1. ENV 301: Environmental Science A Study of Interrelationships
Discussion notes: Scott M. Graves
Text: Enger • Smith
Ninth Edition
Chapter 12 Human Impact on Resources and Ecosystems
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2. Human Impact on Resources and Ecosystems
Chapter 12

3. Chapter Outline
Historical Basis of Pollution
Resource Utilization
Mineral Resources
Ecosystem Modification
Forests
Rangelands
Wilderness
Aquatic
Managing Ecosystems for Wildlife
Extinction

4. Changing Role of Human Impact
As human population grew, and tools became more advanced, the impact a single human could have on surroundings increased.
Environmental modifications allowed larger, dense human populations to arise.
Nearly all earth’s surface has been affected in some way by human activity.

5. Historical Basis of Pollution
Pollution—Anything released into the environment that affects an organism’s survival and reproduction.
Two primary factors affect the amount of damage done by pollution:
Size of the population
Level of technological development

6. Historical Basis of Pollution
When the human population was small, waste products were generally biodegradable.
Human-caused pollution is produced when waste is generated faster than it can be degraded, especially as people began to congregate and establish cities.
Throughout history, humans fought ecosystem degradation with technology.
Short-term solutions.

7. Renewable and Nonrenewable Resources
Natural Resources—Structures and processes humans can use, but not create.
Renewable—Can be formed or regenerated by natural processes.
Soil, Vegetation, Wildlife
Non-Renewable—Not replaced by natural processes, or, rate of replacement is ineffective.
Minerals, Fossil fuels

8. Costs Associated With Resource Utilization
Economic—Monetary costs necessary to exploit the resource.
Energy—Energy expended exploiting the resource.
Environmental—Environmental effect of resource exploitation (often deferred).

9. Mineral Resources Major form of nonrenewable resource.
Distribution is not uniform.
Many deposits have already been exploited.
North America consumes >30% of world minerals.
Steps in Mineral Utilization
Exploitation
Mining
Refining
Transportation
Manufacturing

10. Recycling of Mineral Materials
Many minerals are not actually consumed, but only temporarily held.
In many industries, cost of purchasing recycled raw materials is higher than the cost of purchasing virgin materials.
More costly to produce products from recycled material than virgin materials.
Historically, monetary cost for energy has been low, thus no incentive to recycle.

11. Utilization and Modification of Terrestrial Ecosystems
Natural ecosystems have greater biodiversity than human-managed ecosystems.
Impact of Agriculture on Natural Ecosystems
40% of world’s land surface converted to cropland and permanent pasture.
Most productive natural ecosystems are the first to be modified by humans.
Pressures to modify the environment are greatest in areas with high population density.

12. Managing Forest Ecosystems
1/2 of U.S., 3/4 of Canada, and almost all of Europe was originally forested.
Because of increasing human population growth, forested areas are under increasing pressure to provide wood products and agricultural land.
Efficient methods of harvest and transportation are important to reduce economic cost of using forest resources.

13. Economic and Energy Costs
Major Economic Costs of Utilizing Forests:
Purchasing or leasing land.
Paying for equipment and labor.
Building roads
Major Energy Costs of Utilizing Forests:
Harvesting
Transportation

14. Environmental Costs
Modern forest management practices involve a compromise that allows economic exploitation while maintaining some of the environmental values of the forest.
Forested areas effectively reduce erosion.
Loss of soil (nutrients) reduces soil fertility.
Road building in forests increases erosion.
Forest areas modify climate, and provide recreational opportunities as well.

15. Environmental Implication of Harvesting
Clear Cutting—Removal of all trees in an area. Economical but increases erosion, especially on steep slopes.
Patch-Work Clear Cutting—Clear cutting in small, unconnected patches; preserves biodiversity.
Selective Harvesting—Single-tree harvesting. Not as economical, but reduces ecosystem damage.

16. Plantation Forestry
Many lumber companies maintain forest plantations as crops and manage them in the same way farmers manage crops.
Plant single species, even-aged forests of fast growing hybrid trees.
Competing species are controlled by fire and insects controlled by spraying.
Mature rate as low as 20 years (vs. 100).
Quality of lumber reduced.
Low species diversity and wildlife value.

17. Special Concerns About Tropical Deforestation
Tropical forests have greater species diversity than any other ecosystem.
Not easy to regenerate after logging due to poor soil characteristics.
Deforestation Concerns
Significantly reduces species diversity.
Impacts climate via lowered transpiration.
CO2 trap—Increased global warming.
Human population pressure is greatest in tropics, and still increasing.

18. Managing Rangeland Ecosystems
Rangelands—Lands too dry to support crops, but received enough precipitation to support grasses and drought-resistant shrubs.
Wildlife are usually introduced species.

