Landslide susceptibility and climate change

Avalanches. Landslides. Mudslides. Landslides are among the most destructive natural hazards on Earth, capable of wiping out entire communities, destroying infrastructure, and altering landscapes in a matter of seconds. Structurally, a landslide occurs when the downward gravitational force acting on a slope exceeds the shear strength of the soil and rock materials composing that slope.

While geological factors like steep topography, weak rock formations, and tectonic activity lay the groundwork for slope instability, atmospheric conditions act as the primary triggers. In recent decades, the frequency, intensity, and geographic distribution of these devastating events have shifted dramatically. This escalation is directly tied to global climate change, which disrupts historical weather patterns, alters the hydrogeological cycle, and destabilizes the fundamental mechanisms that hold hillsides together.

The most direct mechanism linking climate change to increased landslide activity is the intensification of extreme precipitation events. As greenhouse gas emissions trap heat in the atmosphere, global temperatures rise. According to basic thermodynamic principles, warmer air holds more moisture—approximately 7 percent more water vapor for every 1 degree Celsius of warming. This increased atmospheric moisture capacity does not merely result in more total rainfall, rather, it alters the character of precipitation, compressing large volumes of water into shorter, more intense bursts.

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When an extreme deluge hits a vulnerable slope, the water rapidly infiltrates the ground. This process fills the pore spaces between soil particles, causing pore water pressure to spike. As water pressure pushes outward against the soil grains, it drastically reduces the friction that binds them together. Essentially, the soil loses its cohesive strength and behaves like a liquid, triggering devastating debris flows and mudslides.

The impact of climate change on landslides is further compounded by its devastating effects on mountain ecosystems, specifically through the destruction of vegetation. Wildfires, driven by rising temperatures and desiccated landscapes, are burning hotter, faster, and more frequently across the globe. Forests and natural vegetation act as a critical defense mechanism against slope failure. Plant roots form a complex, interlocking matrix that physically binds the soil together, acting as natural anchors.

Furthermore, the canopy intercepts rainfall, reducing the kinetic energy of raindrops and slowing the rate at which water hits the forest floor. When a wildfire strips a hillside of its vegetation, this protective cover vanishes. Making matters worse, intense wildfire heat can create a hydrophobic, water-repellent layer just beneath the soil surface. When subsequent rains hit these burn scars, the water cannot penetrate the deeper ground. Instead, it rushes over the surface, carving out channels, and triggering catastrophic postfire debris flows.

In high altitudes and polar regions, climate change aggravates landslides through a different, yet equally alarming phenomena—the degradation of permafrost and the retreat of mountain glaciers. Permafrost is the ground that remains frozen solid for consecutive years. It acts as a literal frozen cement, binding loose rocks and gravel together across steep alpine peaks. As global temperatures climb, this subterranean ice melts. Without the icy adhesive, steep mountain walls lose their structural integrity, leading to massive rockfalls and avalanches of mixed ice and debris.

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Simultaneously, as glaciers rapidly retreat due to warming temperatures, they leave behind sheer, unsupported valley walls and unstable piles of loose glacial debris known as moraines. Without the physical support of the glacial ice mass, these newly exposed slopes frequently collapse under the influence of gravity or minor environmental triggers.

The escalating threat of landslides under a changing climate creates a perilous intersection with human vulnerability. As global populations expand, urban development continuously encroaches onto marginal, hazardous land, such as steep hillsides and the bases of unstable valleys. The convergence of climate-driven slope instability and rapid, unplanned urbanization significantly increases the risk to human life and global economies.

Mitigating this growing crisis requires a dual approach. Nations must aggressively curb global greenhouse gas emissions to stabilize the climate system while simultaneously investing in robust adaptation strategies. This includes developing advanced early-warning systems based on real-time soil moisture data, implementing stricter zoning laws to restrict building on high-risk slopes, and utilizing nature-based solutions like reforestation to restore the natural engineering capacity of the Earth.

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Climate change is actively shifting the ground beneath our feet, and addressing this unstable reality is paramount to protecting vulnerable communities worldwide.

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Dr. Joel Tiu Maquiling may be reached at jmaquiling@ateneo.edu