Socio-environmental dynamics of biological invasions: The case of Kikuyu grass (Pennisetum clandestinum) in the Cotahuasi Valley, southern Peru

This study examines the ecological, biogeographical, and social processes tied to the colonization of the Cotahuasi Valley of Southern Peru by kikuyu grass (Pennisetum clandestinum), an invasive African plant. It represents a detailed national and local-level study of the idea that, during the modern period (1900-present), the invasion of the Central Andes by biological organisms accompanied transformative political and economic events. It argues that these transformations are associated with the processes of globalization and integration of world regions. Diffusion of kikuyu to Peru occurred amid the inception of national agricultural sciences and education, the expansion of the state apparatus, and pressures by British interests. Peruvian government intervention in the Andean countryside sought to incorporate kikuyu into the creation of modern agricultural systems as practiced in capitalist economies of Western Europe and North America.;The Western Cordillera of Peru contains a distinct micro-environment---the agricultural alluvial fans of the mid-elevation sections (2,000-3,200 masl) of river basins---that resembles biophysical environments of highland East Africa, kikuyu's native range. This similarity is fundamental to the invasion of the Andean valleys by kikuyu. My historical study and field research (January 2000-August 2001 and January 2003) determines that kikuyu invasion has been socially mediated, primarily through land users and government institutions, and spatially differentiated, or patchy. Two distinct agricultural systems in place in the alluvial fans of the Cotahuasi Valley---one supporting participation in commercial markets and the other emphasizing household-consumption---made the invasion of kikuyu a socially and spatially differentiated process. The Chococo alluvial fan in the district of Alca is illustrative of social and spatial unevenness within the Cotahuasi Valley, which results from dissimilar economic objectives and land use practices between the townspeople of Alca and Quechua peasants residing in the villages of Cahuana and Yumasca. The study identifies causation linkages between labor availability and the invasion of agricultural plots. The evaluation of the extent of the invasive cover of plots shows that infestation levels in Alca are the highest, followed by Yumasca, and Cahuana. The factors that explain the unequal levels of kikuyu presence (crop rotation, tenure regime, topography, and plot size) also vary among individual plots within these three study sites.