TRIPLE ONLY: Deforestation and fish farming

Deforestation

What are the last natural forests of the world? What is a characteristic they have?

Tropical rainforests

High biodiversity

What is deforestation?

Clearing of trees on a large scale to provide land and wood

What is deforestation a consequence of?

It is a consequence of the enormous growth of human population

Why do humans cut down trees?

For timber, provide land for farming and agriculture, building

Consequences of deforestation

• Leaching

• Soil erosion

• Disturbance of evapotranspiration

• Carbon dioxide cycle disturbance

• Disturbing the balance of atmospheric gases/exacerbating climate change

• Not in PMT or SaveMyExams but yes in textbook: destruction of habitats and reduced biodiversity

How does deforestation cause leaching?

Soil minerals are not taken up by trees and are instead washed away by rain into nearby bodies of water (then todo lo de eutrophication thingy)

How does deforestation cause soil erosion? And decrease in soil quality?

Soil is exposed due to lack of tree cover and is not held together by tree roots and organic matter, so is more likely to be washed and/or blown away

Less trees to return minerals to the soil when they die. Crops in planted in deforested areas rapidly use up minerals in the soil

How does deforestation cause the disturbance of the water cycle (evapotranspiration)?

The removal of trees reduces the release of water vapour into the atmosphere by transpiration, reducing cloud formation and rainfall

How does deforestation cause a disturbance in the carbon dioxide cycle + cause global warming?

The removal of trees reduces photosynthesis, so less carbon is removed from the atmosphere and stored in plant tissues and less O2 released.

The burning of trees (slash and burn method to clear trees) after being cut down releases more CO2

How does deforestation decrease biodiversity?

Rainforests are habitat to many animals and cutting the trees destroys their homes so they don’t have shelter and die.

How can we carry out sustainable timber production and reduce deforestation?

Reforestation allowing sustainable timber production.

Replacing trees that are removed and ensuring there is no ecological damage to the environment

However tackling the problem of deforestation for farming is more complex. What could be an alternative?

To resettle the farmers and give them financial help to establish farms in other areas

What are the advantages of fish farming?

• Water quality can be maintained

• Controlling intraspecific and interspecific predation

• Controlling disease

• Removing waste products

• Controlling the quality and frequency of feeding

• Selective breeding

How is water quality maintained in fish farms?

• Temperature, oxygen levels, water clarity, amount of chlorophyll can be monitored

  • large concentrations of chlorophyll give a warning of chlorophyll of ‘algal blooms’ which harm fish by depleting oxygen in water

  • Air can be pumped to increase amount of oxygen dissolved in the water

  • Water is filtered to remove waste products if the fish and harmful bacteria

Why is it beneficial for fish farms to be built where there is tidal movement?

Circulation of oxygenated water, flushing out waste, distributing nutrients

What is intraspecific predation? What is a solution for this issue?

Intraspecific predation is the competition within the same species

Fish are separated by size and age using nets to prevent it

What is interspecific predation? What is the solution to prevent it?

Interspecific predation is the competition of food between different species

Different species of fish are separated by fences, nets, and tanks to prevent interspecific predation

Why do many fish farms feed fish with pellets rich in protein?

Protein is needed for growth of tissues so fish grow faster

Why is enclosing fish good for fish farming? How are parasites killed?

• restricts movement so less energy is wasted and more is given for growth to increase biomass

• Protects agains predators

• parasites are killed with pesticides

How is selective breed used to improve quality of fish?

Allows for fast growing fish to reproduce resulting in a larger population of fish and bigger fish, also less aggressive fish than wild fish

How has fish farming been criticised?

• fish are so close together that the potential for spread of disease is greater

• Fish farms also cause a pollution problem, producing organic material from the animal’s faeces and from food pellets which can contaminate waters outside the fish farm and cause eutrophication

• Pesticides used to kill parasites may be highly toxic to non-harmful species

• (Fish farming can decrease ‘wild’ fish stocks)

How is the spread of disease controlled in fish farms?

Antibiotics are given to treat and increase resistance to disease and minimise the spread of them

Why is giving antibiotics to prevent disease bad?

Because by the time humans eat the fish, the antibiotics may not have degraded, which leads to bacteria becoming resistant to antibiotics

How is fishfarming having a negative effect on the ‘wild’ fish stocks?

Carnivorous species like salmon are fed with pellets made from other fish. They need to eat several kilograms of wild fish to produce 1 kg of farmed fish. the wild fish used for fish meal are less marketable species