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Lesson 1.5
Pg.27- 36
Factors that Affect Wetlands and Watersheds
• Wetlands and Watersheds are controlled by interactions among chemical, physical, and biological factors
• These interactions are controlled in two ways– Human interactions – Natural events and processes
Human Activities
• More than half of the original 220 million acres of United States wetlands have been lost
• These wetlands were destroyed in a variety of ways due to human activities– Mining - Waste disposal – Agriculture - Mosquito control– Urbanization - Industrial processes – Construction - Draining
Effects of Agriculture
• Agricultural practice can disrupt or even destroy a wetland in different ways
• Examples:– Wetlands are degraded when crops are harvested – Drainage and Irrigation Ditches • Inefficient irrigation leads to build up pesticides,
pathogens, and nutrients • Accumulation of these substances leads to degradation
in water quality in the soil and groundwater
Effects of Agricultural Animals
• Animal wastes can contaminate wetlands• Overgrazing can also damage wetlands– Exposes soil to erosion by wind and water – Increases the amount of sediment that reaches
and often pollutes a wetland
Effects of Agricultural Pesticides and Fertilizers
• Pesticides and Fertilizers are the most harmful effects of agricultural on wetlands
• Contaminate wetlands by direct application in runoff, or by settling out of the air
• When these substances reach high enough levels they can:– Kill wildlife – Poison food sources– Destroy the wetlands
Urbanization• Urbanization is a major cause of Wetland
Impairment – EPA• Urbanization of the modern landscape of
concrete and other materials increase the amount of runoff– Runoff carries harmful substances that:• Increases: turbidity and salinity • Decreases: the amount of dissolved oxygen
Construction• Construction of roads and bridges over
wetlands increases the amount of sediment deposited in these ecosystems
• Paints, cleaners, salts, herbicides, dust-control substances, and other chemicals used along roads contribute to wetland damage
• Roads restrict the movement of species – Leads to death of some species
Urbanization and Construction
• Canals, Ditches, and levees divert water away from its natural flow – Increase the rate at which water flows into and
out of the wetland – Increased flow reduces the buffering ability of
wetlands – Increases turbidity – Decreases aquatic plant life
Mining
• Mining operations can result in the loss of wetlands
• Phosphate Mining– Eliminated thousands of acres of wetlands in Florida
• Peat Mining – Peat = a form of organic matter that is used as fuel– Vegetation is cleared from wetlands – Wetlands are drained and roads are built so they can
access the peat
Mining Rocks and Minerals
• Mining of rocks and minerals (Occurs in PA)• Abandoned and active coal results in acid
drainage – Increases the pH of nearby wetlands– Introduces heavy metals
Industry• Construction of office buildings, factories, and
processing plants can reduce the acreage of wetlands
• Work done in the industrial buildings damages the environment – Water intake causes habitat fragmentation– Release of water causes thermal pollution, which
leads to algal blooms
Waste Disposal
• Waste is a by-product of urbanization• Most urban waste is placed in landfills– Landfills in the US are usually within 1 mile of
wetlands– Landfill leaks are extremely toxic to wetland
organisms
Waste Disposal
• Sludge and wastewater treatment plant effluent are other major forms of waste
• Both are rich in nitrogen and phosphorus – Causes algal blooms
Effects of Algal Blooms
• Excess algae prevents sunlight – Reduces or entirely prevents photosynthesis – Results in plant death – Remove dissolved oxygen from the water , which
kills many organism at the bottom of a wetland ecosystem
Complete the Following…
• Answer Review questions 1 and 2 on page 36 – Hold on to them until you complete the rest of the
review questions
Watershed Quality
• Human activities also affect watersheds • Agencies are responsible for monitoring
watersheds– United States uses the Index of Watershed
Indicators (IWI), to gather and assess data about aquatic resources • Also used to determine whether human activities on
the land within a watershed place them at risk
Condition Indicators
• IWI includes more than a dozen indicators• One group of indicators reflect actual conditions
in a watershed (Condition Indicators)– 1. Presence of Contaminated Sediments • Contaminated sediments can harm or even kill organisms • Can also pose a risk to human who eat contaminated fish• When indicators are high, fish consumption advisories are
issued
Vulnerability Indicators
• IWI includes indicators that measure the vulnerability of a watershed
• Vulnerability Indicators show whether human activities produce negative effects on the watershed– One vulnerability indicator measures the risk of
extinction faced by various organisms • If the indicator is high, measures are taken to protect
the species at risk
Vulnerability Indicator Examples
• One vulnerability indicator measures the risk of extinction faced by various organisms– If the indicator is high, measures are taken to
protect the species at risk
Vulnerability Indicator Examples
• Another vulnerability indicator is human population growth– Rapid increases in population growth can place
stress on watersheds– Need of freshwater and runoff produced by
humans are important vulnerability indicators – When both indicators are high • Watersheds are at risk of becoming depleted or
polluted
Vulnerability Indicator Examples
• Dams are another vulnerability Indicator• Dams decrease water circulation– Leads to increased temperatures – Leads to decreased dissolved oxygen levels– Leads to changes in salinity and pH• If not corrected leads to deaths of many watershed
organisms
Complete the Following
• On the same sheet of paper with the previous review questions – Contrast the two types of IWI indicators • Give two examples of each and explain how they affect
watersheds