Global warming means more extreme weather. By now this is pretty well-established, and we’ve had a look at the implications of that with the increase in droughts, fires, powerful hurricanes, floods, and so on. What does that mean for the landscape around us? Droughts tend to make a place more vulnerable to flooding and erosion, for example, because they kill off the plants that would otherwise stabilize the soil and absorb water during a storm. When it comes to mountains, the main prediction I’ve heard is that they’ll dry up, both from losing seasonal and multi-year snow and ice, and also from warming-fueled increases in both evaporation and transpiration. Beyond that, I hadn’t really thought about it a whole lot. Thankfully, a team of researchers from the University of the Witwatersrand have been thinking about it, and their research has some warnings that we’d do well to heed going forward:
Under the threat of climate change, mountain landscapes all over the world have the risk of becoming more hazardous to communities surrounding them, while their accelerated evolution may bring further environmental risks to surrounding areas.
This is according to a scientist from the University of the Witwatersrand in Johannesburg, South Africa, who, on the eve of the COP27 climate meeting, highlights the sensitivity of mountains to global climate change in a new study. Professor Jasper Knight, from the School of Geography, Archaeology and Environmental Studies at Wits University shows how complex mountain systems respond in very different and sometimes unexpected ways to climate change, and how these responses can affect mountain landscapes and communities.
“Worldwide, mountain glaciers are in retreat because of global warming and this is causing impacts on mountain landforms, ecosystems and people. However, these impacts are highly variable. The latest report by the Intergovernmental Panel on Climate Change (IPCC) treats all mountains as equally sensitive and responding in the same way to climate change. However, this approach is not correct,” says Knight.
“Mountains with snow and ice work completely differently to low-latitude mountains where snow and ice are generally absent. This determines how they respond to climate and what future patterns of mountain landscape evolution we can expect.”
The research also shows how climate change will negatively impact on mountain landscapes and human activity. This includes an increasing risk of hazards such as avalanches, river floods, landslides, debris flows and lake outburst floods. These are made worse because of glacier retreat and permafrost warming. Alpine ecosystems and endemic species are already threatened with local extinction and mountain slopes are becoming greener as lowland forests spread to higher altitudes.
“As snow and ice shrink, mountain land surfaces are getting darker and this dramatically changes their heat balance, meaning they are warming up faster than the areas around them. Therefore, climate change impacts are bigger on mountains than they are anywhere else. This is a real problem, not just for mountains but also for the areas around them,” says Knight.
“Despite not having significant snow or ice, African mountains are also vulnerable. Our work on climate and landscape change and human adaptations in the Maloti–Drakensberg shows how mountains and people are connected together, and these are also threatened. Understanding these connections can help us better protect them against the worst impacts of climate change,” says Knight.
It seems that as the climate becomes less stable, so does the earth under our feet, which is less than comforting. I remember, a while back, when nobody I knew was particularly worried about global warming causing earthquakes or volcanic eruptions. I don’t know if my perception was accurate, or born of ignorance, but at this point I’m of the belief that global warming will cause earthquakes and volcanic eruptions, if it has not done so already. There’s simply too much mass moving around for it to not occasionally tip the balance. Maybe it will only changing the timing of an earthquake that would have happened anyway, but I honestly expect more than that. We’ve seen how things like fracking can cause earthquakes without the presence of a fault line, and when you consider the amount of weight that’s shifted during a mudslide, landslide. or avalanche, it seems reasonable to me that that could introduce new pressures to the landscape. If those events start happening regularly in a given area, either because of changes in precipitation, or because of melting ice, it seems like that would have to cause something eventually, similar to how glacial retreat has been linked to earthquakes.
Of course, I’m not breaking any new ground here, as this Guardian article from 2016 demonstrates:
In a similar vein, it seems that the huge volume of rain dumped by tropical cyclones, leading to severe flooding, may also be linked to earthquakes. The University of Miami’s Shimon Wdowinski has noticed that in some parts of the tropics – Taiwan included – large earthquakes have a tendency to follow exceptionally wet hurricanes or typhoons, most notably the devastating quake that took up to 220,000 lives in Haiti in 2010. It is possible that floodwaters are lubricating fault planes, but Wdowinski has another explanation. He thinks that the erosion of landslides caused by the torrential rains acts to reduce the weight on any fault below, allowing it to move more easily.
It has been known for some time that rainfall also influences the pattern of earthquake activity in the Himalayas, where the 2015 Nepal earthquake took close to 9,000 lives, and where the threat of future devastating quakes is very high. During the summer monsoon season, prodigious quantities of rain soak into the lowlands of the Indo-Gangetic plain, immediately to the south of the mountain range, which then slowly drains away over the next few months. This annual rainwater loading and unloading of the crust is mirrored by the level of earthquake activity, which is significantly lower during the summer months than during the winter.
And it isn’t only earthquake faults that today’s storms and torrential rains are capable of shaking up. Volcanoes seem to be susceptible too. On the Caribbean island of Montserrat, heavy rains have been implicated in triggering eruptions of the active lava dome that dominates the Soufrière Hills volcano. Stranger still, Alaska’s Pavlof volcano appears to respond not to wind or rain, but to tiny seasonal changes in sea level. The volcano seems to prefer to erupt in the late autumn and winter, when weather patterns are such that water levels adjacent to this coastal volcano climb by a few tens of centimetres. This is enough to bend the crust beneath the volcano, allowing magma to be squeezed out, according to geophysicist Steve McNutt of the University of South Florida, “like toothpaste out of a tube”.
As I like to say, we should be viewing this as though we’re trying to survive on a partially terraformed alien planet. We need to avoid danger zones, relocate when an area becomes hostile, and build with the expectation that the planet is going to to make things harder. I don’t think this means that everywhere is now in danger of earthquakes and volcanic eruptions, but I think it’s reasonable to assume that activity will change where it currently exists, and not out of the question that we might get some new activity. The frightening truth is that the world isn’t as stable as we once thought.
“The land is all too shallow
It is painted on the sky
And trembles like the wind-shook rain
When the Raven King passed by”
-Susanna Clarke, Jonathan Strange & Mr. Norrell
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