Earth Day 2022 is on Friday, April 22. It will be the 52nd anniversary of Earth Day and marked by various events around the world. 

According to EARTHDAY.ORG, a nonprofit that coordinates these events, the theme of Earth Day 2022 is "Invest In Our Planet." This theme is meant to encourage businesses, governments and citizens to act now on climate change and other issues for 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.

Earth Day is celebrated to raise public awareness about the environment and mark the annual anniversary of the first Earth Day.  

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.

Earth Day has 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.

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.