Finding Evidence of Climate Change

Don Les, professor of ecology and evolutionary biology, is one of nine authors of a new study showing dramatic climate changes, past and present, in the Andes of Peru.

Les identified a 5,200-year-old plant specimen collected at the edge of an alpine glacier in Peru as Distichia muscoides , a member of the rush family and a wetland plant.

The plant in effect "calibrates" the new study of tropical warming, showing that around 5,000 years ago, an alpine glacier in Peru expanded quickly in a sudden cold period, covering a boggy, wetland area.

The study, led by researchers at Ohio State University and published in the Proceedings of the National Academy of Sciences , shows an unprecedented warming trend over at least the past 2,000 years in an alpine region of Peru.

Three lines of evidence are presented of the abrupt change: photographic records of a dramatic retreat of the Quelccaya glacier in the Andes over the period 1978 to 2000; a large increase in the amount of heavy oxygen in the ice cap over the years 1900 to 2000, which correlates with warmer conditions; and the presence of the plant identified by Les, which shows that the climate in the area was rapidly getting colder 5,000 years ago.

The ice had to move fast to cover the plant and preserve it. The ice layer pressed the plant flat, but it retained enough characteristics that Les, who is director of the herbarium at UConn, was able to identify not only its genus, but its species.

The plant, which was radiocarbon dated by the Ohio State geologists, shows that boggy, wet conditions had existed in the area before the glacier advanced.

The OSU researchers found the plant at the edge of the now melting ice cap and, believing it might be an aquatic plant, they contacted Les, who is an aquatic plant expert.

The plant remains sent to him, flattened by the ice and looking like slivers of tree bark, seemed like a long shot for identification, he said.

But he noticed a specific braided pattern to the leaves, which he was able to exactly match to the rush family, and then to the only species that grows in that area of Peru, where it is still prevalent today.

The specimen is now part of The George Safford Torrey Herbarium in the Biology Collections at UConn and can be seen by other scientists who want to verify the tropical warming study. The plant's characteristics can be found in the Biology's Collections online database at http://collections2.eeb.uconn.edu/collections/chp.html .

The plant is the oldest in the collections, which contain 175,000 plants, 750,000 specimens overall, and one of the most complete databases of any biology collection.

The report of the Peruvian warming trend, "Abrupt Tropical Climate Change: Past and Present," appeared during the week of June 26-30 in the Proceedings of the National Academy of Sciences.