The world is hungry for some joined-up leadership

We live in a world with more overweight people than underweight people. We also live in a world where 1.2 billion middle-class people in developing countries are indulging such a taste for grain-fed meat that their countries are importing huge amounts of grain for livestock feed, even while those same countries are home to millions of malnourished citizens.

We also live in a world where agricultural subsidies have become so absurd that in the US - to cite the economist Paul Hawken - "The Government subsidises agricultural costs so that farmers can deplete aquifers to feed cows that make milk that is stored as surplus cheese that does not feed the hungry". We likewise live in a world where we must try to feed another 3 billion people who will likely come on board Planet Earth in the next four decades.

One may suppose from this book's title that we are going to read about agriculture as the number one issue. In fact, the book proposes that the challenge of feeding the world is at least as much about energy, water, climate and population.

This view is no more than we should expect from Lester Brown, whose forte, eloquently expressed in the course of writing dozens of books over the past four decades, is to emphasise the links that connect all our development sectors, sometimes obviously, sometimes covertly, often crucially.

For instance, fossil fuels are the predominant source of carbon dioxide, which in turn is the predominant source of global warming. A 1C rise in temperature can reduce grain yields by a whopping 10 per cent, which means that if we are to feed the world we must look to energy factors as well as agriculture.

If China continues to meet its energy needs by burning coal, its carbon dioxide emissions will one day induce as much global warming as the US - and push up prices at food checkout counters in Britain. In 2003, the world's grain stocks fell to their lowest levels ever. As Brown succinctly puts it, we are heading for "a shift from a world food economy dominated by surpluses to one dominated by scarcity".

Vital to agriculture, though still overlooked in certain citadels of power, is the environmental resource base that underpins all food-growing efforts.

Alas, as Brown documents in illuminating detail, farm soils are eroding, pasturelands are degrading, water tables are falling, rivers are running dry, crop genetic resources are declining, deserts are expanding, forests are shrinking and climate is heading for gross upheaval.

The bottom-line message of this fine book is that we can surely enable everyone to enjoy a decent diet. But to do that will require contributions by many more people than farmers - especially by those responsible for joined-up government, our political leaders. Will they please lead?

Norman Myers is a fellow of Green College, Oxford.