Non-native Pines Are Homogenizing the Ecosystems of South America

Abstract

A large area previously dominated by native ecosystems in South America is now covered by monocultures of non-native tree species, mainly of the genus Pinus. Currently, pine plantations and the invasions that have been generated from these are causing a homogenization process at the landscape, stand, and even micro-site scales. The continuous and extensive areas covered by pine plantations have replaced the native ecosystem heterogeneity in many landscapes of South America. Within these plantations, the diversity of plants and animals is lower than that of the nearest remnant native ecosystems. These plantations can also act as a barrier to the movement of species across the landscape. In addition, in most places where pine plantations have been established, invasions have occurred into the surrounding ecosystems. Overall, pine invasions are more evident in open ecosystems (e.g., grasslands, steppes, and degraded native forest), but they can also occur in denser vegetation (e.g., temperate forests). Native species loss as a consequence of pine invasions has been recorded in tropical, mediterranean, and temperate ecosystems. Increased pine abundance and the resultant native species loss bring changes to all levels of organization within the ecosystem, from soil microorganisms to invertebrates, plants, and vertebrates. These changes reduce the ecosystem’s spatial heterogeneity and thus cause biotic homogenization. These biodiversity losses can affect the stability of ecosystems by decreasing their resilience to environmental change and disturbances. To mitigate the impacts caused by pines, it is important to implement comprehensive landscape planning, understanding that pine plantations coexist and interact with other land uses in a complex ecological and social setting.