Coyte Farm is situated in rolling countryside on the western side of the market town of St. Austell in Cornwall. The farmer John Richards is approaching retirement and is planning to sell his farm with its 100 acres of agricultural land. Sainsbury's are involved in a plan to acquire the farm from him. Are they interested to take over his farm in order to produce sustainable food with low food miles for their own supermarkets 15 miles away in neighbouring Truro or 40 miles away in Plymouth?

No - Sainsbury's are the joint planning applicants for a development that, if approved, would concrete and tarmac over this 100 acres of farmland in order to create a Sainsbury's superstore, retail park, care home, hotel, pub, golf academy and a housing estate. This greenfield site would become Cornwall's third biggest retail area. Not a single acre of agricultural land would be left for the production of food.

So is there an urgent need for a supermarket to serve the town of St Austell? Again, no - St. Austell already has five supermarkets, with Tesco, Asda, The Co-op, Aldi and Lidl having stores in the town. But it seems that Sainsbury's are desperate to have a store in the town at any cost. Even if that cost is the destruction of farmland.

At this stage, I must declare my interest. I was born in St. Austell and educated at St. Mewan Primary School which borders the green fields of Coyte Farm. I walked past those fields almost every day for the six years of my primary education. In the summer on our walks home from school, we would take a short cut through the fields and watch day by day as the corn grew so high that we could play hide & seek in the long grass. Another highlight of the summer term was a school visit to the farm so we could watch Farmer Richards milking his cows. If this development goes ahead, the pupils of St. Mewan School will have the tarmac of a retail park to run around on on their way home and they can take a school-trip to watch people stacking shelves of milk in Sainsbury's.

Why is farmland so important? Because:

"The global population is rising at a time when natural resources are decreasing. As such, there is increasing pressure on the global food system. The earth's capacity to provide food is threatened by climate change, water scarcity and unsustainable farming practices. We need to find ways to make land more productive and to protect the biodiversity on which all food production ultimately depends.'

These are Sainsbury's very own words from their own recently launched Sustainability Plan. And yet it seems that they are quite happy to destroy food-producing farmland when it suits them, in direct contradiction of their own policy.

Sainsbury's is the UK's third biggest supermarket chain and are primarily a food company - food accounts for over 70% of their sales. Yet they are keen to build over farmland at a time when people are increasingly concerned about how enough food will be produced for the growing populations of the future.

The UK population is estimated to grow by 16% by 2031 but we are losing at least 30,000 acres of agricultural land a year due to urbanisation. We are currently only able to produce 62% of the food that we need to feed the UK population. This means we are becoming more and more reliant on importing food from overseas and it makes Britain weaker in terms of future food security.

This is of great concern to the government with Farming Minister Jim Paice stating in July last year: "With our increasingly hungry world every country must play its part to produce more food and improve the environment. Britain already punches above its weight, but we're a small island with limited space, so we've got to show leadership and play to our strengths more efficiently".

I am not against development and progress. I now live in London and I've witnessed the successful regeneration of brownfield sites in order to create the 2012 Olympic Park. Because of its industrial mining past, St. Austell is an area that has many brownfield sites. In fact the internationally-famous biomes of the UK's first major eco-tourist attraction, the Eden Project, were built in a disused china-clay pit just outside St. Austell. The major downturn in the china-clay industry has led to mass redundancies and a high level of local unemployment that has left its town centre full of empty shops and buildings. St Austell is the biggest town in Cornwall but it lacks the shops and facilities that a town of its size would normally have. In recent months, a new owner has bought the town centre and is keen to regenerate it and turn it back into a bustling place.

In light of this, it seems even more scandalous that Sainsbury's would ignore the town's vacant brownfield sites and empty retail spaces in order to build an out-of-town retail park on green food-producing farmland. Especially as their own sustainability policy is directly opposed to it.

The future of Coyte Farm is causing heated debate in Cornwall but this isn't just a local Cornish issue. It's a national and even a global issue. As populations rise and good agricultural land for growing food becomes ever scarcer, if a food-based company such as Sainsbury's are so keen to destroy agricultural land in the name of commercial expansion then what hope do we have to preserve the precious resource of farming land for future generations?

If, in the future, the pupils of St. Mewan Primary School look out on the empty retail shops left derelict by the domination of internet shopping, they'll ask why we sacrificed the valuable resources of Coyte Farm's land for such short-term gain.

Food sustainability is an issue for everyone and I would urge anyone who's concerned about the loss of farmland to join the Stop Coyte Farm campaign or to make their objection to the plan directly with Cornwall Council. To quote local councillor Bert Biscoe "Will our childrens' children need farmland or supermarkets most?"

Follow Lenny George on Twitter: www.twitter.com/@kernowinthecit