simple ecology

P 410 Guns, Germs and Steel by Jared Diamond.

Why, then did the Fertile Crescent and China eventually lose their enormous leads of years to late-starting Europe? ...
For the Fertile Crescent, the answer is clear. Once it had lost the head start it had enjoyed thanks to its locally available concentration of domesticable wild plants and animals, the Fertile Crescent possessed no further compelling geographic advantages. The disappearance of the head start can be traced in detail as the westward shift in powerful empires. After the rise of Fertile Crescent states in the fourth millennium B.C., the center of power initially remained in the Fertile Crescent, rotating between empires such as those of Babylon, the Hittites, Assyria and Persia. With the Greek conquest of all advanced societies from Greece east to India under Alexander the Great in the late fourth century B.C., power finally made its first shift irrevocably westward. It shifted farther west with Rome’s conquest of Greece in the second century B.C., and after the fall of the Roman Empire it eventually moved again, to western and northern Europe.

The major factor behind these shifts becomes obvious as soon as one compares the Fertile Crescent with ancient descriptions of it. Today, the expressions “Fertile Crescent"and “world leader in food production" are absurd. Large areas of the former Fertile Crescent are now desert, semidesert, steppe, or heavily eroded or salinized terrain unsuited for agriculture. Today’s ephemeral wealth of some of the region’s nations, based on the single nonrenewable resource of oil, conceals the region’s long-standing fundamental poverty and difficulty feeding itself.

In ancient times, however, much of the Fertile Crescent and eastern Mediterranean region, including Greece, was covered with forest. The region’s transformation from fertile woodland to eroded scrub or even desert has been elucidated by paleobotanists and archaeologists. Its woodlands were cleared for agriculture, or cut to obtain constructions timber, or burned as firewood or for manufacturing plaster. Because of low rainfall and hence low primary productivity (proportional to rainfall), regrowth of vegetation could not keep pace with its destruction, especially in the presence of overgrazing by abundant goats. With the tree and grass cover removed, erosion proceeded and valleys silted up, while irrigation agriculture in the low-rainfall environment led to salt accumulation. These processes, which began in the Neolithic era, continued into modern times. For instance, the last forests near the ancient Nabataen capital of Petra, in modern Jordan, were felled by the Ottoman Turks during construction of the Hejaz railroad just before World War I.

Thus, Fertile Crescent and eastern Mediterranean societies had the misfortune to arise in ecologically fragile environment. They committed ecological suicide by destroying their own resource base. Power shifted westward as each eastern Mediterranean society in turn undermined itself, beginning with oldest societies, those in the east (the Fertile Crescent).Northern and western Europe has been spared this fate, not because it’s inhabitants have been wiser but because they have had the good luck to live in a more robust environment with higher rainfall, in which vegetation regrows quickly.