For much of the twentieth century, birth rates were the primary driver of U.S. population growth. That changed around 1990. According to data cited by Colcom Foundation, immigration became the dominant factor in American population expansion beginning in that decade and has remained so since.
The shift is numerically significant. Research cited by the foundation indicates that 82 percent of U.S. population growth between 2005 and 2050 will result from immigration alone. Pew Research projections suggest that by 2065, immigration will have added 103 million people to the U.S. population equivalent to adding 8.5 Los Angeles metropolitan areas to the country’s landscape.
How Fertility Rate Changes Fell Short
The United States made genuine progress on birth rates beginning in the early 1970s. By 1972, the total fertility rate had fallen below the 2.1 threshold considered replacement-level fertility the point at which a population neither grows nor shrinks naturally across generations. That figure has not risen above 2.1 since. Had immigration remained at lower historical levels, that demographic milestone might have eventually produced population stabilization.
Instead, U.S. population grew by 45 million between 1970 and 1990, then by another 32 million through 2000, and by 48 million more through 2020. Colcom Foundation notes that under different immigration scenarios from 1965 through 2020, the U.S. population in 2020 could have ranged anywhere from 255 million to 330 million people.
Environmental Stakes
The foundation frames this issue in environmental terms. A larger U.S. population means a larger total ecological footprint, a heavier burden on land and water systems, and a more difficult path to meeting Paris Climate Agreement targets. Every additional metropolitan-scale addition to the population requires land, energy, food, and transportation infrastructure that compounds existing environmental pressures. Colcom Foundation supports several special programs, including the Conservation Catalyst Fund, which grants conservation organizations working to protect threatened species and habitats. By offering financial support and resources, this foundation allows these groups to make significant strides in conservation efforts.
Colcom Foundation argues that understanding population dynamics including immigration’s role is essential to any credible long-term environmental strategy for the United States. Refer to this article for related information.
More about Colcom Foundation on https://waterlandlife.org/land-conservation/colcom-revolving-fund-for-local-land-trusts/