Objectives :
1. To identify the activities of man that affect the natural ecosystem
2. To cite measures on how to prevent human activities from damaging the ecosystem
Human survival depends on the health of the ecosystem. An ecosystem is comprised of communities of plants, animals and other organisms in a particular area that interact with each other and their surrounding environment. Both living and non- living things are considered part of an ecosystem. Humans threaten ecosystems by producing waste and disposing them improperly, damaging habitats by logging forests, planting crops, construction of dams, conversion of agricultural lands into housing projects, using chemical base pesticides and fertilizers, and removing too many species without giving the ecosystem time to naturally regenerate.
Human activities that affect natural ecosystem Review Questions :
1. Explain the relationship between population and food supply.
1. Introduction of Invasive Species
Invasive species are brought on by transporting species either intentionally or accidentally from other areas of the world. This can be devastating to existing species as invasive species are introduced on a time scale much more quickly than typically would happen with evolution over longer time periods. This can include outcompeting native species in the ecosystem, leading to the decline or extinction of local species, and overpopulation as these invasive species may not have any predators in this new ecosystem.
2. Overexploitation
Overexploitation is a major threat to ecosystems and therefore sustainability. It is the consumption of a natural resource at a rate greater than that natural resource can maintain itself.
Overhunting
When humans overhunt key predators such as lions, tigers and bears, they remove the very animals that keep plant consumers in balance and prevent overgrazing. A healthy ecosystem has a balance of predators and prey that naturally cycle through life and death sequences. Over-hunting often results in ecosystem species imbalance and environmental stress.
Overfishing
Humans also practice commercial overfishing , where massive fishing nets result in “bycatch,” in which unwanted fish are caught in nets and then thrown away. Bycatch results in the death of one million sharks annually. Large weights and heavy metal rollers that are used with the commercial fishing nets also drag along the bottom of the ocean, destroying anything in their path including fragile coral reefs.
Overgrazing
It occurs when plants are exposed to intensive grazing for extended periods of time , or without sufficient recovery periods. It reduces the usefulness, productivity, and biodiversity of the land and is one cause of desertification and erosion.
Illegal logging
Illegal logging contributes to deforestation, degrades forest environments, reduces biodiversity, and contributes to green gas emissions.
Continuous cropping
Continuous cropping refers to a system in which certain crops are ‘‘replanted” in soils that had previously supported the same or similar plant species. Because of limited arable land sand expansive populations, continuous cropping systems are commonly practiced in the production of grain crops and cash crops. However, long-term continuous cropping usually leads to plant growth inhibition and serious soil-borne diseases. Continuous cropping can lead
to soil exhaustion, erosion and low productivity if soil and nutrients conservation practices are not adopted. Excess fertilizers can be washed off by rain into bodies of water that could cause pollution
3. Pollution
Vehicles, trains and planes emit toxic gases that include carcinogenic particles and irritants, creating air pollution. Humans have also dumped large amounts of pesticides, such as organophosphates, onto crops that migrate into groundwater and bodies of water, poisoning ecosystems. Plants and animals die from exposure to pollutants such as excess nutrients from chemical fertilizers and other harmful chemicals. Pollution is increasing around the world and results in loss of biodiversity causing severe damage to self-sustaining ecosystems. 4. Habitat destruction
Deforestation
Humans have always cut down trees throughout history. The world’s rainforests are being destroyed resulting in vegetation degradation, nutrient imbalance, flooding and animal displacement. Trees act as a natural air filter in the carbon cycle by taking in carbon dioxide and releasing oxygen, so deforestation contributes to global warming.
Kaingin System
Kaingin system is the cutting down and burning of trees and plant growth in an area for cultivation purposes. Kaingin is a Filipino word that means clear- ing. Known as swidden farming in other countries, it is a traditional but destructive agricultural system practiced in many parts of the globe.
Land Conversion
Through urban development, the continued rapid construction of road systems and buildings has changed the Earth's natural surface, removing soil nutrients, surface vegetation and trees that filter the air and equalize the carbon cycle. Urbanization also displaces animals and increases environmental pollution from vehicles and factories. A system of highways also causes migratory obstacles for animals and replaces native plants with impermeable concrete, resulting in habitat destruction. This practice of human construction continues at a rapid pace, leading to urban sprawl, where cities are essentially forever expanding outside the traditional inner-city limits.
THE EARTH SAVERS TEN COMMANDMENTS FOR SUSTAINABLE DEVELOPMENT 1. Thou shalt not throw garbage along canals, creeks or rivers.
2. Thou shalt not resort to destructive and illegal methods of fishing.
3. Thou shalt not resort to open burning methods to dispose your drug waste. 4. Thou shalt improve and maintain your care and vehicles in good running. 5. Thou shalt not smoke cigars and cigarettes .
6. Thou shalt minimize if not put to stop the use of CFC products. 7. Thou shalt not waste energy and water.
8. Thou shalt plant more trees and nurture them.
9. Thou shalt protect endangered species of plants and animals. 10.Thou shalt minimize if not totally stop the use of farm chemicals.
CHAPTER TEST :
Identify the word being described by the given statement.
_______________1. tropical grasslands, with few trees, and good for grazers _______________2. It means contamination with pollutants.
_______________3. It is the ratio of total live births to total population in a specified area over a specified period of time.
_______________4. a kind of ecosystem found in bodies of water
_______________5. It is an organism that lives in or on another organism (its host) and benefits by deriving nutrients at the host's expense.
_______________6. It is a measurement of population per unit area.
_______________7. It is the cutting down and burning of trees for clearing purposes. _______________8. Fatality rate is also known as ________.
_______________9. It is the light energy that enters the biological system. ______________10. factors that limit the growth of a population
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