27.0 Introduction

1. Humanity Versus the Earth
1. Effects of Human Population Visible at Great Distance fig 27.1
2. Population Impacts the Environment
1. Total population of the earth in 1995 reached 5.7 billion
2. More people consume more food, water, energy and raw materials
3. More people create greater amount of waste

27.1 The world's human population is growing explosively

1. A Growing Population
1. The Present Situation
1. World population is nearly 6 billion fig 27.2
2. Global birth rate for last 300 years: 30 per year per 1000 people
3. Present rate decreased slightly to 25 per 1000
1. Decreased death rate from 29 to 13 per 1000 people per year
2. Net increase in annual population rate

4. Population increasing at rate of 1.6% per year
1. Will double population in 43 years
2. Annual increase of 100 million per year
3. United Nation estimates population of 6 billion by 2000 AD
4. Expected stabilization at 8.5 to 18 billion by 2090

2. The Future Situation
1. Localization of human populations in year 2000
1. 60% in tropical or subtropical regions
2. 20% in China
3. 20% in developed or industrialized nations

2. Rate of growth
1. Industrialized countries at 0.3% per year
2. Developing countries (excluding China) at 2.2% annually

3. Variable world age structure affects population growth
1. Industrialized nations: 20% of population under 15 years fig 27.3
2. Developing countries have nearly twice as many
3. Populations of developing countries will continue to grow faster fig 27.4
4. Industrialized nations will constitute smaller portion of the global population

3. Population Growth Rate Starting to Decline
1. Estimates of population in 1995 less than expected
1. Growth rate predicted to be 1.57% per year
2. Actual growth at 1.48%
3. Average number of children per woman 2.96 not expected 3.1

2. U.N. attributes decline to family planning efforts, increased status of women
1. Substantial monies spent on family planning
2. Opposition would rather spend it on education, improving economy
3. U.N. reports an increase in education levels after reduction in family size

3. Countries progressing to slow their growth rates
4. Population may stabilize sometime in the next century
5. Quality of life dependent on stabilizing world's population

27.2 Improvements in agriculture are needed to feed a hungry world

1. The Future of Agriculture
1. Immediate World Challenge to Produce More Food
1. Food production increased by 2.6 times since 1950
1. Expanded at greater rate than population
2. Most cultivatable land already in use
3. Topsoil lost from agricultural land

2. Prospects for increased agricultural productivity

2. Finding New Food Plants
1. Major crops have been cultivated for thousands of years
1. Half of all human energy requirements fulfilled by rice, wheat, corn
2. 100 kinds of plants provide over 90% of calories
3. Need to explore properties of plants among 250,000 known species fig 27.5

2. Identify new crops, especially in tropics
1. Few new plants cultivated since 1800
2. Examples: Rubber and oil palms

3. Crops selected for ease of growth

3. Improving the Productivity of Today's Crops
1. Improvement needed in tropical and subtropical regions
1. People cannot be fed on exports from industrial nations
2. Industrial nations contribute 8% of own production

2. Improvement of strains via Green Revolution: 1950-1970
1. Ten-fold increase in Mexican wheat production
2. Food production in India outpaced population growth
3. China became self-sufficient in food production

3. Limitations of Green Revolution
1. Agricultural techniques require great energy output
2. Extensive use of costly pesticides and herbicides

4. U.S. wheat production requires 1000 times more energy than farming in India
5. Present solutions
1. Improve production of current crops
2. Fully apply traditional means of plant breeding and selection fig 27.5
1. Develop new crops in tropics and subtropics
2. Development of "super rice" in Philippines

4. Genetic Engineering to Improve Crops
1. Resistance to specific herbicides results in better weed control
2. Tolerance to soil conditions and mineral toxicity
3. Ability to fix nitrogen

5. New Approaches to Cultivation
1. "No-till" agriculture conserves topsoil
2. Use of hydroponic agriculture problematic
3. Resources of oceans are not inexhaustible
1. Reduce over fishing of specific areas
2. Develop new microorganism-based foods: Spirulina

