Organic farms harbor a greater diversity of soil microbes and insects, which could combat the threat of deadly foodborne pathogens, according to a new study.
Write in the Journal of Applied Ecology, a team of international researchers explain that the spread of pathogens, such as feces E.coli bacteria, on farmland, has caused thousands of deaths and millions of illnesses worldwide. This has prompted farmers to remove natural habitats such as hedgerows and ponds from their land, as they are thought to attract the wild and domestic animals causing the problem by fouling nearby crops with their disease-causing droppings. Although this more simplified view of agricultural land may threaten biodiversity and reduce crucial ecosystem services like pollination, it is nevertheless considered an essential measure for food security.
Yet the new study actually reveals the opposite, showing that as wild habitat disappears, so do microbes and insects – like the ever-industrious dung beetle – which can actually to help to eradicate pathogens from the soil.
To make the discovery, the researchers studied 70 commercial fields of broccoli — a crop susceptible to foodborne pathogens because it is grown close to the ground — in the western United States. They compared conventional farms and organic farms, where wild features were kept intact and pesticide use minimized. By scattering pig droppings over these plots to attract dung beetles that feed on the droppings, they found that organic plots supported higher numbers of these insects. On these farms, the dung beetles cleaned up about 90% of the faeces in a few days, much faster than on conventional farms where there were fewer beetles.
The researchers also sampled the soil from these farms and found that the organic plots had more organic matter in the soil. This supported a greater diversity of soil microbes compared to conventional farms, with possible benefits for the control of foodborne pathogens.
The researchers also conducted laboratory experiments to test whether soil bacteria and dung beetles actually reduced the level of harmful substances. E.coli bacteria, not just by eliminating waste. These showed that the beetles and bacteria in the soil actually suppressed the amounts of pathogens E.coli bacteria in the samples tested. Soil microbes tend to compete with each other, which is why a greater diversity of bacteria would help suppress the level of E.coli the. No one knows for sure why dung beetles also have this effect, but separate research suggests that it’s possible that their bodies contain antimicrobial properties that eliminate bacteria in the droppings as they process them.
That doesn’t necessarily mean pure organic farming is the answer: instead, the results suggest that farms that contain natural habitat and more biodiversity are likely to have enriched soil and more insects. In turn, this natural cleanup team could provide a powerful front against foodborne pathogens. On the other hand, conventional farms that eradicate natural habitats may actually be more susceptible to a pathogen outbreak.
The study establishes a strong link between farmland biodiversity and our health. So perhaps when we think about the benefits of preserving natural habitat on farms, we should look beyond pollinators, the researchers suggest: “Improved food security can be an important ecosystem service , and perhaps underestimated, which is enhanced by on-farm biodiversity. ”
Source: Jones et. al. “Organic agriculture promotes biotic resistance to foodborne human pathogens.” Journal of Applied Ecology. 2019.
Image: Bernard DuPont via Wikimedia Commons