Title: Unit 5 Learning Module
Course: BIS 105 Environmental Biology > Section: BIS 105 Environmental Biology

Unit 5 Learning Module

Easter Island
Copyright
Adapted from CK-12 Foundation, - Biology I Honors (CA DTI-3) by Douglas Wilkin .
Adapted from U of I Open Source Textbook. Sustainability: A Comprehensive Foundation. Connexions. 2 May 2012 .

Easter Island

Hundreds of stone figures, known as moai, measuring up to 10 meters tall and weighing up to 87 tons overlook a low-diversity grassland on Easter Island in the Pacific Ocean. The food sources, woody trees, and rope-yielding plants which helped to build and transport these statues over five hundred years ago are gone.

Pollen analyses suggest that the island was totally forested at least until 1200 CE, but that by 1650 the forests had entirely disappeared. Middens (waste dump sites) show a sudden disappearance of sea bird and fish bones, suggesting that wood for canoes was no longer available. Sediments reveal that half of native plant species had become extinct. Later fire pits indicate the possibility of cannibalism.

Jared Diamond, in his book Collapse: How Societies Choose to Fail or Succeed, examines this bleak scene and other past societies and concludes that doomed civilizations share eight traits which contribute to their collapse. Seven of the eight traits are rooted in overpopulation relative to environmental carrying capacity. Diamond considers Easter Island to be “Earth writ small” – a warning that this island’s environmental devastation could foreshadow a similar fate for our planet. He encourages humans to learn from earlier collapses to conserve the forest, soil, water, animal, fish, photosynthetic, atmospheric, and energy resources upon which our human lives depend. A large group of people sometimes known as “Neo-Malthusians” join Diamond in his belief that human population growth cannot continue without dire consequences.

Julian Simon and a group dubbed “cornucopians” see the human condition differently. Named for the mythical Greek "horn of plenty” which supplied endless food and drink magically, cornucopians believe that the Earth can provide an almost limitless abundance of natural resources, that few natural limits to growth exist, and that technology can solve or overcome population-induced resource scarcity and environmental degradation. Larger human population (within an appropriate political environment) is the answer to the problems of population growth, according to Simon.

Are you, like Diamond and Malthus before him, a “doomster”? Or do you join Simon as a “boomster”? Most “doomsters” and “boomsters” share the belief that we are responsible for managing problems related to population growth. Let’s use our understanding of population biology to study the human population. Our goal will be to shed light on the decisions we – the only species able to consider and alter our rates of birth and death – make about future population growth.

The previous unit discussed how populations in nature grow. You have learned that all populations have the potential to grow exponentially (J-curve pattern of growth), but that exponential growth is limited to ideal conditions, which are rare in nature. In nature, competition for limited resources or unpredictable, density-independent limiting factors restrict populations to densities at or below carrying capacities (S-curve growth pattern). Some populations grow smoothly to a stable carrying capacity, but others overshoot that density and may crash before rebuilding to a relatively stable level. A few crash to extinction. In unstable environments, some populations establish cycles of population growth and decline. Unstable environments favor adaptations for rapid growth (r-selected species), and stable environments favor adaptations for efficient use of resources (K-selected species).

Where do humans fit? Are we built for growth – or conditioned for efficient use of resources? Does our growth pattern resemble a J, or an S? Are we in danger of extinction? What exactly is our “population problem,” and what can we do to solve it?