On Christmas Day, the couple's turkeys will turn up on tables all around Australia. Like other produce from outer area farms, they contribute to filling Sydney's food bowl throughout the year. According to the Sydney Food Futures project, these farmers produced more than half a million tonnes of food in 2011 – 20 per cent of the city's needs, including 55 per cent of the supply of meat, 40 per cent of eggs, 38 per cent of dairy products, 10 per cent of vegetables and 2 per cent of fruit. Up north, the biggest area for perishable vegetables and turf traditionally has been the Hawkesbury area, with chickens around Gosford. In the north-west, it's cut flowers and plants in the Hills district. In the west, eggs around Penrith, ducks near Liverpool and turkeys in the Wollondilly shire. But all sorts of produce is grown all around the city in blocks as small as two to five hectares. But in its Food Futures report, the UTS Institute For Sustainable Futures saw this food supply falling rapidly as urban development expands. In 14 years, it estimates that on current trends these farms will be responsible for just 6 per cent of the city's food needs. Turning point

Joe Grima has 15,000 turkeys on his farm. Credit:Dean Sewell Almost 100 kilometres from the Sydney CBD, the Grimas' turkey farm is surrounded by an orchard on one side and a market garden across the road. Third generation farmers, they have a solid business growing 60,000 turkeys a year. But the couple say the relentless march of urbanisation towards the edges of the Sydney basin is making it tougher for them to keep farming. "Sometimes you feel like you're farming with your hands tied behind your back," Pauline says. "People get upset about the trucks picking up the turkeys at night. But it's not a nine to five job. There's always land conflict and it's getting worse." Across the city, newer residents have complained to their council about the noise, smells, traffic and use of chemicals on farms.

While there is no risk of anyone starving as the food bowl empties, farmers believe there are compelling reasons agriculture should be preserved in what planners call peri-urban – mixed rural and urban – areas. These farms supply good quality, fresh, affordable produce, after all, contributing to the city's food security at a time when global warming raises questions about the reliability of agriculture in inland areas. They help environmentally by reducing so-called food miles and cutting down on wastage during transport. They encourage bio-diversity, preserve wildlife corridors, provide jobs, foster tourism and offset the "urban heat island" effect. The head of the Sydney Peri-Urban Network of Councils, Ally Dench, believes the city is at a turning point. "Do we want to get all our produce from out west where there's higher risk of drought and it's a lot further to bring food, with higher transport costs?" she asks – then answers her own question. "We want good quality fresh food and that's what you produce locally." But the challenge is preserving agriculture as the city gets 725,000 more homes in the next 20 years – the projection by the Greater Sydney Commission, the state agency overseeing planning and development, for the area bounded by the Hawkesbury River to the north, the Blue Mountains to the west and Wollondilly to the south.

"We've got to find somewhere for another million people to live," Dench says. "But we've also got to look at how we can assist our farmers because land speculation and land banking have been big, big problems over the years." At the Biffins dairy in Cawdor: the Sydney basin supplied 38 per cent of the city's dairy products in 2011. Credit:Dean Sewell The research director at the Institute for Sustainable Futures, Roel Plant, supports urgent action to prevent the loss of more farms. "If you look at the latest round of plans that the Greater Sydney Commission has put out, including the five district plans, there is very, very little provision there to preserve agricultural land," he says. "Farmers feel quite marginalised; in general, they don't really feel they're embedded in the Sydney Basin. "They get lots of complaints about spraying or using their tractors early in the morning. They're increasingly seen by new rural residents as nuisances."

But the commission's environment commissioner, Roderick Simpson, questions the figures that show the food supply is dwindling from 20 per cent to 6 per cent. "The average household spends around $250 a week on food," he says. "There's around about 1.6 million households. So the total spend is around $21 billion every year in Sydney." While agricultural production in the outer arc the commission calls the Metropolitan Rural Area is worth about $450 million, just 60 per cent of that is fresh food and the rest is turf, cut flowers, hay and other non-edible products. "You're talking about [a small share] of $21 billion – about 1.5 per cent," he says. "So I don't know where the 20 per cent comes from." Simpson insists the commission wants agriculture to continue in Greater Sydney. In the Metropolitan Rural Area, it recognises there should be only limited urban development and it should be away from crops and poultry sheds.

"There may be a little bit more residential, carefully placed," he says. "There might be little expansions to some of the rural villages ... but we've got to be really careful about where that happens." 'You can only resist for so long' The Biffins Dairy produces 750,000 litres of milk for Sydney each year. Credit:Dean Sewell On his dairy at Cawdor, south of Camden, Tony Biffin tots up how many milk producers have vanished in the Camden-Macarthur area in his lifetime. In the early 1960s, there were 163 dairies supplying milk to Sydney. Now there are – Biffin runs through the list with son Todd – precisely 12 left.

