The Environmental Protection Agency (EPA) is being sued for its alleged failure to protect the monarch butterfly, a species that has gained significant attention as its numbers decline across the country, reports announced Friday.

The Natural Resources Defense Council (NRDC) filed the lawsuit, claiming that the EPA disregarded the dangers that a widely used herbicide, called glyphosate, poses to the monarch butterfly population.

Butterflies have declined by a whopping 90 percent over the past 20 years, according to the US Fish and Wildlife Service (FWS), prompting talks of granting them federal protections under the Endangered Species Act. The use of herbicides is in large part to blame for this, as these chemicals have destroyed monarchs' vital milkweed habitat.

In the last 20 years, these orange-and-black butterflies have lost more than 165 million acres of land once overflowing with milkweed plants - an area about the size of Texas.

Federal law requires the EPA to ensure that pesticides it approves will not cause "unreasonable adverse effects on the environment, including wildlife," the lawsuit states. "However, the agency has never considered glyphosate's impacts on monarchs."

Glyphosate use has risen over the last couple decades as genetically modified crops, able to withstand these types of herbicides, have become more popular.

But, the EPA claims that it was taking numerous measures to protect monarch butterflies.

"With regard to pesticide exposure, EPA is looking holistically at all herbicides, not only glyphosate, to determine the effects on monarchs and resources critical to butterfly populations," the agency said in a statement issued to NBC News.

Despite their defense, the suit is seeking a court order forcing the EPA to evaluate glyphosate's effects on monarchs and impose measures to mitigate harm to the butterflies.

Monarchs in the United States and Canada are known for migrating a stunning 2,500 miles to their wintering habitat in Mexico, and then back again. Where there were once billions making the trip, now this winter was down to 56.5 million butterflies, the second-lowest number ever measured.

Authorities have turned to backyard gardeners for help, asking them to plant native milkweed. But unfortunately, those good intentions went awry. However, this month, the FWS said it was helping launch a $3.2 million campaign aimed at saving the butterfly's habitat.

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