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Lecture 11

BIOC63Fall2013 Lecture 11 Notes.docx

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University of Toronto Scarborough
Biological Sciences
Karen Williams

BIOC63Fall2013 Lecture 11: Tropical Forest  Destroying rainforest for economic gain is like burning a Renaissance painting to cook a meal Tropical deforestation: why a problem?  6% of land surface area but >50% of the earths plant and animal species  ~9000 known bird species o almost half live in the Amazon or Indonesian  by removing tropical rainforest we are decreasing biodiversity at a great rate Causes of deforestation  1. Population pressure o o as the population number increases the deforestation rate also increases o Negative deforestation is regrowth of forest o Negative growth also refers to regrowth  like people moving out of the land, and forest regrows o As population pressure on the land increases, deforestation rate also goes up (left picture) o Population pressure increases, deforestation increases (right picture) o Phillipines has cut down 98% of their old growth forest 2. Logging for timber o 15%  i.e. for mahogany o Make roads through the forest with secondary roads (first picture)  these roads people then use to colonize (like slash and burn famers and etc. (4 picture) o Tropical timber is more valuable than timber here because the wood is uniform and smooth (there are no annual growth rings because there is no winter) o So they start the destruction of the whole forest 3. Mining (multinational stakeholers) o Use toxic chemicals that can seep in run off and groundwater as they are trying to get gold, iron and other stuff o max of 5% for gold, iron, silver etc. 4. Slash and burn, Subsistence farming o 45%  i.e. slash and burn o Main reason for the large scale cutting down of forest o Small family or community move into the first  cut down a patch of land  they do agriculture there o Because the soils are poor, organic nutrients are exhausted within 5-10 years so they then move on to a new patch o The old patch can then re-grow 1 o But this is not sustainable because now there are too many people doing this! 5. Influence of developed countries o International economy, peak oil, first world food preferences o o Developing countries are increasing meat consumption so we increase the amount of plants we grow o Sugar cane we consume, but we also use as fuel o Same with the soybeans, some we eat but some are given to animals for food o Brazil agriculture (picture on the right)  20% of sugar, and 40% of exports of sugar o It is number one in terms of production and in terms of export  this drives what is then going on in the tropics o i.e. sugar cane o sugar cane is a perennial crop, so there is no need for annual seeding o sugar cane production and export has dramatically increased recently o used for fossil fuels o most oil in first world countries comes from sugar cane o soy bean  very vast stretches of land are dedicated to the production of soy beans o Fossil fuel prices – sugar cane – soy bean o o Sugar cane production and export have been and still are increasing o Brazil tries to be independent in terms of fuel, so they use a lot of their sugar cane as fuel o Brazil is number 2 in global soybean production o 2 o Corn needs a lot of fertilizer  Gulf of Mexico anoxia because of run off o Some areas dedicated to soya bean production in Brazil are then used for sugar cane frowth which mean more Amazon soya = increase in deforestation o Higher biodiesel prices means higher soya prices, so more Amazon soya, which again increases deforestation o Trans fats and palm oil o We know transfats are bad for our hearts o So there is high demand for trans-fat free stuff o One oil used is palm oil  trans-fat free o Palm oil is extracted from oil palm o Pressure to produce monocultures of oil palm plantations  grown in low land tropics like Indonesia o There is still some rain forest left o Here soils are water logged  so first companies put in draining canals to divert the water from low lying land to ditches o So soils are very high in organinc matter so when you get the water out , decompos
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