ESC 305.01 Global Climate Change Chapter 6.1 Impacts on Terrestrial Ecosystems

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ESC 305.01Global Climate Change Chapter 6.1
Impacts on Terrestrial Ecosystems
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• An ecosystem is a collection of compounds and
  processes within a section of the biosphere.
• The ecosystem has living (biotic) and non-living
  (abiotic) components.
• When studying an ecosystem, the interactions
  between living and nonliving sections are
  investigated.
• Biotic part of an ecosystem includes all living
  organisms, from the smallest (viruses and
  bacteria) to the top predator.

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• Abiotic part of an ecosystem includes soil, rock,
  water, air, as well as the physical
  characteristics like temperature, humidity,
  slope, etc.

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• Climate, primarily temperature and precipitation,
  determine the geographic distribution of major
  terrestrial ecosystems (biomes) from deserts to
  rain forests.
• Local and regional differences in soil types,
  watershed conditions and sun exposure influence
  the success of different plants.
• However, seasonal patterns of rainfall and
  temperature dictate the type of plant
  associations that dominate an area.

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• Assocations we call
• Tundra
• Desert
• Grassland
• Rainforest
• Each plant association has an optimum climate
  space, that is, a specific combination of
  temperature and precipitation conditions in which
  it best thrives.

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• Terrestrial ecosystems are sub-sections of
  tundra, taiga, temperate forest, tropical
  rainforest, savanna, and desert biomes.
• The geographic distributions of major terrestrial
  ecosystems are largely governed by patterns of
  temperature precipitation.
• Biomes are distinctive ecological systems
  characterized primarily by the nature of their
  vegetation.

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• Terrestrial ecosystems are an integral part of
  the global carbon cycle.
• Grasslands and forests sequester atmospheric
  carbon (CO2) through photosynthesis and store it
  temporarily as organic carbon.
• Below ground, organic carbon is decomposed by
  micro-organisms and released back into the
  atmosphere.
• Both of these processes are influenced by
  temperature and could be altered by global
  warming.

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• Forests and other terrestrial biomes provide
  habitats for a diversity of plants and animals.
• If the forest is damaged or removed, habitat loss
  can endanger the survival of the associated
  living organisms.
• Climate change can directly affect many plants
  and animals by altering the growing season or
  temperature patterns that trigger life cycle
  changes.

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Impacts seen todayRetreat of glaciers

• Over the past 150 years, the majority of mountain
  glaciers monitored have been shrinking.
• Many glaciers at lower latitudes are now
  disappearing, and scientists predict that, under
  some plausible warming scenarios, the majority of
  glaciers will be gone by the year 2100.

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Impacts as seen todayRetreat of glaciers

• As glaciers continue to shrink, summer water
  flows will drop sharply, disrupting an important
  source of water for irrigation and power in many
  areas that rely on mountain watersheds.

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Impacts as seen todayRetreat of glaciers
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Impacts as seen todayRetreat of glaciers
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Impacts as seen todayRetreat of glaciers
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Impacts as seen todayRetreat of glaciers
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Impacts as seen todayRetreat of glaciers
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Impacts as seen todayRetreat of glaciers

• Many glaciers in the European Alps and North
  America have lost 30 to 40 of their glacial
  area and about half of their total volume between
  the 1850s and 1980s (Haeberli and Beniston,
  1998).
• The Himalayan Glaciers on the Tibetian Plateau
  have been among the most affected by global
  warming.

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Impacts as seen todayRetreat of glaciers

• The Himalayas provide more than half of the
  drinking water for 40 of the worlds population
  through seven Asian river systems that all
  originate on the same plateau.

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Pressures to Ecosystems

• Land use changes
• Pollutant and nutrient discharges
• Overharvesting
• Introduction of exotic species
• Natural climate variability

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• Climate change is an additional pressure with the
  following results
• Lengthening of vegetative growing season (by 1.2
  to 3.6 days per decade) in the high northern
  latitudes,
• Warming of lakes and rivers as a result of
  shortening duration of ice cover,
• Shift in vegetation range in mountain regions,
• Increased mortality and range contraction of
  wildlife as a result of the heat stress.

