At 2,520 metres, below the Jatzhorn near Davos, a Norway spruce stands a hand’s height tall. Ten, twenty centimetres. Christian Rixen, a botanist at the WSL Institute for Snow and Avalanche Research SLF, stops to look at it. A little lower, at 2,450 metres, three larches had already surprised him. For a Norway spruce, anything above 2,500 metres is high.
It is a Wednesday morning in August. Rixen and Ingrid Jansen, the project coordinator, are working through one of the 1,104 “flash squares” of Flora Raetica. Each is a hundred metres by a hundred, one hectare, visited one to three times to record every species growing there. Here, between 2,400 and 2,500 metres, among grass and boulders, there are at least 85. The notebook is a smartphone: the records go into FlorApp, the app of InfoFlora, Switzerland’s national data centre for its flora, along with a GPS position and a track of the route walked. The last plant logged that day, at 14:42, is Soldanella pusilla, a small snowbell of acid, silica-rich soils.

The yardstick is a book, the Flora von Graubünden: every plant in the canton, with the places where each had been found. Braun-Blanquet founded phytosociology, the study of plants as communities. Flora Raetica began in 2022 as a working group of twelve, led by Rixen for SLF and by Thomas Wohlgemuth for the Swiss Federal Institute for Forest, Snow and Landscape Research WSL. The group has digitised and georeferenced the old records, giving each one coordinates on a map, and is now comparing them with the present. Fieldwork runs until 2028. The project ends in 2032, a century after the first volume, with an illustrated book and a website.

For Rixen the driver is climate. He explains that the warmer summers of the past fifty years have raised the treeline by about 400 metres, and that the trees are lagging behind. The sentence only makes sense if two things are kept apart. The 400 metres describe how high temperature would now allow trees to grow. They do not describe where the forest has got to. A real forest takes decades to colonise open ground. In the Alps, moreover, centuries of grazing and felling have held it far below its natural limit, and where high pastures are abandoned trees move back up without any help from the climate. WSL itself has set out this distinction in print for twenty years. The Jatzhorn spruce is a clue. On its own it does not measure the shift of the forest.
Warmth does not favour every species either. Many alpine plants need a fixed sum of heat over the year. A scorching summer does not mean more growth for them: they close their season early. On the slope in August, Rixen could already smell the valerian scent of decaying leaves.

The project’s first findings tell a wider story. On 16 September, at the Bündner Naturmuseum, the natural history museum of Graubünden, Wohlgemuth showed some sixty people how much the landscape has changed since 1900. Almost all the cultivated fields around the villages have gone, and with them flax, hemp and rye. Valley floors have lost many wet meadows and stretches of natural river. Lean meadows are now fertilised far up the slopes. Settlements, roads and forest have all grown. The plants followed the landscape. More than fifty new species now grow in the forests, among them trees planted on purpose, such as Douglas fir and northern red oak, and shade-tolerant aliens such as black cherry, Prunus serotina. Along roads and rivers, neophytes, plants brought from other continents after 1492, are spreading; two of them, Himalayan balsam and Japanese knotweed, are actively controlled. The companions of the fields have vanished or grown rare, among them corncockle, Agrostemma githago, and species that lived only in flax fields, such as flax dodder. Several dozen alien species already known around 1900 have left no trace. They never took hold.
The survey also measures rarity. Of the roughly 3,000 species in the canton’s flora, about 400 have so far been found in a single square of five kilometres by five. At the other end stand bilberry and a grass of the genus Koeleria, present in 84 per cent of the surveyed areas. Rixen, in the field, speaks instead of 2,500 species whose past and present positions are known. They may be the ones with comparable historical records, but neither has explained the gap.

The work rests on volunteers. Knowing every plant is not required: the app helps with identification, and newcomers can join the researchers for a trial round. Beyond the flash squares there are smaller missions, such as looking for a rare strawberry on the Hohe Promenade in Davos or rechecking sites of red-listed species. At the end of August a mapping weekend in Tschamut, in the upper Surselva, produced more than 4,800 records of 680 species in three days.
Rixen knows this kind of comparison well. In 2018 he signed, with 52 other researchers, a study in Nature that lined up repeated surveys of 302 European summits over 145 years. The number of species on the peaks was rising, and rising ever faster: between 2007 and 2016 the gain was five times that of the decade 1957–1966, in step with accelerating warming and with no link to the other drivers of global change the authors tested. The data included summits in the Italian Western Alps, surveyed by the University of Turin and the Aosta Valley regional environmental protection agency. More species on a summit is not good news in itself. On the Jatzhorn Rixen asks the question that matters: whether the species climbing from below will end up displacing those already there.
Flora Raetica has not yet published a synthesis with numbers, intervals and methods. The upslope shift of species remains the project’s question, not a measured result. In 2028, with the mapping closed, the data will show how much of that movement belongs to climate and how much to the way people have changed valleys and pastures. For now, below the Jatzhorn, there is a spruce twenty centimetres tall.

References
Bettzieche Jochen, «Auf den Spuren der wandernden Pflanzen» (English version “Tracking the movement of plants”), SLF News, WSL-Institut für Schnee- und Lawinenforschung SLF, 24 September 2026 (press release). https://www.slf.ch/de/news/auf-den-spuren-der-wandernden-pflanzen/
WSL-Institut für Schnee- und Lawinenforschung SLF, “Flora Raetica: Die Flora von Graubünden 1932 bis 2032”, project page, accessed 28 September 2026. https://www.slf.ch/de/projekte/flora-raetica-die-flora-von-graubuenden-1932-bis-2032/
Flora Raetica, “Seit 1900: Neue Arten, verschwundene Lebensräume”, florae.ch, 24 September 2026. https://florae.ch/seit-1900-neue-arten-verschwundene-lebensraeume/
Flora Raetica, “Das dritte Kartierwochenende der Saison ist Geschichte: Tschamut”, florae.ch, 27 August 2026 (figures from the home-page summary). https://florae.ch/
Braun-Blanquet Josias, Rübel Eduard, “Flora von Graubünden”, Veröffentlichungen des Geobotanischen Institutes Rübel in Zürich, 1932–1935 (cited from the project pages; not consulted).
Steinbauer Manuel J., Grytnes John-Arvid, Jurasinski Gerald, Kulonen Aino, Lenoir Jonathan, Pauli Harald, Rixen Christian et al. (53 authors; corresponding authors Steinbauer Manuel J. and Wipf Sonja), “Accelerated increase in plant species richness on mountain summits is linked to warming”, Nature, 556, 7700, 231–234, published online 4 April 2018. doi: 10.1038/s41586-018-0005-6
Hagedorn Frank, Rigling Andreas, Bebi Peter, “Die Waldgrenze. Wo Bäume nicht mehr wachsen können”, Die Alpen, 9/2006, 52–55; online version on waldwissen.net, 10 November 2006.

*Board Member, SRSN (Roman Society of Natural Science)
Past Editor-in-Chief Italian Journal of Dermosurgery