geography sac 1- deforestation

deforestation

occurs when the forest canopy is reduced to between 10-30% of its original size

forest degradation

occurs when more than 3% of the original canopy of a forest remains

afforestation

trees planted on land which was previously unforested

reforestation

forests which have been re-planted/re-seeded following deforestation (eg. after logging)

clearfelling

large sections, or all vegetation, are cleared

selection

selected trees are felled, understory remains intact

group selection

selection of the forest (called a 'coup') is completely cleared

shelterwood

only the mature trees are felled, with an interval before the next step of mature trees are subsequently felled

send-tree retention

most trees are removed but some are left to reduce environmental impacts and assist with forest growth

impacts

the direct effects of an event of process on the environment, economic activity or social conditions

Deforestation causes the environmental impact of habitat loss

issues

the flow on effects or problems that develop as a result of an impact

The impact of the habitat loss leads to an increase of endangered species and loss of biodiversity

challenges

the difficulties or barriers involved in managing in or reducing a problem

The demand for palm oil creates a barrier when trying to address deforestation

human causes of deforestation (globally)

- agriculture

- infrastructure development

- logging for timber

- political factors

- population growth

- fuel wood

- war and civil unrest

- human induced climate change

why does deforestation occur?

- Forests are cleared as a source of wood products

- To change the land use to create settlements, farms, dams and mines

- Natural disasters- drought, fire and landslides

holocene maximum

a period of significant warming during the Holocene epoch, roughly 8000 years ago, that experienced higher temperatures, particularly in the Northern Hemisphere, and was driven by natural climate drivers

holocene climactic optimum

9000-5000 years ago, the Northern Hemisphere was 0.5 degrees higher than today

Sea levels rose- Tasmania was cut off from the Australian mainland

Ice sheets in the Northern Hemisphere melted and retreated

forests

Land spanning more than 0.5 hectares with trees higher than 5 metres and a canopy cover more than 10%

can be classified as tropical and subtropical, temperate and boreal forests

primary forests

virtually pristine and untouched by people

secondary forests

native species that have been disturbed by people and may have been replanted

plantations

a mix of native or non-native trees for commercial production

canopy

is formed by tall trees whose crowns create a continuous cover and capture most sunlight

understory

made up of smaller trees and shrubs adapted to lower light levels

forest floor

contains leaf litter, decomposing organic matter, fungi, and spoil organisms which recycle nutrients and support new plants growth

open forests

Trees are shorter, more spaced out and canopy is less dense

The 'open canopy' allows sunlight to reach the ground and for grass cover to grow

Eg. eucalypt open forest

closed forests

Trees are taller and canopy is dense

The dominant canopy, carriers, storeys and undergrowth make up more than 40% of the land cover

Difficult for grass to grow continuously as sunlight doesn't reach the ground through the canopy

Eg. Cameroon rainforest

biotic disturbances (causing deforestation)

pests and diseases

- affect >2% of forests worldwide, regional or local scales, boreal/temperate forests

abiotic disturbances (causing deforestation)

natural disasters (earthquakes + cyclones)

atmospheric events

- affect 1% of forests worldwide, australia's temperate forests, lightning strikes

climate change

- long term first degradation, emits CO2 into atmosphere