Download Essentials of the Living World

Essentials of the Living World
Second Edition
George B. Johnson
Jonathan B. Losos
Chapter 23
Planet Under Stress
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
23.1 Pollution
• Our world is one highly interactive
biosphere and damage done to any one
ecosystem can have ill effects on many
others
 biologists call widespread effects on the
worldwide ecosystem global change
 the pattern of global change that has become
evident within recent years is one of the most
serious problems facing humanity’s future
23.1 Pollution
• Pollution takes many forms
 air pollution is a major problem in the world’s cities
• some cities, such as New York and Boston, are gray-air cities
because of sulfur oxides from industrial pollution
• other cities, such as Los Angeles, are brown-air cities
because pollutants in the air react with sunlight to form smog
 water pollution
• despite improved methods of sewage treatment, lakes and
rivers are becoming increasingly polluted with sewage
• fertilizers and insecticides also get washed from the land to
the water
23.1 Pollution
• Large quantities of many toxic chemicals,
although no longer manufactured, still
circulate in the ecosystem
 for example, chloronated hydrocarbons, a
class of compounds that includes DDT, have
all been banned for normal use in the US
• these chemicals break down slowly and
accumulate in animal fat tissue
• as they pass through the food chain, they become
increasingly concentrated in a process called
biological magnification
Figure 23.1 Biological magnification
of DDT
23.2 Acid Precipitation
• Acid rain is pollution-acidified precipitation
produced when sulfur products of industry
combine with water vapor in the air and then fall
back to earth as rain or snow
 acid precipitation destroys life
• at least 1.4 million acres of forests in the Northern
Hemisphere have been adversely affected
• Tens of thousands of lakes in the northeastern US and
Canada are dying biologically as their pH levels fall below 5.0
 industrial scrubbers and the Clean Air Act revision of
1990 have begun to address this problem
23.3 The Ozone Hole
• Living things were able to leave the oceans and
colonize the surface of the earth only after a
protective shield of ozone had been added by
photosynthesis
 the ozone shield protects the earth from harmful
radiation
 starting in 1975, the earth’s ozone shield began to
disintegrate, leaving a mysterious zone of lower-thannormal ozone concentration
• this zone is called an ozone hole
Figure 23.4 The ozone hole over
Antarctica
23.3 The Ozone Hole
• Chlorofluorocarbons (CFCs) were found to be
responsible for the breakdown of ozone
 originally thought to be harmless, these chemicals are
used as coolants in refrigeration and cooling, gas in
aerosol contains, and as the foaming agent in
Styrofoam
 CFCs easily catalyze the conversion of O3 (ozone)
into O2
 the drop in worldwide ozone is now over 3% and is
estimated to have led to an increase in perhaps as
much as 20% in lethal melanoma skin cancers
23.4 Global Warming
• Industrial society’s burning of fossil fuels
has released huge amounts of carbon
dioxide into the atmosphere
 the chemical bonds in CO2 transmit radiant
energy from the sun but trap the longer
wavelengths of infrared light (or heat)
 this creates a greenhouse effect of this
trapped heat
 other greenhouse gases include CFCs,
nitrogen oxides, and methanes
Figure 23.5 The greenhouse effect
23.4 Global Warming
• The earth’s greenhouse effect is intensifying
 global warming is a rise in the average global
temperatures associated with increased CO2
concentration in the atmosphere
 some possible effects of global warming include
• changes to rainfall patterns
• increases in agricultural yield but increased risks of drought
• melting of ice in glaciers and the polar ice caps, causing sea
level to rise
23.5 Loss of Biodiversity
• Current rates of extinction are alarmingly high,
constituting a crisis in biodiversity
 biologists have identified three factors that play a role
in extinction
• habitat loss
– this is the single most important cause
• species overexploitation
– species that are hunted or harvested by humans have
historically been at risk of extinction
• introduced species
– the introduction of exotic species results in extinction because
these species have no native predators to keep their
populations in check
Figure 23.6 Factors responsible for
animal extinction
Figure 23.7 Extinction and habitat
destruction
23.6 Reducing Pollution
• The pattern of global change that is overtaking
our world is very disturbing
• We must quickly find ways to reduce the harmful
impact of human activities on the biosphere
• It is important that four areas be addressed




