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Global%20Ecology

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Title: Global%20Ecology


1
Global Ecology
2
Chapter 25 Global Ecology
  • CONCEPT 25.1 Elements move among geologic,
    atmospheric, oceanic, and biological pools at a
    global scale.
  • CONCEPT 25.2 Earth is warming due to
    anthropogenic emissions of greenhouse gases.

3
Chapter 25 Global Ecology
  • CONCEPT 25.3 Anthropogenic emissions of sulfur
    and nitrogen cause acid deposition, alter soil
    chemistry, and affect the health of ecosystems.
  • CONCEPT 25.4 Losses of ozone in the stratosphere
    and increases in ozone in the troposphere each
    pose risks to organisms.

4
Introduction
  • Movements of biologically important elements are
    linked at a global scale that transcends
    ecological boundaries.
  • Humans are increasingly changing the physical and
    chemical environment on a global scale.

5
Introduction
  • Atmospheric emissions of pollutants, dust, and
    greenhouse gases have caused widespread
    environmental problems.
  • A major focus of global ecology is the study of
    the environmental effects of human activities.

6
CONCEPT 25.1 Elements move among geologic,
atmospheric, oceanic, and biological pools at a
global scale.
7
Concept 25.1 Global Biogeochemical Cycles
  • Global cycling of carbon (C), nitrogen (N),
    phosphorus (P), and sulfur (S) are emphasized
    because of their biological importance and their
    roles in human alteration of the global
    environment.

8
Concept 25.1 Global Biogeochemical Cycles
  • Pool, or reservoir Amount of an element in a
    component of the biosphere.
  • Flux Rate of movement of an element between
    pools.
  • Examples Terrestrial plants are a pool of
    carbon photosynthesis represents a flux.

9
Concept 25.1 Global Biogeochemical Cycles
  • The Carbon Cycle
  • C is critical for energy transfer and the
    construction of biomass.
  • C is dynamic, moving between different pools over
    time scales of weeks to decades.

10
Concept 25.1 Global Biogeochemical Cycles
  • Changes in the global C cycle are influencing
    Earths climate.
  • C in the atmosphere occurs primarily as carbon
    dioxide (CO2) and methane (CH4).
  • Both are greenhouse gases that affect the global
    climate.

11
Figure 25.3 The Global Carbon Cycle
12
Concept 25.1 Global Biogeochemical Cycles
  • Anthropogenic release of C to the atmosphere from
    the terrestrial pool results from land use
    change, mostly deforestation (20) and from
    burning fossil fuels (80).
  • Before the mid-nineteenth century, deforestation
    was the main anthropogenic flux.

13
Concept 25.1 Global Biogeochemical Cycles
  • Removing the forest canopy warms the soil,
    increasing rates of decomposition and
    respiration.
  • Burning trees releases CO2, and small amounts of
    CO and CH4.
  • In the 20th century, major deforestation shifted
    from the mid-latitudes to the tropics.

14
Concept 25.1 Global Biogeochemical Cycles
  • Anthropogenic emissions of CO2 more than doubled
    from 1970 to 2011.
  • About half is taken up by the oceans and
    terrestrial biota.
  • But this proportion will decrease because
    terrestrial and ocean uptake will not keep pace
    with the rate of atmospheric increase.

15
Concept 25.1 Global Biogeochemical Cycles
  • Anthropogenic emissions of CH4 have also
    increased.
  • Atmospheric CH4 levels are much lower than CO2,
    but CH4 is a more effective greenhouse gas.

16
Concept 25.1 Global Biogeochemical Cycles
  • Anthropogenic sources of CH4 include
  • Burning fossil fuels
  • Agricultural development (primarily rice grown in
    flooded fields)
  • Burning of forests and crops
  • Livestock production

17
Concept 25.1 Global Biogeochemical Cycles
  • Higher concentrations of CO2 may stimulate
    photosynthesis.
  • But experiments have shown that increased
    photosynthetic rates may be short lived, and
    plants will acclimate to higher concentrations.
  • For forest trees, increased CO2 uptake may be
    sustained longer.

