title: Effect of woody-plant encroachment on livestock production in North and South America.
abstract: A large fraction of the world grasslands and savannas are undergoing a rapid shift from herbaceous to woody-plant dominance. This land-cover change is expected to lead to a loss in livestock production (LP), but the impacts of woody-plant encroachment on this crucial ecosystem service have not been assessed. We evaluate how tree cover (TC) has affected LP at large spatial scales in rangelands of contrasting social-economic characteristics in the United States and Argentina. Our models indicate that in areas of high productivity, a 1% increase in TC results in a reduction in LP ranging from 0.6 to 1.6 reproductive cows (Rc) per km(2). Mean LP in the United States is 27 Rc per km(2), so a 1% increase in TC results in a 2.5% decrease in mean LP. This effect is large considering that woody-plant cover has been described as increasing at 0.5% to 2% per y. On the contrary, in areas of low productivity, increased TC had a positive effect on LP. Our results also show that ecological factors account for a larger fraction of LP variability in Argentinean than in US rangelands. Differences in the relative importance of ecological versus nonecological drivers of LP in Argentina and the United States suggest that the valuation of ecosystem services between these two rangelands might be different. Current management strategies in Argentina are likely designed to maximize LP for various reasons we are unable to explore in this effort, whereas land managers in the United States may be optimizing multiple ecosystem services, including conservation or recreation, alongside LP.
authors.affiliation: Department of Biology, Queens College, City University of New York, Flushing, NY 11367; Schools of Life Sciences, jose.anadon@qc.cuny.edu.
authors.forename: José D
authors.initials: JD
authors.lastname: Anadón
authors.affiliation: Schools of Life Sciences, Sustainability, and Julie Ann Wrigley Global Institute of Sustainability, Arizona State University, Tempe, AZ 85287; and.
authors.forename: Osvaldo E
authors.initials: OE
authors.lastname: Sala
authors.affiliation: Sustainability, and Julie Ann Wrigley Global Institute of Sustainability, Arizona State University, Tempe, AZ 85287; and Geographical Sciences and Urban Planning, and.
authors.forename: B L
authors.initials: BL
authors.lastname: Turner
authors.affiliation: Department of Natural Resource Sciences and McGill School of Environment, McGill University, Sainte-Anne-de-Bellevue, QC, Canada H9X 3V9.
authors.forename: Elena M
authors.initials: EM
authors.lastname: Bennett
mesh_terms: D000818:Animals; D001118:Argentina; D002417:Cattle; D002980:Climate; D003247:Conservation of Natural Resources / Q000639:trends*; D017753:Ecosystem; D004784:Environmental Monitoring; D058751:Livestock; D006109:Poaceae; D014197:Trees; D014481:United States
keywords: food production; global change; social–ecological systems