Biodiverse mountain pastures are being overgrown by green alder shrubs. A study conducted by Agroscope and ETHZ shows that hardy sheep and goats can stop shrub encroachment. In particular, the traditional Engadine sheep has a taste for green alder. By debarking the shrub it damages it, thus preventing its spread and protecting valuable alpine pastures.
Mountain pastures are increasingly being encroached by green alder. Over the past 30 years, shrub encroachment has swallowed up around 7% of the Swiss alpine area. Species-rich habitats and valuable grazing land are being lost. For many centuries, goats were the main grazing livestock in the Alps. Because they debark green alder, they effectively prevent shrub encroachment. Goat-keeping is hardly profitable in modern farming, however, and has been all but replaced by cattle and sheep husbandry.
An experiment 2000 metres above sea level
Researchers from Agroscope and ETH Zurich wanted to find out if there are grazing animals which could replace the goats in preventing shrub encroachment. On a mountain pasture in the Engadine valley they observed hardy cattle, sheep and goats that cope well with steep terrain and harsh weather conditions. The animals were kitted out with GPS neckbands to reveal whether they spend time in the brush or on open pasture. The degree to which the animals damaged the shrubs was also measured.
The experiment showed that cattle damage green alder shrubs only slightly. Although they feed on green alder leaves and trample young shrubs, they cannot debark the plants. That, however, is what is needed for the shrubs to die off and for encroachment to be stopped in the long term.
A somewhat surprising diet
Contrast this with the remarkable behaviour of the Engadine sheep – a hardy breed originating in the Engadin valley. Normally sheep are assumed to do minimal damage to shrubs. But the Engadine sheep showed an exceptional predilection for the bark of green alders, and actually damaged the shrubs to a far greater extent than the goats did. Furthermore, the scientists were able to show that goats and Engadine sheep penetrate deep into the green-alder brush, whilst cattle merely visit the edge of the brush and prefer open pasture. Hence, the recommendation of the hardy sheep and goats as caretakers of the landscape on brush-encroached mountain pastures.
Preserving mountain pastures with the right animals
“Our studies show the importance of site-adapted livestock” says Dr Caren Pauler, co-author of the just-published study. “Hardy, traditional breeds produce only small amounts of meat and milk, but they are capable of reversing shrub encroachment on terrain where no machines can travel. In this way, they preserve the beauty and biodiversity of mountain pastures.” According to Dr Pauler, that’s why it is important to make increasing use of these ancient breeds once more.
Caren M. Pauler, Tobias Zehnder, Markus Staudinger, Andreas Lüscher, Michael Kreuzer, Joël Berard, Manuel K. Schneider (2022). Thinning the thickets: Foraging of hardy cattle, sheep and goats in green alder shrubs (link see below)