Deforestation Clearing of forests for agriculture or buildings; cleared areas may be mined for mineral ores; timber obtained may be used for paper, charcoal, furniture, building material Reduces transpiration, rainfall, humidity Increases risk of fire Increases velocity of rain reaching the soil Soil erosion / leaching of ions Reduces biodiversity More extreme environment / abiotic factors increase / unstable ecosystem Change in (micro)climate / levels of light / temp / humidity Loss of niches/habitats and complex food webs Animals move away/higher death rate/extinction Lower biomass and productivity per hectare Effect on Nitrogen Cycle Growth in human population is increasing the demand for agriculture for land for farming for grazing land to provide animal protein Many decomposing fungi live in association with roots of trees Less NH4+ can be absorbed by plants from decomposition The soil itself is often a poor source of mineral ions Thus, reduced input in the nitrogen cycle; slower and less recycling of NH4+ Nitrogen in soil is lost as smoke but ash is still rich in nutrients for crops Yield falls with subsequent crops Crops are harvested before they die/decompose Nitrogen is not recycled and not returned to the soil Fertilisers (NO3, NH4+) make up that loss Ions from fertiliser readily leach out of the soil by rain into lakes and rivers Increases growth of algae and water plants [EXAM] Ploughing increases the activity of nitrifying bacteria in the soil Oxygen enters the soil Nitrifying bacteria are aerobic Convert ammonia/ammonium ions to nitrite, nitrite to nitrate Nitrate is absorbed/used by plants To make protein/amino acids/DNA/ATP/NAD(P)/chlorophyll Increased yield/growth Affect on Carbon Cycle Lower CO2 (greenhouse gas) uptake by photosynthesis Burning trees for agriculture and fuels releases CO2 Higher conc of CO2 in the atmosphere accelerates greenhouse effect CO2 absorbs outgoing longwave radiation Warms the troposphere (lower atmosphere) Trees can act as carbon sinks [EXAM] Absorb CO2 in photosynthesis Carbon (dioxide) is used in forming permanent plant tissues/biomass/plant structure Carbon is incorporated in organic molecules Reduction in the amount of ploughing lead to more carbon being stored [EXAM] "Less oxygen can enter the soil (from the air) For decomposers/saprobionts/fungi/soil microorganisms/bacteria For use in aerobic respiration Less breakdown of organic matter/humus/dead plants/dead animals Less carbon dioxide released"1 Conservation of Forests is the Sustainable Use of Forests On deforestation Felling one hectare will give space for agriculture for high income But the land loses fertility after a few years Using cleared land for cattle will give a low income per year If the forest is kept Medium income per hectare per year for fruit and rubber production Income from tourists and medicinal plants Gene pools of wild relatives of domesticated organisms - which may be used as a source of genes/alleles in selective breeding or genetic engineering Tropical rainforests should be conserved to avoid [EXAM] "Loss of species / decrease in diversity / loss of niches / disruption of food chains Loss of pharmaceuticals / medicines / timber / wood CO2 build-up in atmosphere / global warming Leaching of ions / minerals / nutrients Soil erosion / mud slides / flooding / desertification"2