We know a lot about glyphosate, the pesticide widely known as Roundup.

We know it kills the only food of the monarch caterpillar, linking it to nearly a 90 percent decline in monarch butterflies over the past two decades.

We know that a report released by the World Health Organization in March links it to cancer.

We know the Netherlands has banned over-the-counter sales of it.

We know this month, France did the same.

And this week, in response to a lawsuit filed by the conservation group where I work, the U.S. Environmental Protection Agency agreed for the first time to analyze how 1,500 endangered plants and animals are impacted by Roundup and atrazine -- the two most commonly used pesticides in the world -- as well as well as two other pesticides similar to atrazine.

Despite the many known risks associated with all four toxins, hundreds of millions of pounds of them are dumped on U.S. fields and gardens every year. So a fair response would be to ask why the EPA wasn't already assessing those risks.

The EPA has a long history of failing to fully assess the risks of pesticides like Roundup. But the need is greater now than ever before: With the introduction of genetically altered "Roundup Ready" crops, the annual use of glyphosate just on corn and soy in the U.S. has swelled from 10 million pounds in 1995 to 204 million pounds in 2013, according to the U.S. Department of Agriculture.

As a result, the U.S. Geological Survey routinely finds glyphosate in our water.

Equally troubling is the widespread use of atrazine in the U.S. Though it is so dangerous to both people and wildlife that it has been banned by the European Union , approximately 60 million to 80 million pounds of it are still dumped on the American landscape every year.

This is despite the fact that numerous studies have found overwhelming evidence linking atrazine to significant human and wildlife health concerns, including an increased risk of prostate cancer and decreased sperm count in men, as well as a higher risk of breast cancer in women.

Atrazine is also a likely cause of declines of endangered amphibians and of many other endangered species throughout the country. It is an endocrine disruptor that directly affects the sexual development of amphibians by changing their hormone cycle. Exposure to atrazine, at levels as low as 0.1 parts per billion, has been shown to affect the development of sex characteristics in frogs.

So it's not surprising that in his historic recent encyclical, Pope Francis didn't just call for a worldwide awakening on climate change, he also denounced pesticides and genetically engineered (GE) crops, declaring "the spread of these crops destroys the complex web of ecosystems, decreases diversity in production and affects the present and the future of regional economies."

Biotech companies claim their products are key to solving hunger, but the Pope, the biotech companies and regulators across the world know this simply isn't true. No commercial GE crops are engineered for increased yield. Five of every six acres of GE crops are engineered for herbicide-tolerance, i.e. to survive being drenched with what would normally be a toxic dose of herbicide, usually Round-up, or glyphosate.

What we all know is that pesticides have already made our earth less beautiful and more gray by nearly wiping out monarch butterflies . The widespread use of pesticides, especially neonicotinoid insecticides , is a leading cause of our current pollinator collapse. With one out of three bites we eat requiring bee-pollination, it's no wonder this issue has drawn widespread attention, including from the White House , which has pledged action to protect pollinators.

EPA recently fast-tracked its approval of a brand new pesticide called Enlist Duo for use in 16 Midwest and Great Plains states.

What's the hurry, you might ask?

The answer: Because of the growing weed-resistance to currently used pesticides in half of U.S. states, pesticide manufacturers have had to come up with a new toxic solution to dump on the American landscape. And toxic it is - a combination of Roundup, and 2,4-D - a World War II-era poison invented for chemical warfare.

Pesticide manufacturers herald Enlist Duo as a solution to the weed-resistance. But history has conclusively shown the chemical war on weeds always results in more weed-resistance, ever-increasing pesticide use, and more environmental harm.

It's clear, in the fight against toxic pesticides, there's much to celebrate, and much left to be done.