When trees defy gravity

If you’ve been reading my newsletters of late, you could rightly accuse me of having an obsession for land and rockslides as well as avalanches.

This content was published on December 12, 2019 - 16:49

At least I have been straight up about it. I even titled my last column, “The slippery slope of Alpine farming”. I’ve also tried to explain why the rapid melting of glaciers matters to us all, and described how researchers have wired the Matterhorn to measure the formation of cracks that could lead to deadly rockfall. It all started this spring when I thought it a good idea to inform you of the huge efforts made to keep unstable slopes stable in the Alps, and therefore people, livestock and infrastructure safe.

At the risk of putting myself on a very slippery slope, I have come across new research that may prove to be very useful to prevent landslides and avalanches.

The study authors, interpreting data collected from over 750 landslides in the Alps and pre-Alps over a 20-year period, have for the first time been able to clearly define the kind of forest that can act best as a protective barrier.

A young protective forest has been planted in a clearing made when hurricane Lothar swept through this part of central Switzerland in 1999. © Keystone / Urs Flueeler

Writing in the December edition of the Swiss Forestry Journal, they argued that the ideal forest consists of a variety of species as well as young and old growth.

The findings are important since the subsoil of between 6 and 8% of Switzerland’s surface area is unstable, and with winter rainfall expected to increase due to a warming alpine climate, the risk of landslides will only increase.

If you’ve ever walked through an alpine forest, you may have seen splashes of paint or other markers on trees, signs of Swiss forestry management at work. In autumn and early winter, foresters place an X or other symbol on trees to be culled. The aim is to create space - not clearings - to avoid a domino effect in the case of a single tree falling, and to promote new growth.

What I really admire about the research though is the detail. The experts sought to understand whether there are differences based on the altitude or steepness of the slope. They concluded that the steeper the slope – with inclinations greater than 38° - the better it is not to have any trees at all. This, they explained, is due to the fact that sheer mountainsides are difficult to manage and are therefore often not maintained, leading to a predominance of shallow-rooted spruce.

What else have I been reading?

I’d like to plug our Instagram feed, and a couple of stories we’ve posted on the platform that highlight the dramatic changes to the Swiss climate over the past few decades, and the changes forecast to come.

Our data journalist, Alexandra Kohler, collaborated with her colleagues at Swiss public radio and television, SRF, to mine data from the National Centre for Climate Services, MeteoSwiss, and Federal Institute of Technology, Zurich.

I’d recommend spending a minute of your time to see their Instagram post on how the number of snow days in Zermatt has decreased, and how snow will be an increasingly rare commodity in the popular ski resort.

The journalists also created a hockey stick graph to illustrate the number of days each winter when temperatures in Zurich drop below freezing.

And hot off the press: UNESCO on Wednesday awarded ‘alpinism’ cultural heritage status. The bid for the label was put in by mountaineering and guide communities in France, Switzerland and Italy. Have a look at our news report on the decision.

That’s reason to flag up an article we’re looking forward to publishing next week, on December 20th, by alpinist Dan Moore. He takes a very personal look at the massive development project currently underway in Grindelwald that could turn the Eiger North Face into yet another tourist attraction.

This is my last newsletter of 2019. Thanks for reading. I’ll be in touch again in 2020. In the meantime, happy holidays!

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