Scientists are taking the unprecedented step of staging marches in more than 600 cities worldwide in the face of what they see as a growing political assault on verifiable information. Thousands of scientists and their supporters are attending March for Science events Saturday across the globe, including those in Australia, Brazil, Canada, Cape Town, London Madrid, Nigeria and Seoul. The March for Science thrusts scientists, who generally avoid advocacy and whose work is based on impartial experimentation, into a more visible spotlight. For nuclear physics graduate student Chelsea Bartram, White House adviser Kellyanne Conway's "alternative facts" were the last straw. President Donald Trump had disputed photographic evidence of the size of his inauguration crowd. Reporters challenged him. Conway's response — that the administration gave "alternative facts" — has become a widely used hashtag for anything demonstrably untrue. Watch: Scientists Speak Out and March for Science "Many scientists I know, myself included, spend so many hours in the lab sacrificing enormous amounts of their life for this abstract idea" that understanding reality can benefit human civilization, said Bartram, who is pursuing a doctorate at the University of North Carolina at Chapel Hill. "And then to have someone say, 'Well, that's not important anymore,' it's so devastating,” Bartram added. So Bartram plans to support science's role in government decisions on health, safety, the economy and more by attending the March for Science in Washington, where demonstrators began gathering Saturday morning. ​ The Washington event was to feature speakers and several large teach-in tents on the National Mall where scientists, educators and leaders from a variety of disciplines would discuss their work, effective science communication strategies and training in public advocacy. Organizers say the event is non-partisan and is not aimed against the Trump administration or any politician or party. The march, which coincides with Earth Day, has more than 200 co-sponsors, including many major scientific and professional societies, zoos, aquaria and advocacy groups. "This is pretty remarkable and unprecedented," said geochemist Eric Davidson, president of the 60,000-member American Geophysical Union, one of the march co-sponsors. Many of the group's members did the climate research that the Trump administration disavows. "I can't think of another example where scientists have organized themselves in as many cities with an event as big as this. Organizers of the international event say it is the first step in a global movement to acknowledge and defend the vital role science plays in everyday life. “Science extends our lives, protects our planet, puts food on our table, contributes to the economy and allows us to communicate and collaborate with people around the world," says Caroline Weinberg, national co-chair for the March for Science. "Policymakers threaten our present and future by ignoring scientific evidence when crafting policy, threatening scientific advancement through budget cuts and limiting the public's knowledge by silencing scientists," Weinberg said. U.S. President Donald Trump's most recent budget proposal calls for cuts to the Environmental Protection Agency (EPA) that would eliminate some 56 programs and drastically reduce funding for the agency's Office of Research and Development and Science Advisory Board. Trump's budget proposal also recommends some $6 billion in cuts to the National Institutes of Health, which is the largest public funder of biomedical research funding in the world. Dr. Mona Hanna-Attisha, a first-generation Iraqi immigrant, is the pediatrician who alerted officials in Flint, Michigan that the city's water was contaminated with lead. She is a March for Science honorary national co-chair. "We march for science so that scientists have the freedom like I did, to speak out, free from politicization and to continue to make the world a better place." Dr. Lydia Villa-Komaroff, another March for Science honorary national co-chair, was one of the first female Mexican-Americans to earn a doctorate in the natural sciences in the U.S. For more than 40 years, she has helped Chicano-Hispanic and Native American scientists attain advanced degrees and increase diversity in science, technology, engineering and mathematics (STEM) fields. "In the past several centuries, science has increasingly affected our lives for the better. But, as seen in Flint, the fruits of science are not always distributed equally to all communities," Villa-Komaroff said. "Equally important, young people who live in underserved communities have not had equal opportunities to become scientists. Science and our society are stronger when the people doing science reflect our society as a whole." Tipping point Organizers have not released expected crowd size estimates. But the dispute over crowd sizes was just one small example of what scientists see as a larger pattern. During the U.S. presidential campaign, Trump dismissed the scientific consensus about the dangers of human-induced climate change. His appointee to lead the EPA, Scott Pruitt, also does not accept climate science. He has repeatedly clashed with the agency he now heads. But scientists say their frustration has been building for decades. "We might have reached a tipping point now, but acting as though this is a new thing is giving too much credit to the current administration," said march co-organizer Weinberg. And it goes far beyond climate change, Weinberg added. "It's about not paying attention to the best research on things like food stamps. It's about cutting things like Head Start and after-school programs," to name a few. "And that all affects health, because that's a time to set kids on the right path." Critics say a public protest risks further politicizing science, turning scientists into just another interest group. Bartram sums up a widespread response: on hot button issues like climate change, opponents have already done it. "I don't think anything we do is going to further politicize it," she said. Disconnect But if the goal is to get policymakers to listen, "A march isn't going to change anything. That's the problem," said Rob Young, head of coastal research at Western Carolina University. Young says much of the problem stems from the growing disconnect between scientists and voters, especially the rural and working class people who voted for Trump. He says most probably have never met a scientist. "It's easy to demonize us if those folks don't know who we are," Young added. Scientists need to get out of the lab more, he said, and explain how their work affects people's health and livelihoods. That's what march organizers hope, too. Many scientists accept much of the blame for the disconnect with voters. The American Geophysical Union's Davidson said a major post-march goal is more public engagement. "I think the day is gone when scientists can stay in their ivory towers and assume that everyone is going to recognize their value," he added.