Andrew Richardson, from Leeds, aims to spend a day running during his 108-mile challenge.
Natural England began switching to cattle grazing at its Ingleborough site in the Dales in 2004.
The pair were suffering from hypothermia on Ingleborough and had to be stretchered to safety.
Other finds include a Bronze Age coffin and human remains thought to belong to shipwreck victims.
The extension will offer greater protection to the rare species found in the Dales upland landscape.
Archaeologists and cave explorers found the remains among Ingleborough's caves and sinkholes.
After rescue of four men, hikers are reminded that in autumn the walk will be completed in darkness.
Matthew Simpson died after falling into the Gaping Gill cavern in the Yorkshire Dales National Park.
Two men in their 50s have died within two weeks of each other on the famous Yorkshire walking route.
