(CNN) -- Twenty years ago last month, the North American Free Trade Agreement was born. The goal of NAFTA was straightforward -- to encourage the free movement of goods and capital between the U.S., Mexico and Canada. Few points in history have been as important in forging bonds between our three countries. While NAFTA is a relatively new pact that ties our nations, there are some things that go back far longer that bind us. Like the annual monarch butterfly migration, which started long before the trades, borders or foreign affairs were even an issue. There's no record telling us when monarch butterflies first began their journeys of up to 2,800 miles between southern Canada, the northern U.S., and central Mexico. It's easy to assume that an end date for the migrations is just as elusive, but reality tells a different story.
@highlight
President Obama and his counterparts from Canada and Mexico will meet at summit
@highlight
Carter Roberts, Omar Vidal: They should discuss plight of monarch butterflies
@highlight
2013 was the worst year for these butterflies in recorded history, they say
@highlight
Roberts, Vidal: They're a special to North America, we must stop their decline
Mexico
Mexico
Mexico
He knows firsthand the significant efforts and sacrifices of @placeholder's local indigenous communities, authorities and civil society organizations to protect the sanctuaries.
Canada
Canada
Canada
This plan must include concrete actions to halt destruction of milkweed in the U.S. and @placeholder, restore monarch habitat in all three countries, and strengthen law enforcement in Mexico to stop deforestation.
North America
We urge our heads-of-state, on behalf of all the people of @placeholder, to use this opportunity to commit to the long-term preservation of one of our most ancient and spectacular bonds.