HUMAN INFLUENCES ON ECOSYSTEMS The last chapter
HOW DO WE INFLUENCE THE ECOSYSTEM
We influence ecosystems in the following aspects: 1) 2) 3) 4) 5) 6)
Agriculture Soil erosion Water pollution Air pollution Pollution by Pesticides and Herbicides Pollution by nuclear fallout
1) AGRICULTURE
How has agriculture evolved? Initially, agriculture was done on small scale because of the lack of machinery and chemicals that assisted in crop growth but now crop production has increased due to the availability of these machines and chemicals.
How is this useful? There will be more food available in a given area of land. So that means that more people will get food ď Š
Has this been the case in all regions of the world? No. In western regions this has been the case because they have more money to support such agricultural programs, while in Africa this hasn’t been the case because of a scarcity in machines and chemicals due to the lack of funds!
2) SOIL EROSION
Soil is a very precious material. It contains minerals that assist a plants growth The only problem is that we tend to think that we own the planet and that we can get to do the following: 1) Deforestation: This is the process by which trees are cut down for the purpose of - using the land to house the growing population - using the wood for building houses - using the trees to make paper - using the wood for the purpose of heating - using the land for crop production Note: Another way that plant cover can be removed is by Overgrazing
SO WHAT IF DEFORESTATION OR OVERGRAZING OCCURS?
Once the plant cover is removed, the soil becomes exposed. If it rains, the topsoil will be washed away by the rain
That means that minerals will wash away and the soil will lose its fertility. This process is called SOIL EROSION.
REDUCING SOIL EROSION
There are many ways in which we can educe soil erosion 1) Stop deforestation 2) Prevent overgrazing
3) Building terracesďƒ this is where the mountain is cut to resemble stairs so that the soil that erodes will be caught on these stairs before it travels to the bottom of the mountain and is lost in rivers. Then we can plant trees on these terraces to anchor the soil again. 4) Adding fertilizers or animal wastes.
5)Keep a cover of plants on the soil all year round . 6) Building stone walls on a mountain slope to catch the eroding soil.
3) WATER POLLUTION
Pollution: the addition of something to the environment which can damage the living organisms within it.
Water can be polluted by: fertilizers sewage Chemical waste
METHODS LEADING TO WATER POLLUTION
A) Water pollution by fertilizers: * Fertilizers are chemicals that contain nitrates. the presence of nitrogen in fertilizers means that the plants take it up and make amino acids these amino acids will in turn make proteins for the plant to grow. * The problem with fertilizers is that they are sometimes overused this results in a horrible condition called EUTROPHICATION.
FERTILIZERS AND EUTROPHICATION
Eutrophication: Is the process by It occurs as follows: - Too much fertilizer is used in a given area of land. - If this fertilizer is not quickly absorbed by the plants roots it will be washed away / leached with rain and carried into a nearby body of water, such as a lake. - Once the fertilizer enters the water t becomes an immediate source of pollution. - Algae in water will take up the fertilizer and will start to grow excessively - The algae will cover the surface of the water - As a result sun cannot enter the water - Plants in the deeper end of the lake will die because they cant photosynthesize. - The plants start to die as well as the algae (because it has outgrown itself) - Bacterial levels will now increase rapidly because they are decomposing the dead plants and algae. - The fish in the pond/lake will now die because the bacteria is using up all of the oxygen in respiration.
EUTROPHICATION GRAPH
PREVENTING WATER POLLUTION BY FERTILIZERS
1) Fertilizers should only be applied when plants are growing so that the roots will absorb them readily. 2) Reduce the mount of fertilizers being used 3) Fertilizers should not be applied before it is going to rain
METHODS LEADING TO WATER POLLUTION (CONTINUED)
B) Water pollution by sewage: Sewage is waste water from houses and industries. It contains human urine and faeces. It may contain many disease causing viruses and bacteria. Many diseases including cholera, typhoid and poliomyelitis can be transmitted in untreated sewage.
In addition sewage dumped in water also leads to EUTROPHICATION.
PROCESS OF SEWAGE TREATMENT
THE PROCESS OF SEWAGE TREATMENT Sewage water arrives at a sewage treatment plant from housing or industries. A typical sewage treatment plant is divided into 4 main chambers: 1) Screen chamber: This is a chamber that contains large, perforated screens. They are responsible for filtering out large objects such as sticks, rags, nappies, rats……….. 2) Grit tank: This tank is anaerobic meaning that it kills aerobic bacteria. It allows the sewage to move up and down within it so that grit (like sand) will fall to the bottom of the tank. 3) Settlement tank: this tank is also anaerobic. It’s the second step in wastewater treatment. It allows for the physical separation of solids and greases from the wastewater. it is held here for several hours. This allows solid particles to settle to the bottom of the tank and oils and greases to float to the top. The sludge that settles at the bottom is collected and is then either used as soil fertilizer or it is placed in a closed tank where anaerobic bacteria decomposes it to form methane gas. 4)Aeration tank: The remaining wastewater enters this tank through a pipe that opens up as a sprinkler. The sprinkled wastewater falls on a bed of rocks within the tank that has bacteria and protoctists on it. These microorganisms use the oxygen in the tan to respire the remaining wastes.
Water has now been cleaned.