16 Human Carrying Capacity: An Overview
The question of how many people the world can support is unanswerable in a finite sense. What
do we want? Are there global limits, absolute limits beyond which we cannot go without
catastrophe or overwhelming costs? There are, most certainly.
— George Woodwell 1985
CASE STUDY: EASTER ISLAND
Theconstraints on the Earth's human carrying capacity are just as real as the wide range of
choices within those boundaries. The history of Easter Island provides a case study of human
choices and natural constraints in a small world.
While exotic in location and culture, Easter
Island is of general interest as one example of the many civilizations that undercut their own
The island is one of the most isolated bits of land on the Earth. The inhabited land nearest to
Easter Island is Pitcairn Island, 2,250 kilometers northwest; the nearest continental place,
Concepción, Chile, is 3,747 kilometers southeast. The island is roughly triangular in plan, with
sides of 16, 18 and 22 kilometers and an area of 166.2 square kilometers (a bit larger than Staten
Island, a borough of the city of New York). About 2.5 million years old, the volcanic island rose
from the sea floor 2,000 meters below sea level. A plateau occupies the middle of the island and
a peak rises nearly 1,000 meters above sea level.
Radiocarbon dating suggests that people, almost certainly Polynesians, occupied the island by
a.d. 690 at the latest; scattered earlier radiocarbon dates from the fourth and fifth centuries are
The first arrivals found an island covered by a rainforest of huge palms. The
islanders were probably isolated from outside human contact until the island was spotted by
Dutch sailors in 1722.
During this millennium or millennium and a half of isolation, a fantastic civilization arose. Its
most striking material remains are 800 to 1,000 giant
two to ten meters high, carved in volcanic tuff and scattered over the island.
Many are probably still buried by rubble and soil. The largest currently known is 20 meters (65
feet) long and weighs about 270 tonnes. It was left unfinished.
According to pollen cores recently taken from volcanic craters on the island, a tree used for rope
was originally dominant on the island.
At different times, depending on the site, between the
eighth and the tenth centuries, forest pollen began to decline. Forest pollen reached its lowest
level around a.d. 1400, suggesting that the last forests were destroyed by then. The deforestation
coincided with soil erosion, visible in soil profiles.
The Polynesian rat introduced for food by
the original settlers consumed the seeds of forest trees, preventing regeneration. Freshwater
supplies on the island diminished. In the 1400s or 1500s, large, stemmed obsidian flakes used as