18
Concept 25.1 Global Biogeochemical Cycles
  • Ocean acidity has increased 30 over the last
    century. Further increase is predicted by models.
  • Many marine organisms form shells of carbonate.
  • Increasing acidity will dissolve existing shells
    and lower carbonate concentrations will decrease
    the ability to synthesize new shells.

19
Concept 25.1 Global Biogeochemical Cycles
  • On Australias Great Barrier Reef, calcium
    carbonate formation declined by 14 from 1990 to
    2009.
  • Anthropogenic CO2 emissions therefore have
    potential to tremendously alter the diversity and
    function of marine ecosystems.

20
Figure 25.5 Rates of Calcification of Corals on
Australias Great Barrier Reef, 19002005
21
Concept 25.1 Global Biogeochemical Cycles
  • Since the mid-19th century, CO2 concentrations
    have increased at a rate faster than at any other
    time in the past 400,000 years.
  • Even if CO2 emissions are reduced dramatically,
    CO2 levels will remain high due to a time lag in
    ocean uptake (decades to centuries).

22
Concept 25.1 Global Biogeochemical Cycles
  • The Nitrogen Cycle
  • N is a constituent of enzymes and proteins and
    often limits primary productivity.
  • N and C cycles are tightly coupled through the
    processes of photosynthesis and decomposition.

23
Concept 25.1 Global Biogeochemical Cycles
  • The largest N pool is atmospheric N2, which is
    not available to most organisms.
  • N-fixing bacteria are able to convert it to a
    useable form.
  • Fixed N compounds are called reactivethey can
    participate in chemical reactions.

24
Concept 25.1 Global Biogeochemical Cycles
  • Humans have altered the N cycle even more than
    the C cycle.
  • Rate of N2 fixation by humans now exceeds natural
    biological rates.
  • Emissions of N from industrial and agricultural
    activities cause widespread environmental
    changes, including acid precipitation.

25
Figure 25.8 Changes in Anthropogenic Fluxes in
the Global Nitrogen Cycle
26
Concept 25.1 Global Biogeochemical Cycles
  • Fertilizers are made using the HaberBosch
    process.
  • Growing N-fixing crops such as alfalfa, soybeans,
    and peas has increased biological N2 fixation.
  • Flooding of agricultural fields for rice has
    increased N2 fixation by cyanobacteria.

27
Concept 25.1 Global Biogeochemical Cycles
  • Many other forms of reactive N are emitted to the
    atmosphere, mostly from fossil fuel combustion.
  • These compounds can undergo chemical reactions in
    the atmosphere and are potentially available for
    biological uptake.
  • They are returned to ecosystems by atmospheric
    deposition.

28
Concept 25.1 Global Biogeochemical Cycles
  • The Phosphorus Cycle
  • P can limit primary productivity in aquatic
    ecosystems and some terrestrial ecosystems.
  • P availability can control the rate of
    N-fixation, which has a high metabolic demand for
    P.

29
Concept 25.1 Global Biogeochemical Cycles
  • The C, N, and P cycles are linked through
    photosynthesis and NPP, decomposition, and N2
    fixation.
  • P has no atmospheric pool, except as dust.
  • The largest pools are in soils and marine
    sediments.

30
Figure 25.9 The Global Phosphorus Cycle
31
Concept 25.1 Global Biogeochemical Cycles
  • P in aquatic systems is lost to the sediments.
    This is cycled again with tectonic uplift and
    weathering of rocks.
  • Human influences on the P cycle include
    agricultural fertilizers, sewage and industrial
    wastes, and increased terrestrial erosion.

32
Concept 25.1 Global Biogeochemical Cycles
  • P fertilizers are made from marine sedimentary
    rock.
  • Mining releases four times more P than natural
    rock weathering.
  • Flux of anthropogenic P from terrestrial to
    aquatic ecosystems can have negative impacts such
    as eutrophication.

33
Concept 25.1 Global Biogeochemical Cycles
  • The Sulfur Cycle
  • S is a constituent of some amino acids, DNA, and
    RNA, but is probably never limiting to growth.
  • Major pools of S are in rocks, sediments, and
    oceans as dissolved sulfate (SO42).

