Since then, Ive gone from being an ant farmer to a crop farmer. Today, when I think about bugs its usually because Im worried about pests eating my plants.

But I still enjoy watching monarchs float across the fields, and seeing my daughter take an interest in them as well. She roams around the backyard with her bug boxes, making her own discoveries.

Thats one of the reasons I was encouraged to see the United States, Canada, and Mexico band together earlier this summer to protect the monarch butterfly. Under the auspices of the NAFTA, they pledged to develop a North American Monarch Conservation Plan.

The monarch is an excellent symbol for NAFTA because monarch butterflies range across the entire continent. They spend the winter in the forested mountains of Mexico, fluttering forth each spring to their breeding grounds in the United States and Canada, where they depend upon milkweed plants to feed their caterpillars. As summer turns to fall, a new generation of butterflies heads south once more.

Its one of the most amazing migrations in the animal kingdom. The notion that some of these little butterflies will fly from Manitoba to Michoacan–possibly crossing my farmland on their journey–is simply astonishing.

The insect is emblematic of the interdependence of our linked ecosystems, said our environmental ministers in a statement. It is our collective responsibility to protect this continent-wide ecological phenomenon.

The monarch is not an endangered species. Yet it does confront significant environmental stress, especially in Mexico, where its wintertime habitat faces constant pressure from loggers. It makes sense for our three countries to work together, both publicly and privately, to ensure the monarchs future.

Environmentalists sometimes complain about NAFTA. They would be much wiser to use NAFTA as a tool for wildlife protection. Without it, people would still love monarch butterflies, but there would be no North American Monarch Conservation Plan.

The environmental benefits of NAFTA extend far beyond the monarch. The Commission for Environmental Cooperation–the body that has called for the butterfly conservation plan–is also taking steps to help the vaquita, a rare species of porpoise that lives in lagoons around the Gulf of California. And it has just introduced an interactive mapping tool that will provide the public with information on industrial pollutants across North America.

Ultimately, NAFTAs greatest environmental contribution will come from economic growth. Wealthy nations are better able to take care of the environment than poor ones. Not only are their citizens more attuned to wildlife conservation and similar matters, but they have the resources to do something about it.

By lowering trade barriers, NAFTA has enriched the people of the United States, Canada, and Mexico. Ultimately, the environment is bound to benefit.

If the monarch is to survive, conservation plans alone wont be enough. Mexicans will require economic alternatives to the subsistence logging that currently threatens the monarchs. Theyre already coming to see that these butterflies are a source of ecotourism dollars. In the future, perhaps free trades broader opportunities will help lessen the pressure on monarchs in other ways as well.

The monarchs face difficulty in the United States and Canada, too, but the most prominent dangers arent manmade–they have to do with the weather, because wet and cool summers appear to inhibit reproduction.

Several years ago, anti-biotech activists claimed that biotech crops threatened monarchs. Their scare tactics made the headlines, but they were hollow allegations: Further investigation showed no such thing. In fact, biotech crops may even help monarchs because they require less conventional pesticide.

Smarter conservation and more cooperation will help monarchs. Thankfully, NAFTA is helping to provide both.

Terry Wanzek grows corn, soybeans, and wheat on his family farm in North Dakota.
Mr. Wanzek serves as a North Dakota Senator and board member of Truth About Trade and Technology (