Among the many problems facing our new president-elect is the world population explosion. Plus its ramifications here at home.

Imagine! It takes only five days for the planet to experience a net population gain (births minus deaths) of 1.25 million, which is about the population of Allegheny County. That means 80 million more people each year. No wonder the present global population of 6.7 billion is expected to grow to as much as 12 billion by 2050.

For the United States, the present population of 304 million is projected to grow to 438 million by 2050. That's the equivalent of adding the current populations of Canada and Mexico.

Those figures come from a local population expert, John Rohe, an official of one of the newest philanthropies in town, the Colcom Foundation. With an endowment of $500 million, Colcom was founded in 1996 by the late heiress Cordelia Scaife May as a vehicle "to ensure quality of life for all Americans by addressing major causes and consequences of overpopulation and its adverse effects on natural resources."

To improve the local quality of life, Colcom has quietly granted $1 million to the Pittsburgh Downtown Partnership to entice matching grants for a Paris-to-Pittsburgh program, which is aimed at improving streetscapes with awnings and tables for outside dining; plus $500,000 for planters. The foundation also has given $3.5 million for the Tribute to Children statue of Fred Rogers on the North Shore and $1 million for the Great Allegheny Passage biking trail.

As for Colcom's work in addressing the population problem, I asked Mr. Rohe: What will global population growth mean for the future of the United States and for our new president?

Mr. Rohe outlined a long list of effects. They include: increased demand for energy as new middle-classes across the globe seek more amenities -- cars, bigger homes, clothes dryers, air-conditioning; various environmental problems, such as pollution, urban sprawl and water shortages that will exacerbate political tensions in many parts of the world; and wars and civil strife as peoples struggle over a wide range of diminishing resources.

All of these will create dislocations that likely will prompt more people to try to immigrate to the United States, a particular problem facing the incoming president. Here Mr. Rohe's background comes into play. As an attorney in Petosky, Mich., he was active in such organizations as the Federation for American Immigration Reform, which is one reason he was brought to Pittsburgh to be Colcom's vice president for philanthropy.

Immigration is an inflammatory topic that makes FAIR a target for pro-immigrant groups. I, conscious of the importance of immigrants in the story of America, disagree with some of its tenets, but I think Mr. Rohe makes some points worth hearing.

He cites a study by the respected Pew Research Center that finds new immigrants and their U.S.-born descendants will account for 82 percent of America's 134 million additional residents between now and 2050. He asks: Can we afford the consequent impact on our environment and quality of life, or do we need to slow immigration in some reasonable way?

But what about the people in desperate circumstances yearning to come to the United States?

Mr. Rohe says there is no way we can absorb everyone in that category. Setting no limits on cheap labor lowers wages and harms the job prospects of low-income people, particularly African Americans.

Clearly, the new president and Congress need to establish a workable immigration policy, a subject on which even President Bush's laudable efforts ran aground. To Mr. Rohe this means enforcing the border and, at least on an interim basis, cracking down on employers who hire undocumented laborers.

Something has to be done about the millions of undocumented workers here already, even though that raises the "forbidden" word -- amnesty. Realism suggests they can't all be shipped home. Mr. Rohe worries that past offers of amnesty already have made U.S. immigration enforcement a joke abroad, inviting new trespassers.

I personally believe the United States must change policies and support birth control around the world to help abate the population explosion. Regrettably, both Christian and Islamic religious groups have pressured the Bush administration to deny funding to the United Nations Population Fund.

Particularly unfortunate in this respect was Pope Paul VI's 1968 "Humanae Vitae" encyclical, which emphasized the Catholic Church's condemnation of artificial birth control. Many American Catholics apparently have ignored that edict, but it has had a deleterious effect in terms of worldwide efforts to control family size.

By this time, I undoubtedly have upset many individuals and groups, including some of my friends. But that is exactly what the incoming president must do if we as a nation are to address the intertwined issues, both nationally and internationally, of quality of life and population growth.