Modern intensive agriculture, with its vast monoculture fields of cash crops, may seem rich in terms of yields and profits, but to an ecologist’s eye these fields are rather poor. In terms of species richness, they are downright impoverished.
Species richness is a measure of biodiversity, simply the number of species present. It does not take their abundance into account. A carefully managed, weed-less field of wheat has a plant species richness of essentially 1, whereas a similarly sized area of native grassland may have dozens of species of plants.
In a study published in October in the Annals of the Entomological Society of America, Zi-Hua Zhao, Ph.D., of the China Agricultural University, along with colleagues based in China, the United States, and South Africa, test whether polyculture (growing more than one crop in a field simultaneously) could help farmers manage pests in their fields.
Zhao and colleagues found that the more species of plants in a plot, the more species of insects found there. Crucially, the ratio of natural enemies (insects that prey on crop pests) to pests (which damage plants by feeding on them) increased with the number of plant species in the plot. This ratio is an indicator of the biocontrol services that these natural enemies can provide—a valuable pest management tool. If there are more predators around, they can keep populations of pests from booming.
Read more about his study at Entomology Today.