Deforestation productivity

Human activity, particularly in the developing world, continues to make it more difficult to sustain the world s biomass growth areas. It has been estimated that tropical forests are disappearing at a rate of tens of thousands of hm per year. Satellite imaging and field surveys show that Brazil alone has a deforestation rate of approximately 8 x 10 hm /yr (5). At a mean net carbon yield for tropical rain forests of 9.90 t/hm yr (4) (4.42 short ton /acreyr), this rate of deforestation corresponds to a loss of 79.2 x 10 t/yr of net biomass carbon productivity. 

The manufacture of sugar was early understood to be an energy-intensive process. Cuba was essentially deforested to obtain the wood that fueled the evaporation of water from the cane juice. When the forests were gone, the bagasse burner was developed to use the dry cane pulp, called bagasse, for fuel. Bagasse was no longer a waste product its minimal value is the cost of its replacement as fuel. 

Biomass Redistribution Associated with Deforestation and Fire. The influence of deforestation on biogeochemical cycles is dependent upon a number of factors associated with the unique characteristics of the ecosystem (climate, soils, topography, etc), the quantity of the total nutrient pool stored in aboveground biomass (Table II), and the level of disturbance (i.e. the degree of canopy removal, soil disturbance, and the quantity of wood or other forest products exported from the site). The quantity of biomass consumed by one or more slash fires following deforestation can also dramatically increase nutrient losses, influence post fire plant succession, and hence, postfire biogeochemical cycles. 

Implications of Deforestation and Fire on Long-Term Site Productivity... 

How have agriculture and deforestation changed the global rates of nitrogen fixation and denitrification How can increased agricultural productivity be sustained without using industrially produced fertilizers ... 

What has changed in the last few hundred years is the additional release of carbon dioxide by human activities. Fossil fuels burned to run cars and trucks, heat homes and businesses, and power factories are responsible for about 98% of carbon dioxide emissions, 24% of methane emissions, and 18% of nitrous oxide emissions. Increased agriculture, deforestation, landfills, industrial production, and mining also contribute a significant share of emissions (5). For example, in 1997, the United States emitted about one-fifth of total global greenhouse gases. 

The additional and steadily increasing demand for biofuels could lead to a situation where production of biomass derived fuels finally compete with food production. People who can afford cars can pay more for biomass for fuels than people in non-industrialised countries can pay for food production. Fertile soil in non-industrial countries might then be used for energy crops instead of food. This may eventually lead to a situation where only bad soil is left for food crops and the poor, which in addition would eventually also lead to further deforestation of the World s rainforests. 

Although timber production and utilization can result in substantial environmental benefits compared with materials extracted from nonrenewable sources, timber utilization and forestry have become associated with negative environmental impacts. Tropical deforestation... 

Given these circumstances, it is possible that countless numbers of new natural products with potential for use as drugs are still waiting to be discovered. As more and more plants and animals are destroyed each year by deforestation, development, and... 

Just as important as evaluating the performance of the nuclear fuel cycle, one must also consider the size of the fluxes and reservoirs of the carbon cycle. Present CO2 emissions from fossil fuels and the production of cement are estimated to be 6.3 + 0.4 GtC/y emissions related to changes in land use (e.g., deforestation) are 1.6 0.8 GtC/y (Schimel et al. 2001). At present, the reduction of C02 emissions that can be attributed to the use of nuclear power is 0.5 GtC/y. Thus, the uncertainties in the major fluxes in the carbon cycle are approximately the same as the present impact of nuclear power on C02 emissions (Sarmiento Gruber 2002). To quote from Falkowski et al. (2000), Our knowledge is insufficient to describe the interactions between the components of the Earth system and the relationship between... 

Desertification is caused by overcultivation, overgrazing, and deforestation. This may result in soil exhaustion and erosion. This will in turn decrease the soil productivity, reduce food production, deprive the land of its vegetative cover, and negatively impact areas not directly affected by its symptoms, by causing floods, soil salinisation, deterioration of water quality, and silting of rivers, streams, and reservoirs (http //www.fao.org). 

Next, when considering the use of renewable resources, one must make note of the competing uses for land and the consequent impact on the environment, such as the competition between food production and industrial use for agricultural land, as exemplified by the growing biofuels industry or the deforestation of land for plantations of palm oil trees. This is a complex area where there is on-going national and international debate and where there are no easy answers. 

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