Article Review: How bat populations impact infant mortality

Greetings!

From time to time, I come across scientific articles that I think are interesting and would like to share more broadly. Below I summarize a research article that was recently published in Science by Dr. Eyal Frank and written about in the NYTimes by Catrin Einhorn. Then, I provide my own perspective on the topic having dug into the published article a bit more.

Article title: "Surprising New Research Links Infant Mortality to Crashing Bat Populations"

Summary:

Dr. Frank found that infant mortality increased in U.S. counties where farmers sprayed more insecticides. They attribute the need to spray more pesticides to the die-off of local bat populations which should naturally control the abundance of crop pest. The number of bats, in turn, have been decimated due to habitat loss, climate change, and especially, white-nose syndrome (an invasive fungus). This research highlights what scientists call "ecosystem services", where the ecosystem provides a benefit in some way to humans. It's likely that more ecosystem services will be lost as we continue to degrade our environment.

My perspective:

I learned quite a bit in my Extension Master Gardener course about Integrated Pest Management (IPM). IPM is a science-based approach that that promotes preventative measures against pest populations (e.g., site selection, crop rotation, row covers, physical removal, etc.) rather than interventions (e.g., pesticides) to improve land management, lower costs, and decrease any harmful risks to humans and the environment. Biological controls can be used by farmers (e.g., introducing soil nematodes), but are also often provided by natural populations.

In the case of Dr. Frank's article, bat populations are providing biological pest management which allowed farmers to spray approximately 31% less insecticides on their fields. Though, as bat populations have declined, primarily due to white-nose syndrome, crop revenue decreased and agricultural land rental rates were slightly lower.

Dr. Frank also estimated the number of infant deaths attributed to increases in insecticide spraying at 1,334. From what I can tell, infant mortality is reported at the US county level, but he does not specify a mechanism through which infants become exposed to pesticides. I would presume that the insecticides are sprayed on farm fields and the toxins making their way into the water supplies of families living nearby through agricultural runoff. There isn't any indication (in these studies at least) that insecticides are affecting the crops themselves. As an economist, he uses economic estimates to value the loss of crop profits as well as the cost of infant mortality to society at a combined $39.4 billion, or $1932.20 per capita, in the counties with decimated bat populations (representing losses from 2006 to 2017). These numbers clearly show the losses we have incurred by losing bat populations, which can be translated into a loss of ecosystem services.

Lastly, I want to touch on the topic of ecosystem services more generally. This is a term used to describe what nature provides to us humans (whether we can economically value it or not). The article by Dr Frank is an excellent example in that bat populations contribute to our agricultural sector by decreasing pest populations, and so, 1) saves farmers the costs on using more insecticides against crop pests, 2) increases farm profits, and 3) protects human health and environmental integrity.

There are many other examples of ecosystem services. Other insects and birds are considered pollinators and are a hugely important part of the agricultural sector. Certain wasps only target garden pests. Altogether, these natural communities benefit our agricultural sector by providing free services to us. Ecosystem services aren't limited to those helping farmers, but are found all around us.

Yet, some are more difficult to notice and less quantifiable. The National Wildlife Federation nicely summarizes four major categories of ecosystem services:

• provisioning (anything we can extract from nature; example: medicines)
• regulating (any service nature provides; example: trees produce oxygen)
• cultural (nature as a cultural importance; example: maple trees in New England or walleye in Minnesota)
• supporting (any service that sustains all other services; example: photosynthesis)

All in all, the article about bats and infant mortality is shocking and exciting! Of course, no one wants infant mortality to increase, but perhaps this article is just what is needed to show that we must coexist with the plants and animals of our planet, lest we find out what happens when they are all gone.

My favorite quotes:

Disruption to biological pest control has a meaningful impact on human well-being. I demonstrate how declines in insect-eating bat population levels induce farmers to substitute with insecticides, consequently resulting in a negative health shock to infant mortality. - Dr. Frank

This result highlights that real-world use levels of insecticides have a detrimental impact on health, even when used within regulatory limits, which highlights the difficulties of assessing the public health impacts of pesticides when regulating them individually. - Dr. Frank

Disruptions to ecosystems and wildlife populations present us with an opportunity to learn more about what is lost in their absence. - Dr. Frank

Across many species and ecosystems, making informed decisions about conservation policies and priorities requires a rigorous evidence base. Even if manipulating wildlife populations across large areas is not feasible, we can still use other sources of disruptions to ecosystem functioning to learn about their importance to humanity. - Dr. Frank

Please let me know what you think about this article in the comments below!