27.3 Human activity is placing the environment under increasing stress

1. Nuclear Power
1. Chernobyl Incident
1. One of four reactors exploded in April 1986
1. Emergency safety systems shut off
2. Power surge precipitated the explosion

2. Released over 100 megatons of radioactivity
1. Millions of times greater than Three Mile Island
2. Significant human exposure to radiation
3. Death due to radiation poisoning

2. The Promise of Nuclear Power
1. Fossil fuels no longer cheap sources of energy
2. Nuclear power could provide new source
3. Undesirable side effects to burning fossil fuels
1. Produces sulfur, principal cause of acid rain
2. Produces carbon dioxide, primary greenhouse gas

4. New problems associated with nuclear power
1. Safe operation of power plants
2. Disposal of radioactive wastes and safe decommission of power plants
3. Prevention of terrorism and sabotage

5. Important to develop other alternative energy sources
1. Includes solar and wind energy
2. Improve efficiency of electrical appliances

2. Carbon Dioxide and Global Warming
1. Changing Concentrations of Gases in Atmosphere
1. CO₂ maintains world temperature 25º higher than without it
1. Traps heat-producing infrared light
2. Creates greenhouse effect fig 27.6

2. Associated with increased energy use
1. Most gas from burning of fossil fuels
2. Burning of forests also increases atmospheric gas

3. Global warming results from increased CO₂
1. Mean global temperature increased 1ø since 1900
2. Level of CO₂ could double by 2035
3. Warming exacerbated by trace gases
1. Include nitrous oxide, methane, ozone, chlorofluorocarbons
2. Effects similar to CO₂

4. Ancillary problems
1. Rising sea levels
2. Leads to global climate changes, shift of desert and agricultural regions

3. Pollution
1. Rhine River as an Example
1. Fire in chemical warehouse washed chemicals into river
1. Deadly mercury and pesticides killed fish and plants
2. Water became unsafe to drink

2. River slowly cleaned itself

2. The Threat of Pollution
1. Results from industrial byproducts
1. Plastics cannot decompose
2. Efforts being made to develop new microorganisms yet unsuccessful

2. Agricultural pollution
1. Widespread use of pesticides, herbicides, fertilizers
2. Toxic chemicals remain in ecosystems
1. Chlorinated hydrocarbons banned in U.S.
2. Biological magnification: Toxins concentrate in the food chain fig 27.7

4. Acid Precipitation
1. Mechanism for Production of Atmospheric Acids
1. Sulfur compounds produced when coal burned fig 27.8
2. Effects seen far from where acids are produced
1. Mixes with atmospheric water to produce sulfuric acid
2. Acid dispersed by winds high up in atmosphere

2. Biological Consequences
1. Death of thousands of fresh water lakes fig 27.9
1. pH below 5.0 is usually life-threatening
2. Seepage into groundwater

2. Destruction of forests fig 27.10
3. Expensive to capture and remove emissions
1. Polluter and recipient far apart
2. Neither wants to pay for problems

4. Success of Clean Air Act in U.S.

5. The Ozone Hole
1. Visible to Electronic Equipment Over Antarctica fig 27.11
1. Hole is nearly the size of the U.S.
1. Thinning of ozone layer first appeared in 1975
2. Presence of hole coincides with Antarctic spring

2. Cause of ozone hole attributed to chlorofluorocarbons (CFCs)
1. Chemicals used in cooling, fire extinguishers and styrofoam
2. CFCs reduce O₃ ozone molecule to O₂ gas

3. Global agreements to halt CFC production
1. Problem will get worse before it gets better
2. Quantity currently in lower atmosphere will reach upper atmosphere in later years

4. Biological consequences
1. Increased ultraviolet light penetration
2. Increases incidence of human skin cancers

6. Destruction of the Tropical Forests
1. Rainforests Are Rapidly Disappearing
1. Rainforests are biologically richest biomes
1. Other forests with better soils destroyed for agriculture long ago
2. Rainforests now destroyed even though soils are poor

2. Undisturbed rainforests occupy only 5.5 million square kilometers
1. Area about two-thirds the size of U.S. (Without Alaska)
2. Represents half the original size of the rainforests

