Thousands of people filled Philip St in Sydney for the March for Science.

Thousands of people have rallied across Australia as part of a global movement calling on political leaders to focus more on science.

Crowds gathered in cities and towns including Sydney, Melbourne, Hobart, Perth, Brisbane and Townsville as part of the inaugural March for Science, which is taking place in 500 locations worldwide.

The movement was started by scientists sceptical of the agenda of US President Donald Trump, but Stuart Khan, one of the organisers of the Sydney march, said it quickly went global.

He said marchers were calling on politicians to take note that the public wanted policy based on fact.

"The gaps that we see between what science tells us and what we actually see being translated into policy is very large, particularly when you look at things like climate change and the Great Barrier Reef," Professor Khan said.

"We're calling on politicians to make laws that are based on evidence that are appropriate for our future … Australians want to understand how science and how evidence is being incorporated into policy.

"Disease, famine, communicable disease, pollution of the ocean, climate change, all of these challenges are addressable by science."

Professor Khan emphasised that the march was not for scientists, but for anyone.

"I'm participating as a community member, I'm participating as a dad," he said.

"It is very important that the March for Science is a community-led march, it's a statement that is coming from the community.

"It's not led by the academics, it's not led by eminent scientists because it's not about them, it's about the community saying 'This is what is important to us'."

Among the thousands attending the Sydney rally was former Liberal leader John Hewson, who told AM ahead of the march he was concerned about "the lack of evidence being used as the basis of public policy".

"I think science is probably more useful and more relevant to society today than it's probably ever been. But there's been a widening gap between science and the public," he said.

"We need to stop and recognise the significance of science and the importance of funding it properly and using the evidence that it produces as the basis of good public policy."

Scientist and Macquarie University Associate Professor Josh Madin attended the Sydney rally with his young family and said politicians needed to pay attention to scientific evidence.

"We do a lot of work on the Great Barrier Reef and we've seen first hand the devastation up there and I just think there are some decisions being made that don't have the best interests of our children's future in mind," he said.

Indigenous science in the spotlight

Among those throwing their support behind the March for Science is Luke Briscoe, chief executive of Indigi Lab, which works to get more recognition for Indigenous science.

Mr Briscoe said Indigenous science, a form of science in its own right, needed to be better understood in Western culture.

"The honeybee dance from where I'm from in Kuku Yalanji country in far north Queensland, that dance talks about how the bees are sustaining our ecologies," he said.

"It's passing on those customs and traditions that our sciences are embedded in and … it's hard to really put value and monetise the importance of that in a Western world."

Mr Briscoe said having Indigenous participation in the decision-making process would be the only way to ensure better recognition of Indigenous science.

"I think it's important that we ensure that Indigenous voices are heard in the science sector and are at the table in decision-making processes for how we roll out science programs," he said.

"In terms of the workforce, making sure that that it's not just a one-way science understanding — it's looking at two ways of learning and two ways of teaching science and practicing science."