Using historical records to reconstruct how species presence/absence and altitudinal ranges have changed between 1815 and today.
Above: The northern slope of Tenerife island, with the Orotava valley, The sea of clouds and the Teide peak (3718 m,) climbed by Humboldt & Bonpland (1799) and von Buch & Smith climbed (1815) (Photo: José María Fernández-Palacios).
Humboldt’s most famous illustration undoubtedly is his Tableau physique des Andes, which came out in a French and a Germany version in 1807. Encouraged by the success of this illustration, and wanting to further cement his role as a leading biogeographer, he was interested in applying his concept of distinct altitudinal belts to other high mountains. A natural candidate was Mt. Teide, which he and Bonpland had visited late June 1799, at the beginning of their long voyage.
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Renner, S. S., R. Otto, J. L. Martín-Esquivel, M. V. Marrero-Gómez, J. M. Fernández-Palacios. 2022. Vegetation change on Mt. Teide, the Atlantic’s highest volcano,inferred by incorporating the data underlying Humboldt’sTableau Physique des Iles Canaries. Journal of Biogeography 50(2). DOI: 10.1111/jbi.14503
Humboldt and Bonpland spent only six days on Tenerife and made only 16 collections of which six come from the Teide. None of their 16 collections are linked to precise elevations, which is readily understandable because measuring the altitude of a place above sea level involved complicated formulas to convert air pressure from barometer readings into height a.s.l. Nevertheless, Bonpland collected a violet at the crater rim and observed that it was the highest-occurring flowering plant they saw.
To achieve his goal of linking plant occurrences to altitudes on the Teide, Humboldt had to rely on collections and measurements made by his close friend Leopold von Buch (1774-1853) and the Norwegian botanist Christen Smith (1785-1816), who together visited the Canary Islands and climbed the Teide twice, taking slightly different routes.
Las Cañadas plain ca. 1830, in the route to the Teide ascension from Orotava valley. It can be seen the sparse vegetation existing, product of the herbivory pressure of introduced goats and rabbits (Source: J.J. Williams).
Our study explores how species presence/absence and altitudinal ranges have changed between 1815 and today. We relied on von Buch’s letters to Humboldt, two book-length studies by von Buch, Smith’s diary, and herbarium material Paris, Berlin, London, Copenhagen, and Oslo. The 224 plant names for 179 species shown at different altitudes in Humboldt’s drawing of Mt. Teide by themselves are unreliable because many of them are shown several times are different altitudes, without any explanation.
Based on old maps, roads, and landmarks, we reconstructed the two paths up the Teide taken by Buch and Smith on 18 May and on 25 August 1815. We then compared modern elevation data come from the Canary Is. Biodiversity Data Bank, which includes records for animals and plants in 500 x 500 m Universal Transverse Mercator grid cells, with the occurrences that Buch and Smith noted. These comparisons were only possible because of the extensive local knowledge of members of our team, especially José Maria Fernández-Palacios, José Luis Martín Esquivel,and Manuel V. Marrero-Gómez, who have worked on the fauna and flora of the Teide park for many years.
The Teide peak (3718 m, the highest elevation in the Atlantic Ocean) seen from the south (Photo: José María Fernández-Palacios).
Climate warming on Tenerife is occurring rapidly, with an average temperature increase of 0.14 ± 0.07oC/decade between 1944 and 2010 in the Teide summit region, twice as fast as the rest of the island. However, many abiotic factors have also changed since 1799/1815. Since the establishment in 1954 of the Teide National Park, timber cutting has been prevented and goats, which were abundant during Humboldt’s time, have been eradicated. Other animals, however, have increased in abundance, including European rabbits and European mouflon sheep.
These multiple biotic and abiotic changes made it almost impossible to securely assign cause and effect for the drastic changes in species presence/absence and upper range limit that we found in the 23 species for which the 1799/1815 observations could be georeferenced with sufficient precision. Species have shifted upward, with the average shift being 36.4 m per decade, and four species that today are abundant were not recorded in 1815, suggesting population expansion, probably due to goat eradication.
In many ways, the project was frustrating because of the imprecision of the historic data. Among the outcomes is a list of the species seen in 1815, with up-dated taxonomy and notes (available as online supporting material), and this might in the future be useful for ecological studies of particular species on the Canary Islands.
Written by:
Susanne Renner
Department of Biology, Washington University, Saint Louis, Missouri, USA
Las Cañadas zone ca. 1830, with a goat and her calf and a beehive, indicative of the important use given to this part of the island at that time (Source: J.J. Williams).