19. Environmental Costs of Utilizing Rangelands
Management techniques and selective grazing of animals may lead to the elimination of non-preferred species.
Important to regulate number of livestock on rangelands, especially in dry areas.
Desertification—Process of converting arid and semi-arid land to desert.
Over-grazing
Firewood cutting

21. Wilderness and Remote Areas
Many areas in the world have had minimal human impact.
Some are remote and may have harsh environmental conditions.
Wilderness Act (1964)—Wilderness:
“An area where the earth and its community of life are un-trampled by man, where man himself is a visitor who does not remain.”

22. Managing Aquatic Ecosystems
Aquatic ecosystems divided into:
Freshwater, Brackish, Marine
Environmental costs related to utilizing marine ecosystems fall into two categories:
Over-fishing
Environmental effects of harvesting
UN estimates 70% of world’s marine fisheries are over-exploited.
Capacity should be reduced by 30%.

24. Managing Aquatic Ecosystems
Coastal regions are most productive regions of the oceans.
Sunlight penetration—shallow—warm
Nutrient deposition from land
Wind/wave action stirs nutrients
Fishing pressure and pollution are greatest in these areas.
Trawls—nets dragged along bottom.
Large by-catch
Disturbs seafloor

25. Environmental Costs Associated with Utilizing Freshwater Ecosystems
Two primary human alterations:
Water Quality —Erosion, toxic run-off
Exotic Species—Introduced species
Humans have great access to freshwater ecosystems.
Many North American freshwater fisheries are primarily managed for sport fishery.
Fisheries managers must balance:
Sport fisheries
Commercial harvesters

26. Aquaculture
Fish farming is becoming increasingly important as a source of fish production.
Currently, about 60% of all aquaculture production is from freshwater systems.
Problems
Nutrient overloads
Escape into natural waters
Land conversion

27. Managing Ecosystems For Wildlife
Habitat Analysis and Management
Animals have highly specific habitat requirements that change throughout the year.
Once habitat requirements are understood, steps can be taken to alter habitat and improve species success.
Fire to eliminate poor habitats.
Kirtland Warblers—Jack Pine stands.
Encourage growth of certain plant species.

28. Population Assessment and Management
Wildlife managers use population censuses to check if populations are within appropriate levels.
With suitable habitat and protection, most wild animals can maintain a sizeable population.
But high reproductive capacities and/or heavy protection can cause very large populations.
Whitetail Deer in Eastern U.S.
Elephants in Zimbabwe

29. Population Assessment and Management
Wildlife management often involves harvesting for sport and meat.
Hunting regulation is crucial.
Seasons usually occur in the fall to take advantage of surplus animals.
When populations get too small, artificial introductions can be implemented.
Native species for augmentation.
Non-native species for empty niches.

30. Managing a Wildlife Population

31. Predator and Competitor Control
At one time it was believed populations of game species could be increased if predators were controlled.
Still used in some situations.
But, in many cases, human modification of habitat has a greater impact than natural predation.
Many species do require refuges where they are protected from competing species or human influence.

32. Migratory Waterfowl Management
Migratory birds can travel thousands of kilometers.
North in spring to reproduce.
South in fall to escape cold temperatures.
International agreements necessary to maintain appropriate habitat.
Canada
United States
Mexico

33. Extinction and Loss of Biodiversity
Small, dispersed populations are more prone to extinction.
Successful breeding more difficult.
Local weather conditions can severely impact population size.

34. Human-Accelerated Extinction
Wherever humans have become the dominant organisms, extinctions have occurred.
Food
Animals Parts
Pest Status
Habitat Alteration
Most Important Cause
Habitat Fragmentation

36. Why Worry About Extinction ?
Useful to Humans:
Medical—Less than 1% of tropical rainforest plant species have been tested for pharmaceutical use.
Food Resources
Ecological—Species play specific roles in ecosystem function.
Ethical—Animals have a fundamental right to exist.

37. Extinction Prevention
Endangered—Very low populations, could become extinct in very near future.
Threatened—Still exist in large numbers in current range, but are declining in most areas.
Could become extinct if a critical environmental factor is changed.

38. Extinction Prevention
Most extinction prevention interest occurs in developed countries. Most vulnerable species already eliminated.
Less-developed and developing countries have both highest population growth and the majority of the world’s species.
More concerned with immediate needs of food and shelter than long-range issues such as species extinction.

39. Endangered Species Act (1973)
Gave U.S. government jurisdiction over threatened and endangered species.
Directs that no activity by a government agency should lead to the extinction of an endangered species.
Directs government agencies to use whatever means necessary to preserve the species in question.

40. Chapter Summary
Historical Basis of Pollution
Resource Utilization
Mineral Resources
Ecosystem Modification
Forests
Rangelands
Wilderness
Aquatic
Managing Ecosystems for Wildlife
Extinction