Those pictures are about to reappear -- African children whose staring eyes and matchstick limbs remind us of the depths of pain that is death by starvation.

The rains haven't come for two years in a row, so 13 million people are at risk of famine in Sudan, Ethiopia and a half dozen other Sahelian countries. That's about the population of New England's six states.

Drought is nothing new in those parts of Africa. The defining characteristic of all arid regions is that rainfall is not just scarce, but wildly variable. What is new is massive, recurring famine. It is the result of an imported -- or more accurately, an externally imposed -- way of life combined with rapid population growth. Together these have caused the swift collapse of a fragile and unforgiving environment and, in turn, a human tragedy.

Africans once knew how to wrest a dependable, albeit poor, living from their arid landscape. Allowing land to recover after a few years of cultivation and taking livestock to the rains when the rains didn't come to them, were aspects of a semi-nomadic culture tuned to the limitations of its environment.

Then came the European colonists, and later the well-meaning development specialists. In their eyes, the shifting, pastoral system seemed messy, hard to control and the cause of Africans' poverty. Accustomed to rich soils and reliable rainfall, they drew borders on maps, built infrastructure, sank wells and induced people to settle in one place. By unlucky chance, two decades of abnormally wet weather in the 1950s and '60s made it look for a while as though their policies were working.

What was really happening was that as population grew, fallow land had to be reused before it could recover. Larger livestock herds around the new wells overgrazed the land. The gradual disappearance of fuel wood forced farmers to burn crop residues and manure instead of"Human and environmental calamities are indivisible. using these as fertilizer. As the land lost its green cover, it could no longer nourish crops or absorb what rain did fall. As its vulnerability grew, agriculture declined and in dry years collapsed completely.

What is most ominous about this sequence is how fast it has happened. As recently as 1960, sub-Saharan Africa was a food exporter. Today it has the world's heaviest reliance on imports. Children under 5, the most susceptible to malnutrition, account for 50 percent to 80 percent of total mortality, compared to 3 percent for the same age group in Europe. In a well-studied region of Mali, the desert has moved 220 miles south in two decades. Trees have all but disappeared from much of Ethiopia.

There are plenty of economic policy failures to blame for these woes. Over the years, everything from food subsidies and price controls to overvalued currencies has been cited, and correctly so. But until very recently, the experts ignored the environmental constraints that were undoing their best efforts.

A few thousand miles to the north and east, an eerily similar crisis is unfolding in Soviet Asia on the arid plains surrounding the Aral Sea. Thirty years ago, large scale irrigation projects were started there, principally to grow cotton for hard currency exports. The rivers that were tapped for their water also feed the landlocked sea. Today they have dried to a trickle. Some years they deliver no water at all. The land has taken a savage revenge.

The Aral Sea itself has lost half of its volume. Once a fishing town, Muynak is now 30 miles from the shore. In between, fishing boats lie abandoned and rusting in the drying mud. In the saltier waters only a few fish survive. There are plans to ship fish 1,000 miles from the Baltic Sea to supply the town's processing plant.

From the air one can see traces of older irrigation systems beneath sand dunes on land that is now irreclaimable desert. In 20 years, 4,000 square miles of agricultural land has been lost. The land that is still cultivated is so salty that yields are meager. The region's natural dust storms are now also salt storms, and the rain is not acid, but salt. The drinking water, brackish and contaminated with pesticides, is deadly. Mortality has skyrocketed in a decade.

The Aral's colonists were Moscow bureaucrats who exploited the region for what it could ship west. As in Africa, population growth has been among the world's fastest. And, as in Africa, the length and depth of the drought of the past 20 years makes experts suspect a man-made cause. More dust in the atmosphere, the greater reflectance of devegetated earth and less moisture in the air due to the loss of moisture from vegetation, may all be creating a self-reinforcing downward spiral of less and less rainfall. Global warming may also be a culprit.

Arid lands magnify the consequences of environmental mistakes. But what happens in these regions is not fundamentally different from what happens when humans put too much stress on any environment, either because of mismanagement, too many people or both. The unraveling is just faster and in human terms, harsher. The rest of the world sees Africa's famine as a human tragedy, not an environmental one. The dying Aral Sea is painted as an environmental horror; its human costs are largely ignored. The lesson of both is that human and environmental calamities are indivisible.