Sustainability Issue #2 July 2009

The alpine ecosystem and its biodiversity are facing drastic changes as a consequence of the ongoing climate change. Forecasts from the UN Climate Panel IPCC show that warming will occur fastest in the northerly part of the northern hemisphere, something that has already been found in climate stations in Alaska, Canada, Sweden and Russia. The ecosystems of the tundra, adapted to existence at low temperatures and short summers, are at the same time extremely sensitive to changes in the climate, and they are therefore the optimal environments for monitoring the effects.

The aim of this Formas project was to evaluate the function and vulnerability of the most exposed ecosystems. A total of seven ecosystems or environments in the northern Scandes were identified for special investigation, four of which were studied during the project in 2005-08: (1) snowbeds, (2) high alpine fellfields, (3) mesic heaths, and (4) tussock tundra. These environments make up a large proportion of the alpine landscape at the Latnjajaure field station in the Abisco alpine region where this research project was conducted. Of the other three, talus screes, alpine tall-herb meadows and palsa bogs, the last two were left out since they have a low presence in the experimental area and/or have already been investigated in the region. Talus screes were found to be logistically difficult (and sometimes downright dangerous) to work on, but new techniques obtained from New Zealand (William Evans research fellow, University of Otago, New Zealand, January-February 2008) provide possibilities for the future.

At the same time, the biodiversity of talus screes is closely associated with nearby cliff ecosystems, and the importance of cliff ecosystems for the alpine biodiversity became clear later on. During the project, Henrik Antonsson was also involved as the holder of the first doctorate in Sweden in cliff ecology (GU, April 2007).

The results and our work can be summarised as follows:

1. Snowbeds. In the mid-alpine region (elevation of 900-1250 m in the northern alpine region) snowbeds are an important component in the alpine landscape. They provide a lot of ecosystem services to the landscape, such as continual irrigation of, and provision of nutriments to, habitats lower down. Snowbeds are important sites for foraging by snow buntings and alpine ptarmigans, the first of which species has now greatly declined in numbers in Sweden. Snowbeds which melt late have a flora of specialised plant species, many of which are now under acute threat. Robert Björk presented a thesis on the ecology of snowbeds at GU in 2007, and our joint review paper has already been frequently cited.
2. High alpine fellfields. Already in the third report of IPCC in 2001, snowbeds and high alpine fellfields were pointed out as ecosystems under particular threat during the ongoing climate change. In this project, Henrik Antonsson worked on the concept "facilitation" with the focus on cushion-forming moss campion (Silene acaulis). It was found that many other plant species became established in the shelter provided by these cushions in the high alpine region, while there was competition in the mid-alpine region. The tipping point was at 1250 MASL, the present boundary between the mid and high alpine regions, above which vegetation only occurs in patches. This boundary may be drastically raised in the next few decades.
3. Mesic heaths. Mountain birches are spreading upwards in the alpine world. In the mesic heaths (900-1200 MASL) young birch plants are now occurring in large numbers, which are only kept down by winter grazing by hares. In the project, Maja Sundqvist studied other forest species that are "on the march" towards the alpine heaths, such as blueberries, and found that the invasion is not coordinated. Ecosystems as a whole are therefore not on the move, every species is conducting its own race. Maja is today a research student at Umeå University.
4. Eriophorum tussock tundra. This covers over 300,000 square kilometres in the arctic coastal tundra, but in Sweden we have only small remnants. With the decline in permafrost, which is the essential condition for the ecosystem, we have only a few hectares of tussock tundra left in Sweden today, and the prognosis is unfavourable. The dominant species of this ecosystem, the harestail (Eriophorum vaginatum) was nominated as the target system in the international tundra experiment ITEX already in 1992, and shortly after this permanent test sites with control grids and mini-greenhouses were installed at Latnjajaure. After twelve years' monitoring of the tussock tundra (1995-2006), it is seen that boreal species, especially lingonberry, take over the ecosystem when the permafrost disappears and the soil is drained.
5. Cliff ecosystems. The significance of cliff ecosystems for biodiversity in the alpine world became clearer during the project, and a new research programme was generated. These environments comprise 25-40% of the total species richness, ranging over groups of organisms. The proportion of cushion-forming mosses is perhaps as high as 50%. Cliff ecosystems are less sensitive to climate changes than other environments in the alpine region, but may come to play an important part as a "launching pad" for species on the move upwards and as a last outpost for high-alpine specialists. Cliff ecosystems have so far received very little study, either in Sweden or internationally.

Conclusions

The sensitivity of ecosystems to climate changes must be anaysed and evaluated in a landscape perspective. All the components are essential for the retention of a "magnificent alpine environment" but have different functions in the landscape. Their vulnerability is  also highly variable, with snowbeds and tussock tundra as the most sensitive and cliff ecosystems as the most resilient. The various ecosystems all provide different ecosystem services to the alpine landscape, and a holistic approach is therefore essential.

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