10
Sep
Healthy Ecosystems Essential to Cost-Effective Pest Management and Protection of Health
(Beyond Pesticides, September 10, 2024) Results from a natural experiment, published in Science, shows ecosystem disruption of bat populations with cascading impacts on human health. Eyal Frank, PhD, an assistant professor of the Harris School of Public Policy at the University of Chicago, links increased insecticide use in croplands in the absence of bat species to a rise in infant mortality. As Dr. Frank says in an article in Science Daily, “[B]ats do add value to society in their role as natural pesticides, and this study shows that their decline can be harmful to humans.”Â
Many farmers rely on bats as alternatives to pesticides to protect their crops from insects, but White-Nose Syndrome (WNS) has greatly impacted bat populations since 2006. With the collapse of many bat populations in counties in North America, these farmers turn to toxic chemicals to replace the ecosystem services bats usually provide. These chemicals, however, lead to ripples through the ecosystem and endanger human health.Â
WNS is an invasive fungus (Pseudogymnoascus destructans) found in caves that affects bats during hibernation. As highlighted in an article in the New York Times, three species of bats in North America have been decimated by this syndrome, and bats with WNS have been confirmed in 40 states and nine Canadian provinces. According to bat experts, 52% of bat species in North America are also at risk of severe declines over the next 15 years. Â
Multiple crises impacting biodiversity, human health, and climate change are threatening ecological balance. Bats are one of many beneficial species that provide important ecosystem services, such as mosquito management and pollination, that are underappreciated until their services are no longer available.Â
As Dr. Frank highlights in his latest study, “Bats provide biological pest control through their high population size and predation rates on a variety of insects, many of which are crop pests. Insectivorous bats consume 40% and above of their body weight in insects each night.†When fewer bats are available to remove these insects, especially ones known to damage produce and other crops, farmers are left seeking other pest control options. Â
WNS has caused high mortality in bats, with rates averaging above 70%. This syndrome causes premature awakening from hibernation, which leaves bats with scarce food and low temperatures that threaten their survival over the winter. “By 2010, mortality rates of infected populations were between 30 and 99%, with a mean of 73%, characterized by rapid disease dynamics that can lead to local extinctions within 5 to 6 years,†Dr. Frank specifies. He continues, “As of 2024, 12 of the roughly 50 insectivorous bat species in the US are negatively affected by WNS.â€Â
To determine the impacts on human health from these population declines, Dr. Frank collected data from counties experiencing WNS regarding insecticide use and infant mortality from 2006-2017. In comparing these numbers, “after the onset of bat die-offs, farmers in the county increase their insecticide use by 31.1%, on average,†he states. “Infant mortality rates due to internal causes of death (i.e., not due to accidents or homicides) increased by 7.9%, on average, in the affected counties. This result highlights that real-world use levels of insecticides have a detrimental impact on health, even when used within regulatory limits.†These rates correspond to an additional 1,334 infant deaths which shows for every 1% increase in pesticides, there is a 0.25% increase in the infant mortality rate.Â
This study calls attention to the observable and statistically significant increases in insecticide use in counties that document WNS compared to non-WNS counties, with increased infant mortality also occurring in those areas. This correlation highlights the direct agricultural and health benefits that bats provide, as these effects were not seen in the years preceding WNS detection.Â
Dr. Frank also evaluates “the magnitude of the losses attributable to the decline in bat populations and estimates total agricultural losses, crop revenue, and chemical expenditure on the magnitude of $26.9 billion (2017 dollars) for the WNS-confirmed counties across the 2006-to-2017 period. To anchor this magnitude, consider that crop revenue across the entire US in 2017 alone was around $190 billion (2017 dollars).†He also estimates that the additional 1334 infant deaths during that period “reflect damages valued at $12.4 billion. Combined, these amount to damages of $39.4 billion, or $1932.20 per capita, in the WNS-confirmed counties.†Â
As the Science Daily article adds, the quality of the crops during this period “likely declined, as farmers’ revenue from crop sales decreased by nearly 29 percent.†These statistics prove the loss of crucial bat populations impacts biodiversity, human health, and the economy in considerable ways. The article concludes: “‘When bats are no longer there to do their job in controlling insects, the costs to society are very large—but the cost of conserving bat populations is likely smaller,’ says [Dr.] Frank. ‘More broadly, this study shows that wildlife adds value to society, and we need to better understand that value in order to inform policies to protect them.’â€Â
As previously stated by Beyond Pesticides, bats, among other wildlife including birds and bees, provide important ecosystem services to farmers by helping to manage pest populations and increase plant resilience and productivity. While degradation of ecosystems is attributable to many factors, pesticide use accounts for an important element in harm to bats and biodiversity. Â
Species of bats are crucial for ecosystem functioning and maintaining ecological balance. Also previously reported is the fact that they are one of the only nocturnal pollinators and the only nocturnal insect predator in the U.S., playing a key role both for plants and for farmers. Organic farmers, in particular, are reliant on bat pollinators as a pest management tool: one brown bat can kill between 3,000 and 7,000 insects per night. A study published in 2011 in Science estimated that bats provide $3.7 billion to $53 billion per year worth of pest control services to agricultural operations, and that number does not include pollination services. Bat pollination, technically known as chiropterophily, is integral for many wild and commercial tropical fruits. Over 500 plants worldwide are completely or partially dependent on bat pollination.Â
Aside from the cascading effects involving bats, pesticide use, and human health, bat species can be directly impacted by harmful chemicals. In another Beyond Pesticides article, it was noted that because bats are unusually long-lived for animals their size—lifespans range from 20 to 40 years—their bodies can accumulate pesticide residues over a long period, exacerbating adverse effects associated with those pesticides that can accumulate in fatty tissue. Also, during migrations or winter hibernation (when their fat stores are metabolized), bats’ consumption of large volumes of pesticide-contaminated insects can mean that these compounds may reach toxic levels in their brains—making them more susceptible to WNS. Bats also tend to have only one offspring each year, making them vulnerable to the population impacts of negative reproductive effects caused by pesticides, because low reproductive rates require high adult survival rates to avoid population declines.Â
The direct and indirect effects of pesticides on target and nontarget species are widely documented. As highlighted by Dr. Franks’ work, the loss of natural predators for managing insects has led to an increased reliance on toxic substitutes with many harmful, unintended consequences while safer alternatives exist. Organic agriculture provides land management techniques that safeguard biodiversity and the health of all organisms.Â
Organic systems offer a path forward that would mitigate severe human health impacts, such as the infant mortality noted here. As the management of insects becomes increasingly important with insect-borne diseases like EEE (eastern equine encephalitis), it is vital to take action and call for safer strategies to combat these health issues. Â
The organic solution provides a holistic approach with health benefits as well as environmental benefits. Keeping Organic Strong is essential to protect all organisms and the environment. Through National Organic Standards, organic integrity needs to be continuously improved upon. Tell the National Organic Standards Board (NOSB) to guide the U.S. Department of Agriculture (USDA) in its administration of the Organic Foods Production Act (OFPA) towards the best practices that support the ecosystem, mitigate climate change, and enhance human health. Â
All unattributed positions and opinions in this piece are those of Beyond Pesticides. Â
Source:Â
Frank, E. (2024) The economic impacts of ecosystem disruptions: Costs from substituting biological pest control, Science. Available at: https://www.science.org/doi/10.1126/science.adg0344.
