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Slash And Burn Agriculture & Continental Drift
Transcript of Slash And Burn Agriculture & Continental Drift
Biological Interactions cont
Slash and Burn Agriculture Overview
Pros and Cons of Slash and Burn
Slash and burn agriculture is a process where natural vegetation is cut down and completely burned off to clear land for cultivation
It is practiced by 200 to 500 million people around the world currently
The ash from the burned vegetation adds another layer of nutrients to the soil, and that with the time resting allows the soil to regenerate.
Places where open land for farming is not readily available such as central Africa, northern South America, and Southeast Asia, and typically within grasslands and rainforests are where slash and burn is most commonly practiced.
Deforestation: When practiced by large populations there is a temporary or permanent loss of forest cover.
Erosion: When fields are slashed, burned, roots and temporary water storages are lost and unable to prevent nutrients from leaving the area permanently.
Nutrient Loss: fields may gradually lose the fertility they once had.
Biodiversity Loss: When plots of land area cleared, the various plants and animals that lived there are swept away. If a particular area is the only one that holds a particular species, slashing and burning could result in extinction for that species.
Returns nutrients to the soil
A controlled burn also reduces the fire risk of debris left on farm land
It is cheaper to burn the debris on-site than mulch or remove the debris off site.
Burns may be used to scare animals out (either those that are dangerous for farmers, e.g. snakes, or for those that can be eaten, e.g. rabbits) May eliminate pests from destroying new crops too.
Removes all debris
Slash and Burn Agriculture is based on nutrient cycling.
Burning releases to the soil about half of the nitrogen and phosphorus of the burning biomass and all of the other nutrients in the form of ash.
Higher soil temperature after burning accelerates the decomposition of soil organic matter.
These factors provide high nutrient availability for 1-2 yrs to grow crops
In relation to environmental problems, burning releases half of the nitrogen and most of the sulphur and carbon into the atmosphere, thus contributing to green house gases.
Big Idea 4: Biological systems interact, and these systems and their interactions possess complex properties
Enduring understanding 4.B: Competition and cooperation are important aspects of biological systems.
Slash and Burn Agriculture is all about finding enough land to burn within a close proximity. As more and more forests burn out from this method, it becomes more and more harder to find new land.This leads to competition to find large areas of forestation to cultivate. The process of destroying crops and burning them shows the cooperation of techniques used to successfully develop cultivated land.
Essential knowledge 4.B.4 Distribution of local and global ecosystems changes over time.
-Human accelerates change at local and global levels.
This is applicable to slash and burn agriculture because as areas are burned and eventually lose productivity, people move to new areas to slash and burn.
However Slash and Burn techniques allow communities to survive when land is unproductive.
When used by large communities, it leads to habitat loss
Continental Drift Overview
Continental drift is a theory proposed by Alfred Wegener in 1915 that states that continents are slowly moving toward or away from each other. Wegener noticed continents could be fit together, much like pieces of a puzzle.
The main difficulty with Wegener�s theory was that it contained no explanation of how entire continents could move.
In 1968, the theory of tectonic plates attempted to solve this problem.
The tectonic plate theory states that the main elements of the Earth�s surface are not the continents, but huge pieces of rock spanning the surface. These pieces of rock are covered by continents and ocean.