Earth Day was marked Sunday across the U.S. It was started in 1970 and is considered by many to be the birth of the modern environmental movement. KJZZ's Bri Valdivia reports.

Earth Day and Arbor Day highlight ways to think about our environmental impact, and acts as a way to get people to consider the habits they have year-round.

Some critics though, including this CNN viewer on iReport, describe Earth Day as an outdated and pointless celebration that people only use to make themselves feel good.

"We've relegated Earth Day, we've made this a cause. The Earth is so much bigger than any one cause."

But Donna DiFrancesco, the Conservation Specialist for the City of Mesa, works year-round to get people educated about living green and conservation at home. She sees Earth Day and Arbor Day as a way to kick-start environmentally friendly habits by showing people that it is easy to be green.

"It's the idea of, like, encouraging people to take that step and make it a special event. Show them that, hey, this is pretty easy to do, and it might be something that encourages them to do it all the time," DiFrancesco said.

Earth Day isn't about being nice to the Earth for one day; it's about encouraging people to think about their actions all the time.