Summer, 1990 (v2n4)
Ponting, C.
Environment 32(9):4-9, 31-33.
1990
Reviewer's note: This
article is derived from the author's book: Ponting, C. 1991. A Green History
of the World. Sinclair Stevenson, Ltd.., London.
Solving today's environmental
problems takes on a new sense of urgency when considered in light of the
decline of natural resources of past eras. Historical texts fail to acknowledge
the direct relationship which often existed between the rise and fall
of civilizations, and poor soil and water management. This article investigates
that relationship and poses questions about the future of our own civilization.
Before the development of
agriculture, people lived in small, migratory groups. This period was
one of great ecological stability; nearly all parts of the globe were
inhabitable and people had enough food and water to survive. The development
of agriculture about 10,000 years ago enabled people to live in concentrated
population centers. Expanding populations led to increased demand for
resources and ultimately to massive disruption of natural ecosystems.
The article examines how three societies exploited their natural resources,
attempted to deal with their ecological problems, and ultimately declined
as a result of the deterioration of the resource base.
Mesopotamia. A classic
example of an agricultural system that was not sustainable is seen in
the southern Mesopotamian region (Sumer) during the third and second millennia
B.C. Because of lack of rain during the growing season, water storage
and irrigation were necessary. Rapid evaporation of water from soils,
caused by high temperatures, and high water tables led to the buildup
of salts on the soil surface. Allowing the land to lie fallow would have
lowered water tables, however limited land availability and rising population
only increased the pressure to intensify food production.
In about 3500 B.C., wheat
and barley were grown in roughly equal amounts. Gradually less and less
wheat could be grown due to high salinity, and by 1700 B.C., only the
salt-tolerant barley could be grown throughout the entire region. Crop
yields also drastically declined during this period and entire fields
turned white with salts and became unproductive. The most interesting
feature noted about this time period involves the political history of
the region. Military conquests of the region, outlined in the article,
closely followed the steady decline of the agriculture base. Ultimately,
Mesopotamian society shifted permanently to the north, while Sumer became
underpopulated and impoverished.
The Mediterranean Region.
Environmental degradation and the shift in the plant species of the region
occurred as a result of "relentless pressure of long-term human settlement
and growing population." The natural vegetation of the Mediterranean
basin was a mixed evergreen and deciduous forest, but forests have been
cleared steadily for fuel and for use in agriculture and construction.
For example, about 90 percent of the original forests along the eastern
Mediterranean have been removed. Of notable stature and importance were
the famed cedars of Lebanon, of which only four small groves remain.
All other areas of the Mediterranean
have suffered a similar environmental decline as well. In Greece, over-grazing
caused severe soil erosion, mostly during the seventh century B.C. This
led to the widespread planting of olives, which were the only tree that
had roots strong enough to penetrate the limestone rock underlying the
badly eroded land. Rapid deforestation in Italy resulted in soil erosion
so severe that numerous ports in estuaries became silted up from the eroded
hillside soils. The ecology of North African provinces declined much more
slowly, but intensified after the fall of Rome. Tribes brought in large
flocks of grazing animals that denuded the remaining vegetation and led
to increasing desertification.
The Maya. The Mayan
civilization of Central America consisted of large and complex population
centers which date back to 2500 B.C. Recent archaeological work indicates
that some cities had populations of 30,000 to 50,000, and the entire Mayan
lowland jungle may have had as many as 5 million people. Pyramids were
built in these cities between 600 and 800 A.D., after which population
levels fell abruptly, and the cities became covered by the encroaching
jungle.
Many historians formerly
believed that the Mayans obtained their food primarily by using swidden
agriculture. Swidden agriculture involves temporarily clearing and burning
a patch of jungle, growing maize and beans for a couple of years, and
then abandoning the plot for 20 or more years until the jungle grows back.
This form of agriculture was clearly incapable of supporting such a large
population.
Recent investigations have
found an intensive agricultural system, which included extensive terracing
on highly erodible hillsides, as well as raised fields constructed in
swampy areas. Increasing population likely pushed agriculture largely
onto the most marginal soils, and forests were cleared for crop production,
fuel, and construction. Eroded hillsides probably became unarable, and
silt carried by rivers would have seriously damaged the flatland raised
fields. The continuous warfare now known to have occurred among Mayan
peoples likely intensified because of reduced food production and declining
natural resources. The result was a rapid population decline and a return
to far less intensive methods of food production.
The author concludes by posing two increasingly important questions: "Are contemporary societies any better than ancient ones at controlling the drive toward ever greater use of resources and heavier pressure on the environment? Is humanity too confident about its ability to
avoid ecological disaster?" Finally, "Given the 2-million-year history of humans on Earth, it is still an open question whether the 10,000-year-old development of agriculture and settled societies and the more recent dependence on nonrenewable fossil fuels constitute an ecologically sustainable strategy."
Contributed by Chuck Ingels
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