Resource Science: US population growth and immigration

Immigration into the U.S. is a big issue. There is currently intense debate and protest over immigration policy, particularly deportations of illegal immigrants. Immigration, legal or illegal, increases the population of the country, and as I’ve noted previously, human population growth is the root cause of environmental impacts (WLJ March 2021, September 2023, May 2024 and November 2024, see the References).

The more people there are, the more demand there is for resources, roads and open space as cities and residential areas expand into forest, rangeland and farmland. I’m writing about this issue again to provide an update on population numbers, and because I think it has been largely ignored in the debate on immigration policy, with the notable exception of Arizona Attorney General Mark Brnovich (see the References).

Politicians and economists have expressed concern that a decline in birth rate per woman in the U.S. will result of a shortage of people and that more immigration is needed for economic growth. For example, former President Bill Clinton recently expressed concern that the U.S. has the lowest birth rate in more than 100 years and we need immigrants to grow the economy. The Penn Wharton Budget Model at the University of Pennsylvania reported that U.S. population growth is projected to decline, the population will become older and more immigration is needed for the economy.

We need clear terminology on this issue. Clinton refers to a lower birth rate and Penn Wharton refers to population growth declining. I think we should focus on population numbers. I’m sure Clinton and the Penn Wharton people are smart, but they should recognize that the population is increasing. The Census Bureau reports that the U.S. population continues to increase with one birth every nine seconds, one death every 11 seconds, one international migrant every 22 seconds and a net gain of one person every 16 seconds.

As of today, the U.S. population is now more than 342 million (342,003,556 people), an increase of more than 4.7 million (4,734,216) from Oct. 15, 2024, to June 25, 2025. This increase over 253 days (about eight months) equals a rate of more than 6.8 million (6,829,509) people per year, which is an increase of about 2% of the current population per year. The rate of increase has been generally steady since the year 1900 when the population was 76 million (see the graph). If the rate of population increase remains the same or increases, there will not be a shortage of people, but there will be increasing demands for resources and land.

I don’t know the number of illegal immigrants in the U.S., but it’s been reported to be more than 10 million. I haven’t studied the Penn Wharton model of future population growth either. But it is clear that the U.S. population is growing at a steady rate and immigration contributes to this growth. This population growth results in increased environmental impacts, crowding and traffic, loss of open spaces and impacts on forests and agricultural land.

It might be a simple observation, but our population can’t grow forever. China has about 1.4 billion people and the world population is now 8.1 billion, showing the result of long-term population growth. Population growth is evidently important for the economy and markets, but I think this needs to be balanced with environmental quality. Recent large-scale immigration has contributed to the U.S. population growth and is an important consideration on this issue.

Immigration is the one source of population growth that our government can control. In the U.S., with our rights and freedom, the government cannot control citizens’ choices on having children. Politicians need to make policies considering many factors, and impacts of immigration on the U.S. population, the economy, and the environment need to be assessed together. — Matt Cronin, WLJ columnist 

(Matt Cronin is a biologist with Northwest Biology and Forestry Company LLC in Bozeman, MT, and a teaching professor at Montana State University. He may be contacted at croninm@aol.com.)