If demography is destiny, then news of America's decline is (like Mark Twain's death) decidedly premature.

Statisticians tell us Oct. 17 (at 7:46 a.m. EDT, according to the Census Bureau's estimate) was the day America's population reached, then surpassed, 300 million people. That's a three followed by eight zeroes.

Unfortunately, Oct. 17 was Halloween with an extra "Boo" (B with two zeroes) for various "greens" and ecological radicals mired in Malthusian desperation and myths of looming disaster.

For decades, the doomsayers have been predicting catastrophe wrought by the "population explosion" and diminishing resources.

Author and columnist Mark Steyn notes in his new book, "America Alone" (Regnery Publishing), "The end of the world's nighness isn't something you'd want to set your watch by. "

Steyn provides a collection of the dire predictions made by "Chicken Little's eminent successors."

Steyn's list includes:

-- 1968, in "The Population Bomb," distinguished scientist Paul Ehrlich declared, "In the 1970s the world will undergo famines -- hundreds of millions of people are going to starve to death."

-- 1972, in "The Limits to Growth," the Club of Rome announced that the world would run out of gold by 1981, of mercury by 1985, tin by 1987, zinc by 1990, petroleum by 1992, and copper, lead and gas by 1993.

-- 1976, Lowell Ponte published a huge bestseller called "The Cooling: Has the New Ice Age Already Begun? Can We Survive?"

-- 1977, Jimmy Carter confidently predicted that "we could use up all of the proven reserves of oil in the entire world by the end of the next decade."

"None of these things occurred," Steyn writes. "Contrary to the doom-mongers' predictions, millions didn't starve."

Steyn, however, isn't against gloomy prognostications, per se. In fact, "America Alone" is a doom book of a peculiar sort -- it's insistently witty and trenchantly written. Both are achievements, given the core subject matter: American demographic success and vitality (fecundity, folks) compared to the demographic decline of other democracies and modern, industrialized nations.

Steyn is an arch "Euro-pessimist," who backs his pessimism with numbers.

Europeans are reproducing below the "replacement rate" -- thus the average age of their populations is increasing sharply. If current trends continue, by 2050 one in three Germans and Italians will be over 65 years old. In the United States, only one in five will be so gray.

As a result, the Europe of the European Union (Steyn disdainfully calls it "Eutopia") faces economic decline and risks systemic change. Steyn writes: "Tax revenues that support the ever growing numbers of the elderly and retired have to be paid by equally growing numbers of the young and working. The design flaw of the radically secularist Eutopia is that it depend on a religious-society birth rate."

Japan faces the same "gray threat." Even China has a birthrate below the demographic replacement rate. Among the modern industrial nations, only the United States (and possibly India) has the knack for reproduction.

The United States also grows through immigration that includes political and cultural integration.

Europe's Muslims, however, are multiplying -- but they are not integrating culturally. Steyn argues that if European nations fail to culturally integrate Muslims, Europe faces profound political changes.

"As fertility dries up," he writes, "so do societies. Demography is the most obvious symptom of civilizational exhaustion, and the clearest indicator of where we're headed."

Islam cannot enjoy "political sovereignty" in Europe. Steyn adds: "Those lefties who bemoan what America is doing to provoke 'the Muslim world' would go bananas if any Western politician started referring to 'the Christian world.' When such sensitive guardians of the separation of church and state endorse the first formulation but not the second, they implicitly accept that Islam has a political sovereignty, too."

America remains an exception among democracies, Steyn concludes. America's population climbs at a healthy rate, and America politically and culturally integrates immigrants.

At least part of America remains an exception. "Demographic trends," Steyn observes, cheekily, "suggest that the blue state ought to apply for honorary membership in the EU; in the 2004 election, the Bush-voting states had fertility rates 12 percent higher than Kerry-voting states. Barring a sudden change in electoral fortunes, Democrats are going to be even more depressed at their 2010 and 2020 reapportionments."