Download Human impacts and climate change

Human impacts and climate change
Overfishing
Deforestation
Pollution
 Any physical, biological, or chemical change in environmental quality that
adversely affects living organisms can be considered pollution
Point sources
 Discharge pollution from specific locations
– Factories, power plants
– Easy to control through regulations
Non-point (diffuse) sources
 Non-point sources - Scattered or diffuse, having no specific location of
discharge
– Agricultural fields
– Very difficult to monitor and regulate
– Largest pollution problem currently
Water pollution
Infectious agents
 Main source of waterborne pathogens is improperly treated human waste
 Animal wastes from feedlots and fields is also important source of pathogens
Infectious agents
Oxygen-demanding wastes
 Certain organic materials added to water stimulates oxygen consumption by
decomposers
– Sewage
– Paper pulp
– Food-processing wastes
Oxygen sag
Gulf of Mexico hypoxia
 In 1974, scientists found areas where oxygen had disappeared from bottom
sediments and the water column
 Hypoxic area in 1993 after Mississippi floods doubled in size
 Stays from May to September
 Influx of nitrogen from Midwest/Great Plains is cause
 Hypoxic area continues to grow
Harmful algal blooms (HABs)
 HABs have become increasingly common in slow-moving and shallow waters,
usually due to nutrient enrichment
 Algal blooms produce toxins
 Red tides are blooms of deadly aquatic algae
 Cryptosporidium in 1993 entered the Milwaukee public water supply, making
400,000 people sick and killing at least 100 people
Sediment
 Human activities have accelerated erosion rates in many areas
 Fills lakes, obstructs shipping channels, makes drinking water purification
more costly
Organic chemicals
 Thousands of natural and synthetic organic chemicals are used to make
pesticides, plastics, pharmaceuticals, pigments, etc.
 Many are highly toxic and bioaccumulate
Biomagnification
 Cells have special mechanisms for bioaccumulation - selective absorption and
storage
– Dilute toxins in the environment can build to higher levels inside cells and
tissues
 Biomagnification - toxic contents of a large number of organisms at a lower
trophic level is accumulated and concentrated by a predator at a higher trophic
level
Thermal pollution
 Raising or lowering water temperatures from normal levels can adversely
affect water quality and aquatic life
– Oxygen solubility in water decreases as temperatures increase
 Species requiring high oxygen levels are adversely affected by warming
water
Air pollution
Sulfur compounds
 Two thirds of total sulfur in the atmosphere is from human activity
– Predominant form of anthropogenic sulfur is sulfur-dioxide from fossil-fuel
combustion
 Can react with water to form acid rain or acid deposition
Acid deposition
 pH and atmospheric acidity
– pH scale ranges from 0-14
 7 = Neutral; <7 = Acidic; >7 = Basic
– Unpolluted rain generally has ph of 5.6
Acid deposition
 Aquatic effects
– Many fish unable to reproduce at low pH
 Forest damage
Carbon oxides
 Predominant form of carbon in the air is carbon dioxide
– Increasing levels due to human activities
 Carbon monoxide is a colorless, odorless, toxic gas produced by incomplete
fuel combustion
Particulate matter
 Respirable particles smaller than 2.5 micrometers are among most dangerous
 Diesel fumes dangerous
 Reduces visibility and leaves dirty deposits on surfaces
Nitrogen compounds
 Also called NOx
 60% of NO emissions are anthropogenic
 Produced by fuel combustion in transportation and electric power generation
 Excess nitrogen causing eutrophication in water bodies
 Encourages growth of weedy plant species
Photochemical oxidants
 Products of secondary atmospheric reactions driven by solar energy
– Ozone formed by splitting nitrogen dioxide
Metals
 Many toxic metals occur as trace elements in fuel
 Since leaded gasoline was banned, children’s average lead levels have
dropped 90% and IQs have risen by 3 points
 Mercury
 Released from coal burning power plants and waste incinerators
 Bioaccumulation in aquatic ecosystems
Long-range transport
Grasshopper effect
 Contaminants evaporate from warmer areas and condense and precipitate in
cooler areas
Stratospheric ozone
 Discovered in 1985 that stratospheric ozone levels were dropping rapidly
during September and October
– Occurring since at least 1960
 At ground-level, ozone is a pollutant, but in the stratosphere it screens UV
radiation
Stratospheric ozone depletion
 CFCs were main culprit
– Persist for decades
– Ban established in 1987
– Models show that stratospheric ozone levels could reach normal levels by
2040
Free Cl is a catalyst
Is global climate changing?
– Global average surface temperature rose 0.6o C during 20th century
– Cold and frost days decreased for nearly all lands in the 20th century
– The 1990’s were the warmest decade of the past 1000 years
– Average summer and winter temperature in Alaska are 4°C higher than
average
Keeling curve
IPCC
 In 1988, the Intergovernmental Panel on Climate Change (IPCC) was formed
– Released third report in February 2001
 700 scientists from 100 countries reviewed results from 3,000 studies
 Recent changes in world’s climate have had discernable impacts on
physical and biological systems
 Human activities are at least partially responsible
IPCC in 2007
 IPCC now recognizes that humans are responsible for global climate change
and that there is even more evidence of effects on biological and physical
systems
What effect is climate change already having on physical systems?
What effect is climate change already having on biological systems?
What are the disagreements among scientists?
Potential global climate change
What is being done?
International Climate Negotiations
 Kyoto Protocol (1997) - United Nations Pact
– 178 nations agreed to roll back carbon dioxide, methane, and nitrous oxide
emissions about 5% below 1990 levels by 2012
Controlling greenhouse emissions
 Reducing carbon dioxide levels
– Renewable energy sources may offer the best solution to climate problems
 Capturing and storing carbon dioxide
– Carbon management
 Other countries are already doing it!