It’s good to learn something new, especially if it encourages optimism, a commodity in short supply at present in whichever direction we care to look.

What I learned recently was that there is an estimated 100 times as much water in the rocks of the world as there is in all its lakes and rivers. As I’ve read enough from environmentalists and conservationists about looming world water shortages I found that estimate about rock supplies encouraging and hopeful; I knew some water was there, I just didn’t realize how much.

No surprise either that the optimistic note was struck by a report from an international group of engineers because – harsh, but I think fair – while I usually equate the green movement in general with the Dad’s Army’s Private Fraser school of optimism, I think of engineers as genuine optimists.

In their line of work, a profession where, as Murphy’s Law has it “If anything can go wrong, it will”, they have to be as they carry on designing, building and constructing in the belief that they’re making a better world for us all to live in.

I realise there are arguments about that. We only have to look at the number of “back to the past” programmes on television, such as the series about an Edwardian farm – not to mention the soft focus fantasy Lark Rise to Candleford and the marginally more realistic Downton Abbey – to see there is a market for nostalgia. But read between the lines, to the utter, mind-numbing, drudgery of farm work before engineers and designers produced, say, the fore-end loader and hydraulic lift for tractors, and to the 14-hour days that 10-year-olds worked in big house kitchens, and the good old days were pretty bleak for those doing the work.

Engineers have helped change that, and they haven’t done it by hankering for a rosy-glow past that never existed.

If the report by engineers was optimistic, the conclusions of the recent Foresight report were not, at first glance. Saying “first glance” is the wrong expression because, like almost everyone else in the world except the 400 scientists who contributed to a detailed report of many hundreds of pages, I haven’t read it.

But I did spend quite a lot of time that won’t come again listening to discussions on it and how its well-meaning, if woolly, recommendations could be achieved, such as “affordable food supplies, food price stability, global access to food and an end to hunger” and “mitigating climate change and maintaining biodiversity and ecosystems while feeding the world.”

The short answer to much of the above would be “with great difficulty.” Look at the horrors of world news on any day and it’s hard to think how common, concerted world action could be achieved on anything, even something as necessary to us all as global food production and farming.

Anyone with experience of trying to get a village hall committee to agree might even wonder how 400 scientists agreed about a need for urgent action on global food supplies.

Nor are they talking long term. The report says that world population will be 8.3 billion within 20 years and anyone over 30 knows how quickly 20 years can go. Also within that time, two thirds of the world population will be living in cities and many of the horrifying shanty towns around some of them. Demand for food will increase by a forecast 40 per cent, demand for energy by 50 per cent and demand for fresh water by 30 per cent.

Never mind 20 years ahead, an immediate problem is that while most of us in the world are comfortable and well fed, almost a billion are short of food now and know what hunger means, including much of Africa.

It can be argued that as much of that is due to corrupt political systems – it’s worth remembering that in spite of the MPs’ expenses scandal we really don’t know what political corruption is in this country – as to climate, drought and disease. But the Foresight report pointed out the simple fact that world-wide, an estimated one third of food grown is wasted. Immediate action is needed on that.

It also pointed out that intensive farming has become a dirty word when it will probably be the answer to more food for more people and that “every tool in the box” must be looked at, including genetic engineering.

For Britain’s farmers, one tiny part of the global production scene, the Foresight report could be encouraging. They might start to feel needed again and supermarkets might be encouraged to start paying home producers more for supplies if there is a danger that overseas supplies could be lost or diverted.

On the other hand, it could be one more well-meaning report that is just too big to read and its effect on world food production in the next 20 years will be nil. The bottom line, certainly for British farmers, will be whether they can make a profit and whether European Union subsidies continue.

The link between those two factors was confirmed again last week. Total income from farming in Scotland, essentially the gap between farmers’ returns and what they spent, was £618 million in 2010. Subsidies received? £597 million. Without subsidies, Scottish farming would be lucky to break even.