Deforestation and slash and burn agriculture Definition and

Deforestation and slash and burn agriculture

Definition and Introduction - Slash and Burn Agriculture * Slashing and burning of forest vegetation to inject nutrients from ash into soil - Deforestation * Clearing of trees in a forest * Deforestation rates in 2000's are estimated to have been about 12. 9 -16. 3 million hectares per year (IPCC, 2007, Loarie et. al. , 2009).

1. Intervals too long. Potential not realized. 2. Optimal interval. Potential just exhausted. 3. Intervals too short. Production potential devasted. FIGURE 1 Degradation and recovery in slash-and-burn systems as related to the cropping interval and when no agronomic adjustments are made. Modified after Guillemin (1956). (Hauser & Norgrove, 2001).

Figure 9. 1 : Net change in forest area between 2000 and 2005. Source: FAO, 2006 a. (IPCC, 2007)

Impacts on Biomass - Biomass : mass of living organismes in an area - Biomass as studied by Fearnside (1995) * Primary (original) forest: 463. 5 t/ha * Secondary (regenerated) forest: 28. 5 t/ha - Loarie, Asner, and Field (2009): * Deforestation in encroaching into more biomass riche area of Amazon

Impacts on local weather - Increase form forest albedo of. 11 -. 13 to grassland albedo of. 2 * Less radiation absorbed > evaporation down - Decrease in biomass means less plant transpiration * Less plant transpiration > transpiration down * Less forest to intercept rain > evaporation down - Result: less evapotranspiration

Impacts on Carbon Stocks and Emissions - Above ground biomass is the most vulnerable carbon stock (Kotto. Same et. al. 1997) - How much ? * Estimates for carbon lost per hectare in Brazilian Amazon: 183 -184 t C/ha cleared (Fearnside, 1998; Loarie et. al. , 2009) * Up to 201 t C/ha in 2007 because more biomass rich areas being cleared (Loarie et. al. , 2009) * Average carbon stock that replace forest: 12. 8 t/ha (Fearnside, 1998).

Impacts on Carbon Stocks and Emissions IPCC (2007) estimated emissions of 2. 8 Gt C/yr in the 1990's because of deforestation Global antropogenic GHG emissions.

Relation to climate change - IPCC (2007) is clear about relationship between anthropogenic GHG emissions and global warming - GHG's reradiate IR radiation. This warms the earth.

Relationship to climate change - Graphs from IPCC (2007) reporting increases in GHG concentrations and the effects of the increase. Change in temperature, sea level and Northern Hemisphere snow cover Change in GHGs from lce core and modern data

Solutions - Framwork for understanding options (Tomich et. al. , 1998) * Global community : Forest biodiversity and forest as carbon sink * Local users: private interests and extracting living from forest * Alternatives must : 1. Be more profitable for farmers. 2. Increase food security for farmers. 3. Fund any extra labor they require. 4. be sustainable in the long term.