Unit 3 - Deforestation
Cattle let off methane gas!

Unit 3 - Deforestation

Sustainable forestry is when new trees are planted to replace ones that have been deliberately cut down and removed. Deforestation is the removal of trees from their natural habitat and it happens where unsustainable forestry or deliberate clearance of trees to provide a change of land use is taking place. In this GCSE Biology quiz we look at its causes and also its effects.

Deforestation takes place all around the world but is often most associated with tropical rainforests since that is where clearance of forest is happening at a great rate at the present time. Some of this clearance involves slash and burn farming techniques. This is where the trees are chopped down and then burnt, leading to the release of large quantities of carbon dioxide and smoke into the atmosphere. The ash from the burnt trees and vegetation fertilises the ground for a while but after a few years, the soil becomes too poor to support agriculture and so a new area is slashed and burnt.

The biggest problems are when deforestation occurs on an industrial scale. Large areas of rainforest are lost each year to mining, and exotic timbers, like teak and mahogany, are deliberately and illegally felled for furniture making and building. Deforestation is also used to provide land to grow crops for making biofuels and to provide cattle and rice fields for food production.

8,000 years ago, much of Western Europe, including the British Isles, was heavily forested. These forests contained many food chains and food webs and some of the top predators included wolves and bears. Although there are still a lot of trees around, the area covered by forests is a tiny fraction of what it was before humans started to clear the forests in order to grow their crops and build their settlements.

But what are the problems associated with deforestation?

Removal of trees contributes to global warming by removing the chance for carbon dioxide uptake by those trees, so less carbon dioxide is removed from the air. It reduces biodiversity and exposes the soils to erosion creating barren land, flooding, mudslides and landslides. Deforestation can nowadays only be prevented by political means in the countries involved, but the economic loss to those countries is a major issue.

One reason for deforestation is to provide...
clean water
Timber is another word for wood
Deforestation leads to what change in biodiversity?
A decrease in biodiversity
An increase in biodiversity
No change in biodiversity over many years
A decrease in biodiversity, followed by an increase
For a given area, biodiversity is a measure of the population size, number of species of animals and plants as well as the genetic variation within each species living there, the differences between species and the differences between ecosystems and habitats. If trees are removed, there are fewer habitats for plants and animals leading to a decrease in biodiversity
Deforestation leading to increased cattle farming also increases global warming because of the release of which greenhouse gas?
Cattle let off methane gas!
Greenhouse gases can increase the temperature of the Earth by...
trapping heat in the atmosphere
increasing heat radiation
disappearing during the day
letting go of heat at night
Warmer conditions may sound pleasant but it's not as simple as that. Deserts will grow larger meaning there is less area for growing food crops and weather patterns will change as there is more energy in the atmosphere
Global warming can lead to...
climate change
new species
an ice age
Some areas like the British Isles will have more rainfall and high winds. Other places will have less rainfall, turning them into deserts
What is deforestation?
Removal of carbon dioxide
Removal of water
Removal of trees
Removal of plants
Sustainable forestry avoids deforestation as new trees are planted to replace those cut down
Slash and burn releases which gas into the atmosphere?
Carbon monoxide
Carbon dioxide
This carbon dioxide comes from the combustion of carbon compounds in the trees. Oxidation of carbon produces carbon dioxide
If peat bogs are removed, this can increase...
ozone levels
carbon dioxide levels
water vapour
Destroying the peat bogs in order to build on them will reduce the uptake of carbon dioxide, leading to its build up in the atmosphere. Many gardeners now choose to use peat-free compost products in their gardens and greenhouses
Burning trees contributes to global warming because...
combustion releases carbon dioxide
combustion needs oxygen
the trees die
there are more rice fields
This is a greenhouse gas. Greenhouse gases trap heat in the Earth's atmosphere making it warmer than it would be without them. This means that there is more energy available to power wind and other weather phenomena
Deforestation makes global warming worse because...
the trees have all gone
the trees would have taken up carbon dioxide
the trees would have given off oxygen
there are still plenty of trees left
Fewer forests means that there is less photosynthesis and so less carbon dioxide is removed from the air
Author:  Donna Maria Davidson

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