I have to be careful about wading into this topic, as it is highly controversial, but I feel the need to discuss it.
But before I talk about Dicamba, I need to talk about Roundup. Roundup is the most widely used herbicide *in the world*. Like WD-40, it is also a desiccant (it dries out crops like soybeans so that they can be harvested), but it was discovered by a Monsanto chemist to be an herbicide in 1970. After Monsanto developed Roundup-ready crops, the usage of Roundup increased exponentially.
Figure made from data published in Benbrook 2016
The incredible increase in usage of Roundup had an important side effect (other than making Monsanto incredibly wealthy): the evolution of Roundup resistant weeds (aka superweeds) (a huge number of them). The Mortensen et al (2012) paper has a table describing 28 species of Roundup resistant weed species and the extent of their distributions. You should read that paper if you want to better understand this whole issue, by the way. I’m summarizing very complex issues here, so of course a lot of the nuance is lost.
Fig 4 from Mortensen et al 2012
One of the nuances, which I will only briefly touch on here, is that any herbicide has negative impacts on the wild habitat that insects in general, and particularly wild pollinators, rely on. Here’s a quote from the paper that says it better:
“All herbicides can have negative impacts on nontarget vegetation if they drift from the intended areas either as wind-dispersed particles or as vapors evaporating off of the application surface.” Mortensen et al 2012
If we put this together with dramatic declines in insect biomass, loss of many aculeate pollinator species, population declines in monarchs, population declines of insectivorous birds…we should know that our widespread usage of pesticides and herbicides IS having global impacts. Obviously, all of these are influenced by multiple factors, but doubtless our chemical usage is contributing. Part of this is the direct effects of insecticides on insects, and part of this is loss of habitat, partly because of herbicide usage destroying weedy habitat.
Okay, let’s bring this back to Dicamba. In a strong parallel to the evolution of antibiotic resistance (leading to some scary stuff), the response to the increasing problem of Roundup resistant weeds has been to develop NEW herbicides! Enter Dicamba…the new broad spectrum herbicide designed to combat agricultural weeds. And, thusly, Monsanto developed Dicamba-ready crops.
The problem(s)? 1) We should have learned from our battle with antibiotic resistance that producing an endless line of new herbicides will NOT stop the evolution of new resistance. 2) Dicamba is a way more dangerous herbicide than Roundup (for a number of reasons, discussed more below). 3) We know from the pattern of Roundup that there is the potential for any Monsanto developed herbicide resistant crop to exponentially increase in global application, meaning its impacts could be enormous.
Why is Dicamba so dangerous?:
A Meta-Analysis on the Effects of 2,4-D and Dicamba Drift on Soybean and Cotton Egan et al 2014
Quantifying vapor drift of dicamba herbicides applied to soybean Egan and Mortensen 2012
Inheritance of Dicamba Resistance in Wild Mustard (Brassica kaber) Jasieniuk et al 2017 (Yes there are already Dicamba resistant weeds)
The movement and persistence of Dicamba in soil Friesen 1965
I personally know scientists that battled the release of Monsanto’s Dicamba-ready crops by publishing multiple papers on its potential detrimental impacts and even testifying multiple times in front of Congress. Yet, in 2015/2016, Dicamba-ready crops were legalized in many states. I met with a scientist who had been battling it for more than a decade and he was just devastated. He had provided incredible amounts of evidence that the release of Dicamba would be a disaster, yet it was still released*.
I thought that would be that, but…break out the horrified popcorn. Here’s what’s happened since Dicamba-ready crops being rolled out last year:
So if the Dicamba drift is such a problem for other crop fields, can you imagine its impact on wild and weedy habitat in the surrounding landscape? Of course, this is harder to quantify economically, but the environmental impacts are easy to see. We have massive drift of a broad scale herbicide that can kill almost any plant. Seems like our habitat loss problem is about to get a lot worse…
*Can you guess why?? ($$$)