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The Effects of Human Activities on Freshwater Ecosystems

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Feriza Fernando

on 5 September 2014

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Transcript of The Effects of Human Activities on Freshwater Ecosystems

Wrong use of the land
• Destructive land use practices that result in vegetation loss can have negative impacts on freshwater ecosystems.
• The forests and native plant communities surrounding lakes, rivers, and wetlands help protect water quality and quantity by filtering and storing runoff. Changes in land use brought about by agriculture and urbanization (such as deforestation, chemical fertilization, and paving) lead to increased runoff with higher levels of nutrients and other pollutants.
• These plants in these ecosystems are especially important because they help regulate temperature through the giving of shade and supplies organic material such as falling leaves, insects, and woody debris to freshwater systems.

Review
What is a Freshwater Ecosystem?
A freshwater ecosystem is an ecosystem that includes lakes, ponds, rivers and streams. They also consist of drinkable water that has nearly no salt content.
The ecosystems are home to more than 40 percent of the world's fish species.
They are essential for human survival because these ecosystems provide most of humanity’s drinking water.

The Sad Reality
Despite their value and importance, many lakes, rivers, and wetlands around the world are being severely damaged by human activities and are declining at a much faster rate than terrestrial ecosystems.
More than 20 percent of the 10,000 known freshwater fish species have become extinct or imperiled in recent decades.
Watersheds, which catch precipitation and channel it to streams and lakes, are highly vulnerable to pollution.


Why?
Invaders are often adaptable generalists who breed and disperse quickly, endangering native species through highly efficient competition, predation, or habitat alteration.
Human Activities that have an effect on freshwater ecosystems
Channelization and Dams
Channelization – the dredging and straightening
of stream channels

What is channelization used for?
1. Divert water for irrigation
2. Drain fields for agriculture
3. Increase “usable” land
4. Prevent flooding
The Effects of Human Activities on Freshwater Ecosystems
Channelization and Dams
Water Diversion/Withdrawal
Deliberate Introduction of non-native species to an ecosystem
Filling or draining of shallow habitats
Pollution
Wrong use of the land
Overexploitation
Channelization
Problem with Channelization
1. Altered flow regimes
- Many species not adapted to different flows
2. Loss of habitat
- Within the stream
 Dredging removes snags, habitat complexity
- Floodplains

Dams
Benefits of Dams
1. Water supplies
2. Navigation
3. Hydropower
4. Flood Control

Problems with Dams
1. Alteration of flow
- Prevents movement of sediment, nutrients downstream
- Slower flows upstream
 leads to settling of sediment
- More unpredictable flows downstream
- Disturbs normal flood-pulse in spring
 Interchange of nutrients between river and floodplains
2. Interrupts fish migration
3. Loss of important spawning/foraging habitat in floodplain
4. Changes in plant communities, reduced species richness below dams

Deliberate Introduction of non-native species to an ecosystem
Filling or draining of shallow habitats
The Wetlands
Transitional habitats between aquatic and terrestrial environments, where water table is at or near the surface
Includes marshes, swamps, bogs, estuaries, temporary ponds, etc.
Wetland loss
• Wetland Loss
- Wetlands provide important ecosystem services
1. Reduce flooding
2. Retention of sediments, nutrients, pollutants
 Natural sewage treatment plants
3. Wildlife habitat
 20% of threatened and endangered species
associated with wetlands
 Important habitat for waterfowl (type of bird)

Pollution
Why?
Pollution in freshwater ecosystems can devastate local ecosystem and endanger human food sources.
Heavy metals, such as arsenic, zinc, selenium, and mercury are also released from mining and other industrial activities. =>These can become unstable in warmer parts of the globe, enter the atmosphere, and re-condense in cooler areas, often contaminating pristine sites and indigenous food supplies
Acid rain containing high levels of sulfuric and nitric acids are also a serious threat to many freshwater ecosystems, particularly lakes at high altitudes and latitudes.
Over exploitation
Over exploitation is the over use of wildlife and plant species by people for food, clothing, pets, medicine, sport and many other purposes.
Over harvesting of aquatic species has occurred repeatedly in freshwater ecosystems throughout the world.
Excessive hunting of terrestrial animals also affects the freshwater ecosystems.
Water Diversion/Withdrawal
Why?
1. In order to meet the water needs of a growing population, large quantities of water are diverted or withdrawn directly from rivers and lakes.
2. Withdrawal of water for human needs can reduce the total amount of water available to aquatic ecosystem.
3. Leads to large losses of habitat used for spawning/breeding because there is no enough water for them to live in.
4. Withdrawal of groundwater for agriculture in adjacent areas can completely dry up valuable wetlands


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