While the area likely produces a similar volume of milk to the 1960s because of advances in farming, the economics of dairy farming are challenging. Running 120 milking cows on 250 hectares of family-owned and leased land, Biffin jokes that he is subsistence farming. "We just manage to feed ourselves," he says. As the price of milk has fallen from 55¢ to 48¢ in the past two years – since rebounding to 52¢ – energy and transport costs have increased. And higher land prices have pushed up Biffins' rates to almost $10,000 a year. So he is wondering about the future for a dairy that produces 750,000 litres of Devondale milk for the Sydney market every year. "Once the suburbs start getting built this side of the river, we're probably getting out of here," Biffin says. "You can only resist for so long then you just accept it.

"I don't know when that will happen but I do know that the rest of Australia is not that good at producing food. They only think they are. The water issues they have are 10 times worse than the water issues we have on this side of the mountains." Once the suburbs start getting built this side of the river, we're probably getting out of here, says Tony Biffin. Credit:Dean Sewell Asked about the future of his stone fruit orchard at Oakdale, west of Camden, Ed Beil has a droll line. "Are you writing an obituary?" he says. A thoughtful, straight-talker, Beil and wife Marilyn have been growing peaches, plums, nectarines, apricots and citrus and native fruits on 16 hectares for more than three decades. He drives his produce to Flemington Markets and farmers' markets at Camden, Warwick Farm and Everleigh. "In my experience, the agriculture industry in general and the orchard industry specifically is on its last legs in the Sydney Basin," Beil says. "The returns aren't there but the pressures to sell your property for very large sums of money – not only to developers but lifestylers – makes farming very unattractive."

While the cost of labour, cardboard packaging, fertiliser and power have increased steadily, prices for his fruit have hardly improved in 25 years. "When I first bought my farm, there were in excess of 70 orchards in the Oakdale district," Beil says. "Now there are two. In the Sydney Basin, there were probably more than 400 orchards. Now I'd say there are less than 40. "It will be a terrible shame, even if just from the heritage perspective, to see it all disappear." A trial scheme to protect farmland When Ed Beil of Wanaka Orchard bought his farm, there were more than 70 orchards in the Oakdale district. Now there are two, he says. Credit:Dean Sewell

For Beil, the threat is from what he calls city folk who buy properties for a rural lifestyle but get upset by the noise, smells and traffic emanating from farms. "We're getting tremendous pressure upon local councils to cease doing what we've been doing for a couple of hundred years because it's interfering with some newcomers' comfort and they seem to be winning," he says. With his farm zoned for rural use, there won't be a windfall from selling his land for an urban subdivision any time soon. But Beil is hoping a proposed agricultural enterprise credit scheme that will soon be trialled in the Wollondilly shire could make his farm viable enough to continue. The idea is that a farmer would earn credits from a crop that a developer could buy to increase the size of a new building or subdivision blocks somewhere else in the city. "That would link the protection of farming – not a subsidy but a reward, if you like, for the public good of producing food and fibre in the Sydney region – to development," he says. "Most producers are small family producers who don't have economies of scale.

"Some years we'll make a small profit; other years we'll have a significant loss. If we could be rewarded with credits every year which could be banked, that could well be the difference between agriculture remaining in the Sydney Basin or disappearing forever." Beil believes farms have another benefit for the city – minimising the air pollution that he can see from his farm, 400 metres in the foothills on the city's south-western rim. "On a clear day I can see the Sydney Harbour Bridge from my front paddock," he says. "When I first moved here, I could see it probably two or three days a week. Now I'm lucky to see it one or two days a month. "The basin by its very nature is a bowl and the prevailing wind in the summer is a nor-easter so [it] has pretty well got a visibility of less than five kilometres. If you've ever seen Beijing, that's Sydney's future if the basin fills up completely with houses and cars and tarmac." Some years we'll make a small profit; other years we'll have a significant loss, says Ed Beil. Credit:Dean Sewell

Even with a growing population nearby, many farmers believe they need more support to survive. Back at the turkey farm, Joe Grima believes the state government should strengthen "right to farm" regulations to protect agricultural areas. "The more we keep losing it, the more we have to rely on outsourcing our food," he says. Just back from a 150-kilometre round trip to Flemington markets, Beil sounds almost resigned to the end of local agriculture. "I know a lot of farmers in the Sydney Basin," he says. "And not one of them is making a good living." But the Greater Sydney Commission's Simpson believes that with advances in farming, it is "more than conceivable" there will be more food produced in Greater Sydney rather than less. Poultry, eggs and mushrooms – based in sheds rather than large tracts of land – make up 60 per cent of total agricultural output by value. Planned buffers can give other farmers the security of knowing housing developments won't keep getting closer.

"There's actually quite a lot of extra capacity for food production," Simpson says. And there is more potential in a proposed agribusiness district near the new airport at Badgerys Creek, which Simpson believes would stimulate production, especially for export. "With the ability for people to take high-quality, super fresh produce to a bio-secure area for further processing and packaging for export, there are some real competitive advantages that would be gained," he says.