Much like overpopulation, the alleged horrors of DDT and the notion that logging is the chief threat to the bizarrely ennobled spotted owl, the supposedly impending depletion of the world's oil supplies has long been a source of enthusiastic panic for liberals.

So, how about an update?

• Multiple nations -- particularly in Europe and developed parts of Asia -- face not-too-distant fiscal catastrophe because of underpopulation. Citizens in liberal nirvanas such as Denmark, for instance, "are producing fewer babies than it takes to replace themselves, continuing a trend that is worrying demographers, who fear that declining population growth will undermine the welfare system," The Copenhagen Post helpfully notes. "(T)here will be fewer taxpayers to shoulder the burden of tomorrow's pensioners and other benefit recipients."

• Tens of millions worldwide have died of malaria because of environmentalist-backed bans on DDT, which had been used effectively against malaria-carrying mosquitos and would have prevented those deaths.

• And even after vast, federally imposed, job-killing reductions in logging in the Northwest, populations of spotted owls have continued to decline.

The spotted owls' more aggressive cousins, barred owls, appear to be a major culprit, competing with spotted owls for food and sometimes killing their kin. Oops.

That brings us back to oil depletion and related hysteria.

Oil is going to dry up, liberals clamor, so the federal government simply must subsidize development and production of wind and solar power -- and fast!

The assumptions embedded in that hypothesis are ludicrous to thinking people. First, while oil supplies are not infinite, there is little cause to believe they'll disappear anytime soon. Recall a recent point in an Associated Press article: "U.S. oil output is surging so fast that the United States could soon overtake Saudi Arabia as the world's biggest producer." U.S. production is expected to rise 7 percent this year alone.

Then there is the inconvenient fact that we still have mind-boggling supplies of coal, as well as bountiful, greenhouse gas-free nuclear energy and the potential for a lot more.

In short, all three purchasers of "The Collected Witticisms of Al Gore" can keep reading it at night without benefit of a candle.

But let's suppose we do begin to approach the depletion of world oil supplies. The idea that that's an excuse for even more failed federal green energy investment is nutty. Even in the tattered remains of America's free market, when supply drops but demand stays the same or rises, it creates a natural incentive to invest in alternatives. If oil supplies begin decreasing, prices will rise. (That is not to be confused with current high prices that are often related to absurd bans on production in various locations.)

When oil prices finally rise enough to make wind and solar power competitive -- and to make consumers actually consider them even when they aren't dipped in tax-credit sweeteners -- private development and production dollars will flood those industries and make them more feasible.

But when federal busybodies indulge their appetite for economic guesswork and opt for subsidies over the self-correcting workings of the free market, we wind up with taxpayer-robbing debacles such as Solyndra.

Someone will no doubt protest that oil companies, too, have gotten subsidies from one Congress and one president after another. In truth, oil companies haven't received direct handouts in years. But if they had, they would be as inexcusable as the unconstitutional giveaways to green energy.

Congress should tear all energy giveaways out by the root, let energy companies compete without governmental favors and let the American people vote with their dollars on how they will heat their homes and fuel their cars.