Short communication Land use change patterns in the Rı ´o de la Plata grasslands: The influence of phytogeographic and political boundaries Ernesto Vega a, *, German Baldi b , Esteban G. Jobba ´ gy b , Jose ´ Paruelo a a Laboratorio de Ana ´lisis Regional y Teledeteccio ´n, IFEVA-FAUBA/CONICET; Av. San Martı´n 4453 (C1417DSE) Buenos Aires, Argentina b Grupo de Estudios Ambientales-IMASL, Universidad Nacional de San Luis/CONICET, Avenida Eje ´rcito de Los Andes 950 1er piso, D5700HHW San Luis, Argentina 1. Introduction Land Use and Land Cover Change (LULCC) is a key component of global change (Dale et al., 2000; Vitousek et al., 1997). Its global importance derived mainly from the impact of the accumulation of small local changes. LULCC may affect climate by modifying water dynamics (Gordon et al., 2008; Nosetto et al., 2005), increasing of greenhouse gases (CO 2 and nitrous oxide) (Searchinger et al., 2008), or changing the surface energy balance (Pielke and Avissar, 1990). Biodiversity is directly affected by LULCC, through the effect of agricultural practices on specific populations (Mattison and Norris, 2005) and habitat losses (Foley et al., 2008). The plains located in the southern portion of the Rı ´o de la Plata Basin in eastern South America (Fig. 1) hold one of the largest area of temperate grasslands of the world, the Rı ´o de la Plata grasslands (RPG onwards) (Soriano, 1991, pp. 367–407; Paruelo et al., 2007, pp. 232–248). Although the RPG is a physiognomically homo- geneous region, eight phytogeographic districts can be identified (Leo ´ n, 1991, pp. 369–387) (Fig. 1). Rı ´o de la Plata grasslands have an area of 3.4  10 6 km 2 at the center-east of Argentina, south of Brazil and Uruguay. The presence of three countries adds an important socioeconomic, political and cultural heterogeneity to the region. A huge transformation process started in century XVI with the introduction of domestic cattle brought by European conquerors and it was accelerated with century XIX farming expansion (Hall et al., 1991, pp. 413–450). Nowadays RPG is perhaps one the regions with highest rates of land use change in the world (Paruelo et al., 2005, 2006; Baldi and Paruelo, 2008). The Agriculture, Ecosystems and Environment 134 (2009) 287–292 ARTICLE INFO Article history: Received 12 May 2009 Received in revised form 30 July 2009 Accepted 31 July 2009 Available online 4 September 2009 Keywords: Afforestation Crop expansion Markovian matrix models Matrix sensitivity analysis ABSTRACT The Rı ´o de la Plata grasslands (RPG) in South America are one of the largest temperate grasslands regions of the world. This region plays a key role in international crop production and land use change rates in some areas are among the highest detected nowadays. Our objective was to characterize the spatial heterogeneity of land use change dynamics in the RPG and to relate it with biophysical and political boundaries. Based on Landsat imagery we characterized land use changes at two time periods (1986– 1990, 2002–2005) and we performed a comparison of markovian models and their properties (stable proportion vector and sensitivity analysis) for each phytogeographic district and country of the region. Temporal transitions between natural and implanted forests (Fo), crops (Cr), and grasslands (Gr) were calculated in order to build matrix probabilistic models. We found that 1.2  10 6 ha of grassland surface has been transformed into implanted forests and croplands (6% reduction of grasslands, 60% increase of afforestations, 3% increase of croplands). Transition probability Cr ! Cr displayed the largest spatial variation, followed by the other three transitions linking croplands and grasslands (Cr ! Gr, Gr ! Gr, Gr ! Cr). The less variable transition rate among districts was Cr ! Fo. Projections for Argentina and parts of Uruguay suggest that grassland loss would continue in most of analyzed territory, whereas in Brazil and parts of Uruguay the projected trend was the opposite, grassland cover would increase. Forested area increment would continue in Uruguay and partially in Argentina, while in Brazil it would decrease. Considering the whole region, crop area would maintain the increasing trends. Transition probabilities for the same phytogeographical district (Northern Campos) differed significantly among the three countries that occupy it, showing the relative importance of human context driving land use change. ß 2009 Elsevier B.V. All rights reserved. * Corresponding author. Present address: Laboratorio de Ecologı ´a Gene ´ tica, CIECO-UNAM, antigua carretera a Pa ´ tzcuaro 8701, col. Ex-Hacienda San Jose ´ de la Huerta, CP 58190, Morelia, Michoaca ´ n, Mexico. Tel.: +52 443 322 2704x42608; fax: +52 443 322 2719. E-mail addresses: ernesto.vicente.vega.pena@gmail.com, evega@oikos.unam.mx (E. Vega). Contents lists available at ScienceDirect Agriculture, Ecosystems and Environment journal homepage: www.elsevier.com/locate/agee 0167-8809/$ – see front matter ß 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.agee.2009.07.011