Last week the U.S. Department of Agriculture approved a new line of genetically modified corn and soybeans for use in the U.S. The crops, made by Dow Chemical Company and running under the brand name “Enlist,” may be the future of genetically modified crops. This future, though, has been largely determined by the problems caused by the last generation of GM crops.

Dow's new Enlist genetically modified crops are the intellectual descendants of Monsanto's genetically modified “Roundup Ready” crops. Like Monsanto's crops, Dow's are designed to be resistant to a patented herbicide. By planting the modified crops, farmers can spray the herbicide to kill weeds without worry that it will affect their crops.

In the 1990s, Monsanto's plan sounded like a good one. Farmers bought in and started spraying Roundup in spades. There was only one problem: nature is resilient. Soon, weeds were evolving to be resistant to glyphosate, the herbicide in Roundup. Now, glyphosate-resistant weeds, rather than just normal weeds, are choking farmers' fields, says Brandon Keim for Wired.

Dow's recently approved solution will do something similar, but with a different formulation. Their Enlist crops are resistant to two herbicides: glyphosate and another compound called 2,4-D. (Monsanto has a similar multi-herbicide project in the works.)

So what's to stop Enlist from running into the same problem as Monsanto's Roundup Ready crops? Not much, says Keim:

[M]any scientists say simply using more, different herbicides will hasten the evolution of ever-more-resistant superweeds, putting agriculture on what some scientists have called an herbicide treadmill: more herbicides and more resistance, over and over.

If the problem sounds familiar, it should. Widespread and overzealous use of antibiotics have lead to rapid evolution of antibiotic resistance in bacteria that have trapped the healthcare system in a corner. The situation is threatening to throw us into a “post-antibiotic era,” according to the World Health Organization.

Solving the problem, says Keim, would require a fundamental rethinking of how farmers farm—a move away from herbicides and monocultures, and the adoption of ecologically-conscious techniques and crop rotations.

On a more practical note, the USDA's approval of Dow's Enlist crops doesn't completely open the door to their use. For that, says Reuters, the Environmental Protection Agency would still need to approve the modified crops' sibling herbicide.