3. 160,000 square kilometers clear cut each year
1. Additional loss due to shifting cultivation, gathering firewood, cattle ranching
2. Equal to the size of Indiana per year
3. At the present rate they will be gone in thirty years

2. A Serious Matter
1. Loss of biodiversity
2. Damage to complex, productive ecosystem
1. Need to change from one-use to continuous agriculture fig 27.12
2. Natural resources not available for use again

3. Biologists must learn more to sustain agriculture in tropical regions

27.4 Solving environmental problems requires individual involvement

1. Environmental Science
1. Attempts to Find Solutions to Environmental Problems
1. Studied by environmental scientists
2. Applied science associated with ecology, geology, meteorology, social sciences

2. Solving Environmental Problems
1. Assessment
1. Gathering information
2. Construct model of situation
3. Use model to predict future events

2. Risk analysis
1. Analyze environmental impact
2. Evaluate potential for solving problem
3. Determine adverse effects of solution

3. Public education
1. Address problem in terms the public can understand
2. Present alternative actions
3. Explain costs and results of various choices

4. Political action
1. Choice made through elected officials
2. Difficult to implement if multinational problems

5. Follow-through
1. Monitor results of environmental actions
2. Evaluate and improve initial analysis and modeling

3. Individuals Can Make the Difference
1. The Nashua River
1. New England river severely polluted by mills
2. Declared ecologically dead in 1960s
3. Stoddart approached state to set apart a greenway along river, rejected
4. Formed Nashua River Cleanup Committee
5. Led, in part, to Massachusetts Clean Water Act of 1966
6. Industrial dumping banned, river recovering

2. Lake Washington
1. Freshwater lake east of Seattle
2. Sewage discharged into lake in 1940-1950s
3. Effluent though to be harmless,
4. Actually fertilized lake, promoted growth of blue-green algae
5. Algae expected to deplete deep lake's oxygen supply, kill lake
6. Sewage rerouted to dumping in sea
7. Lake now clean

2. Preserving Nonreplaceable Resources
1. Destruction of Nonreplaceable Resources in U.S.
1. Topsoil
2. Groundwater
3. Biodiversity

2. Topsoil
1. U.S. Is among most productive agricultural regions due to fertile soils
1. Much of Midwest was once extensive prairie
2. Substantial topsoil accumulated over countless generations
3. Rich soit once extended down several feet

2. Lost at a rate of several centimeters per decade
1. Loss through repeated tilling of soil to eliminate weeds
2. Rain washes away more of topsoil

3. Utilize new approaches to reduce intensive cultivation
1. Genetically engineer crops resistant to weed-killing herbicides
2. Terrace areas via contour farming to recapture topsoil fig 27.13

3. Groundwater
1. Groundwater is water trapped within porous rock, in aquifers
2. Originated from seepage of glaciers during last ice age
3. Large portion of water wasted for non-productive activities
4. Great deal also polluted by poor disposal of chemical wastes

4. The Loss of Biodiversity
1. Serious and rapidly accelerating problem
1. Loss of species of known plants and animals
2. Loss of habitat, especially in tropics
3. Calculate loss of 20% of biodiversity within in next 30 years
4. Loss greater considering only 15% of world's eukaryotic organisms have been named

5. Why Preserve Biodiversity?
1. Loss important on moral, ethical and aesthetic grounds
2. Organisms necessary to sustain our own existence fig 27.14
1. Also lose potential benefits of these organisms
2. Opportunity to study them lost

3. Upset balance of living communities and their physical environment
1. Effect soils, water regulation, nutrient cycles, atmosphere, absorb pollution
2. Creating conditions of instability and nonproductivity

6. Ecological Reserves
1. New discipline of conservation biology
1. Better understanding of causes of extinction
2. Better management of habitats and ecosystems

2. Creation of megareserves in tropics
1. Isolated patches lose species more rapidly than large areas
2. Preserve reserve and still allow local land use
3. No activity in core region, nondestructive use of remainder
4. Pioneering efforts in Costa Rica