Ecosystem loss & degradation
Chapter 8
Human footprint
Habitat degradation & loss
Ecosystem degradation & loss
Contamination
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
Colorless corrosive gas that directly damages both plants and animals
Can react with water to form acid rain
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
Major component of smog
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
Nickel, beryllium, cadmium, arsenic
Air pollutants
Halogens (Fluorine, Chlorine, Bromine)
CFC’s
Air pollution has far-reaching effects
Long-range transport
Increasingly, sensitive monitoring equipment has begun to reveal industrial contaminants in places usually considered among the cleanest in the world
Contaminants evaporate from warmer areas and condense and precipitate in cooler areas
Plant pathology
Chemical pollutants can directly damage plants, or can cause indirect damage by disrupting normal growth and development patterns
Certain environmental factors have synergistic effects in which the injury caused by the combination is more than the sum of the individual exposures
Crop damage estimated at $10 billion per year in North America
Lichens as indicators
Acid deposition
Aquatic effects
Thin, acidic soils and oligotrophic lakes of southern Norway and Sweden have been severely affected by acid deposition
Air pollutants are acidifying many North American lakes
Forest damage
Air pollution and depositions of atmospheric acids are believed to be important causes of forest destruction in many areas
Pesticides as air pollution
Climate change is caused by air pollution
Water pollution
Point sources
Discharge pollution from specific locations
Non-point sources
Non-point sources - Scattered or diffuse, having no specific location of discharge
Atmospheric deposition
Ultimate in non-point source pollution
Contaminants carried by air currents and precipitated into watersheds or directly onto surface waters
•For example, agricultural (atrazine, toxaphene) and industrial (PCBs, dioxins) contaminants in the Great Lakes that cannot be accounted for by local sources alone
Eutrophication
Gulf of Mexico hypoxia
Harmful algal blooms (HABs)
Cichlids
Oxygen demanding wastes
Sedimentation
Thermal pollution
Inorganic pollutants
Metals
Many metals such as mercury, lead, cadmium, and nickel are highly toxic
•Highly persistent and tend to bioaccumulate in food chains
Road salts
Organic chemicals
Thousands of natural and synthetic organic chemicals are used to make pesticides, plastics, pharmaceuticals, pigments, etc.
Many are highly toxic and bioaccumulate
Diflonac
Pesticide runoff
Bioaccumulation of pesticides
Endocrine disrupters
Feminization of males
Sex ratio shifts
Barriers to movement
Roads cover 20% of the area of the US
Altered fire regime
Erosion
Caused by wind and water
Desertification
Salinization
Deforestation
Forests
Cover less than 6% of the earth’s total surface area
Habitat for majority of earth’s known species
Lost at faster rate than regeneration
Why are forests so diverse?
Forests found in favorable conditions
Forests contain reservoir of organic matter
Forests are very three-dimensional
Forests are dynamic ecosystems
Fragmentation
Edge effects
Size and shape matter
Penetration distances
Island biogeography
Larger areas have more species
Filling
Draining
Channelization
Dredging
An aside
Dikes