Speaking in Moffat yesterday, Dr Tony Waterhouse, who is head of hill and mountain livestock research at the Scottish Agricultural College, said: "We have retreated off the hills. There are less livestock and there are less people. If the demand is for more food in the future, it will be difficult to turn the tap back on quickly."
Part of the problem was that farmers had put down "rough grazing" in describing some of their acreage on their Integrated Agricultural Control System documents. In a previous era, this land would have been described as "improved pasture".
With the new classification, there is a requirement to get permission before putting the land under the plough or putting in drainage ditches, and Waterhouse believes a number of government or environmental agencies would resist such moves.
"Land improvement nowadays would be a challenge. Some agencies would find it difficult to accept. We currently have a society which has different demands of the Highlands."
He believes that, with changes predicted in the world's climate, some of the more benign land in the hills and uplands of Scotland could return to providing more food than it currently does.
"We are in a warmer, wetter period, and if this continues and if the predicted demand for increased production comes, then Scotland and its uplands will gain advantage," he said.
"We have capacity in the hills to expand. We will be looking for more production from our hills, and this will be part of a wider vibrant rural economy."
Waterhouse accepted traditional sheep and cattle farming on the hills did contribute to methane production and nowadays that was seen as a bad thing. But, he claimed, there was a balance to be struck between food production and gas emissions.
Part of the problem is the financial circumstances they operate in. While other farm livestock sectors have been able to concentrate on improving food and genetic efficiencies, the returns earned by hill sheep and cattle farmers has been very low and there have been poor incentives to improve performances.
If hill farming was more profitable, he believes there was considerable scope to improve feed regimes and genetics and this would reduce the levels of greenhouse gas emissions.