34
Figure 25.10 The Global Sulfur Cycle
35
Concept 25.1 Global Biogeochemical Cycles
  • In the atmosphere, S compounds are transformed to
    SO42 and H2SO4 (sulfuric acid), which are
    removed quickly by precipitation.
  • Anthropogenic emissions have quadrupled since the
    Industrial Revolution. Most comes from burning
    sulfur-containing coal and oil and from smelting.

36
CONCEPT 25.2 Earth is warming due to
anthropogenic emissions of greenhouse gases.
37
Concept 25.2Global Climate Change
  • Climate change, especially change in frequency of
    extreme events (droughts, storms, etc.) will have
    profound effects on ecosystems.
  • Extreme events are often critical in determining
    species geographic ranges.

38
Concept 25.2Global Climate Change
  • Weather Current state of the atmosphere at any
    given time.
  • Climate Long term description of weather,
    including average conditions and the full range
    of variation.
  • Climate variation occurs at multiple time
    scalesfrom daily and seasonal to decadal.

39
Concept 25.2Global Climate Change
  • Climate change refers to directional change in
    climate over a period of at least three decades.
  • Earth is currently experiencing significant
    climate change (IPCC 2013).
  • Average global surface temperature increased
    0.8C between 1880 and 2012.

40
Figure 25.11 Changes in Global Temperature and
Precipitation (Part 1)
41
Concept 25.2Global Climate Change
  • Associated with this warming, there has been
  • Widespread retreat of mountain glaciers
  • Thinning of the polar ice caps
  • Melting permafrost
  • A 19-cm rise in sea level since 1900

42
Concept 25.2Global Climate Change
  • The warming trend has not been consistent around
    the globe.
  • Some regions have seen greater warming,
    especially mid- to high latitudes in the Northern
    Hemisphere.

43
Figure 25.11 Changes in Global Temperature and
Precipitation (Part 2)
44
Concept 25.2Global Climate Change
  • Precipitation in the high latitudes of the
    Northern Hemisphere has increased, but weather
    has been drier in the subtropics and tropics.
  • There is also a trend of increasing frequency of
    extreme weather events such as hurricanes and
    heat waves.

45
Concept 25.2Global Climate Change
  • Greenhouse effect Warming of Earth by
    atmospheric absorption and reradiation of
    infrared radiation emitted by Earths surface.
  • It is due to greenhouse gases in the atmosphere,
    primarily water vapor, CO2, CH4, and N2O.

46
Figure 25.12 Atmospheric Concentrations of
Greenhouse Gases
47
Concept 25.2Global Climate Change
  • The Intergovernmental Panel on Climate Change
    (IPCC) was established in 1988.
  • It includes experts in atmospheric and climate
    science from around the world.
  • They use modeling and analysis of data from the
    scientific literature to evaluate underlying
    causes of observed climate change and scenarios
    for the future.

48
Concept 25.2Global Climate Change
  • The IPCC releases assessment reports to promote
    understanding of climate change among scientists,
    policymakers, and the general public.
  • In recognition of their efforts to spread
    knowledge about man-made climate change, the
    IPCC was awarded the Nobel Peace Prize in 2007.

49
Concept 25.2Global Climate Change
  • In the third report (2001), the IPCC concluded
    that the majority of the observed global warming
    is attributable to human activities.
  • While this conclusion is debated in the political
    arena, it is backed by the majority of the
    worlds leading atmospheric scientists.

50
Figure 25.13 Contributors to Global Temperature
Change
51
Concept 25.2Global Climate Change
  • The certainty of anthropogenic cause of climate
    change has increased with each new IPCC report.
  • The 2013 report states It is extremely likely
    (95100 probability) that human influence has
    been the dominant cause of the observed warming
    since the mid-20th century.

52
Concept 25.2Global Climate Change
  • Paul Crutzen and Eugene Stoermer have suggested
    that we have entered a new geological period,
    called the Anthropocene epoch, to indicate the
    extensive impact of humans on our environment.

53
Concept 25.2Global Climate Change
  • IPCC models predict an additional temperature
    increase of 1.1 to 4.8C in the 21st century.
  • The range is associated with uncertainty of
    future greenhouse gas emissions and the behavior
    of Earths climate system.