reducing pollution
finding other sources of energy
preserving nonreplaceable resources
curbing population growth
23.6 Reducing Pollution
• Economists have now identified an
“optimum” amount of pollution based on
how much it costs to reduce pollution
versus the social and environmental costs
of allowing pollution
 if more pollution than the optimum are
allowed, the social cost is too high
 if less than the optimum is allowed, the
economic cost is too high
Figure 23.8 Is there an optimum
amount of pollution?
23.6 Reducing Pollution
• Two approaches have been devised to
curb pollution in the US
 antipollution laws are designed to curb
pollution by setting stiff standards for what can
be released into the environment
 pollution taxes are assessed in order to
balance the conflicting demands of
environmental safety and economic growth
23.7 Finding Other Sources of
Energy
• The pollution generated by burning coal
and oil, the increasing scarcity of oil, and
the potential contributions of CO2 to global
warming, all make it desirable to find
alternative energy sources
 there are many possible candidates including
• nuclear power
• solar power
• wind power
Alternative Energy Sources
Figure 23.9 Three Mile Island
nuclear power plant
Figure 23.10 Alternative energy
sources
23.8 Preserving Nonreplaceable
Resources
• In the US, there are three sorts of
nonreplaceable resources that are being
reduced at alarming rates
 topsoil
• over one quarter of topsoil has been lost since 1950
 groundwater
• groundwater in aquifers is being depleted or polluted
 biodiversity
• loss of species creates instability in ecosystems and reduces
productivity
Figure 23.12 Tropical rainforest
destruction
23.9 Curbing Population Growth
• The world population reached 6.5 billion
people in 2004 and will double in about 58
years
 such growth cannot continue because our
world cannot support it
 slowing population growth will help sustain the
world’s resources but per capita consumption
is also important
Figure 23.13 Growth curve of the
human population
Figure 23.15 Distribution of
population growth
23.9 Curbing Population Growth
• Human population growth is not occurring
uniformly over the planet
 the rate at which a population can be
expected to grow in the future can be
assessed graphically by means of a
population pyramid
Table 23.1 A Comparison of 2003 Population Data
in Developed and Developing Countries
Figure 23.17 Population pyramids
23.9 Curbing Population Growth
• The AIDS epidemic in
Africa will have a
huge impact on
population sizes
• In sub-Saharan
Africa, AIDS has
reduced life
expectancy at birth by
20 years
Figure 23.18 Projected AIDS effect on
Botswana population (year 2025)
23.9 Curbing Population Growth
• We in the developed countries need to pay
more attention to lessening the impact of
our resource consumption
 an ecological footprint is the amount of
productive land required to support an
individual at the standard of living of a
particular population through the course of his
or her life
• the ecological footprint of an individual in the US is
10X greater than that of someone in India
23.10 Preserving Endangered
Species
• Once you understand why a particular
species is endangered, it becomes
possible to think of designing a recovery
plan





habitat restoration
captive propagation
sustaining genetic diversity
preserving keystone species
conservation of ecosystems
Recovery Plans
Figure 23.20 Habitat restoration
Figure 23.21 Sustaining genetic diversity
Figure 23.22 Preserving keystone
species
23.11 Individuals Can Make the
Difference
• One person can make
a difference in solving
environmental
problems
 for example, many US
families recycle
Figure 23.23 Cleaning up the
Nashua river
Inquiry and Analysis
• What fraction of the
155 years do not
deviate from the 1961
- 90 mean value?
• Has the global air
temperature been
warming
progressively over the
last century and a
half?
Graph of History of Changes in
Global Air Temperature