Tropical mountains cover 5% of the global landscape yet they supply critical water services to local and downstream users, including flood mitigation, dry season flow for agriculture, and clean water for household consumption. Although many tropical montane landscapes have been managed by humans for centuries and even millennia, we still know little about the impacts of diverse land transitions--forest conversion to pasture, coffee agroforest conversion to monoculture coffee, tree plantation establishment, and recent glacier retreat--on how ecosystems "work" (their function), and in particular how ecosystems cycle water and nutrients.

Given their importance in the hydrologic cycle, tropical mountains are currently focal landscapes for payments for watershed services programs. Through these innovative programs, downstream water users compensate upstream landowners for land management activities that maintain or protect watershed services. In order for these programs to be effective, however, there is a pressing need to understand how changes in the land caused by humans or by climate affect water flows, linkages, and associated nutrient fluxes across these landscapes.

Alexandra Ponette-González (Geography, UNT) and colleagues Erika Marín-Spiotta (U Wisconsin), Kate Brauman (U Minnesota), Kathleen Farley (San Diego State), Kathleen Weathers (Cary Institute), and Ken Young (U Texas, Austin) examined this question by reviewing the findings of scientific studies carried out at high elevations (greater than 1000 m above sea level) in the Latin American tropics. The authors found some surprising results. For example, contrary to prevailing wisdom, many studies did not show much higher levels of runoff from established grasslands than from forests. In addition, tree plantations established on alpine grasslands decreased runoff substantially and appeared to have a much greater relative effect on runoff than did established grasslands. Overall, the group found many gaps in our understanding of water and nutrient cycling in the high-elevation tropics. In their article featured on the cover of Bioscience, they highlight opportunities that exist for future research and the implications of their findings for watershed services programs.

For more information on Dr. Ponette- González's research, you can visit her webpage at http://geography.unt.edu/~agp0040/

Ponette-González, A.G., E. Marín-Spiotta, K.A. Brauman, K.A. Farley, K.C. Weathers, and

K.R. Young. 2014. Hydrologic connectivity in the high-elevation tropics: heterogeneous responses to land change. BioScience 64: 92-104.

Cover Photo: The extinct volcanoes Derrumbadas de Fuego (left) and Derrumbadas de Agua (right) in Puebla, Mexico, loom above early morning fog and over a mosaic of forest plantations, cattle pasture, agricultural fields, and surface mines. Photograph: Matthew Fry, Department of Geography, University of North Texas.