First, some good news:
GM crops have increased agricultural yields, alleviating pressure to convert natural habitat into farmland.
Insect-resistant GM crops have not been found to have a direct toxic effect on non-target insects.
Pest-resistant GM crops have been found to have few or no effects on soil organisms.
Adopters of GM crops have reduced insecticide use and switched to more environmentally friendly herbicides.
Herbicide tolerant GM crops facilitate adoption of conservation tillage, which decreases erosion and pesticide-runoff and increases soil water retention.
Conservation tillage also reduces fuel use and improves soil health.
GM crops reduce CO2 emissions by facilitating conservation tillage and improving soil health and water retention. In 2012, GM crops were estimated to have reduced CO2 emissions by the equivalent of 11.8 million cars taken off the road.
By reducing pesticide use, GM crops protect farm workers from exposure to pesticides.
Coming soon: GM technology to increase nitrogen use efficiency would reduce run-off of nitrogen fertilizer into surface waters.
Coming soon: GM technologies to increase drought and salinity tolerance, which would alleviate the pressure to convert high biodiversity areas into agricultural use by enabling crop production on suboptimal soils.
And some less pleasant news:
Herbicide tolerant GM crops do impact the abundance of birds and insects to the extent that they control weeds (which are another food source for insects and birds).
Since herbicide-resistant GM crops tolerate specific weedkillers, like glyphosate, some farmers have actually increased use of those herbicides (because they’re not worried about harming their crops).
Insect resistance is increasing in GM crops, especially those engineered to produce the bacterial Bt toxin, which is also a natural insecticide used by organic farmers.
So what can be done about these problems? Lots, starting with expanding the USDA’s Conservation Reserve Program (CRP), which pays landowners to retire lands, thereby providing alternative habitats for flora, birds and insects. Unfortunately the US Congress missed its 9/30/18 deadline for passing the Farm Bill, which means the CRP will run out of funds after this year. However, both the House and Senate included the CRP in their not-yet-reconciled versions of the Farm Bill, so it will likely continue once the bill is finally passed.
The USDA and National Institute of Food and Agriculture do have a bunch of suggestions on how to deal with insect resistance, many of which would also help protect vulnerable birds and non-target insects. As follows:
Monitor insect population development in fields. Calibrate treatments based on observed populations. Continue monitoring after treatments.
Focus on economic thresholds. Insecticides should be used only if insects are numerous enough to cause economic losses that exceed the cost of the insecticide plus application.
Take an integrated pest management approach to insect control. Use as many different control measures as possible, such as synthetic insecticides, biological insecticides, beneficial arthropods (predators and parasites), transgenic plant varieties, crop rotation, pest-resistant crop varieties and chemical attractants or deterrents.
Select insecticides with care and consider the impact on future pest populations and the environment.
Avoid broad-spectrum insecticides when a narrow-spectrum or more specific insecticide will work.
Time applications correctly. Apply insecticides when the pests are most vulnerable.
Mix and apply carefully. As the potential for resistance increases, the accuracy of insecticide applications in terms of dose, timing, coverage, etc. assumes greater importance.
Avoid the repeated use of the same insecticide or insecticides in the same chemical class, which can lead to resistance and/or cross-resistance. Rotate insecticides across all available classes to slow resistance development.
Protect beneficial arthropods. Select insecticides in a manner that is the least damaging to populations of beneficial arthropods. For example, applying insecticides in-furrow at planting or in a band over the row rather than broadcasting will help maintain certain natural enemies.
Preserve susceptible individuals within the target population by providing a haven for susceptible insects, such as unsprayed areas within treated fields, adjacent "refuge" fields, or habitat attractions within a treated field that facilitate immigration. These susceptible individuals may out-compete and interbreed with resistant individuals, diluting the resistant genes and therefore the impact of resistance.
Consider crop residue options. Destroying crop residue can deprive insects of food and over-wintering sites. However, review your soil conservation requirements before removing crop residue.
Finally, although I’m a big fan of transgenic agriculture, GM crops aren’t the be-all/end-all. They are a tool, one of many, to increase agricultural productivity while protecting the environment. The more farmland that can revert to wild habitat, the better for the biosphere. The greater crop resilience to drought, extreme weather, and salinity, the better for humans.
Next: Protect the Bird and Bees - Plant flowers. Everywhere!
Links and References:
https://theaggie.org/2018/02/19/genetically-modified-food-thought/
https://www.skepticalraptor.com/skepticalraptorblog.php/the-solid-gmo-scientific-consensus/
Brookes, G. and P. Barfoot (2015). "Environmental impacts of genetically modified (GM) crop use 1996–2013: Impacts on pesticide use and carbon emissions." GM Crops & Food 6(2): 103-133.
Carpenter, Janet E. (2011) Impact of GM crops on biodiversity, GM Crops, 2:1, 7-23, DOI: 10.4161/gmcr.2.1.15086
Lombardo, L. and S. Zelasco (2016). "Biotech Approaches to Overcome the Limitations of Using Transgenic Plants in Organic Farming." Sustainability 8 (5): 497.
Mall, T., L. Han, et al. (2018). Transgenic Crops: Status, Potential, and Challenges. Biotechnologies of Crop Improvement, Volume 2: Transgenic Approaches. S. S. Gosal and S. H. Wani. Cham, Springer International Publishing: 451-485.
National Research Council. Impact of Genetically Engineered Crops on Farm Sustainability in the United States. Washington, DC: The National Academies Press, 2010.