1. Environmental Science A Study of Interrelationships
Tenth Edition
Enger • Smith
Chapter 12
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2. Biodiversity Issues
Chapter 12

3. Outline
Biodiversity Loss and Extinction
Describing Biodiversity
Genetic
Species
Ecosystem
The Value of Biodiversity
Threats to Biodiversity
Habitat Loss
What is Being Done to Preserve Biodiversity

4. Biodiversity Loss and Extinction
Biodiversity is a broad term used to describe the diversity of genes, species, and ecosystems in a region.
Extinction is the elimination of all the individuals of a particular species.
Natural and common event in the history of biological evolution.

5. Causes of Extinction
Local extinctions, although relatively common, indicate the future of a species is not encouraging.
As population is reduced in size, some of the genetic diversity is likely to be lost.
Species Likely to Go Extinct
Small, dispersed populations.
Successful breeding is difficult.

6. Species Likely to Go Extinct
Organisms in small, restricted areas.
Environmental changes have large effect.
Specialized Organisms
Relying on constancy of few key factors.
Organisms at higher trophic Levels.
Low population sizes and reproductive rates.

7. Extinction as a Result of Human Activity
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.
At expense of previously existing ecosystems.
Nearly all earth’s surface has been affected in some way by human activity.

8. Describing Biodiversity
Genetic Diversity is a term used to describe the number of genes present in a population.
High genetic diversity indicates many different kinds of genes present in individuals of a population.
Low genetic diversity indicates nearly all individuals share the same genes.

9. Genetic Diversity
Influences on a Population’s Genetic Diversity
Mutations
Introduce new genetic information into a population by modifying current genes.
Migration
Allows movement of genes from one population to another.
Sexual Reproduction
Generates new genetic combinations.

10. Influences on a Population’s Genetic Diversity
Population Size
The smaller the population, the less genetic diversity it can contain.
Fewer variations for each characteristic.
Selective Breeding
Elimination of undesirable characteristics.
Domesticated Plants and Animals.

11. Species Diversity
Species diversity is a measure of the number of different species present in an area.
Species Richness - Number of different kinds of species.
Taxonomic Richness - Takes into account the number of different taxonomic categories of the species present.

12. Species Diversity
When humans exploit an area, they influence species diversity.
Convert natural ecosystems to human-managed ecosystems.
Harvest certain species for their use.
Specifically eliminate species that compete with desirable species.

13. Species Diversity
Estimates of actual number of species range from a few million to 100 million.
About 1.4 million species have been described.
Many species are naturally rare, and others live in areas difficult to reach.

14. Ecosystem Diversity
Ecosystem diversity is a measure of the number of kinds of ecosystems present in an area.
Many regions of the world appear to be quite uniform in terms of ecosystems.
Deserts
Each is different and has specific organisms typical to the region.
Local topographic conditions create unique patches of landscape.

15. The Value of Biodiversity
Value of Biological and Ecosystem Services
Humans rely on organic molecules produced by other organisms for food.
Vegetation holds soil together and protects watersheds.
Plants remove carbon dioxide from the atmosphere.
Decomposers recycle organic wastes.

16. The Value of Biodiversity
Choices between competing uses for ecosystems are often determined by economic values.
Value can be assigned to services provided by intact, functioning ecosystems.
Current estimate of $33 trillion per year.
Some resources are difficult to assign specific monetary value:
Wildlife
Medicinal Plants

17. Ethical Values
A case can be made that all species have an intrinsic value and a fundamental right to exist.
Extinction is not necessarily bad, but human-initiated extinction is.
Experiencing natural landscapes and processes is an important human right.

18. Ethical Values
The values held by a person are typically shaped by experience.
As the shift from rural to urban continues, there is continual erosion of natural experiences that can shape the values of people.
Important in determining how society will approach threats to biodiversity.

19. Threats to Biodiversity
Four major human activities threaten to reduce biodiversity.
Habitat Loss
Overexploitation
Introduction of Exotic Species
Persecution of Pest Organisms

20. Causes of Extinction

21. Habitat Loss
World Conservation Union estimates that 80%-90% of threatened species are a result of habitat loss or fragmentation.
Habitat loss and fragmentation are thought to be a major cause of past extinctions.

22. Conversion to Agriculture
About 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.

23. Forestry Practices
Originally, 1/2 of US, 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.
Deforestation

24. Changes in Forest Area

25. Managing Forest Ecosystems
Modern forest management involves a compromise that allows economic exploitation while maintaining some environmental values of the forest.
Forested areas effectively reduce erosion.
Loss of soil (nutrients) reduces soil fertility.
Road building in forests increases erosion.

26. Environmental Implications of Various Harvesting Methods
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.

27. 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.
Currently, few tropical forests are being managed for long-term productivity.

28. Special Concerns About Tropical Deforestation
Significantly reduces species diversity.
Impacts climate via lowered transpiration.
Deforested lands are easily eroded.
CO2 trap - Increased global warming.
Human population pressure is greatest in tropics, and still increasing.

29. 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.

30. Rangeland and Grazing Practices
Rangelands - Lands too dry to support crops, but receive enough precipitation to support grasses and drought-resistant shrubs.
Often used to raise low-density populations of domesticated, or semi-domesticated species.
Wildlife are usually introduced species.

31. Use of Rangelands

32. Rangeland and Grazing Practices
Conversion of rangelands by domesticated animals has major impacts on biodiversity.
Selective eating habits of livestock tend to reduce certain species of native plants and encourages others.
Important to regulate number of livestock on rangelands, especially in dry areas.
Desertification
Over-grazing
Firewood cutting

33. Desertification

34. Habitat Loss in Aquatic Ecosystems
In marine ecosystems, much of the harvest is restricted to shallow parts of the ocean where bottom-dwelling fish can be easily harvested.
Trawls and nets dragged along the bottom.
Habitat Damage
About 25% of catch is undesirable, and thus discarded.

35. Habitat Loss in Aquatic Ecosystems
Freshwater systems are often modified for navigation, irrigation, flood control, or power production.
May alter natural ecosystem and change numbers or kinds of aquatic organisms present.

36. Changes in World Marine Fish Harvests

37. Conversion to Urban and Industrial Uses
About 4.3% of U.S. land is developed as urban centers, industrial sites, and transportation infrastructure.
Large proportion covered with impermeable surfaces that prevent plant growth and divert rainfall.
Difficult to generalize impact of urban centers on a worldwide basis.
Trend is toward greater urbanization.

38. Overexploitation
According to World Conservation Union, overexploitation is responsible for over 30% of endangered animal species and 8% of endangered plant species.
World Wildlife Fund estimates illegal trade in wild animals globally produces $2 - $35 billion annually.
Already resulted in local extinctions.

39. Overfishing of Marine Fisheries
U.N. estimates 70% of world’s marine fisheries are over-exploited or are in danger of being fully exploited.
Amount of fish caught has remained relatively constant since 1989.
Commercial fishing industry has been attempting to market species previously regarded as unacceptable.

40. 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

41. Unsustainable Harvest of Wildlife and Plants
Meat from wild animals is often referred to as bush meat.
Hunting of wildlife is a part of all subsistence cultures.
Wildlife Conservation Society estimates 70% of wildlife species in Asia and Africa and about 40% of species in Latin America are being hunted unsustainably.
Endangered species such as chimpanzees and gorillas are often harvested.

42. Unsustainable Harvest of Wildlife and Plants
Harvest of living animals for the pet and aquarium trade is a significant problem.
Method of capture is often problematic.
Destruction of bird nests.
Toxins used to stun fish.
Wildlife are also hunted because parts of the animal may have particular value.
Ivory
Traditional Medicines

43. Introduction of Exotic Species
Some exotic introductions are purposeful, while others are accidental.
World Conservation union estimates about 30% of birds and 15% of plants are threatened because they are unable to successfully compete against invasive exotic species.

44. Introduction of Exotic Species
Introduction of disease has had considerable impact on American forests.
Chestnut Blight
Dutch Elm Disease
Various insects have had effect on ecosystem structure.
Asian Longhorned Beetle
Freshwater ecosystems greatly affected.
Zebra Mussel

45. Control of Pest Organisms
Systematic killing of certain organisms that interfere with human activities also results in reduced biodiversity.
Large Predators
Preyed on domestic animals.
Passenger Pigeons
Increased conversion of forested land.

46. Control of Pest Organisms
Predator and competitor control activities are still used in some special situations.
Generally not considered to be cost-effective in most cases.
Wolves in Northern areas are exception.
Control of cowbird populations have been used to enhance breeding success of Kirtland’s Warblers.

47. What is Being Done to Preserve Biodiversity?
World Conservation Union (IUCN) estimates by the year 2000, at least 500,000 species of plants and animals have been exterminated.
IUCN classifies species in danger of extinction into four categories:
Endangered
Vulnerable
Rare
Indeterminate

48. Legal Protection
Most interest in extinction prevention 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.

49. Legal Protection
U.S. Endangered Species Act (ESA -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.

50. Legal Protection
Endangered Species - Very low populations, could become extinct in very near future.
Threatened Species - Could become extinct if a critical environmental factor is changed.
Preservation question ultimately becomes one of assigning value to the species.
Amendments to ESA have weakened ability of U.S. government to add new species to the list.

51. Legal Protection
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.”

52. Sustainable Management of Wildlife Populations
Habitat Analysis and Management
Animals have highly specific habitat requirements that change throughout the year.
Steps can be taken to alter habitat and improve species success.
Fire to eliminate poor habitats.
Kirtland Warblers - Jack Pine stands.

53. Population Assessment and Management
Game species are often managed so they do not exceed carrying capacity of their habitat.
Wildlife managers use population censuses to check if populations are within appropriate levels.
With suitable habitat most wild animals can maintain a sizeable population.
High reproductive capacities and heavy protection can cause very large populations.

54. 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.

55. Managing a Wildlife Population

56. Special Issues with Migratory Animals
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

57. Migration Routes for North American Waterfowl

58. Sustainable Management of Fish Populations
Coastal regions are most productive regions of the oceans.
Sunlight penetration - shallow - warm.
Nutrient deposition from land.
Wind/wave action stirs nutrients.
Fishing pressure is concentrated.
One of the major problems associated with the management of marine fisheries is achieving agreement on harvest limits.

59. Sustainable Management of Fish Populations
Humans have easy access to freshwater ecosystems.
Typically easier to regulate because of containment within a smaller political region.
Many N.A. freshwater fisheries are primarily managed for sport fishery.
Fisheries managers must balance:
Sport fisheries
Commercial harvesters

60. Review
Biodiversity Loss and Extinction
Describing Biodiversity
Genetic
Species
Ecosystem
The Value of Biodiversity
Threats to Biodiversity
Habitat Loss
What is Being Done to Preserve Biodiversity