The birds and the bees (and the frogs!) of pesticide exposure.

This is a continuation of something I started back on my old blog. While the majority of those who read this blog are scientists, I hope to convey science in a more accessible manner through popular science pieces. Hopefully this turns into a somewhat regular thing. Enjoy!

Pop Sci Fri: The birds and the bees (and frogs damn it!) of pesticide exposure.

Growing up, I remember watching many made-for-TV movies (we didn’t have cable). While the topics of these movies ranged from horror, to sci-fi space fantasies and suspenseful thrillers, for some reasons there was also a fair share of the “Attack of the Killer Bees” type movies. We’ve all seen some variation of this; some force (usually anthropogenic) causes bees to start breeding at a dangerous rate while also turning them all into lean, mean, human-attacking and killing machines. The films usually revolve around a family that boards itself up in a cabin or home, but has to eventually flee and usually loses a few members. Since it’s made-for-TV, the endings usually involve everyone dying or are unresolved (since the produces probably are not too concerned with ratings). This is the accepted notion of a worse-case scenario regarding bees. So, when in the fall of 2006 a Pennsylvania beekeeper reported one of the first cases of Colony Collapse Disorder (CCD) in roughly 20 years, people were shocked.
CCD is a phenomenon where worker honeybees just disappear. If this happens to enough workers, the colony can’t function and be maintained, and, as the title suggests, the colony collapses. Needless to say, if colonies collapse, honeybees decline, and declining honeybees is not a good thing for anyone or anything. Honeybees pollinate a large variety of crops, some of which include almonds, blueberries, strawberries, broccoli, soybeans, and alfalfa. Up to $30 billion of U.S. agriculture production is dependent on honeybee pollination. Billion, with a “B”. And independent of the cost to humans, the environmental costs are, in my opinion, even greater. Bees pollinate a wide variety of naturally occurring flowers. Moreover, they are an important part of the food chain. As a conservationist myself, I am aware of, and preach the effects and consequences of the complete removal of any organism from an ecosystem. So it is generally agreed upon that the bee die offs are not good. But what’s the cause?
In 2012, three peer-reviewed studies (there are more) were published linking the bee declines to the use of a specific group of pesticides. The first, “A common pesticide decreases foraging success in honeybees“, showed that exposure of bees to a neonic pesticide (neonics attack the nervous system, causing paralysis and eventual death) called thiamethoxam, significantly affected bees’ ability to find their way back to their hives. The second,’ “Combined pesticide exposure severely affects individual- andcolony-level traits in bees“, found that exposure of bumblebees to a neonic (and pyrethroid) pesticide significantly reduced brood development and colony success. Finally, a third study entitled “Assessment of the environmentalexposure of honeybees to particulate matter containing neonic insecticidescoming from corn coated seeds“, essentially corroborated the results of the previous studies. Since these studies, numerous others have been published with similar findings. The evidence is so compelling that the European Union has recently banned three neonic pesticides. Is this the solution to the bee problem? The jury’s still out on that. When declines occur, the cause is rarely (if ever) singular; however, less pesticides out in the environment is probably a good thing, no matter how you look at it.
It should come as no surprise that my interest in this topic stems from my professional interests; I’m an ecotoxicologist. So, when anything tox-related comes to the attention of my peers or advisors, I usually get an email. That’s why in late March, I received an email with a link to a MotherJones article entitled, “Not Just the Bees: Bayer’s Pesticide May HarmBirds, Too.” This is especially pertinent because the sender of the email is a professor who studies avian endocrinology, so he has a dog in this fight. The article outlined the results of the American Bird Conservancy’s report entitled, “The Impact of the Nation’s Most Widely Used Insecticides onBirds“. The report made the argument that neonics are highly persistent and mobile and are a serious threat to birds and insects on which they feed. Most convincing, the report outlined the results of a study that showed for some bird species, consuming just two corn seeds coated with a neonic pesticide can be lethal. That’s a pretty convincing argument.
So what we have here is the “birds and the bees” of pesticide-induced declines. Not quite the story we’re all familiar with, but perhaps one that should be approached with a similar gravitas. But here is the issue with all of this. Bee declines are a major, major problem and if pesticides are a potential cause, then that should be dealt with. Also, if this problem reaches into the avian world, that’s an even bigger problem. However, what about all the other organisms out there are experience the negative effects of pesticides, yet are rarely talked about? What about the damn frogs?
We’ve already established and I am a conservationist and an ecotoxicology. I also dabble in epidemiology, but my main interest is my study organism. I study amphibians, specifically frogs. What doesn’t make it into the public press nearly as often as it should is that amphibians are experiencing the greatest decline of any group of animals in recent history. According to recent estimates, upwards of 40% of all amphibians are threatened or endangered. That’s t from a group of >7,000 species. Do the math, that’s a lot of animals. There are currently 5-10 major hypotheses for the drivers of such declines including habitat loss, trade, disease, global climate change, and contamination. Get that last one? Contaminants. A vast majority of contaminant-related work with amphibians has examined how pesticides affect amphibians, mostly frogs, throughout all levels of development. And guess what, the news isn’t good. According to arecent review, pesticides have negative effects on amphibian survival, size, how long it takes to hatch from eggs, and how long it takes to complete metamorphosis (become frogs). Pesticides have also been linked to increased occurrences of morphological abnormalities (e.g., alterations to gonads or extra limbs). So the story isn’t good here either, yet few people know about the problem(s).
While there have been many pop-sci pieces about amphibian declines and the role of pesticides in such declines, the coverage isn’t nearly as comprehensive as with more iconic species. For example, pretend that tomorrow a mysterious disease started wiping-out pandas. The general public would (excuse the language) lose their shit. But the same thing has been happening to amphibians over the past decades. Were you aware? Unlikely.
Bees are important, very, very important, both to the environment and humans. So are amphibians! They are important bioindicators of environmental health (so we should probably take notice that they’re in such a sharp decline). Their diets consist of many things that cause us harm (e.g., insects that carry diseases such as Malaria, Dengue Fever, or West Nile). And finally, they are important in human medical research. Treatments for high blood pressure, peptic ulcers, diabetes, staph, and HIV have all been derived from amphibians. While I’m not a huge proponent of the “we should save ‘X’ because it benefits us” argument, the direct benefits of frogs to humans are pretty clear.
Save the bees, save the birds, and seriously, save the frogs! When I tell people that I study amphibians, the usual reaction is, “I love frogs!” If that’s the case, why aren’t more people aware of the (largely human-induced) problems they face? No, they’re not bees and not directly responsible for billions of dollars of crops. And no, they’re not birds and aren’t part of our daily scenery. But they are important, and I can’t imagine a world without them. So next you see an article about “X” species being affected by “Y” factor, remember the frogs, because they’re likely victims as well.

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