Lesson 14: Threats to the Biological Cycle Flashcards
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
What is afforestation is made up of?
Monoculture e.g. palm oil
Where in China was a green wall built to reduce desertification?
Three-North Shelterbelt Project
How long was the green wall?
4500 km
What are the impacts of afforestation on the carbon cycle?
-Monocultures of commercial trees such as in palm oil plantations often store less carbon
-Biodiversity may be impacted as a result of habitat changes
-Monocultures tend to be more disease prone
What are the impacts of afforestation on the hydrological cycle?
-Monocultures tend to use more water leading to less infiltration and groundwater rates
-Decreased raindrop erosion.
-Evapotranspiration rates may alter downwind ecosystems
What are the two types of grassland?
Temperate
Tropical/savannah
When was there a biofuel rush across the American midwest?
2007 and 2015
What crops were farmers encouraged to grow in the biofuel rush?
Corn, soya, canola, sugar cane
What was the aim of grassland conversion in the USA?
-Increase the amount of ethanol being used in petrol
-Boost the economies of rural US states
-Reduce US dependence on overseas oil imports
-Reduce CO2 emissions from transport
How much did corn rise by in 2013?
Trebled
How many hectares of natural grassland were removed in the USA?
5.5 million hectares
Which countries did the loss of grassland equal in terms of deforestation?
Brazil, Malaysia and Indonesia
What are the benefits of natural grassland?
-Trap moisture and floodwater
Absorb toxins from the soil, maintaining their health
-Prevent soil erosion
-Acts as a carbon sink and a terrestrial carbon store
What are the negatives of conversion?
-Soils release CO2 when grasslands are initially removed and through annual ploughing
-Biofuel crops need carbon-based nitrogen fertiliser and chemical pesticides
-Biofuels consume a lot of water
-Cultivated soils are liable to erosion
