(CNSNews.com) - "As Americans commemorate Earth Day on April 22, the country's ecology and resource base continue to be imperiled by mass immigration," says a group that wants the "rule of law" enforced at the nation's borders.

"More than any other factor, population growth in the United States is adding to the stress on our environment, and nearly all of the nation's projected population growth over the next 40 years will be a direct result of current and future immigration," said the Federation for American Immigration Reform (FAIR).

The group notes that since the first Earth Day in 1970, the U.S. population has grown by more than 100 million people -- "driven by ever increasing levels of immigration." It points to Census Bureau predictions that the current U.S. population of around 300 million will increase to 435 million by 2050.

"It is unrealistic to believe that we can address issues like pollution, urban sprawl, and the depletion of water and other vital resources, while continuing on the population path we have been on over the past several decades," said FAIR President Dan Stein.

FAIR was founded in 1979 to address concerns about the role of immigration in U.S. population growth. On Earth Day 2008, the organization is renewing its call for a rollback of "excessive" immigration to the United States -- as well as a "thoughtful consideration" of how immigration policies will affect the long-term environmental health and security of the nation.

Unless the government does something about the ever-increasing levels of immigration, Americans will face a future that holds worsening environmental conditions, dwindling resources, and greater dependence on foreign energy sources, Stein said. "This was not the sort of future envisioned by people like the late Senator Gaylord Nelson who initiated the Earth Day celebration," he added.

"As we observe Earth Day, we call upon our nation's leaders to get off the immigration and population growth spiral that can only lead to further environmental degradation."