CH 57 - Global Ecology

CH 57 - Global Ecology

Effects of Sun, Wind, Water

• Biosphere: Includes all living communities on Earth.
• Global patterns of life on Earth are influenced by:
  • The amount of solar radiation that reaches different areas.
  • Patterns of global atmospheric circulation, which influence oceanic circulation.

Global Ecology

• Biosphere: Includes all living communities on Earth.
• Global patterns of life on Earth are driven by solar energy.
  • More sun at the equator.
  • More sun in summer.
  • More seasonal change nearer the poles.

Global Circulation Patterns

• Hot air rises relative to cooler air.
• Warm air holds more moisture.
• Wet tropical climate near the equator.
• Dry deserts near 30° latitude.

The Coriolis Effect

• The Coriolis effect: The curvature of the paths of the winds due to Earth's rotation.
  • Northern hemisphere: counterclockwise - winds curve to the right.
  • Southern hemisphere: clockwise - winds curve to the left.
  • Important in the age of sail.

Ocean Circulation

• Ocean currents like the Kuroshio current, North Pacific subtropical gyre, N. Equatorial current, Equatorial countercurrent, S. Equatorial current, South Pacific subtropical gyre, Humboldt current, Gulf Stream, Atlantic tropical gyre, Labrador current, South Atlantic subtropical gyre, and Antarctic circumpolar current influence global climate and nutrient distribution.
• Cold water currents and warm water currents play a significant role.

Elevation

• Elevation: Temperature and other conditions change with elevation.
• Going up in elevation is similar to going up in latitude (moving towards the poles).

Regional and Local Effects

• Regional and local differences affect terrestrial ecosystems.
• Rain shadows:
  • Rain falls as air rises.
  • Remains dry on the leeward side of the mountain.

Coninents

• Land heats more quickly than water.
• The interior of continents has the greatest temperature variation; coasts have the least.
• Monsoons: Seasonally shifting winds.
  • Asia is so huge that heating and cooling of its surface causes massive regional shifts in wind patterns.
  • Winds blow off the water into the interior in the summer.
  • Winds blow off the land onto the water in the winter.
  • Winds affect rainfall patterns.

Biomes

• Biomes: A major type of ecosystem on land.
• Defined largely by temperature and moisture.
• Examples: polar ice, tundra, taiga, mountain zone, chaparral, temperate grassland, savanna, semidesert, desert, warm, moist evergreen forest, tropical monsoon forest, tropical rainforest, temperate deciduous forest, temperate evergreen forest.

Biomes cont.

• Moisture: wet -> dry: Forest, grassland/savanna, desert.
• Temperature: tropical, temperate, frozen (tundra).
• Taiga: Northern coniferous forest of Canada and Siberia.

Aquatic Habitats

• Less temperature fluctuation compared to terrestrial habitats.
• Three main factors influencing aquatic habitats:
  • Sunlight at the top.
  • Nutrients - generally fall to the bottom.
  • Oxygen.

Continental Shelf Ecosystems

• Continental shelf ecosystems provide abundant resources.
  • 99% of ocean food supply comes from neritic waters.
• Coral reefs occur in subtropical and tropical latitudes.
  • Defining feature is stony corals.

Estuaries

• Estuaries: Ecosystems where fresh water from streams or rivers mixes with ocean water.
• Intertidal habitat: Area that is exposed to air at low tide but is underwater at high tide.
• Salt marshes: In the intertidal zone.
• Mangrove swamps: Occur in tropical and subtropical intertidal zones.

The Pelagic Zone

• Sunlight and nutrients are separated.
• Food originates in the photic zone; 99% eaten as it drifts down through the water column.
• Nutrition depends on up-welling of deep water to the surface.
• Localized in oceans, seasonal in lakes - water density depends on temperature.

Hydrothermal Vent Communities

• Water temperature up to 350°C.
• Depend on sulfur-oxidizing bacteria, not the sun's energy.
• Contain large-bodied animals.

Freshwater Habitats

• Main factors: oxygen availability and nutrition.
• Oxygen added by photosynthesis and aeration from the atmosphere.
• Oxygen is removed by animal and detritivore respiration and through decaying organic matter.
• Warm water holds less O2 than cooler water.
• Often: low nutrients & high O2 OR high nutrients & low O2.

Oligotrophic Lakes & Streams

• Oligotrophic: Low in nutrients.
  • Associated with mountains.
  • Rocky soil, less biomass, fast-running streams.
  • Usually high in oxygen.
  • Cooler water, more turbulence (aeration), less biomass for decay.

