The Environmental Protection Agency declined to study restricting the use of a pesticide believed to harm the monarch butterfly’s habitat.

The EPA told the Natural Resources Defense Council (NRDC) it rejected the green group’s petition regarding glyphosate, a pesticide marketed by Monsanto Co. as Roundup.

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“The agency at this time has not determined that glyphosate causes unreasonable adverse effects to the monarch butterfly,” the EPA told the green group.

The NRDC and other green groups have long argued that Roundup is responsible for killing large swathes of milkweed, a plant that monarchs rely on for habitat and development.

While the agency recognized that the drop in milkweed is causing the butterfly’s population drop, it agreed instead to to undertake a study of other actions it could take toward protecting monarchs.

The NRDC slammed the EPA’s decision, saying it does not make sense.

“The EPA apparently plans to study the monarch migration to extinction,” Dr. Sylvia Fallon, an NRDC senior scientist, said in a statement.

“Everyone loves the monarchs, including the Obama White House,” she continued. “But love isn’t going to save monarchs from glyphosate. It’s inexcusable for the EPA to call for more time to show glyphosate’s harm while at the same time approving new glyphosate-based pesticides that kill the sole food source monarchs need to live.”

The EPA said that it is taking the problem seriously.

“While the EPA has denied NRDC’s petition, the EPA concludes that its ongoing efforts to protect bees, in conjunction now with this effort to protect the monarch butterfly, are in line with the objectives of the NRDC petition,” the agency said in the notice about its new butterfly project.

The agency announced in March that it would crack down on Roundup use by requiring Monsanto to formulate a plan to limit the development of weeds resistant to the product.

Elsewhere in the federal government, the Fish and Wildlife Service is currently studying whether the monarch deserves protections as an endangered or threatened species, which would likely include protections for its habitat.