Jul 07 2023

GMOs and Butterflies

Are attitudes towards genetically modified organisms (GMOs) in our agriculture softening? Back in 2015 a Pew survey found that the gap between public opinion and that of scientists was greatest on acceptance of GMOs (more than any other topic surveyed), with a 51% gap. But more recent data shows declining opposition. Regulators are also softening their stance, with Mexico walking back a ban on GMO corn from the US, and the EU considering softer rules on GMOs. Some countries, like the US, have also adopted new terminology, such as bioengineered, and carved out separate rules for crops made with altered genes but not with transgene insertions.

We still have a way to go, and there is still enough opposition to slow adoption of useful agricultural technology. I like to think this is because the science is slowly winning the day. I do think many environmentalists have their heart in the right place, but sometimes get distracted by ideological positions, such as an aversion to anything “unnatural” or high tech. But if the stakes get high enough, the more moderate environmentalists can change their position. I think we are seeing this with nuclear power and the need to combat global warming. And I think we are seeing this with GMOs and the need to feed the world without destroying the environment. The benefits of GMOs are ultimately just too great to ignore.

But there is a lot of inertia in the anti-GMO propaganda that Greenpeace, the organic lobby, and others have been spreading for two decades. I was just recently asked about one specific claim that reflects the nature of this propaganda and how sticky it can be – aren’t GMOs killing the butterflies? The short answer is no, but as always the full story has lots of details. Here is a typical headline from the Environmental Working Group (who I personally find to be more ideological than science-based) – GMO-Linked Herbicide May Doom Monarch Butterflies. This framing was lazily reproduced by most mainstream reporting, but it is nothing but anti-GMO propaganda.

What is this “GMO-linked herbicide” they speak of? Of course, it’s glyphosate. Here is the dubious chain of logic they used. Monarch butterfly populations are declining. This is non-controversial. This trend is continuing for eastern monarchs, but in the last two years the western populations have rebounded a bit. But the long term trend is down. This decline is partly caused by a reduction in the density and distribution of milkweed, a plant that the monarch butterfly is dependent on to reproduce – that’s where they lay their eggs. Milkweed is decreasing partly because of herbicide use, the most common herbicide in use today is glyphosate. Some GMOs are engineered to be glyphosate resistant, which is coupled with the use of glyphosate. So the real problem, you see, is GMOs. Because of the deliberately deceptive or lazy headlines, many in the public are left with the bottom-line impression that GMOs are killing the butterflies.

It turns out, every link in this chain is dubious, or only partially true, and is ultimately misleading. I will start with the final link – because some GMO applications include herbicide resistance, it is the GMO technology that is the problem. This is nonsense. GMO technology itself has nothing to do with any particular application, and the risks vs benefits of any one application say absolutely nothing about the risks vs benefits of any other application or the technology itself. But the anti-GMO lobby has made a concerted effort to link GMOs in the minds of the public with pesticides (herbicides and insecticides), just because that is one of the early applications of the technology.

But as we work our way back through the logical chain it gets even worse. If herbicides are the problem you can’t just blame the current most common herbicide in use – you have to put the effects of glyphosate in the context of all the alternatives. Glyphosate is actually less toxic than many of the herbicides it replaced. It’s not as if, absent herbicide-resistant crops, we would not be using herbicides to manage our crops. Further, any change in agricultural practices that reduces yield increases land use in order to produce the same amount of food. And guess what is a bigger problem for milkweed populations?

In fact, it is questionable what the true role of herbicides is in the decline of milkweed and hence monarchs. Another factor that clearly has an effect is the number and size of farms. Farms themselves have displace meadows and fields that would normally contain milkweed. But the plant continues to exist in fallow land and also along the edges of farmland. Over the last 70 years there has been a massive consolidation in farms, which means that there are fewer but larger farms. This in turn means less farm edges, and therefore less milkweed.

One strong bit of evidence here is that milkweed and monarch populations have been steadily declining since 1950 – decades before GMOs came into existence. A recent large review of the evidence found:

Herbicide-resistant crops, therefore, are clearly not the only culprit and, likely, not even the primary culprit: Not only did monarch and milkweed declines begin decades before GM crops were introduced, but other variables, particularly a decline in the number of farms, predict common milkweed trends more strongly over the period studied here.

They estimate the total effect of herbicide use and farm size to predict only 20% of monarch butterfly decline, so other factors are playing a role. It is also important to note that the introduction of herbicide resistant GMO crops did not alter the trend lines of declining monarch populations. It just doesn’t seem to be a significant factor.

Land use is likely a major factor. In 2020 it was estimated that agricultural land (% of land area) in the World was reported at 36.46 %. Agricultural land is land that is under permanent crop use or pasture use. The situation is only going to get more extreme as we try to feed our increasing population – now at 8 billion and likely to exceed 10 billion before world population peaks. Leveraging technology to maximize yields, minimize loss and waste, and minimize inputs will be critical to maintaining our food supply while minimizing our environmental footprint. The bottom line is that we need bioengineering to do this. Environmentalist opposition to GMO and bioengineering technology, based on ideology and dubious arguments, is ironically very dangerous for the environment. They have already done great harm with their propaganda, which still resonates to today, including the false link between GMOs and butterfly decline.

But there has been some pushback against the propaganda from agricultural experts, such as this from Purdue University:

GM crops don’t harm honeybees or monarch butterflies. On the contrary, they may reduce the need for pesticides that do harm them.

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