The campaign is the initiative of the Save Capel group, fighting to oppose a garden village of 2,800 homes at Tudeley, plus further housing allocations for another 2,160 homes at East Capel, a total of 4,960.
They will be joined by scores of groups equally concerned about housing developments in their own area.
Dave Lovell, who is the lead organiser, said: "There doesn’t appear to be an official total for green field sites being built on across Kent - I’m not sure that councils are doing it even for their own boroughs. I guess it wouldn’t be in their interests to publicise the damage.
"We’ve therefore been collating as best we can from what the campaigns tell us and what we can find through other sources, or by working out what is most likely from the number of houses.
"To date we are over a staggering 15,000 acres of green space in Kent about to be sacrificed to development. That is clearly not going to be everything and the actual acreage is going to be far higher, but the full total may never come to light."
To date 29 community groups have pledged to join in the Day of Action this Sunday, with more expected to sign up.
Dave Lovell explains why they are campaigning
Residents who are concerned about the issue, but don't have a campaign group in their immediate locality can email for advice on where they can find one to join in.
The protest will be "polite and peaceable" with different groups planning different activities ranging from community walks, dog walks, picnics, a children’s wildlife hunt or simply gathering at the their local threatened space.
Mr Lovell said: "Groups and individuals can do anything they like in their local green spaces to show what they mean to them."
Against Lidsing Development is one of the groups taking part. They are meeting at Blacksmiths Barn in Forge Lane at 10.45am for a photocall, followed by a walk to Bredhurst's Area of Outstanding Natural Beauty to see the area where a new spur road for the M2 is proposed.
Cllr Vanessa Jones, the chairman of Bredhurst Parish Council said: "Please everyone, come and join us."
The Broadwater Action Group is another taking part. They are inviting residents to "Cake by the Cwylla." The Cwylla is an ancient pond first documented in 945AD within the green fields currently threatened by a proposal from Berkeley Homes to build 900 homes on agricultural land at East Malling. Their event runs between 11am and 12noon.
Becky Robinson-Hugill said: "We would like to see everyone enjoying the local footpaths and Quiet Lanes around the New Barns and Broadwater Farm Conservation Areas and we will be serving drinks and cakes as long as supplies last!"
For details, email email@example.com
In Benenden, the Friends of the East End, Benenden, are meeting at 11am on the footpath on Goddards Green Road, near the junction with Mockbeggar Lane. Spokesman Hazel Strouts said: "We're glad to be one of many groups joining the Save Kent’s Green Spaces campaign.
"Almost all Benenden's new housing is planned for land around an old isolation hospital, three miles distant from the village. Half of the land is classified as a Local Wildlife Site!"
In Maidstone, the Valley Conservation Society will be meeting at 11am outside Bockingford Steps, off Bockingford Lane, in Tovil, before walking to Abbeygate Farm, where Maidstone council is proposing to allocate for 250 homes.
The groups taking part include: Against Lidsing Garden Development, Birchington Action Group, Borden Residents Against Development, Broadwater Action Group, Burham Says No To Further Development, Cliffe and Cliffe Woods Residents Development Group, Eccles Action Group.
Also Farms, Fields and Fresh Air Faversham, Friends of Dukes Meadow, Friends Of East End - Benenden, Friends Of Old Park and Chequer's Wood, Hartley: Save Our Fields, Keep Kent Green, Keep the East Cliff Green, Meopham Village Not Town and Protect Land West of Teynham.
In addition there is Residents Against Ramslye Development, Rural Protection Group, Save Capel, Save Capstone Valley, Save Old Wives Lees from Industrial Solar, Save Our Heath Lands, Save Our Orchards Selling Village and Save Prince's Parade.
And also: Save Turnden, Stop Exploitative Development in Dover District, Stop Overdevelopment of Paddock Wood, Valley Conservation Society, and Westgate and Garlinge Action Group Against Housing Development.
For further details visit the Save Kent's Green Spaces Facebook page here.