The foundation of every civilization is an adequate food supply: human beings simply cannot live at the density of population that civilization implies without a reliable agriculture. But the supply of good agricultural land is limited, and the number of human beings is not.
You can postpone the problem for a while by increasing the yield of the available land: irrigate it, plant higher-yielding crops, fertilize the soil artificially, use pesticides and herbicides to protect the crops as they grow. But even these techniques have limits, and in many cases we have reached or exceeded them. So we are running into trouble. Why isn't anybody taking action?
Governments everywhere are well aware of the problem: we are now 7 billion people, heading for an estimated 11 billion by the end of this century, and the food situation is already getting tight. So tight, in fact, that the average price of the major food grains has doubled in the past 10 years. But everybody finds local reasons to ignore that fact.
The developing countries know that they are under the gun, because the standard predictions of global warming suggest that it is the tropics and the sub-tropics where the warming will hit food production first and hardest.
A (still unpublished) study carried out by the World Bank some years ago concluded that India (all of which is in the tropics or sub-tropics) would lose 25 percent of its food production when the average global temperature is only 2 degrees C higher. China would lose an astounding 38 percent, even though most of it is in the temperate zone. And all that is before their underground water sources are pumped dry.
Most governments in the developing countries know the facts, but the short-term political imperative to raise living standards takes precedence over the longer-term imperative to curb the warming. So headlong industrialization wins the policy debate every time, and we'll worry about the food supply later.
The developed world's governments do nothing, because until recently they secretly believed that the catastrophe would mostly hit countries in the former Third World. That would unleash waves of climate refugees, plus local wars and a proliferation of failed states, but the rich countries reckoned that they would still be able to feed themselves and their military could hold the other problems at bay.
But what is becoming clear, just in the past few years, is that the developed countries will also have trouble feeding themselves. Part of the problem is that many of them depend heavily on underground aquifers for irrigation, and the water is running out.
It's running out even faster in China, India and the Middle East: for example, grain production has dropped by a third in Iraq and Syria in the past ten years. But it is hitting the big producers in the developed countries, too, and especially the United States.
For example, the amount of irrigated land in Texas has dropped by 37 percent since 1975. The amount in Kansas has fallen by nearly 30 percent in the past three years. And now it is becoming clear that the impact of warming will also be much greater than anticipated in the developed countries.
In these countries, the problem is extreme weather causing massive floods and prolonged droughts like the heat wave that hit grain production in the U.S. Midwest last summer, or the coldest spring in 50 years in England, which has cut wheat yields by a third.
Combine the steep fall in irrigation, the crop losses to wild weather, and the diversion of large amounts of cropland to grow "biofuels" instead of food, and it is not at all certain that the developed world will be able to grow enough food for its own citizens in five or 10 years time. So are the leaders of these countries launching crash programmes to stop the warming, cut down on water losses and end the lunacy of biofuels?
Of course not. The smarter ones just reckon that since their countries will still be rich, they will buy up whatever food is available elsewhere and feed their own people that way. It will be other people, in other countries, who go hungry.
And the slower ones? They're just frogs.