Bracken Fern Invasion in Southern Yucatan: A Case for Land-Change Science*

Article excerpt

Land-change science seeks to understand land dynamics and their various consequences through an examination of coupled human-environment systems. This synthetic approach is used to address the recent, fourfold spread of bracken fern (Pteridium aquilinum (L.) Kuhn) throughout the cultivated landscapes of the southern Yucatan Peninsula, in Mexico. By joining biophysical, socioeconomic, and remote sensing-geographic information system (GIS) evidence, some of the one-dimensional explanations for the advance and persistence of the invasive species are rejected in favor of those focused on the synergy between human and environmental dimensions of the problem.

Global environmental change and related studies increasingly recognize the usefulness of integrative approaches that address the dynamics of coupled human-environment systems (Kates and others 2001; Steffen and others 2003; Turner and others 2003; Rindfuss and others 2004). Such approaches combine the human, ecological, and remote sensing and GIS sciences (Liverman and others 1998) and have been labeled "integrated land-change science" (Klepeis and Turner 2001; Turner 2003; Moran, Skole, and Turner 2004; Rindfuss and others 2004). Since 1997 the Southern Yucatan Peninsular Region (SYPR) project has exemplified this kind of science in its efforts to understand and model the interactions and consequences of tropical deforestation and agricultural expansion around and within the Calakmul Biosphere Reserve and Mesoamerican Biological Corridor in the states of Campeche and Quintana Roo in Mexico (Turner and others 2001; Turner, Geoghegan, and Foster 2004). The SYPR project early on identified an invasive species, bracken fern, as an important element of land-use dynamics in the region. That role, which is examined in this note, illustrates the kind of understanding that results from using a broadly integrated approach.

Research on invasive species is centered within the ecological community and on how invasion affects ecosystem structure, environmental productivity, biotic diversity, and other factors related to ecosystem function in the face of land-cover change (Elton 1958; Lodge 1993; Vitousek 1994; Vitousek and others 1997; Hobbs 2000; Mooney and Hobbs 2000; Sutherst 2000). Although this research recognizes the human-environment relationships embedded in invasions, most attention to date has focused on the ecological consequences of the invasion, as well as on the resulting land-cover changes (Hobbs 2000). This is attested by the Global Invasive Species Programme and its concern for the effects of biological invasions on ecosystems services (for example, productivity and nutrient cycling; D'Antonio and Kark 2002). Much less attention has been given to assessing the human-environment interactions in which the biological nature of plant invasions is explicitly linked to social, economic, and cultural causes of land transformation.

The Southern Yucatan Peninsular Region provides an ideal setting for the study of human-environment relationships and an increasing plant invasion that threatens forest ecosystems (function and structure), landscapes (homogenization), and human well-being (agricultural production). The region's designation as a hot spot of biodiversity at great risk of deforestation is due in part to the significant growth of its agrarian population since the 1960s (Achard and others 1998). At the same time, much of the region's forest has been set aside as the Calakmul Biosphere Reserve and is now connected to El Mundo Maya, an archaeoecotourism scheme, and to the World Bank and Global Environment Fund's Mesoamerican Biological Corridor (Primack and others 1998; Kaiser 2001; Turner and others 2001; Turner, Geoghegan, and Foster 2004). Plant invasions, which affect ecosystem recovery and household economics, are an important part of land-use change in the region and are closely related to ecosystem function and landscapes. Bracken fern has increased fourfold in the area since 1985, impeding regular succession of the vegetation and increasing the areas under forest opened for cultivation (Schneider 2004). …