The Colorado River — which supplies water to around 40 million people across seven states — is rapidly drying up. California recently agreed to cut 10% of its Colorado River allocation, year over year, for the foreseeable future. Arizona has already slashed its allocation by half over the last 10 years.

Meanwhile, Utah is busy renegotiating its Colorado River agreement, which expires along with other states’ in 2026. Currently, 27% of the Beehive State’s water derives from the Colorado River. Six in 10 Utahns benefit directly from its streams.

These sorts of resource challenges are only becoming more pervasive across the country. Climate change is unquestionably a contributor, and it’s imperative that our leaders pursue policies that realistically deal with it instead of using climate change as an excuse for not taking actions that can protect the nation’s national resources.

Like the elephant in the room that most policymakers refuse to acknowledge: explosive population growth.

The U.S. population has increased by a staggering 50 million people since 2000, with arid Southwestern states like Utah experiencing some of the most rapid growth. Today, the Beehive State ranks among the five fastest-growing states in the nation. Utah added more than 50,000 people last year. Weber County alone grew by over 2,400.

Such growth isn’t the result of Americans having more kids. The U.S. birth rate has actually trended downward over the last several decades.

Yet, the population keeps booming because we’ve opened our doors to tens of millions of immigrants. Those immigrants — most of whom are indeed seeking a better life — have good reasons for wanting to come here. The United States, despite its flaws, is still arguably the best place on earth for the global poor to accrue material wealth and enjoy the political and personal freedoms in a modern, advanced society.

But providing these opportunities to everyone in the world who wants to come here is not why U.S. immigration policy exists or what it should ever become, and to continue to ensure that America remains a place where people can continue to come and to thrive, our nation needs sustainable immigration policies that ensure we have enough water, land and jobs for everyone already here.

For much of our country’s history, newcomers to the United States could pursue “Manifest Destiny” all the way to the West Coast, where the American landmass drops into the Pacific. But that era ended long ago. There’s no more frontier to settle. Now, adding more people inevitably means draining more reservoirs, bulldozing more forests and scraping up more open spaces to construct additional houses, businesses and shopping centers.

Simply put, we’re operating a 19th century immigration policy — which has been completely mythologized — with 21st century resource constraints. And nearly unlimited demand for limited resources is a recipe for disaster.

Look no further than India for an example of unsustainable growth. The nation has added over a billion people since gaining independence from Great Britain in 1947. India recently overtook China as the most populous country in the world.

Such unchecked growth comes with costs. By 2040, some 270 million Indians are projected to be living in the nation’s cities, where overcrowding is already a major issue. Experts predict that future overcrowding will exacerbate existing crises like severe pollution and crumbling infrastructure.

The problem comes down to the nation’s land and water supplies. India makes up just 2% of the globe’s total landmass. It simply doesn’t have the resources to support 1.4 billion inhabitants — a whopping 18% of the entire world population.

The United States faces a similar, though not quite as dire, problem. With about 345 million residents, we’re the third most populous country behind India and China. And we’re projected to reach 404 million inhabitants by 2060, according to the U.S. Census Bureau, almost entirely due to immigration rather than births.

Unfortunately, that pace of growth is straining our natural resources. Over the last four decades, we sacrificed nearly 69,000 square miles — an area larger than Florida, comprising around 3,455 acres per day — to make room for burgeoning cities and towns. That’s goodbye to approximately 11.1 million acres of cropland, 13.1 million acres of pasture and rangeland, and 18.8 million acres of forest.

And here’s the kicker: A startling 60% of this land loss resulted directly from population growth, as opposed to consumption habits.

It’s even beginning to imperil our most treasured national parks, like Yellowstone. Several of Yellowstone’s fauna, including bison, bighorn sheep and songbirds, rely on the areas surrounding the park for migration. But many of these crucial habitats are now being razed to create commercial centers and housing developments. That isn’t sustainable.

Too many Americans still hold to the false idea that our nation has the capacity to grow indefinitely. It’s past time to reject that narrative — along with policies of infinite expansion that drain our aquifers, deplete our rivers and transform our stunning natural landscapes into strip malls.

Eric Ruark is director of research for NumbersUSA.