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