Heritage Lottery Fund chair Dame Jenny Abramsky said: "Parks face greater challenges than they have faced before and those challenges are increasing.
"It’s a non-statutory responsibility of local authority, money is tight and more and more volunteers are going to be needed.
But she told the UK Public Parks Summit, hosted by the HLF and Big lottery funds at the Royal Geographical Society, that volunteers had their limits.
"We need to ensure our parks remain safe, healthy and well maintained: you can have lots of volunteers but they can do more damage if not directed in the right way."
Abramsky said new economic models would also be needed as well as ways of enabling people to learn from each other and share best practice.
She added: "We can put £4m into a park but if it’s not looked after for the next two years that money is wasted. We have to ensure money is not wasted."
Big Lottery Fund chair Peter Ainsworth told the conference: "We are lucky to be able to distribute money rather than cut it, but it’s maintenance of parks that could be under pressure as local authority budgets are so strained."
To learn more about the latest HLF funding round of £100m click here