A study conducted on farms in New Jersey and Pennsylvania by professor in the Department of Ecology, Evolution, and Natural Resources Rachel Winfree and colleagues, demonstrated the relationship of diversity in wild pollinators and crop pollination in accordance with spatial scale. The research showed that to provide crop pollination in natural systems, the number of bee species must increase by at least one order of magnitude compared with that in limited scale field experiments.
The study was published in Science. Read more about the research at Rutgers Today.