VEGETATION SUCCESSION IN RELATION TO GLACIAL FLUCTUATION IN THE HIGH MOUNTAINS OF AFRICA

Abstract

Dramatic changes are taking place in the glacier-covered high mountains of Africa. The glacier-covered area on Kilimanjaro is now only half as large as it was in the 1970s. The Tyndall Glacier on Mt. Kenya, which retreated at approx. 3 m yr–1 from 1958 to 1997, retreated at ca. 10 m yr–1 from 1997 to 2002. Pioneer species such as Senecio keniophy- tum, Arabis alpina, mosses, lichen, and Agrostis trachyphylla have advanced over areas formerly covered by the glacier. The rate at which this vegetation migrated up the former bed of the glacier (2.1–4.6 m yr–1 from 1958 to 1997) is similar to the rate of glacial retreat (2.9 m yr–1). In the interval from 1997 to 2002, pioneer species advanced at a rapid rate of 6.4 –12.2 m yr–1 when the glacier retreated at 9.8 m yr–1. Rapid glacial retreat has been accompa- nied by rapid colonization by plants. Pioneer species improve soil conditions and make habi- tat suitable for other plants. If warming continues, alpine plant cover may extend all the way to mountain summits, and then eventually diminish as trees colonize the areas formerly occupied by the alpine plants. Larger woody plants such as Senecio keniodendron and Lobelia telekii, which showed no obvious advances before 1997, have advanced quickly since 1997.