the lowland Amazon rainforest, are what turned an extreme climatic event into a humanitarian disaster. Over the past 20-40 years, pristine Amazon forest has been converted into mostly cow pasture, around Mocoa and many other parts of the Amazon. Mining, both legal and illegal, has impacted the integrity of the land around Mocoa as well. The Putumayo department, including the region around Mocoa, is also a known hotspot for coca cultivation, coca being the base ingredient for cocaine. Intact forest was cleared to plant these fields of coca. While cow pastures, mining and coca directly led to large amounts of deforestation around Mocoa, this “deforestation frontier” was more fundamentally the result of road construction and perverse Colombian land-titling laws that encourage forest-clearing.

As more of the forest around Mocoa was cleared over the past decades, much of the soil became degraded, losing its function of absorbing, filtering and cycling water and nutrients. These lost “ecosystem services” proved costly when more than a month’s worth of rain fell in the course of a few hours during the late night – early morning of March 31st – April 1st, 2017. There had been advanced warnings, and March 2017 had been an uncharacteristically wet month for much of the Andes and Western Amazon. Approximately 130mm (5.1 inches) of rain fell during the storm, causing the Mocoa, Mulato and Sangoyaco rivers to flood. These flooded rivers mixed with loose soil and storm runoff, sending massive amounts of water and earth hurtling towards the city of Mocoa at incredible velocity and force.

“Flash Flood” – Vannessa Circe – Oil on Canvas – 2018

The climate-change related torrential rains caused flash flooding and landslides that washed away some of Mocoa’s most impoverished neighborhoods. These devastated areas were full of poorly constructed houses along the vulnerable riverbanks, and occupied by many already displaced individuals and families. Residing in these neighborhoods were many displaced indigenous people, including known spiritual leaders from the region that had been forced from their territories by Colombia’s persistent violent conflict and the targeting of social and indigenous leaders by a variety of militant groups.

As a consequence of so many egregious global and local decisions, the uprooted and degraded lands and lives around Mocoa were swept away and buried.

References and Further Reading

Recent publication in Nature connecting increased storm runoff to anthropogenic climate change:

Landslides and Climate Change:

Changes in hydrological cycle linked to both record wet and dry months:

Increased flooding in the developing world:

“Global Catastrophe Recap” from April 2017:

March 2017 was a wet month for the entire region:

Ignored alerts prior to the Mocoa disaster:

Spiritual leaders among the dead in Mocoa disaster: