Biodiversity Issues

1
Biodiversity Issues

• Chapter 12

2
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.

3
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.

4
Table 12.1
5
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.

6
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 earths surface has been affected in
  some way by human activity.

7
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.

8
Genetic Diversity

• Influences on a Populations 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.

9
Influences on a Populations 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.

10
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.

11
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.

12
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.

13
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.

14
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.

15
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

16
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.

17
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.

18
Threats to Biodiversity

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

19
Causes of Extinction
20
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.

21
Conversion to Agriculture

• About 40 of worlds 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.

22
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

23
Changes in Forest Area
24
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.

25
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.

26
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.

27
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.

28
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.

29
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.

30
Use of Rangelands
31
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

32
Desertification
33
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.

34
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.

35
Changes in World Marine Fish Harvests
36
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.

37
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.

38
Overfishing of Marine Fisheries

• U.N. estimates 70 of worlds 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.

39
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

40
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.

41
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

42
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.

43
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

44
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.

45
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 Kirtlands Warblers.

46
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

47
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
  worlds species.
• More concerned with immediate needs of food and
  shelter than long-range issues such as species
  extinction.

48
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.

49
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.

50
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.

51
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.

52
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.

53
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.

54
Managing a Wildlife Population
55
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

56
Migration Routes for North American Waterfowl
57
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.

58
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

59
Fig. 12.2
60
Fig. 12.3
61
Fig. 12.5
62
Fig. 12.7
63
Fig. 12.8
64
Fig. 12.9
65
Fig. 12.10
66
Fig. 12.11
67
Fig. 12.12
68
Fig. 12.14
69
Fig. 12.15a
70
Fig. 12.15b
71
Fig. 12.16
72
Fig. 12.17
73
Fig. 12.18
74
Fig. p.251
75
Fig. p.277
76
Table 12.2
77
Table 12.3
78
Table 12.4
79
Table 12.5