Skadeinsekters populationsdynamik i ett heterogent jordbrukslandskap

Sammanfattning: Chemical pesticides have long been used to keep crops free from pests, but in modern agriculture biological control is viewed as a viable alternative to pesticides. The concept of biological control is to implement predators that feed upon the pests. It can however be difficult to follow the effects of the biological control in the field, which is why a theoretical mathematical model has been designed to estimate the impact of biological control on the population dynamics in a heterogeneous farmland. Six different scenarios, each consisting of two habitats, have been set up in order to answer questions related to population dynamics and what factors might affect the population size for pests and predators. Each scenario has a different setting which is designed to answer the questions in this study. According to the model the species that have lower competition and predation pressure are more likely to succeed and grow to larger population sizes. These factors correlate to the niche width and the traits of the species and how much they overlap with each other, where a higher overlap increases the competition and predation pressure. The proliferation of the species in the system affects how many individuals of a population spread to another habitat, but it does not affect the balanced state if the change is the same for all species. Since the ecosystem in the model strives to achieve a balanced state, some pests will always remain in the system. This could be seen as a drawback with biological control as it does not eradicate the pests completely.