Scientists and their supporters across the globe are expected to march in the thousands Saturday amid growing anxiety over what many see as a mounting political assault on facts and evidence.
Anchored in Washington, with satellite marches planned in more than 600 cities worldwide, the first-ever March for Science was described by organizers as a rallying call for the importance of science in all aspects of daily life.
"The march has generated a great deal of conversation around whether or not scientists should involve themselves in politics," said a statement on the official website, MarchforScience.com.
"In the face of an alarming trend toward discrediting scientific consensus and restricting scientific discovery, we might ask instead: can we afford not to speak out in its defense?"
Organizers say the march is non-partisan and is not aimed against US President Donald Trump or any politician or party, though the Republican US leader's administration has certainly "catalyzed" the movement, according to honorary national co-chair Lydia Villa-Komaroff, a molecular and cellular biologist.
She spoke of a growing "disconnect between what science is and its value to society."
"Fundamental basic science really underlies all of modern life these days. We have taken it so for granted," Villa-Komaroff told reporters this week.
Trump has vowed to slash budgets for research at top US agencies, including the National Institutes of Health, NASA, the National Oceanic and Atmospheric Administration, and the Environmental Protection Agency, which could lose a third of its staff if Congress approves the proposal.
He also named as head of the EPA Oklahoma lawyer Scott Pruitt, who claimed last month that carbon dioxide is not the main driver of global warming, a position starkly at odds with the international scientific consensus on the matter.
"In the response to this absurdity lies cause for hope," Paul Hanle, chief executive officer of independent scientist and journalists group Climate Central wrote in an op-ed this week.
"Seeing the assault on fact-based thinking, scientists are energized."
- Marches worldwide -
The US capital rally begins Saturday at 8:00 am (1200 GMT), and will be capped with a march from the National Mall to the Capitol at 2:00 pm.
Hundreds of satellite marches are planned across the United States and worldwide -- with more than 600 listed as of Friday -- including in Australia, Brazil, Canada, many nations in Europe, Japan, Mexico, Nepal, Nigeria and South Korea.
At a time when the Earth has marked three consecutive years of record-breaking heat, and ice is melting at an unprecedented rate at the poles, risking massive sea level rise in the decades ahead, some marchers say it is more important than ever for scientists to communicate and work toward solutions to curb fossil fuel emissions.
"I will be marching in London on Saturday not so much to fly the flag for science -- though I believe it is something worth celebrating -- but because I think that in these fractious political times, when we are facing challenges that are truly global, it has never been more important for scientists to go public," said Stephen Curry, vice-chair of Science is Vital and Professor of structural biology at Imperial College, London.
Some scientists, however, expressed concern that the march might increase polarization.
"The right will say the demonstration is the tool of the political left," Robert Young, a geologist at Western Carolina University, told AFP.
"That is why a march is a problem, it's the wrong way to try to communicate."
Despite his concerns, Young said he planned to join the march.
David Reay, a professor of carbon management at the University of Edinburgh, said scientists "are not famous for their camaraderie. We are trained to question, criticize and, where needed, contest each other's work."
"That we are now marching together is testament to just how threatened our disparate community feels," he added.