I'm not an expert on this by any means, but I do work in the food industry as a primary supplier, just a different area. I thought that somewhere along the way I've heard GMO actually decreases the amount of herbicide used per acre. Also doesn't Glyphosphate totally break down when wet and in the soil?
Also couldn't the increase in herbicide use simply be from more acreage world wide?
From what I have learned, and I fully admit I do not hold a science degree, the claim that less is used isn't possible to measure. A couple of comments on the possibility though...
1- herbicides have different levels of biological activity. So the amount of active ingredient per acre will differ, and thus cant be equally measured. Is 1 pound of one herbicide A better than 2 pounds of herbicide B if both A and B have the same amount of biologically active ingredient? Well herbicide A covered the field with half as much liquid, so that's two times better than herbicide B, right? But they used the same amount of biologically active ingredient, so then there is no net benefit.
To actually answer if less herbicide is used now versus 30 years ago(or more), one would have to be able to measure the total active ingredient weight of all combined herbicides then compared to now.
2- I worded my comment poorly. I should have specified and stated that the increased use of glyphosate over the last 3 decades is astonishing.
Forgot to mention earlier that glyphosate use has had a literal butterfly effect. 20 years ago the Monarch population in North America was a 1BILLION. It is now estimated to be 60million. That's over a 90% decline in two decades. Glyphosate kills milkweed, which used to be all over the Midwest in prairies and is typically found growing on the perimeter of corn and soy fields. Well, it USED to by found growing on the perimeter.
Guess what the Monarch's favorite plant is? The one plant that it will lay its eggs in? Guess what plant is the only plant a Monarch caterpillar will eat? Yup- milkweed.
In the Midwest, the variety called 'common milkweed' is much hardier than other varieties and it managed to survive the destruction of prairies being turned into farmland. Only 1% of the amount of common milkweed that was present at the turn of the century is still around. So 99% of what was around 15 years ago is gone.
Oh, and glyphosate use increased 20fold from 1995 until now.
To sum up- glyphosate use increases by 20fold in 2 decades. This corresponds with the introduction of glyphosate resistant seed to the marketplace. Glyphosate kills milkweed and there is now only 1% of what was around at the turn of the century. In the time since glyphosate resistant seed has been on the market, Monarch butterflies have decreased by over 90% due to their nesting and food source being eliminated.
Now I understand correlation does not imply causation. And yet...