Chapter 21 Human Influences on Ecosystems

Question 1

How does Modern Technology result in increased food production?

Answer 1

Modern technology has resulted in increased food production in terms of:
1. Agricultural machinery is used to clear the land, (prepare the soil and plant , maintain and harvest crops) to improve efficiency.
2. Chemical fertilisers are used (to provide minerals) to increase the yield of crops.
3. Pesticides are chemicals that destroy agricultural pests or competitors
i ) Insecticides are chemicals that destroy insects that eat and damage the plants, hence improving quality and yield.
ii) Herbicides are chemicals that kills plant that compete with the crop plant for root space, soil minerals and sunlight, hence reducing competitors.
4. Selective Breeding to improve production by crop plants and livestock, e.g. cattle, fish and poultry.

Question 2

Describe the negative impacts to an ecosystem of large-scale monocultures of crop plants

Answer 2

In a monoculture, every attempt is made to destroy organisms that feed on, compete with or infect the crop plant.
So, the balanced life of a natural plant and animal community is displaced from the farmland and left to survive only in small areas of woodland or hedgerow.

Question 3

Describe the negative impact to an ecosystem of intensive livestock production

Answer 3

• Chickens and calves are often reared in large sheds instead of open fields. The urine and faeces are washed out of the shed with water, forming slurry. If this slurry gets into rivers and streams it supplies an excess of nitrates and phosphates for the microscopic algae. This starts a chain of events which can lead to eutrophication of the water system.
• Overgrazing can result if too many animals are kept in a pasture. They eat the grass down almost to the roots, and their hooves trample the surface soil into a hard layer. As a result, the rainwater will not penetrate the soil so it runs off the surface, carrying the soil with it. The soil becomes eroded.

Question 4

Discuss the social, environmental and economic implications of providing sufficient food for an increasing human global population.

Answer 4

There is not always enough food available in a country to feed the people there.
A severe food shortage can lead to famine.
Food may have to be brought in (imported).
The redistribution of food from first world countries to a poorer one can have a detrimental effect on the poorer country’s local economy by reducing the value of food grown by local farmers.
Some food grown by countries with large debts may be exported as cash crops, even though the local people desperately need the food.

Question 5

Discuss the problems which contribute to famine

Answer 5

1. Climate change and natural disasters such as flooding and drought; waterlogged soil can become infertile due to the activities of denitrifying bacteria, which break down nitrates
2. Shortage of water through its use for other purposes, the diversion of rivers, building dams to provide hydroelectricity
3. Eating next year’s seeds through desperation for food.
4. Lack of money to buy seeds, fertilisers, pesticides or machinery.
5. An increasing population
6. Pest damage or disease
7. Poor education of farmers and outmoded farming practices.

Question 6

Describe the reasons for habitat destruction

Answer 6

increased