Eutrophic Lakes & Rivers

• Eutrophic water: High nutrients.
  • Associate with lower elevations.
  • Rich soil at the bottom, slower flows, densely populated with algae and plant material.
  • Low in dissolved oxygen.
  • Warmer water (especially in summer), less turbulence (aeration), more biomass -> more decay.

Human Impacts

• Human impacts can cause adverse changes in ecosystems.
  • Pollution:
    • Terrestrial, marine, atmospheric
  • Resource Extraction/habitat destruction
  • Invasive species

Overfishing

• Overfishing of the ocean is the single greatest problem in the ocean realm.
• Aquaculture is only a quick fix, needing feed and land to grow fish.

Human Impacts: Pollution

• Point source pollution: Comes from an identifiable location.
  • Factories, Sewage-treatment plants, mines.
  • Laws and technologies can be applied because the source is known.
• Diffuse pollution: Result of many many small decisions.
  • Runoff from thousands of lawns, farms, golf clubs, etc.
  • Plastic use.
  • Solutions depend on public education and political action.

Destruction of Coastal Ecosystems

• Estuaries subjected to severe eutrophication.
• Destruction of salt marshes.
• Major contributing factor to hurricane destruction along the coast of Louisiana (e.g., Katrina).

Deforestation

• Cutting of large tracts of virgin forests.
  • Used commercially.
• Burning of forests to open up land for farming (e.g., for soybeans).
• Rates of deforestation are rising.

Zoonotic Disease

• Contagious diseases that spread between animals and humans; ~60% of human pathogens are zoonotic.
• Historically: the plague, the flu, cholera, salmonella.
• Recently: HIV, West Nile, hantavirus, Middle Eastern respiratory syndrome, SARS, zika, Covid-19.
• Increases from habitat fragmentation and increased use of forests and contact with its inhabitants.
• Lyme in the U.S.

Atmospheric pollution

• Stratospheric ozone is important because it absorbs UV radiation (UV-B).
  • UV-B damages tissue and increases risks for skin cancer.
  • Detrimental to amphibian eggs.
• A major cause of ozone depletion is chlorine- and bromine-containing compounds (CFCs) used for refrigeration.
  • Being phased out in many countries; atmospheric CFCs are chemically stable for many years.

Stratospheric Ozone Depletion

• Ozone hole: Over Antarctica, between 1/2 to 1/3 of original ozone concentrations are present.

Greenhouse Gases

• Greenhouse gasses let the shortwave (UV) energy from the sun in but trap the longwave (infrared heat) energy.
• Human activities are increasing CO_2 and other greenhouse gas levels dramatically.

Greenhouse Gases cont.

• Trapping more of the sun's energy warms the planet.
• This is dramatically and quickly reversing the global cooling that happened over the last 1000 years.

Effects of global warming

• A few degrees of warming seems small.

High Variability

• A few degrees of warming seems small - global average temperature.
• Expect more variable weather.
  • Colder freezes in addition to heat waves.
  • Droughts and flooding.

More severe weather

• Droughts, heat waves, severe precipitation and hurricanes
• Energy in atmosphere -> severe precipitation
• Energy in oceans -> severe hurricanes

Rising global sea levels

• Greater flooding during storm surges.

Bigger problems

• Disruption of seasons and ecosystems.
  • Changing seasons disrupts reproduction.
  • Early run-off -> drier trees -> more forest fires.
  • Stressed organisms + immigration means:
    • More invasive species.
    • Greater disease, parasitic and non-parasitic.
  • Change is too fast for evolution to follow.

Ocean acidification

• CO2 absorbed forms carbonic acid H2CO_3.
• Short term: coral reefs & fishing.
• Longer term: collapse of marine food webs.

Bigger problems

• Stopping/slowing the "global ocean conveyor belt".

Why no action?

• Hard to experience the scale of the problem.
• Decision-making in the face of uncertainty.
• Uncertain risk & Uncertain effectiveness.

Responding to Climate Change

• Reduce energy use.
• Greater efficiency.
• Personal/societal change.
• Renewable energy.
• Ecosystem Services.
• Carbon capture.
• All-of-the-above strategy.
• Only need 50 ideas that make 2% difference.

Responding to Climate Change cont.

• Science
• Progress is being made!
• Politics
• Do Something!