Honestly i do not know the full scope of this one, but if there's one thing I've learnt from observing her work over the last decade...it's humans need to stop adding chemicals to water bodies with the goal of thinking they're helping something.
I can imagine her having some long explanation about the unknown risks of man spreading this substance, even if its not a chemical agent. I lean on the edge of listening to Grandpa Simpson on these kind of things: https://i.imgur.com/MdjduDH.png
It is not meaningful to allow every conceivable unknown unknown (to channel Rumsfeld) suck out any sense of agency.
It might well be safe, but the question is what are the downstream affects of reducing the population of mosquitos (or other bugs in the water that this substance impacts). Maybe they've exclusively positive, but I assure you determining that is no walk in the park.
I don't know, what are the possible effects of antibiotics? What are the possible effects of uprooting weeds, which some organisms may depend on? What are the possible harmful effects of putting out wildfires?
For every action that someone might think of as beneficial, there are all sorts of "harmful" effects that can be posited. In the examples above, these harms are not even just theoretical, and yet people do not constantly wring their hands worrying about wildfire fighting, weed control, or the proper use of antibiotics.
That this seems to happen only with mosquitoes seems quite weird to me, especially when it occurs even with efforts to reduce mosquitoes that spread malaria and other diseases. People are oddly very worried about some nebulous harm caused by reducing real and serious harm now.
Wildfire - controlled wildfires are actually beneficial to prevent the real bad ones and help refertilize. So they now let them burn down if possible and just control the edges where necessary.
Weed control - poisoned groundwater from herbicides/pesticides is a huge headache, so these are tightly regulated on substances and amounts.
Antibiotics - multiresistant bacteria have taken over since years. In turn, antibiotics are now prescribed more rarely and for longer periods (to make it resistant survivors less likely) and new antibiotics had to be developed.
"Mosquito dunks linked to declining bear population - farmers struggling with deer populations"
Agreed. I'm in South Texas where we have Aedes mosquitoes that are an invasive species and spread Malaria, Dengue, Zika, and other infections which kill people. I consider disrupting their lifecycle to be an unvarnished good. I carry mosquito dunks in my pocket when I go on walks and toss them into any puddles, drains, storm sewers, and ponds I encounter, and it seems to have helped a lot anecdotally. I care a lot about nature/ecology, but also fuck mosquitoes.
Also massively illegal if you live anywhere that has a state level wetlands protection type law and the enforcement authority decides to exercise their discretion to make your life hell. They typically claim jurisdiction and authority over all activity in/around wetlands so theoretically you should be getting a state permit before digging a mailbox post hole or doing any sort of "management" of plants/animals but most of the time they just turn a blind eye to private homeowners who are being reasonable.
Wetlands laws and rules (non-criminal code generally, but wetlands are some of the worst) are written in a way to make RICO look like a meticulously scoped out piece of technical legislation.
Second, most states that regulate wetlands beyond the federal minimum adopt some sort of absurd expansive standard far above what the feds want. It's complex and varies by state. Sometimes there's a square footage minimum, sometimes there isn't. There's also "gotchas" where manmade areas can become wetlands if they are let to be that way too long, so like farmer Johnson can absolutely get screwed by his grandfather's bright idea to make all the drainage converge in one spot 40yr ago. Sometimes there are exemptions, sometimes not. There's huge variation by state and some states allow local governments to enforce rules above and beyond the state ones.
But yeah I don't mess with wetlands.