54
Concept 25.2Global Climate Change
  • What does a 1.1 to 4.8C change in temperature
    mean for biological communities?
  • It can be compared with elevational climate
    change on a mountain.
  • The median value (2.9C) would correspond to a
    500 m shift in elevation.

55
Concept 25.2Global Climate Change
  • Because climate change will be rapid, most plants
    and animals will not be able to respond with
    evolutionary change.
  • Dispersal may be the only way to avoid
    extinction.
  • Dispersal barriers and habitat fragmentation will
    be important constraints.

56
Concept 25.2Global Climate Change
  • Plant dispersal rates are generally much slower
    than the predicted rate of climate change.
  • Ruderal (weedy) herbaceous plants and plants with
    animal-dispersed seeds can disperse and establish
    quickly.
  • Shrubs and trees have much slower dispersal
    rates there may be time lags in their response.

57
Concept 25.2Global Climate Change
  • For animals, their habitat and food requirements
    are associated with specific vegetation types.
  • Barriers to dispersal can prevent migration of
    many kinds of organismsdams, habitat
    fragmentation, etc.

58
Concept 25.2Global Climate Change
  • Organisms have already begun to respond to
    climate change (e.g., earlier migration of birds,
    local extinction of amphibian and reptile
    populations, earlier leaf-out of vegetation).
  • Geographic ranges of many species have shifted.

59
Concept 25.2Global Climate Change
  • Ranges of plant species in the European Alps were
    compared with historical records (Grabherr et al.
    1994).
  • A consistent trend of upward movement of species
    from lower elevations onto the summits was
    reported.

60
Figure 25.15 Plants Are Moving Up the Alps
61
Concept 25.2Global Climate Change
  • Extinction of lizard populations in Mexico has
    been linked to warmer spring temperatures, which
    limits foraging time during the breeding season
    (Sinervo et al. 2010).
  • Using models of lizard physiology and projections
    for climate warming, they predict 39 of lizard
    populations will go extinct by 2050.

62
Concept 25.2Global Climate Change
  • Migratory animals may be affected
  • Fish and whales may have to make longer journeys
    to find prey.
  • Birds arrive earlier in spring, but plants and
    invertebrates they depend on for food may not be
    available at the same time.

63
Concept 25.2Global Climate Change
  • Changes in community composition and local
    extinctions may be indicators of climate change.
  • Example Warmer water has affected coral reef
    community structure.

64
CONCEPT 25.3 Anthropogenic emissions of sulfur
and nitrogen cause acid deposition, alter soil
chemistry, and affect the health of ecosystems.
65
Concept 25.3Acid and Nitrogen Deposition
  • Since the Industrial Revolution, air pollution
    has been associated with urban industrial
    centers, power plants, and oil and gas
    refineries.
  • Increasing emissions from cars, taller
    smokestacks, and widespread industrial
    development have increased the spatial extent of
    air pollution.

66
Concept 25.3Acid and Nitrogen Deposition
  • Emissions of N and S have resulted in two related
    issues
  • Acid precipitation
  • N deposition
  • Sites affected by these problems now include
    national parks and wilderness areas.

67
Figure 25.17 Air Quality Monitoring in Grand
Canyon National Park
68
Concept 25.3Acid and Nitrogen Deposition
  • Awareness of the widespread effects of acid
    precipitation, even in pristine areas, increased
    during the 1960s.
  • Damage to forests and aquatic ecosystems became
    well-known.

69
Concept 25.3Acid and Nitrogen Deposition
  • Large-scale mortality of trees in European
    forests during the 1970s and 1980s was associated
    with acid precipitation, Ca and Mg deficiencies,
    and other stresses.

70
Figure 25.18 Air Pollution Has Damaged European
Forests
71
Figure 25.19 Decreases in Acid Precipitation
72
Concept 25.3Acid and Nitrogen Deposition
  • Increased N supplies might be expected to
    increase plant growth and production.
  • Primary production has increased in some
    ecosystems.
  • It may be partly responsible for a greater uptake
    of atmospheric CO2 by terrestrial ecosystems.

