I found this so 60% seems a reasonable figure. But %40 of a lot of food is a lot of food.
"But Britain, as an island nation, is particularly vulnerable. We have not been self-sufficient in food since the late 18th century, but the situation is rapidly worsening.
In 1995, 27 per cent of UK food was imported. By 2006 it was 37 per cent. The situation is obviously more critical in cities: London imports more than 80 per cent and a food shortage would hit the capital the hardest.
The situation is worsened, of course, by the fact that we are having to compete for supplies on the global market with many more nations than ever before.
For centuries, the typical Chinese diet consisted of rice and vegetables, but as the Chinese pour into the newly emerging cities, so their diets are changing. In 1962, the average Chinese ate just 4kg of meat per year: by 2005 that figure was 60kg and rising.
The result has placed huge pressure not only on prices, but on natural resources required to cope with this increased demand.
It is not simply that we do not have enough land to grow the grain to feed the animals which in turn feed us. In the past two decades, pressure on our natural resources has increased to a level which many experts fear has become unsustainable.
For example, in the U.S., the use of hydrocarbon pesticides has increased 33 times as farmers sought to increase production and yet, as soil structures weaken due to over-use and mono-crop cultivation, more crops are being lost to pests every year.
The world has a finite supply of fresh water too, yet 70 per cent of all freshwater is used for agriculture, often horribly wastefully.
Here's a good read
http://www.ifr.ac.uk/waste/Reports/DEFRA-Ensuring-UK-Food-Security-in-a-changing-world-170708.pdf.
Thanks people for the debate. I've said this before but part of the reason I post on BF is to get people's responses. I have a range of ideas ( I don't konw if they are right/wrong) that I check out by chucking them on here. Today I've looked at BBRC and Defra. I wouldn't have done this witout your responses.