For most of U.S. history, population growth was driven primarily by the birth rate. That changed around 1990. Colcom Foundation’s research traces a shift in the primary driver of U.S. demographic growth that, the foundation argues, has profound consequences for the country’s environmental future.

The Turning Point in Population Dynamics

The United States reached a total fertility rate below 2.1, which is replacement level, in 1972. Sustained at that level, the birth rate would have led to population stabilization over several decades. The fertility rate has not exceeded 2.1 since that year. Despite this demographic achievement, U.S. population continued to grow. By the time of the 1990 census, 45 million people had been added since 1970. Immigration had become the primary engine of that growth.

Colcom Foundation cites Pew Research data showing that 82 percent of U.S. population growth between 2005 and 2050 will result from immigration. By 2065, immigration is projected to account for 103 million of the 110 million people added to the U.S. population, the equivalent of adding 8.5 Los Angeles metro areas to the national landscape.

Environmental Consequences at Scale

Colcom Foundation argues that the environmental consequences of this trajectory are not abstract. A larger population means more land consumed by development, greater biocapacity demand, higher aggregate emissions even as per capita figures improve, and more pressure on species and ecosystems already under stress. The foundation notes that scenarios modeling different immigration levels between 1965 and 2020 produce 2020 populations ranging from 255 million to 330 million, a difference with significant environmental implications.

The foundation does not frame this as an anti-immigration argument but as an environmental one. Its position is that a country committed to meeting Paris Climate goals, conserving native species, and reducing ecological overshoot cannot afford to treat population size as a politically untouchable variable. Colcom Foundation continues to push for that conversation to take place in policy and public discourse. Refer to this article to learn more.

Find more information about Colcom Foundation on https://waterlandlife.org/land-conservation/colcom-revolving-fund-for-local-land-trusts/