Seven major threats to biodiversity that result from human activity

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• Seven major threats to biodiversity that result
  from human activity
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• -these threats stem from human population growth
• Figure 9.1, Table 9.1

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9.1 Human activities create multiple threats to
biological diversity
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• -100 million/year is the estimated growth of the
  human population
• -more people less biodiversity
• -population growth is not the only cause,
  overconsumption of resources is also responsible.
  Mostly done by a wealthy minority in developing
  countries and those in developed countries
• Ex. USA has 5 worlds population but consumes
  25 resources
• USA produces a large ecological footprint
  number of hectares (1 ha2.5 acres) of land
  required to support the lifestyle of a single
  person
• -not sustainable in the long run. If this
  pattern is adopted by the expanding middle class
  in the developing world it will cause massive
  environmental destruction Figures 9.2 9.3 9.4

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9.2 An ecological footprint for a nation is the
number of global hectares needed to support an
average citizen
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9.3 Threats to the worlds species
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9.4 Many of the worlds major biomes have had a
large proportion of their area converted to human
use. Temperate forests are expected to gain
because of abandoned farms in these areas.
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Habitat destruction

• 1) Tropical rain forest
• -large losses of forest habitat Ex. Table 9.2
• -tropical rain forests cover 7 of earth's
  surface and contain 50 of its species
• -Loss of about 1 of original area of Tropical
  rain forest per year
• -60 of rain forest destruction results from
  shifting cultivation (slash and burn agriculture)
  Figures 9.5 9.6
• -20 is lost to commercial logging
• -10 is lost due to clearing to establish cattle
  ranches
• -remaining percent is lost due to 1) cash crop
  plantations such as oil palm, cocoa, and rubber
  2) road building 3) mining

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9.5 Displacement of rain forest for agricultural
purposesShifting cultivation aka slash and burn
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9.6 Due to intensive agriculture, rain forest
has been declining rapidly in South America
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Habitat destruction

• 2) Tropical deciduous forest
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• -large losses also Ex. lt 2 of original extent of
  dry forest left on Pacific Coast of Central
  America and only 3 in Madagascar, where lemurs
  are endangered Fig. 9.7
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• -better ranching country and there is a 5X
  greater human population density in Central
  America than in the adjacent rainforest

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9.7 One species of lemur, a lineage of primates
found only on the large island of Madagascar
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Habitat destruction

• 3) Grasslands
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• -most are gone as they are easy to convert to
  farmland and rangelands are often overgrazed
• Ex. 97 tall grass prairie of North America
  converted to farmland

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Temperate grasslands are valuable for protecting
biodiversityNational Bison Range, Montana
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Grasslands are an important biome for ranching
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If ranchers overgraze, the grassland ecosystem is
destroyed.
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Habitat destruction

• 4) Wetlands and aquatic habitats
• -during the last 200 years, 1/2 of wetlands in
  the USA have been destroyed
• -tropical wetlands often dominated by mangroves
  have been decimated in some areas Ex. 15
  mangrove communities in SE Asia have been
  destroyed to make room for aquaculture of rice
  and shrimp

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Habitat destruction

• 5) coral reefs
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• -20 of all coral reefs have been destroyed
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• -90 in the Philippines
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• -losses of coral reefs are mainly due to
• 1) pollution that often causes algal blooms that
  when they die off and decay, remove oxygen from
  water killing reef life
• 2) sedimentation following deforestation
• Overharvesting
• Fig. 9.9

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9.9 Extensive areas of coral will be damaged or
destroyed without conservation measures
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Habitat destruction

• A variety of habitats around the world have been
  degraded into man-made deserts desertification
• -not functional desert ecosystems but wastelands
• -loss of soil gives the area the appearance of
  deserts
• -initially these areas supported agriculture but
  during dry and windy years, soil erosion and loss
  of the water holding capacity of the soil occurs
• -overgrazing and cutting forests for fuel often
  start the process of desertification
• Fig. 9.10

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9.10 Arid areas of the world are experiencing
encroaching desertification (Part 1)
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Habitat fragmentation

• Habitat fragmentation
• -process where large areas of continuous habitat
  is reduced in area creating fragments of habitat
  Figures 9.11 9.12
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• Differ from the original habitat in two ways
• 1) fragments have a greater amount of edge per
  area of habitat
• 2) center of each habitat is closer to an edge
  Figure 9.13

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9.11 Forested areas of Tropical Asia have
experienced fragmentation due to deforestation
Sumatra, a large island in Indonesia
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9.12 Rural development of the road network in
Colorado causes habitat fragmentation
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9.13 Habitat area is severely reduced by
fragmentation and edge effects
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Habitat fragmentation

• Consequences of habitat fragmentation
• 1) Certain species may not have enough room to
  live and breed Figure 9.14
• 2) potential for dispersal and colonization is
  often reduced
• 3) reduces foraging ability of animals
• 4) increases rate of population decline and
  extinction by dividing an existing widespread
  population into two or more subpopulations that
  are more vulnerable to inbreeding depression and
  genetic drift (allele frequencies changing by
  chance) Figure 9.16
• 5) Edge effects-changes in microclimate,
  incidence of fire, interspecific interactions,
  and potential disease along fragment edges

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9.14 The probability of sighting a wood thrush in
a mature forest in Maryland
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9.16 (A) Former wild reindeer herds in southern
Norway (B) The range has now been divided
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Habitat fragmentation

