Crop pests and Natural Enemies in Agricultural Landscapes in Relation to Spatial Heterogeneity of Wild Trees and Forests

The conversion of natural habitat for human use such as, agricultural intensification and others cause the simplification of landscape and loss of biodiversity. The fragmentation of landscape may influence the ecological functions like trophic cascades or predator-prey-primary producer interactions either directly or indirectly. This paper presents the review of the major theories in population regulation, island biogeography, and general concepts in brief and some reports of research findings in trophic cascades, population dynamics of natural enemies in agricultural landscape in both temperate and tropical contexts. The result of the review indicated that the heterogeneity of agricultural landscape (e.g. from simple crop habitat to complex natural habitat) determines not only the cross-edge spillover but also affects the magnitude (abundance), direction of flow and diversity of natural enemies and crop pests. As a result, the efficiency of natural regulation of crop pests in top-down and bottom-up processes may vary accordingly. Nevertheless, from the literature I have assessed, I would suggest that further empirical research is needed to get a comprehensive understanding concerning the relationship between natural pest regulation functions (top-down and bottom-up mechanisms) and crop pests in agroecosystem both at local and regional scales. This suggestion may be vital mainly in tropical regions context where the high biodiversity is declining rapidly on one hand and where little information is currently available on the other verge