Former church envoy Terry Waite is warning that expansion of Stansted airport could lead to "unbroken concrete" in the south east of England.
Stansted is the very last place that should be developed, says Terry Waite
Mr Waite was speaking on Sunday as he planted a tree in a field where a second runway is likely to be sited.
Campaigners aim to create a wood in the field at Broxted on land that has been a farm for around 400 years as part of their protest against a second runway.
They have marked the proposed runway with a line of flags.
Mr Waite, 65, of Bury St Edmunds, Suffolk, is a leading campaigner against the development of the airport.
"When you see the countryside where they are proposing to build the second runway it is incredible. It wasn't until I looked out and saw those flags that I quite realised the reality of what would happen," he said.
The government was pressing ahead with plans for expansion despite opposition from major airlines, environmentalists and planning inspectors, he told campaigners.
"If we are not careful what we will have is unbroken concrete from Stansted to the south coast," he said.
Mr Waite, who spent almost five years as a hostage of Islamic radicals in the
Lebanon while working on behalf of the Archbishop of Canterbury, said
development of the airport would not affect him personally but he was concerned that some of England's richest countryside would be lost.
Expanding the airport would destroy ancient swathes of countryside and mean
losing scores of listed properties.
"This place is the very last place that should be developed - very, very
last," he said.
"There will be no going back. There will be no restoring these
communities. Our heritage will be gone forever.
"This is not a case of not in my backyard. I would not be personally affected by
the expansion of Stansted. My interest is in preserving our heritage and the
precious British countryside."
He said independent experts had opposed the idea of more runways at Stansted.
Campaigners, who are posed to challenge the Government's expansion plans in
the High Court later this year, say scores of houses in villages near Stansted
would be bulldozed and thousands of people would suffer from an increase in
noise and pollution.