• Edge effects
• a. microclimate changes
• 1. temperature varies more (hotter in day and
  cooler at night)
• 2. light and wind are greater
• 3. humidity is less
• b. increased incidence of fire because of
  microclimate changes
• c. interspecific interactions
• increases chances for invasion by exotic and
  native pest species
• 1. wind dispersed seeds and fruits Ex.
  Asteraceae
• 2. omnivorous animals that respond well to
  disturbance Ex. raccoons, skunks, bluejays
• 3. predators that like disturbance and
  decimate amphibian and insect populations Ex.
  coyotes
• 4. herbivores that like disturbance Ex. deer
• d. greater potential for disease due to
  increased contact with domestic organisms
• Figure 9.15

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9.165 Edge effects in the Amazon Rain Forest
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Habitat degradation and pollution

• Several major categories
• 1) Pesticide pollution
• Rachel Carson Silent Spring 1962
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• -described biomagnification-chemicals move
  through the food chain becoming more concentrated
  at each level Figure 9.19
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• -raptors such as the American bald eagle, osprey,
  and peregrine falcon were particularly
  susceptible
• -inactivate enzymes and other proteins
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• -banned the use of organochlorine compounds (Ex
  DDT diphenyltrichloroethane) in this country
• -more details are available in Box 9.1

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9.19 Toxic chemicals in water become
successively concentrated at higher levels in the
food chain
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Box 9.1 A captive peregrine feeding young
affected by DDT
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Box 9.1 Peregrine populations have gradually
recovered after DDT banned along with population
augmentation and nest protection
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Habitat degradation and pollution

• 2) Water pollution
• Several major problems
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• a. cultural eutrophication
• -human sewage, fertilizers, detergent, and
  industrial processes that release large amounts
  of nitrates and phosphates cause algal and
  cyanobacteria blooms. This shadows bottom
  dwelling plants and algae and if their is a rapid
  die-off, oxygen is removed from the water during
  the process of decomposition. Figure 9.20

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9.210 Fish in Rio de Janeiro died off as a result
of eutrophication
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Habitat degradation and pollution

• b. influx of eroding sediments
• -kills plant and algae populations and clogs
  filter feeding adaptations in invertebrates Ex.
  coral
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• c. oil products
• -blocks light from algae and plants and clogs
  tissues involved in gas exchange and filter
  feeding
• Figure 9.17
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• d. heavy metals and other types of chemical
  pollution
• -inactivate enzymes and other proteins
  (cytochromes)
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• e. destruction of bottom habitat and sediment
  resuspension caused by trawling
• Figure 9.18

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9.17 Marine birds after the Deepwater Horizon
oil spill.
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9.18 The aquatic environment faces multiple
threats
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Habitat degradation and pollution

• 3) Air pollution
• Several major problems
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• a. acid rain
• -nitrates and sulfates from burning fossil fuels
  combines with water in the atmosphere lowering
  the pH of rain Figure 9.21, 9.22
• -lowered pH changes enzyme activity and other
  proteins

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9.21 Mountain forests near power plants
industry have acid rain Bavarian Forest in
Germany
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9.22 The pH scale, indicating ranges at which
acidity becomes lethal to fish
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Habitat degradation and pollution

• b. ozone production and nitrogen deposition
• -hydrocarbons and nitrogen oxides react and
  produce ozone and airborne nitrogen compounds
• -high levels of ozone damage tissue (oxidize them
  and make them brittle)
• -airborne nitrogen compounds are deposited by
  rain and if this is excessive contributes to
  eutrophication
• -ozone in the upper atmosphere helps to filter
  ultraviolet radiation and deposition of air borne
  nitrogen compounds created by lightning is a part
  of the nitrogen cycle
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Habitat degradation and pollution

• c) toxic metals
• -leaded gasoline (used outside the USA) and
  industrial processes (mining and smelting)
  release lead, zinc, and other toxic metals into
  the air. These inactivate enzymes and other
  proteins in living things

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Global Climate Change

• -caused by increases in greenhouse gases--carbon
  dioxide, methane, water, and nitrous oxide
  Figure 9.24
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• -greenhouse gases keep the earth warm and allows
  for life as we know it

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9.24 The greenhouse effect (Part 1)
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Global Climate Change

• -levels of greenhouse gases have increased over
  the past 100 years Figure 9.25, Table 9.3
• -if this trend continues, greenhouse gases could
  cause global temperatures to increase (2-6
  degrees Celcius) by 2100 Figure 9.26

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9.25 Carbon emissions from fossil fuel use and
forest destruction has increased dramatically
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9.26 Computer models of global climate predict
that temperatures will increase significantly
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Global Climate Change

• If the temperature rises, the following changes
  would occur in temperate and tropical climates
• 1) Rising sea levels
• -mountain glacier and polar ice caps melting
  could cause sea levels to rise 20-60 centimeters
  over next 100 years and flood some coastal
  communities Fig. 9.27
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• Warmer waters
• -this along with pollution, and spread of disease
  is killing coral
• 2) Radical reconstruction of communities and
  changes in range for species
• -will need to evaluate protected natural areas
  and provide more along elevational gradients and
  north-south migration routes Fig. 9.29

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Figure 9.27 (A) The result 1-m sea level rise by
the end of this century. (B) Result of a 3-m rise
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9.29 Protected areas along elevational gradients
are needed