The Role of Lichens, Reindeer, and Climate in Ecosystem Change on a Bering Sea Island

Archived reports from an international controversy in the early 1890s over management of the harvest of fur seals, Callorhinus ursinus, on the Pribilof Islands in the southeastern Bering Sea provided an unanticipated record of observations on the growth of lichens in association with the prevailing climatic conditions. The abundance of lichens observed in plant communities on the Pribilof Islands prompted the introduction of reindeer, Rangifer tarandus, in 1911. Grazing pressure by the introduced reindeer brought changes to lichen presence in the plant communities of St. Paul Island of the Pribilofs: lichens were depleted, and vascular plants expanded to replace the depleted lichens in a climate that became markedly warmer and drier in comparison to that of the late 19th century. These changes are described primarily through the use of historical documentation. Dominance of lichens in the plant communities on the Pribilof Islands at the time of their discovery and settlement appears to have been a relict of their development in the cooler and moister climate that characterized the southern Bering Sea in the mid-Holocene.