Volunteering Australia CEO Mark Pearce said the long-term decline of formal volunteering across the country was "structural and systemic in nature".

"[The problem] looks to be not just the resilience of volunteering and communities by extension but the sustainability of volunteering," Mr Pearce said.

A Volunteering Australia survey estimated that 26.7 per cent of adults volunteered in Australia in the 12 months to April 2022.

This was down from 36 per cent in the 12 months before late 2019.

Only 38 per cent of surveyed people who stopped volunteering due to the COVID-19 pandemic said they'd returned.

Mr Pearce said while COVID-19 was a major factor in recent declining numbers, it reflected a longer-term problem in participation rates.

"One of those is the expectation around how people give their time, give their treasures to make community better - that has changed," he said.

"People are looking for more flexibility, they're looking for more choice."

Red Cross Australia couldn't operate without its more than 20,000 volunteers, making the long-term decline of donating time an ever-present problem.

"The trend is heading south," Red Cross Australia head of volunteering Chris Kwong said.

"It's causing great concern."

Mr Kwong said the trend was partly because traditional volunteering was designed to attract an older demographic of people.

"There is a level of natural attrition," he said.

"We've also got a generation coming afterwards who have a whole range of things they need to balance in their lives."

Allowing people to "dip in and out" of roles, change between organisations and seeing tangible results of their work were all necessary aspects of attracting volunteers.

Organisations must also find a way to reach the roughly 14 per cent of Australians who say they don't volunteer because they've never been asked.

But despite recent "compounded disasters" like floods, fires and the pandemic, Red Cross Australia volunteers are still showing up.

"We can't rely on that goodwill indefinitely," he said.

A Volunteering Australia survey found that 83 per cent of respondents needed more volunteers immediately or in the near future.

Of the 1208 organisations that took part in the survey, 11 per cent reported they needed more than 101 volunteers for their organisation alone in the short term.

Ronald McDonald House Wagga fundraising and marketing manager Kiara Breust said the southern NSW non-profit had 107 volunteers in its rotation.

"It sounds like a lot but to be honest, it's always still a struggle for us," Mrs Breust said.

The NSW Riverina house operates 24/7, 356 days a year, supporting seriously-ill children and their families.

With only three full-time staff and over 150 families supported in 2022, Mrs Breust said the team was "pretty okay" but ideally, they would have at least 130 volunteers available to them.

The heights of the COVID-19 pandemic saw the house run with 20 per cent of those volunteers but Mrs Breust said even with fluctuating numbers and rolling recruitment, no family was ever turned away.

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With recent compounded flooding disasters, NSW SES has relied on the tireless work of more than 10,000 volunteers.

A NSW SES spokesperson said research showed that more broadly, volunteer numbers nationally were trending downwards.

"However, the NSW SES is still able to attract new members at a steady rate," the spokesperson said.

"Often after large or significant events there is a spike in interest and an increase in volunteer applications."

That is partly because the emergency service is boosted in times of crisis by "spontaneous volunteering", that doesn't require the same long-term commitment of its formal counterpart.

It can include protecting properties from floods, cleaning debris, answering phones or providing updates to local residents.

NSW RFS operational officer Bradley Stewart said like everyone else, the agency was competing for people's time.

The NSW Riverina zone will take measures like suspending fire permits from Friday to help manage the imposition on rural volunteers, an overwhelming majority of whom work on the land and are entering harvesting operations this time of year.

"The last thing we want to be doing is unnecessarily pulling them off a harvester and having to respond to a permit burn that's escaped," Mr Stewart said.

Led by Volunteering Australia, February 2023 will mark the National Volunteering Conference in Canberra and launch the first national strategy in a decade, responding to modern issues facing the sector.