The role of mycorrhizal fungi in preventing landslides

It is well-established that there is a strong inverse correlation between forests and landslides.  In general, careless removal of woodland can increase the susceptibility to landslides, and sometimes the restoration of forest can be an effective way to stabilise slopes.  I sometimes worry that we oversimplify this relationship – for example, restoration of slope stability through tree planting is far from straightforward, and in general requires professional input.  And of course the ways that forests provide improvements in slope stability are far from simple too – indeed as this topic has been investigated in more detail it has proven to be more complex than had been appreciated (which of course is often the way).

Widespread shallow landslides on slopes in New Zealand that have been deforested.

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There is an interesting piece on the Waldwissen.net website about the complexity of this relationship.  This is not a new article – it was published in 2017 – but it points out an issue that I had not considered previously.  The article comes out of a research project undertaken in Switzerland that looked at the ways in which vegetation influences slope stability.  One finding was that plant diversity plays a key role:

“Forests containing a wealth of species, a diverse root structure and trees of various heights and ages are especially effective in increasing soil stability. The study also showed that slopes with ideal vegetative cover and root mass can remain stable up to 5° steeper than bare slopes.”

But the more interesting insight is that Mycorrhizal fungi can also play a key role:

“Mycorrhizal fungi, which live in a symbiotic relationship with plants and trees, can improve the stabilising effect of the vegetation.”

The term mycorrhizal does not refer to a type of fungus, but rather to the symbiotic relationship between different types of fungi and plants.  The concept is that this relationship is key determinant of the ways that plants influence soil structure and texture, and thus the mechanical behaviour of the soil.  The take home message is that improvements in slope stability can be optimised if both the plants and their associated fungi are carefully nurtured.

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Quickslide 1: The village of Gardenstown in Scotland is being affected by a landslide

The Scotsman newspaper reports that a landslide in Aberdeenshire is threatening to close the only access road to Gardenstown.

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Quickslide 2: improving the disaster warning system in Japan

The Asahi Shimbun has a good article about improvements that are needed to the disaster warning system in Japan. This focuses on a clearer set of warnings of the need to evacuate.  There are lessons to be learnt here for many other locations.

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