Climate variability and human impact in South America during the last 2000 years: synthesis and perspectives from pollen records oleh S. G. A. Flantua, H. Hooghiemstra, M. Vuille, H. Behling, J. F. Carson, W. D. Gosling, I. Hoyos, M. P. Ledru, E. Montoya, F. Mayle, A. Maldonado, V. Rull, M. S. Tonello, B. S. Whitney, C. González-Arango