The holiday remains one of the largest secular observances in the world, used to spotlight ongoing threats including plastic pollution, deforestation, and global warming. According to EarthDay.org, "more than one billion people now participate in Earth Day activities each year, making it the largest civic observance in the world."

Earth Day falls on April 22 each year but is not a federally recognized holiday, according to USA TODAY. Why do we celebrate Earth Day? The roots of Earth Day t