What is Earth Day and why do we celebrate it?

Millions across the globe will pause this Wednesday to observe Earth Day, an annual event conceived to ignite activism for the preservation of a planet now home to some eight billion humans and countless other organisms.

The origins of Earth Day lie in the escalating environmental concerns of the 1960s. Rachel Carson’s seminal 1962 work, "Silent Spring," which exposed the devastating effects of the pesticide DDT on the food chain, became a bestseller and significantly heightened public awareness of nature’s delicate balance.

However, it was US Senator Gaylord Nelson, a Democrat from Wisconsin, who conceived the idea that would become Earth Day. Nelson, long a vocal advocate for environmental protection, was profoundly affected by a massive offshore oil spill in 1969 that deluged the Southern California coast with millions of gallons of oil. After witnessing the devastation firsthand, Nelson envisioned a national "teach-in" focused on the environment, drawing inspiration from similar events held on college campuses to protest the Vietnam War.

Nelson, alongside activist Denis Hayes, expanded this concept beyond university grounds, orchestrating events across the US and coining the name Earth Day.

Climate activists hold a rally to protest the use of fossil fuels on Earth Day at Freedom PlazaAP Photo/Carolyn Kaster

The inaugural Earth Day on 22 April 1970 was strategically scheduled to fall on a weekday between spring break and final exams, aiming to maximise student participation, according to EarthDay.org, where Hayes remains board chair emeritus.

While not a federal holiday, Earth Day serves as a focal point for numerous groups to organise volunteer initiatives, such as natural area clean-ups. A comprehensive list of global events, or the option to register your own, is available at EarthDay.org.

The impact of Earth Day has been considerable. The overwhelming public response to the first observance is widely credited with pressuring the US Congress to address pollution more robustly, leading to landmark legislation including the Clean Air Act and Clean Water Act.

More broadly, it is recognised as the genesis of the modern environmental movement. In subsequent years, Earth Day evolved into a truly global phenomenon, now claiming to have spurred action in over 192 countries. Since 2000, Earth Day has increasingly focused its efforts on climate change, an issue that has gained critical urgency in recent times.

This year’s Earth Day is centred around the powerful slogan "Our Power, Our Planet," encouraging collective action against environmental degradation.