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• Satellite data reveal that between 1970 and 1990,
  the overall Northern Hemisphere winter snow cover
  decreased by about 10 (Folland et al., 1990).
• Land use conversion and intensive use of land has
  resulted in decreased soil fertility and
  increased land degradation, as well as
  desertification.
• Land degradation already affects more than 900
  million people in 100 countries (mostly
  developing countries).

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• SRES scenarios indicate increased droughts,
  higher intensity of rainfall, more irregular rain
  patterns and more frequent tropical summer
  drought in the mid-latitude continental
  interiors.
• Optimum temperature and precipitation patterns
  defining the current distribution of vegetation
  types can be measured.
• Global climate models can predict future
  geographic shifts in defined climate spaces.
  Thus, the possible geographic distribution of
  available future habitat for a vegetation type
  can be mapped.

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• Impact of future greenhouse effect on global
  vegetation and climate was predicted through use
  of coupled atmosphere-ocean-land model FOAM-LPJ
  (Center for Climatic Research, University of
  Wisconsin-Madison).
• According to the model, tropical rainforests will
  suffer due to high temperatures and reduced
  rainfall.
• Boreal forests will continue to shift poleward.

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• Predictions by Ecological Models (MAPSS and BIOME
  3)
• The Tundra decreases by as much as 1/3 to 2/3 of
  its present size, under all scenarios and with
  both ecological models.
• The boreal forest expands in size under all
  scenarios, ranging from 108 to 133 of its
  present size.
• Temperate forests increase in area (107 to 158
  ).

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• BIOME3 shows a competitive displacement of
  tropical savannas by neighboring forests, due to
  the superior competitive ability in the model of
  the trees over the grasses under elevated CO2.
• The total area of grasslands and shrub lands in
  these simulations remains largely unchanged or
  expands by as much as 27 , depending on the
  scenario.

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• MAPSS (Mapped Atmosphere-Plant-Soil System) is a
  global vegetation distribution model that was
  developed to simulate the potential biosphere
  impacts and biosphere-atmosphere feedbacks from
  climatic change.
• Model output from MAPSS has been used extensively
  in the Intergovernmental Panel on Climate
  Change's (IPCC) regional and global assessments
  of climate change impacts on vegetation and in
  several other projects.

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Worldwide MAPSS ( Source US Forest Service)
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• Greenhouse warming will increase the frequency of
  disturbance weather events (summer/autumn drought
  thunderstorms) that impact mid-latitude
  temperate forests (Overpeck et al., 2001).
• In temperate and boreal forests of North Anerica
  and Russia, a number of studies suggest that the
  climate change induced increases in forest fire
  seasonal severity, seasonal length, and areal
  extent (Stocks et al., 1998).

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• An increase in forest fires is already
  responsible for increasing releases of CO2 into
  the atmosphere.
• Climate change will radically increase species
  loss and reduce biodiversity, particularly in the
  higher latitudes of the Northern Hemisphere
  (Malcom and Markham, 2000).
• Global warming has the potential to significantly
  alter 35 of the worlds existing terrestrial
  habitats during this century.

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• Deforestation will probably have serious
  long-term irreversible effects on the climate of
  the Amazon Basin.
• Once removed, the Amazon forest will be unable to
  re-establish itself.
• Deforestation of tropical rainforests elsewhere
  will probably have similar effects on regional
  climates.

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• Increasing atmospheric CO2 generally increases
  photosynthetic rates in individual plants.
• However, the plants do not necessarily benefit
  from this increased productivity.
• When several species are grown together,
  increased competition and nutrient availability
  diminishes any benefit of enhanced atmospheric
  CO2.

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• IMPACTS ON TERRESTRIAL ECOSYSTEMS-
• SUMMARY
• The geographic distributions of major terrestrial
  ecosystems are largely governed by patterns of
  temperature and precipitation.
• There can be little doubt that climate change
  during this century will significantly alter the
  distribution and abundance of terrestrial
  species.
• Climate change appears to be responsible for many
  documented life cycle changes in plants and
  animals over the past 50 years or more.