Although most of the world’s species diversity is found in tropical areas, there are very few studies that have examined whether tropical mountain species are affected by climate change to the same extent as temperate species. A new study has now determined that major changes have taken place during the last two centuries.
By comparing the migration of plant communities on the Chimborazo volcano in Ecuador with historical data from 1802, Aarhus University researchers found an average upslope shift of more than 500 metres. The entire vegetation boundary has moved upwards from 4,600 metres to almost 5,200 metres. The main explanation for this dramatic shift is climate change over the last 210 years.
In Humboldt’s footsteps
The German scientist Alexander von Humboldt travelled to South and Central America around the 1800s to map the distribution of plants and to explore what determines the different vegetation boundaries. He collected plants over a period of many years, and his collections led to a better understanding of the link between climate and species distributions, which he described in several works. One of his most noteworthy works was the Physical Tableau, a cross-section of the Chimborazo inscribed with the names of the plants he found on the mountainside.
“Humboldt’s Tableau and the accompanying descriptions make up the oldest known data set in the world of vegetation along elevation gradients. It provided us with a unique opportunity to study how plant distributions have changed in the tropics during the last two centuries,” says Professor Jens-Christian Svenning, Department of Bioscience, Aarhus University, who is one of the authors of the study.
In summer 2012, the team of researchers followed in Humboldt’s footsteps to Chimborazo to map the current distribution of the plants. The fieldwork was carried out at an altitude of up to 5,200 metres.
“Right up at 5,185 metres, we found the last trace of vegetation. A defiant little plant belonging to the sunflower family and half covered in snow – in full flower in spite of the cold conditions, the thin air, and the harsh wind,” says Naia Morueta-Holme, the lead author of the study. The fieldwork was carried out in connection with her PhD studies at the Department of Bioscience, Aarhus University.
Upward shift of vegetation zones
By comparing the two data sets, it became clear that not only the vegetation growth limit has moved, but also the vegetation zones defined by Humboldt. The individual plant species are now found more than 500 metres upslope than they were 210 years ago. These changes in the vegetation are more than expected as a result of today’s warmer climate.
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Mountain landscape image via Shutterstock.