Biological Limits on Agricultural Intensification: An Example from Resistance Management

Agricultural intensification could reduce pressures on natural habitats, but biological constraints may mitigate the long-term benefits of improved agricultural technologies. We consider one such constraint: that imposed by resistance to pesticides. The application of pesticides places selective evolutionary pressure on pest populations. Those organisms that survive show resistance. Resistance can be managed by planting ‘refuge areas’ in which susceptible pests breed. We use a simple model to characterize the optimal refuge strategy when a social planner values both agricultural output and natural habitat. We also examine land use consequences. The amount of land devoted to agriculture is an increasing function of the discount rate. A related finding is that more land would be devoted to agriculture when pest resistance must be managed than would be with a hypothetical ‘neutral’ technology affording the same yield-per-hectare as in the steady state, but not requiring the management of any biological stocks.