Ecosystems do not dance on the head of a pin: Consequences of space in ecological pest management

Abstract

Ramón Margalef noted the need to include the space in the metaphors used to understand ecosystems. More recently, John Vandermeer and Ivette Perfecto made a similar call thinking in agroecosystems. In this paper we show some possible effects of space on Ecological Pest Management (EPM). For this we evaluated theoretical models that simulate networks of ecological interactions in agroecosystems. Generalized Lotka-Volterra models were used, where the space is included, or not. In the first place we evaluated (based on field data) the possibility of persistence of agroecosystems that simulate traditional farming systems and monocultures. Subsequently we studied hypothetical agricultural systems. As results we found that: 1) In the case of real systems, only the traditional are persistent; 2) In the hypothetical systems species extinction occurred, although this was markedly minor when the space was taken into account. The results of this research suggest that monocultures are inherently non persistent. They showed a rapid increase in the densities of some species, followed by the total collapse of the system. On the other hand, in the traditional systems bounded oscillations occurred at densities. It is known that traditional agricultural knowledge is threatened and in many places has disappeared. Under these condi-tions, hypothetical systems suggest that for the establishment of complex ecological communities (needed in the EPM) the involvement of several agroecosystems is essential. Under these circumstances, the success of EPM depends on an emergent property at a meta-community scale. This situation may be determined by the participation of more than one farm in the EPM. In the latter case, the possibility of a successful EPM, can be understood as a situation of a Common Good management.