From climate researchers to oceanographers and bird watchers. Thousands of scientists from around the United States rallied across the US on Saturday to express their objections to the cutbacks in scientific research proposed by President Donald Trump.

The protest, dubbed the March for Science and coinciding with Earth Day, took place in 500 cities around the world, but all eyes were on Washington, where more than 75,000 people demonstrated, according to organizers.

The occasion had tens of thousands of scientists leaving their labs to debate in the street about the role science should play in public life, an important change of pace for the US scientific community, accustomed to separating politics from their professions.

Marchers held a range of signs. Some attacked Donald Trump, depicting the president as an ostrich with his head in the sand or bearing the words: “What do Trump and atoms have in common? They make up everything.”

For others, like Carol Trosset, 57, this was the first political act she ever took part in, the first demonstration she had ever attended in her life. She came to Washington from Northfield, Minnesota, because she felt upset about Trump's idea of increasing military spending in exchange for cutting the budgets of scientific agencies like NASA and the Environmental Protection Agency (EPA), as she explained to EFE.

Trosset, a biologist and cultural anthropologist, said the US political leadership is ignoring a lot of scientific evidence, adding that if we act on the basis of opinions and emotions, instead of evidence, we're in trouble. We must have knowledge, and science is the process of knowing what we know and what we don't.

However, the marches, the first of their kind, were officially non-political. They were, however, conceived by three US-based researchers – Caroline Weinberg, Valorie Aquino and Jonathan Berman – after Trump’s inauguration. Organizers have said science is “under attack” from the Trump administration and many protesters excoriated the president with signs that likened him to a dangerous orange toxin or disparaged his now defunct university.

Trump released a statement that insisted his administration was committed to preserving the “awe-inspiring beauty” of America, while protecting jobs.

Some students from San Francisco wore white, blue and green caps - blue for the ocean, green for the land and white symbolizing the melting ice of climate change.

Climate change? Trump has even said it's a "hoax" invented by China, Nathan Gamarra told EFE.

Gamarra, 25, depends on a scholarship from the National Science Foundation to continue his doctorate studies at the University of California, San Francisco, and said that if Trump cuts funding for that institution, his research project on molecular structure will be threatened.

While hundreds of people lined up to join the march, dozens of volunteers were handing out signs with the official slogan of the protest: "Science, not Silence."

The organizers had insisted that the march should not be an anti-Trump event but rather a reminder of the important role science should play, so that those in power can take sensible decisions based on "facts" and not "alternative facts."

No, not mentioning Trump was not on the cards. Many were the signs around the country with slogans like "Science = Reality, Trump = Lies"..."Hypotheses not Hypocrisy"..."With Trump WE Are the Endangered Species," and many more.

Meanwhile Trump responded by saying that "my Administration is committed to keeping our air and water clean, to preserving our forests, lakes, and open spaces, and to protecting endangered species."

Pharmaceutical companies, concerned about the impact on research talent of Trump’s attempts to ban or restrict travel from certain Muslim-majority countries, risked his wrath by supporting the march. In a video, Pfizer said it was “proud to stand behind our scientists”, as reported in The Guardian.

Trump has galvanized scientists with his comments about climate change, which he has called a “hoax”, as well as questions about whether vaccines are safe and threats to cut funding to universities that displease him.