Comparison of organic and conventional farms: challenging ecologists to make biodiversity functional

With the rise of organic farming in the United States and worldwide, ecologists are being presented with new opportunities to link basic and applied ecology through research on biodiversity and ecosystem services. We present evidence from our own research and a review of the literature to assess the evidence for enhanced insect pest control as a consequence of greater biodiversity on organic farms. Despite the frequency of claims in the literature that biodiversity is beneficial, we found that few studies have measured biodiversity effects on pest control and yield on organic farms compared to conventional farms. Relevant studies in agricultural or natural settings suggest that an increase in the diversity of insect predators and parasitoids can have positive or negative effects on prey consumption rates. We therefore call for a stronger scientific basis for evaluating pest suppression effects due to enhanced natural enemy diversity. We suggest several avenues of research to assess the relationship between biodiversity and effective biological control, to obtain the information needed to manage natural enemy diversity, and to estimate the value-added component of on-farm biodiversity in terms of pest control services.