Funding to protect elm trees from disease in the South Downs could be at risk, countryside managers have said.
Brighton remains vigilant against Dutch Elm Disease
The South Downs Joint Committee said that higher administration costs and a fall in council funding will affect the tree disease treatment programme.
Sussex and Hampshire have the largest population of elms dating from Victorian times.
The council would receive more money if the area had national park status, said the committee chairman.
The South Downs Joint Committee chairman Robin Crane CBE said there is an urgent need for a national park.
A government decision on the creation of a national park is expected in 2007.
More than 30 million trees across the country were lost to Dutch Elm Disease which hit Britain in the 1970s.
Since the epidemic, most elm trees can be found around the South Coast.
Brighton still has 15,000 elms in its streets after city tree experts brought in measures to protect them.
The city's Edwardians and Victorians had planted about 25,000 elms, a species that copes well with coastal exposure and the salt in the wind.