1. Department of Biology, Nicholas School of the Environment and Earth Sciences, and Center on Global Change, Duke University, Durham, NC 27708–1000, USA.
2. Grupo de Estudios Ambientales–Instituto de Matematica Aplicada de San Luis (IMASL), Universidad Nacional de San Luis and Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET), San Luis 5700, Argentina.
3. Department of Civil and Environmental Engineering, Duke University, Durham, NC 27708, USA.
4. Commonwealth Scientific and Industrial Research Organisation (CSIRO) Land and Water, Canberra, ACT, Australia 2601.
5. Natural Resources and Environment CSIR, Stellenbosch 7599, South Africa.