Lesson 14: Threats to the Biological Cycle Flashcards
(38 cards)
What % of tropical forests have been lost since the 1960s?
50%
Where have tropical forests been lost in particular?
Africa and South America
Which country has overtaken Brazil in rates of deforestation?
Indonesia
How much rainforest has been cleared in Indonesia in how many years?
25% in 25 years
How much temperate forest was deforested in the 19th century?
90%
What forests have been threatened since mid-20th century?
Boreal forests
How much CO2 does the terrestrial biosphere sequester?
1/4
By 2015 what % of global forest cover had been cleared?
30%
What % of forest was degraded or fragmented by 2015?
20%
How many hectares of land is deforested annually?
13 million hectares
What % of the Earth covered by forest? What % of this is natural?
30% covered
15 % natural
What % of deforested land is for palm oil, soy, beef and paper production?
50%
What are other reasons for deforestation?
Dams and reservoirs
Infrastructure
Open cast mining for rare minerals
What are methods of deforestation?
Clear cutting - removes all primary forest
Slash and burn - used for agriculture- ash provides nutrients
What impacts does deforestation have on the water cycle?
- reduced interception
- increased raindrop erosion and surface run-off increasing sediment in rivers
-increased aridity downwind from loss of evapotrasnpiration
What impacts does deforestation have on the carbon cycle?
- reduction in storage in soil and biomass
- reduction in CO2 intake through photosynthesis
- increased combustion flux to atmosphere
How many hectares of tropical forests were there before 1950?
11.6 million hectares
How many hectares of tropical forest were there by 1985?
3.8 million hectares
How much forest has been deforested in Madagascar?
90%
Why are the forests in Madagascar so vulnerable?
Expanding population with no other resources, no international aid, no help/money from the government, people have to fend for themselves, growing international demand for tropical hardwood
How much does soil erosion now exceed in some areas of deforested land in Madagascar?
400 tonnes per hectare per year
What causes coastal waterways to become clogged with sediment and become red?
Extensive logging of inland rainforests and coastal mangroves means that, after heavy rainfall, soil is washed from the hillsides into streams and rivers
Define afforestation
Planting trees on land that has never had forest, or has been without forest for a long time
Define reforestation
Planting trees in places with recent tree cover, replacing lost primary forests
