This iconic Humboldt map may need crucial updates

An influential diagram of plants growing on the slopes of some Andes Mountains needs an update, scientists say. Created 212 years ago by German explorer Alexander von Humboldt, the Tableau Physique is still used to study how plant ranges have shifted due to climate change.

But the original diagram contains some big errors — including that some of the highest-altitude plants described as growing on one volcano were actually found on a different mountain, researchers report online May 27 in the Proceedings of the National Academy of Sciences. Humboldt continually revised and refined his diagram, but the revisions are less well-known. So modern researchers might not be using the most accurate data, the team says.

Humboldt, a geographer, geologist and cartographer, produced 23 volumes of observations from his travels around the Americas from 1799 to 1804 (SN Online: 2/24/19). (This year is the 250th anniversary of the scientist’s birth.) The 1807 Tableau Physique marked a new kind of scientific visualization, combining physical and ecological data from two Ecuadoran volcanoes, Chimborazo and Cotopaxi.

Researchers led by geographical historian Pierre Moret of Toulouse University in France pored over later works by Humboldt and his colleagues. Those documents included updated elevation estimations and high-altitude vegetation catalogs. In particular, the researchers found that much of the data about high-altitude plants on Chimborazo were actually collected on a different volcano, Mount Antisana. That alters the findings of some previous research, such as a 2015 study that determined that plants had marched at least 500 meters up Chimborazo’s flanks over the last 200 years. 

The new paper underlines the need for caution in using historical data to document long-term change, Moret’s team says. That’s especially true with highly influential works such as the Tableau Physique.