The marginal zones, the remaining after a grubbing-up, fragmented forests of rest, lose more high vegetation after the silence of the saws. Get annually more than 2 billion tons of carbon into the atmosphere through burning and decomposition of fallen trees, a large part of it comes from the tropics. Dr William Laurance of the Brazilian National Institute, for research in the Amazon in Manaus but stresses that this CO2 even up to 42 percent higher must be set on emissions by an average of 7 percent, in some areas. “Cause is a the ragged edge phenomenon”: the marginal zones, the remaining after a grubbing-up, fragmented forests of rest, lose even after silencing the saws more high vegetation. In a field study spanning 18 years, Dr. Laurance and his team investigated greenhouse gas emissions by 66 isolated residual forest area of various sizes.
They noted that in their peripheral regions due to their vulnerable against strong winds and other extreme climate conditions position trees and Underwood will wither and die, rather than to continue to grow. Was the effect of the forest up to 300 metres into the Interior of the remaining forests that are measurable and persists for at least four years after the actual clearance. In the thinned areas more than a third of biomass was lost as compared to intact rainforests. The decomposition of this dead organic matter by fungi and bacteria cause significant amounts of methane, CO2 stored in the wood is released, both major contributors to the greenhouse effect. At the same time biomass is lost by this additional vegetation loss, which could absorb CO2 from the atmosphere. In a follow-up project, the scientists using computer simulations calculated the resulting from the loss of CO2 emissions for different fragmentation scenarios typical in Amazonia. They simulated three logging methods with degrees of deforestation from 5 to 95 percent: the many small plots of smallholder farmers in southern Amazonia, the large-scale deforestation for cattle farms in Eastern Amazonia -. both together are for the majority of tropical forest loss in the Amazon area responsible – as well as a random scenario, in which wild deforestation were simulated.
The highest amounts of carbon were lost – at each all degrees of deforestation – uncontrolled grubbing-up and the small farming plots scenario. Due to the occurring here larger number of fragmented forests of rest in addition occurring forest and CO2 loss was two to five times higher than in deforestation for cattle farms, which remain comparatively large and uniform remaining forests. Uncontrolled grubbed-up forest areas with their usually very irregular running forest edges proved vulnerable to the loss of vegetation, even at low degrees of deforestation. After the calculations by William Laurance which amount to the ragged edge phenomenon”caused additional CO2 emissions in the Brazilian Amazon region between 3 and 15.6 million tonnes and between 22 and 149 million tons in all tropical forests. These numbers appear first rather unspectacular. One must recall, that occur in the many small residual forests carbon emissions of an annually in addition destroyed rain forest area of 150,000 to 1.1 million hectares correspond to”, says Laurance, who at the same time indicates that its results to reflect the problem not once in its entire extent. Its surface to measure of biomass loss were surrounded by forests of reforestation and so relatively sheltered from the wind. Usually are remnants of forest that remain with the reclamation of pastures and fields, completely unprotected. Therefore, Laurance and his colleagues call that grubbing-up measures largely avoids the formation of fragmented forests of rest. U. Karlowski