Glen Colton

Americans planted trees, organized park clean-ups and hosted community events to promote conservation and sustainability for Earth Day 2019.

All those activities are important. But they don't address one of America's biggest environmental challenges — rapid population growth. Since the first Earth Day in 1970, the U.S. population has increased from 205 million to 327 million. It'll surge to 404 million by 2060, according to the U.S. Census Bureau.

Would adding another 77 million people to the United States cause great harm to the environment? It’s a question we need to ask ourselves.

The answer to that question is obvious if one considers the effects of U.S. population growth. We'd have to develop millions of acres of open space to house and feed all these new people.

It's not too late to put America on a more sustainable path, but that would mean having an honest discussion about what’s driving U.S. population growth. Almost 90 percent of population growth is fueled by immigration, according to Pew Research. Humanely scaling back future levels of immigration would help America pursue a sustainable future.

Earth Day's founder, the late Senator Gaylord Nelson (D-Wisconsin), recognized the need to address immigration levels.

"It's phony to say 'I'm for the environment but not for limiting immigration,' " he noted. "It's just a fact that we can't take all the people who want to come here."

He's right. Nearly 160 million people around the world want to move to the United States. There's no feasible way to accept them all. Which means Americans need to make hard choices about who we let in and, most importantly, how many.

Right now, we're refusing to make those choices. Our immigration system is running on autopilot due to "chain-migration" policies, which allow recent immigrants to sponsor their extended family members for green cards. Most of the 1 million legal immigrants who arrive in America each year come through chain migration.

Another 1 million illegal immigrants will slip through our porous southern border this year.

These levels of immigration are historically high. For much of the 20th century, America took in just 250,000 or so foreigners each year. It wasn't until the Immigration and Nationality Act of 1965 that immigration levels started to surge.

The ensuing population growth has already damaged the environment. Developers have paved 40 million acres of forests and fields — an area the size of New York, Massachusetts and New Jersey combined — since the early 1980s to make way for more housing, roads and other structures.

Florida is all too familiar with immigration-fueled urban sprawl. It adds 900 new people to its population each day, and more than half of that total are immigrants. That's equivalent to adding the population of Orlando to the state every year. If this trend continues, more than 5 million acres of farms, forests and open space in Florida will be lost to development by 2070.

This sprawl doesn't just lay waste to beautiful open spaces. It threatens our quality of life in other tangible ways.

Consider water pollution, for instance. Developers are paving over fertile cropland to construct housing developments, shopping centers and highways. To feed a growing population with less land, farmers will turn to harmful pesticides and fertilizers to boost their crop yields. And since we're paving over natural land with impermeable asphalt and concrete, much of that fertilizer will run off into our water supply.

This future isn't inevitable. If Congress simply ended chain migration for recent immigrants' non-nuclear family members, it'd reduce the projected U.S. population in 2060 by tens of millions of people — without forcing anyone currently in the United States to leave.

Likewise, requiring all employers to use E-Verify, a free online system that vets people's ID papers to confirm their work eligibility, would humanely deter illegal immigration. Most illegal immigrants come here to work -- if they know they won't find jobs, they won't make the dangerous journey north in the first place.

Planting trees and cleaning up parks is great. But if Americans really want to preserve open spaces for future generations, they'll need to think bigger. It's time for environmentalists to call for humane reductions in immigration levels.

Glen Colton is an environmentalist and long term sustainability activist who lives in fast growing Fort Collins, Colorado.