September 20, 2015, by Tim Radford
Endemic to Ecuador, these nototriche plants are nearly 5,000 metres up Chimborazo
Image: Hans Stieglitz via Wikimedia Commons
In just two centuries many plant species have scrambled 500 metres up the Andes in search of cooler temperatures, Danish scientists say. LONDON, 20 September, 2015 – In 1802, the great explorer Alexander von Humboldt went up a mountain in Ecuador, and made a note of every plant and its elevation as he climbed. In 2012, Danish researchers retraced his footsteps. They found that, in response to global warming, the plants Humboldt recorded had moved more than 500 metres uphill. When Humboldt, whose “physical tableau” became one of the oldest plant data sets in the world, climbed the 6,268-metre Chimborazo volcano the highest plant was at 4,600 m. Naia Morueta-Holme of Aarhus University and colleagues report in the Proceedings of the National Academy of Sciences that they found that the vegetation had gone up in the world. “Right up at 5,185 m, 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,” she said.
The scientists found changes all the way up the mountain. Individual species have moved up 500 m in the last 210 years. Glaciers are in retreat, the snow cover is lighter, and the lower parts of the mountain are now cultivated. Humboldt’s tableau provides an insight into potential response to climate change as a consequence of rising carbon dioxide levels in the atmosphere, driven by fossil fuel combustion by human society. “Even though the plants have kept up on average until now, we see many individual species that are lagging behind, while others – especially common species that are good at spreading and living under many different conditions – are moving upslope. “We can thus expect even more drastic changes in the vegetation in the future, and there are concerns about how the rare and specialised species will survive, particularly in the tropics, where most of them grow,” Dr Morueta-Holme, now at the University of California at Berkeley, said.
And according to a new study in the Proceedings of the Royal Society B, in the far north the Arctic mosquitoes are hatching earlier and growing faster. Lauren Culler of Dartmouth College in the US and colleagues made computer models of mosquito populations as a consequence of climate change and predict that, as Arctic temperatures rise by 2°C, the probability of mosquito survival and emergence from the tundra snowmelt would increase by half. Since Arctic mosquitoes have a reputation for being more than usually ferocious, this could be uncomfortable for the caribou and any other potential donors of a blood meal. And since mosquitoes are also pollinators of tundra plants, and prey for Arctic birds, the overall impact on Arctic ecology could be significant. The scientists used laboratory studies and fieldwork in western Greenland to follow the changing life cycle of the mosquito: warmer spring temperatures caused the creatures to emerge two weeks early and their larval and pupal stages were shortened by 10% for every 1°C increase in temperature. Diving beetles consumed more of the immature mosquitoes, but they were at risk for shorter periods, so overall their chance of survival was greater. At 2°C, the chance of survival increased 53%. And as the insects increased in abundance, and moved further north, Dr Culler predicted “negative consequences for the health and reproduction of caribou.” – Climate News Network
Tim Radford, a founding editor of Climate News Network, worked for The Guardian for 32 years, for most of that time as science editor. He has been covering climate change since 1988.