Climate Change’s Hidden Impact: Landslides

#Climate change could increase likelihood of landslides due to more extreme rain events, more intense wildfires & rising sea levels.

It is easy to view the ground as stable, as fixed, as immovable, even when deep down we know that it’s not. Sometimes the earth seems to shudder, as with an earthquake, and sometimes it pops, as with a volcanic eruption. Other times the earth slips, bits of dirt, handfuls of pebbles, beads of water combining and shifting until they coalesce into a cascade that blocks roads, shears homes from their foundations, and claims precious lives.

This happened in Ecuador earlier this year, when heavy rains triggered a hillside collapse in Quito, killing at least 24 people. It happened in Montecito, California, in 2018, when a type of landslide called a debris flow killed 23 people. And it happened in the Indian state of Uttarakhand in 2013, when roughly 13 inches of rain caused a slope along the eastern snout of a nearby glacier to fail. That landslide, along with the floods that helped trigger it, killed an estimated 6,000 people.

Landslides happen for many reasons, set off by earthquakes, volcanic eruptions, or human behavior. But “probably the most common driver we see for landslides worldwide is rainfall,” Ben Leshchinsky, an associate professor in the College of Forestry at Oregon State University, told me. “Say you have lots of rain. What that effectively does is it reduces the strength of the soil. When that soil strength decreases, it can reach a point where it fails, and naturally just slides away.” And climate change is creating more extreme rain events. The 13 inches of rain that triggered the landslide in Uttarakhand was a more than 400 percent increase over the daily norm of 2.5 inches. Rain is why landslide researchers are warning that climate change may make landslides more likely, and that we are not prepared for this growing risk. In High Mountain Asia, a landslide-prone region that includes Uttarakhand, climate-related shifts in rainfall will increase landslide risk by as much as 50 percent in certain areas, a 2020 study in the journal Geophysical Research Letters found. “These places that were wet and would get the precipitation are now going to get more of it,” Sarah Kapnick, a co-author of the study, said. (Now a senior climate scientist with J.P. Morgan, Kapnick was a research physical scientist at the National Oceanic and Atmospheric Administration when the study was published.) More rain, on its own, might increase landslide risk, but that risk is amplified by the timing of the precipitation—much of which is happening in the summer, when it’s falling as rain, as opposed to earlier in the year, when it would fall as snow. These patterns set the stage not only for more landslides, but for cascading catastrophes.

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