73
Concept 25.3Acid and Nitrogen Deposition
  • But N deposition is also associated with
    environmental degradation, loss of diversity, and
    acidification.
  • Nitrogen saturationN deposition may exceed the
    capacity of plants and microbes to take it up.

74
Figure 25.21 Effects of Nitrogen Saturation
75
Concept 25.3Acid and Nitrogen Deposition
  • N export to nearshore marine ecosystems
    contributes to eutrophication and oxygen
    depletion.
  • Anoxic conditions over large areas are called
    dead zones.

76
Concept 25.3Acid and Nitrogen Deposition
  • In nutrient-poor environments, many plants have
    adaptations that lower their nutrient
    requirements, which lowers their capacity to take
    up excess N.
  • Faster-growing species may then outcompete them,
    resulting in loss of biodiversity and change in
    community composition.

77
Concept 25.3Acid and Nitrogen Deposition
  • In Holland, species-rich heath communities,
    adapted to low-nutrient conditions, have been
    replaced by species-poor grassland communities as
    a result of very high rates of N deposition.

78
Concept 25.3Acid and Nitrogen Deposition
  • A survey of grasslands in Great Britain looked at
    a range of N deposition rates (Stevens et al.
    2004).
  • Of 20 factors that may have influenced species
    richness, N deposition rate explained the most
    variation.
  • Higher N inputs were associated with lower
    species richness.

79
Figure 25.22 Nitrogen Deposition Lowers Species
Diversity
80
Concept 25.3Acid and Nitrogen Deposition
  • Many experimental studies have also shown that
    adding N to experimental plots decreases species
    richness, often resulting in loss of rare
    species.
  • High N deposition rates also facilitate the
    spread of some invasive plant species.

81
CONCEPT 25.4 Losses of ozone in the stratosphere
and increases in ozone in the troposphere each
pose risks to organisms.
82
Concept 25.4 Atmospheric Ozone
  • Statospheric ozone (O3) protects Earths surface
    from high-energy ultraviolet-B (UVB) radiation.
  • UVB radiation causes damage to DNA and
    photosynthetic pigments, impairment of immune
    responses, and cancerous skin tumors in animals.

83
Concept 25.4 Atmospheric Ozone
  • Stratospheric ozone concentrations decrease in
    spring in polar regions.
  • In 1980, British scientists measured an unusually
    large decrease in springtime ozone over
    Antarctica.
  • This phenomenon is known as the ozone hole, and
    it has increased in intensity and spatial extent.

84
Figure 25.23 The Antarctic Ozone Hole (Part 1)
85
Figure 25.23 The Antarctic Ozone Hole (Part 2)
86
Concept 25.4 Atmospheric Ozone
  • An ozone hole is not really a hole, but an area
    with low ozone concentrations.
  • In the Arctic, the decreases have not been as
    great (the Arctic ozone dent).

87
Concept 25.4 Atmospheric Ozone
  • Molina and Rowland (1974) predicted the decrease
    in stratospheric ozone due to manmade compounds
    called chlorofluorocarbons (CFCs).
  • CFCs were developed in the 1930s as refrigerants
    and propellants in spray cans of paint,
    deodorants, hair spray, etc.

88
Concept 25.4 Atmospheric Ozone
  • In the stratosphere, CFCs react with other
    compounds to produce reactive chlorine atoms that
    destroy ozone.
  • A single free chlorine atom can destroy 105 ozone
    molecules.
  • Amount of UVB radiation at Earths surface
    increased as stratospheric ozone concentration
    decreased.

89
Concept 25.4 Atmospheric Ozone
  • Increased UVB radiation is correlated with higher
    incidence of skin cancer in humans.
  • UVB radiation influenced evolution of skin
    pigmentation in humans. The pigment melanin was
    selected for in populations at low latitudes
    where ozone levels are naturally lowest.

90
Concept 25.4 Atmospheric Ozone
  • Several international conferences on ozone
    destruction took place in the 1980s.
  • The Montreal Protocol is an international
    agreement calling for reduction and eventual ban
    on CFCs and other ozone-degrading chemicals.
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