Video report by Andy Dickenson
A new report claims that ten percent of our National Parks must be allowed to grow completely wild if we want to protect nature and biodiversity.
Charity group Rewilding Britain say modern farming, irresponsible tourism and over-development risks nature in the places where it should be protected most.
Those that manage areas like the South Downs National Park say re-wilding is one solution to help. But not everyone agrees - the National Farmers Union argue that different habitats need to be created for different species.