It's been nearly 50 years since the first Earth Day was celebrated in the United States, but the increasing urgency now at the heart of the global climate justice movement is making the once radical environmental holiday seem nearly quaint by comparison.

The environmental movement has grown in recent years, driven by an urgency fueled by scientific warnings and a generation of inaction.

In a Los Angeles Times op-ed Monday, Rhea Suh, president of the Natural Resources Defense Council, said that the lessons of the past can help the modern environmental movement make a difference in more dire circumstances.

"The effort Earth Day kicked off relied on grassroots citizen activism forged in the 1960s movements for civil rights, women’s rights and opposition to the Vietnam War," said Suh. "It was about empowering people who'd not been heard to stand up, speak out and work for change."

"A half-century later," Suh said, "we must listen again to the voices that have been silenced too long, from people of color, low-income communities, indigenous people and others who often pay the highest price for environmental hazard and harm."

Politicians, activists, and citizens alike pushed a message of climate justice and immediate action on April 22. A number of commentators used this year's Earth Day as a springboard for pushing bold solutions to the climate crisis—and emphasized the tight timeline to change the future.

"Ecological depletion is being experienced communally as a mounting loss of access and an erosion of possibility," Australian writer Tim Winton said in a column at The Guardian last week.

"It's expressed as grief, and the most palpable, widespread and immediate expression of it is now brewing over climate change," Winton added. "Beneath that grief there's rage."

As part of its ongoing and escalating campaign, hundreds of protesters with the group Extinction Rebellion held a massive "die-in" at the Natural History Museum in London on Monday.

In response to the group's actions over the past week—over 1,000 protesters have been arrested in London as Extinction Rebellion continues to up the ante on its civil disobedience—London Mayor Sadiq Khan announced that the protesters had worn out their welcome and that it was time to move on.

That dismissal drew a sharp retort from progressive writer and political activist Owen Jones on Twitter.

"Climate change is an existential threat to humanity," Jones said. "We're not doing nearly enough to stave it off."

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"Increase the protests, expand the civil disobedience, demand a new economic and social order that protects human survival," said Jones.

Strongly disagree. Climate change is an existential threat to humanity. We’re not doing nearly enough to stave it off. Increase the protests, expand the civil disobedience, demand a new economic and social order that protects human survival #ExtinctionRebelion https://t.co/sijAFIZR8f — Owen Jones (@OwenJones84) April 21, 2019

American journalist Kate Aronoff took a direct, blunt approach to the current environmental reality.

"Happy Earth Day," tweeted Aronoff. "The fossil fuel industry is trying to kill you."

Happy Earth Day the fossil fuel industry is trying to kill you — Kate Aronoff (@KateAronoff) April 22, 2019

Government accountability organization Public Citizen listed the ways the Donald Trump administration is making things worse.

-A coal lobbyist runs the EPA



-An oil lobbyist runs the DOI



-A Monsanto exec runs US Fish & Wildlife



-A BP oil attorney is the nation's top enviro lawyer



-A fossil fuel lobbyist is the EPA's air pollution chief



-A big energy insider regulates our power grid



Happy #EarthDay — Public Citizen (@Public_Citizen) April 22, 2019

Left-leaning American politicians, hoping to harness Earth Day to continue to promote the Green New Deal resolution, stressed the necessity of immediate movement to a green future.

"A generation of inaction on climate change created this emergency," said Rep. Ro Khanna (D-Calif.).

A generation of inaction on climate change created this emergency.



Young activists like @GretaThunberg know that short-term fossil fuel profits are not worth sacrificing the long-term health of our planet.



The next generation will lead on climate. #EarthDay pic.twitter.com/b51TsTDQCL — Ro Khanna (@RoKhanna) April 22, 2019

Rep. Ilhan Omar (D-Minn.) told her followers on Twitter that celebrating Earth Day without targeting the climate crisis was a disservice to the planet.

"Climate change is expected to force more than 100 million people into extreme poverty by 2030," said Omar. "Half of all plants and animals are at risk of extinction. [The] UN says [we] have 12 years to avert catastrophe."

"You cannot discuss #EarthDay without acknowledging the greatest threat to the earth," added Omar.