Peak oil has already happened in the United States, in Australia, Britain and in 49 out of 65 of the world's oil producing regions. Yet 51 million new cars continue to hit the world's roads every year.

Just as farmers have little control over who snatches their land, water and other assets, they have little control over who takes their fuel. By 2040 dwindling reserves of fossil oil may well be reserved for the military and everyone else will have to get by as they can, including food producers.

The average citizen of a developed country today consumes the diesel distillate from 66 barrels of oil a year, such is the dependency of our modern food systems on fossil fuels. The high-yielding crops we pin our hopes on will be of little use if there is not enough fuel to sow, harvest or transport them.

One of the most pressing questions is where the energy to power the world's tractors, trucks, trains and ships that move the food will come from in future. It cannot come from the farm: to do that would reduce world food output by 10 - 30 per cent, at the same time as we need to double it.

Optimistically, we may have until 2030 to solve this problem and convert the whole of the world's advanced farming systems to another energy source, algal biodiesel maybe. Or hydrogen. Or solar-electrics. But there seems little sense of urgency about this issue from governments.

Natural gas will also peak shortly and since it helps make 97 per cent of the world's nitrogenous fertilizer, an N scarcity is also on the cards. Using coal to make fertiliser does not seem smart, as its contribution to climate change is to create more drought and hence lower crop yields.

By the 2040s it is unlikely we will be using fossil fuels in agriculture.  There needs to be a crash global research effort to head off a farm energy crisis. For the following reason:

Consumers may be more than a little annoyed if asked to pay $30 for a loaf of bread. Yet compare how much real food prices increased in the recent oil price surge - with how much they went up under the major oil shock of the 70s. The risk of soaring global food prices in the event of a world energy shortage is real.

Julian Cribb is an award winning science writer with over 7000 published articles. He is a Fellow of the Australian Academy of Technological Sciences and Engineering (ATSE) and principal of Julian Cribb & Associates, consultants in science communication.

His forthcoming book The Coming Famine is about the global food crisis.