What will America stand for in 2050?

President Obama has encouraged Americans to start laying a new foundation for the country – on a number of fronts. He has stressed that we'll need to have the courage to make some hard choices. One of those hard choices is how to handle immigration. The US must get serious about the tide of legal and illegal immigrants, above all from Latin America.

It's not just a short-run issue of immigrants competing with citizens for jobs as unemployment approaches 10 percent or the number of uninsured straining the quality of healthcare. Heavy immigration from Latin America threatens our cohesiveness as a nation.

The political realities of the rapidly growing Latino population are such that Mr. Obama may be the last president who can avert the permanent, vast underclass implied by the current Census Bureau projection for 2050.

Do I sound like a right-wing "nativist"? I'm not. I'm a lifelong Democrat; an early and avid supporter of Obama. I'm gratified by his nomination of Sonia Sotomayor to the Supreme Court. I'm also the grandson of Eastern European Jewish immigrants; and a member, along with several other Democrats, of the advisory boards of the Federation for American Immigration Reform and Pro English. Similar concerns preoccupied the distinguished Democrat Barbara Jordan when she chaired the congressionally mandated US Commission on Immigration Reform in the 1990s.

Congresswoman Jordan was worried about the adverse impact of high levels of legal and illegal immigration on poor citizens, disproportionately Latinos and African-Americans. The principal beneficiaries of our current immigration policy are affluent Americans who hire immigrants at substandard wages for low-end work. Harvard economist George Borjas estimates that American workers lose $190 billion annually in depressed wages caused by the constant flooding of the labor market at the low-wage end.

The healthcare cost of the illegal workforce is especially burdensome, and is subsidized by taxpayers. To claim Medicaid, you must be legal, but as the Health and Human Services inspector general found, 47 states allow self-declaration of status for Medicaid. Many hospitals and clinics are going broke because of the constant stream of uninsured, many of whom are the estimated 12 million to 15 million illegal immigrants. This translates into reduced services, particularly for lower-income citizens.

The US population totaled 281 million in 2000. About 35 million, or 12.5 percent, were Latino. The Census Bureau projects that our population will reach 439 million in 2050, a 56 percent increase over the 2000 census. The Hispanic population in 2050 is projected at 133 million – 30 percent of the total and almost quadruple the 2000 level. Population growth is the principal threat to the environment via natural resource use, sprawl, and pollution. And population growth is fueled chiefly by immigration.

Consider what this, combined with worrisome evidence that Latinos are not melting into our cultural mainstream, means for the US. Latinos have contributed some positive cultural attributes, such as multigenerational family bonds, to US society. But the same traditional values that lie behind Latin America's difficulties in achieving democratic stability, social justice, and prosperity are being substantially perpetuated among Hispanic-Americans.

Prominent Latin Americans have concluded that traditional values are at the root of the region's development problems. Among those expressing that opinion: Peruvian writer Mario Vargas Llosa; Nobelist author Octavio Paz, a Mexican; Teodoro Moscoso, a Puerto Rican politician and US ambassador to Venezuela; and Ecuador's former president, Osvaldo Hurtado.

Latin America's cultural problem is apparent in the persistent Latino high school dropout rate – 40 percent in California, according to a recent study – and the high incidence of teenage pregnancy, single mothers, and crime. The perpetuation of Latino culture is facilitated by the Spanish language's growing challenge to English as our national language. It makes it easier for Latinos to avoid the melting pot and for education to remain a low priority, as it is in Latin America – a problem highlighted in recent books by former New York City deputy mayor Herman Badillo, a Puerto Rican, and Mexican-Americans Lionel Sosa and Ernesto Caravantes.

Language is the conduit of culture. Consider: There is no word in Spanish for "compromise" (compromiso means "commitment") nor for "accountability," a problem that is compounded by a verb structure that converts "I dropped (broke, forgot) something" into "it got dropped" ("broken," "forgotten").

As the USAID mission director during the first two years of the Sandinista regime in Nicaragua, I had difficulty communicating "dissent" to a government minister at a crucial moment in our efforts to convince the US Congress to approve a special appropriation for Nicaragua.

I was later told by a bilingual, bicultural Nicaraguan educator that when I used "dissent" what my Nicaraguan counterparts understood was "heresy." "We are, after all, children of the Inquisition," he added.

In a letter to me in 1991, Mexican-American columnist Richard Estrada described the essence of the problem of immigration as one of numbers. We should really worry, he wrote, "when the numbers begin to favor not only the maintenance and replenishment of the immigrants' source culture, but also its overall growth, and in particular growth so large that the numbers not only impede assimilation but go beyond to pose a challenge to the traditional culture of the American nation."

Obama should confront the challenges by enforcing immigration laws on employment to help end illegal immigration. We should calibrate legal immigration annually to (1) the needs of the economy, as Ms. Jordan urged, and (2) past performance of immigrant groups with respect to acculturation.

We must declare our national language to be English and discourage the proliferation of Spanish- language media. We should limit citizenship by birth to the offspring of citizens. And we should provide immigrants with easy-to-access educational services that facilitate acculturation, including English language, citizenship, and American values.

Lawrence Harrison directs the Cultural Change Institute at the Fletcher School, Tufts University, in Medford, Mass. He is the author of "The Central Liberal Truth: How Politics Can Change A Culture And Save It From Itself."