We all suspected this would happen sooner or later, but it was nonetheless received as a milestone of historic significance this week when China surpassed the U.S. to become the world’s largest consumer of energy. This reverses 100 years of the United States as the world’s energy consumer and in many ways it is good news. Considering that China has about four times as many people as the United States, it should be consuming more power.

The not-so-good news is that this shift is not a result of conservation on the part of consumers so much as it reflects the impact of the economic downturn in the United States. The International Energy Agency, which reported the new data on world energy consumption, said that the average American consumer still uses significantly more energy than his Chinese counterparts, but that the surge in overall power consumption in China reflects mass industrialization there and the comparable slowdown in manufacturing activity here.

But a bigger concern has to do with supply. As the world’s top energy consumer, the U.S. had to make sure it had enough energy to satisfy that demand. Along with cobbling together a host of traditional and alternative energy sources produced here at home, we’ve long had to tap overseas sources of oil. Now, that another country has become the world’s biggest consumer of oil, we are reminded that we are competing for a limited supply of world oil. By now we all should be well aware of the economic and the national security dangers risks of being too dependent on foreign oil. But a potentially bigger risk would be losing access to some of that worldwide supply that we’ve always depended on. Of course, the way to mitigate that risk is to bolster our domestic supplies.

The fact that the typical Chinese consumers are not yet a major factor in the country’s increase should offer some sense for how much demand outside of the U.S. still stands to grow. In fact, this week’s rise in oil prices is being attributed to the news of China’s increased consumption. “The market is growing concerned about the future supply of oil,” said one analyst.