Earth Day: When is it and why do we celebrate it?

Earth Day 2025 takes place on Tuesday, April 22. It is the 55th anniversary of Earth Day and marked by various events around the world.

The theme of Earth Day 2025 is "Our Power, Our Planet," and calls for the world to unite around renewable energy in order to triple global clean energy generation by 2030.

"We need people power to support the big switch to renewable energy," Kathleen Rogers, President of EARTHDAY.ORG said in a statement announcing the 2025 theme. "We encourage everyone to talk to your local mayor, boss, neighbors, community leaders, and local and national legislators, to explore and to champion switching to renewables."

According to the statement, 49 countries already generate more than half of their electricity from solar, wind, water and geothermal resources, including Austria, Brazil, Canada, Denmark, New Zealand, Norway, Sweden and Switzerland; Iceland obtains 99.99% of its energy from renewable sources.

In the first half of 2023, renewable energy represented 25% of the US's total electricity output, and experts at the think tank Energy Innovation Policy & Technology predict that this could rise to 90% by the year 2035 at no extra cost.

Renewables not only reduce carbon emissions, but they also offer significant economic opportunities, according to the U.N., which estimates that a total of 30 million jobs could be created by renewable energy industries by 2030.

"This presents an enormous opportunity for entrepreneurs, industries, and those seeking well-paying careers." Tom Cosgrove, Chief Creative and Content Officer at EARTHDAY.ORG, said in the statement.

Rogers added: "Change can be daunting, but we must move away from our dependence on fossil fuels and embrace a sustainable future."

Despite there having been more than 50 Earth Days, climate change and other environmental issues still threaten the health of the planet. Michael Mann, a distinguished professor of atmospheric science at Penn State and author of "Our Fragile Moment: How Lessons from Earth's Past Can Help Us Survive the Climate Crisis" (PublicAffairs, 2023), notes Earth Day is an opportunity to take stock of where we stand in the battle to live sustainably on this planet.

"We are not yet on the path toward stabilizing the warming of our planet below dangerous levels," Mann previously told Live Science in an email. "Earth Day is an opportunity to have a conversation about what we need to do. Truth be told, every day should be Earth Day. Without a livable planet, we have nothing."

Nelson started Earth Day after seeing the environmental damage of an oil spill in Santa Barbara, California in 1969. Inspired by student anti-Vietnam War protests, he organized a national "teach-in" on college campuses that focused on educating the public about the environment, according to EARTHDAY.ORG.

Nelson persuaded Rep. Pete McCloskey of California to be co-chairman and recruited political activist Denis Hayes as national coordinator. With a staff of 85 built by Hayes, they were able to rally 20 million people across the U.S. on April 22, 1970, according to a 2012 blog post on the United Nations Foundation website by John Maleri, then associate director of Earth Day.

The team chose April 22, a Wednesday, because they thought a weekday falling between Spring break and students' exam finals would encourage the highest number of students to participate, according to EARTHDAY.ORG. On that day, thousands of colleges and universities held protests against environmental destruction. But it wasn't just students who participated, the event gained national media attention and many people gathered in public areas to talk about the environment and find ways to defend the planet. In total, about 10% of the entire U.S. population participated.

"It was on that day that Americans made it clear that they understood and were deeply concerned over the deterioration of our environment and the mindless dissipation of our resources," Nelson wrote in the EPA Journal in 1980.

The annual event grew in size and popularity after 1970. In 1990, Earth Day went global, with 200 million people in 141 countries participating in the event, according to EARTHDAY.ORG.

Related: Why celebrate Earth Day? Here are 12 reasons.

Earth Day is celebrated to raise public awareness about the environment and mark the annual anniversary of the first Earth Day. Decades later, environmental issues continue. EARTHDAY.ORG notes the fight for a clean environment is becoming more urgent to address environmental issues, especially climate change.

Climate change is caused by human activities such as burning fossil fuels, which emit heat-trapping carbon dioxide and other greenhouse gases into the atmosphere that raise global temperatures and disrupt weather patterns. The impacts of climate change around the world include extreme weather events such as massive floods and intense wildfires. In 2021, thousands of scientists warned that ignoring climate change will yield "untold suffering" for humanity.

"We need to fight climate change harder, to keep our planet habitable and flourishing," Jonathan Overpeck, dean of the School for Environment and Sustainability at the University of Michigan, previously told Live Science in 2020, as Earth Day celebrated its 50th anniversary.

The first Earth Day helped put environmental issues on the national agenda in the U.S. The event also inspired various environmental legislation in the 1970s, including the Clean Water Act (1972) and the Toxic Substances Control Act (1976), according to Columbia University's State of the Planet news website.

And the impact of Earth Day has gone far beyond the U.S. For example, the United Nations General Assembly formally recognized April 22 as International Mother Earth Day in 2009, according to the United Nations Environment Programme. On Earth Day 2016, the United Nations adopted the Paris Climate Agreement, which saw nations around the world aim to keep global warming preferably below 1.5 Celsius (2.7 Fahrenheit) and well below 2 C (3.6 F) compared to pre-industrial levels.

However, despite Earth Day moments such as the Paris Climate Agreement pledges, climate change is far from resolved. The UN Secretary-General António Guterres said at the Economist Sustainability Summit in 2022 that the 1.5-degree goal is on "life support," and with emissions continuing to increase, "we are sleepwalking to climate catastrophe."

Each year, organizations and individuals engage in Earth Day activities, projects, and campaigns to promote, protect or restore the environment. Earth Day quizzes are one popular activity, and organizations such as NASA, Conservation International and EARTHDAY.ORG have online quizzes for people to test their environmental knowledge. Children in the U.S. often celebrate by creating Earth Day-themed school projects such as Earth Day crafts and Earth Day drawings.

"There are two simple ways to celebrate Earth Day to make the world a little better," Nathaniel Weston, an associate professor of environmental science at Villanova University in Pennsylvania previously told Live Science. "The first is to promote understanding of important environmental issues so that more people are aware of the critical actions we need to take to protect our environment. The second is to commit yourself to service on or around Earth Day — plant some trees, clean up a stream or help your local community garden."