The first Earth Day in 1970 often gets credit for jumpstarting worldwide environmental awareness and the holiday has sure taken off since then. According to The Earth Day Network, a group founded by the organizers of the first celebration, about a billion people will mark the day with concerts, rallies and neighborhood cleanups. Retailers and corporations are also jumping on the bandwagon, offering special shopping events. For the Environment Report, Rebecca Williams explains how companies hope we’ll buy our way to a greener world.

You can't watch TV lately without tripping over ads around Earth Day.

ambi: commercial montage

And at the grocery store, Campbell's soup is wearing an Earth Day label. Campbell's says condensing soup means smaller, lighter cans. So, that means less waste. Of course, they've been doing that since 1897. Long before Earth Day and the environmental movement.

Even Barbie's excited about Earth Day. She's got a limited edition line of accessories. They're made from scraps of fabric that would otherwise have been thrown away. She's so crafty. Of course, there's a reason why it's raining Earth Day ads.

LYON: Companies advertise in ways they think people will respond.

Tom Lyon directs the Erb Institute for Global Sustainable Enterprise at the University of Michigan.

LYON: Five years ago they didn't think they were getting a whole lot of mileage out of advertising green. Now you could say green is the new black, in some sense, every company is moving in this direction.

Lyon says the reality of climate change has been more widely accepted in the past couple years. People are wondering what they can do about it. And companies are trying to tap into that.

Joel Makower has been studying green marketing for 20 years. He's the executive editor of Greenbiz.com. He says Earth Day marketing ebbs and flows over the years. But he hopes Earth Day never turns into a marketing event on the scale of Christmas.

MAKOWER: I think most people recognize the very clear reality that we're never going to shop our way to environmental health and so to the extent that Earth Day becomes an excuse to consume, then we'll have sent all the wrong messages.

But Makower says a lot of companies actually are making big changes in their practices and they should talk about that. He says Earth Day advertising makes sense if the company's doing something to improve all year long. Otherwise he says it might just be a stunt. Others think Earth Day as a marketing opportunity is probably here to stay.

Adam Werbach is the Global CEO of Saatchi and Saatchi S. It's a major ad agency. He says companies see Earth Day as another holiday.

WERBACH: The reason that works so well this year is that Easter came very early and there was a large gap between Easter and Memorial Day and Earth Day fit in really well so that stores could get through their Easter merchandise and start putting green merchandise on the shelves and then move into Memorial Day.

Werbach thinks that's actually not a bad thing. He's had feet in both worlds - as a former president of the Sierra Club. More recently he's been a consultant for Wal-Mart. He thinks consumers should be the ones driving companies to improve their practices.

WERBACH: Our hope is of course that people who have tried these new products will return and buy them in the next month so that in the end you're creating a cycle of demand for green products on shelves so that they don't go away and be a one time occurrence.

But at the same time, Adam Werbach is a little conflicted. He wishes Earth Day could be the one day of the year we could take a break.

No branding. No ads. No buying. Just Earth. Hey, that might make a nice commercial.

For the Environment Report, I'm Rebecca Williams.