Transplanting plants

The Swiss Jura landscape, a mosaic of forests, pastures and human settlements is the result of centuries of co-evolution of nature and human activities. Plants continually conquer every niche available to them, while humans graze their herds on pastures, log the forests for wood, rely on the ground for drinking water, and use the rolling hills, lakes and plains for recreational activities. But a changing climate could unsettle the subtle balance that underlies this biologically and functionally rich region, says Alexandre Buttler. He would like to find out what can be done to minimize the impact of climate change on the habitat and resources that mountain ecosystems provide.

These questions have been addressed in over a dozen peer-reviewed articles, featured in three special issues of national and international journals. The articles are the final outcome of Mountland, an ambitious four-year project of the Competence Center Environment and Sustainability (CCES) that brought together researchers, policy makers and farmers from around Switzerland.

Alexandre Buttler is the director of the Ecological Systems Laboratory (ECOS) at ENAC, one of nine teams involved in the Mountland project. As an ecologist, he doesn’t mind getting his and his students’ hands dirty in the field. While others rely exclusively on computer simulations to assess the impact of climate change on plant biodiversity, Buttler and his team of researchers don’t shy away from picking up a shovel.

In a unique field campaign, the ECOS team transplanted blocks of vegetation covered soil from three habitats – densely and moderately wooded, and open pastures – at a high altitude to two lower lying sites. By analyzing the transplants over three years, they were able to observe how the vegetation actually evolves when the average temperatures surrounding them go up by two and four degrees and annual precipitation drops. In the experiment, plants growing on open pastures fared worst, losing up to 40% of biomass, while those growing under moderate or dense tree cover were able to retain or even increase their productivity thanks to the buffering effect of the tree cover.

Mixed pastures with a moderate tree cover are therefore best adapted to sustain biodiversity and forage production in the Jura Mountains under warmer and dryer climate conditions. But the current evolution is going the other way. A historical analysis shows that socio-economic factors such as agricultural subsidies and the price of milk have made small productive pastures more attractive to farmers. As a result, trees are given free reign to encroach onto less productive ones, leading, over the years, to a segregation between open pastures and dense forests, with mixed pastures in a steady decline.

Simulations show that these trends are likely to continue. Using a combined vegetation and socio-economic simulation model, researchers working with Alexandre Buttler attempted to peer into the future and make predictions on how these mountain ecosystems might evolve in the face of climate change. They found that, overall, their functional and biological diversity is expected to decrease in the 21st century. Increasingly open pastures are likely to be exploited beyond their capacity, unsustainably, threatening the balance in this half natural, half artificial mountain ecosystem. Addressing these issues, says Alexandre Buttler, will require innovative and adaptive management approaches, capable of responding to changing environmental and socio-economic conditions. Rather than imposing a single solution onto a diverse area, local conditions will have to be considered.

The Mountland project could be considered a dress rehearsal for the challenges that lie in store for the Jura and other mountain regions in the near future. And according to Buttler, the outcome of the project should be grounds for optimism. It showed that scientists, politicians, agricultural experts and farmers, can work together efficiently to develop new means of addressing these complex challenges. A perfect example of the kind of cross-cutting academic, political, ecological and economic initiative that will make these landscapes more resilient in a changing world.