Earth Day is 40 years old this week, and it's an anniversary worth celebrating.

There are still plenty of threats to the planet, but there has been heartening progress, too, in the four decades since the first Earth Day on April 22, 1970.

Heading the list are the environmental laws, cleanups and societal changes that have resulted in the significant reversal of the fouling of land, air and water.

We urge everyone to take advantage of this occasion and learn something -- about recycling, energy conservation, sustainable food production, reduced waste and pollution -- and to think about ways to preserve the planet for everyone and everything that lives here.

This is truly an endeavor in which one person can make a difference.

We also encourage everyone to make that commitment permanent -- and non-partisan. Keeping the planet clean and green should not be a left/right issue.

Earth Day is a reminder, too, that as the planet's population grows, and the world becomes more "developed," there will likely never again be a time when people won't have to consider the environment.

To some, Earth Day is an easy target, an observance they deem quaint, corny and naive. We disagree with that kind of dismissive criticism.

Everyone has a stake in the planet's health, and while the Earth's resources are vast, they are not infinite, inexhaustible or incorruptible.

Earth Day is more than an opportunity to talk in catch phrases or simply to think back with nostalgia to a time when environmental matters went under the heading of "the ecology."

Earth Day's 40th birthday should be a time to be reinspired, and to affirm that not only can people coming together make changes, sometimes they can make all the difference.