In Peruvian Amazon were recorded more than 200 species of trees (> 10 cm of diameter at breast height) per hectare . Slash-and-burn agriculture, which is here widely practised, causes high deforestation and soil degradation at high rates and at the same time decreases natural regeneration of many valuable timber tree species. This inappropriate land use system together with exaggerated selective logging (extraction of all superior individuals) in the surrounding forest leads to genetic erosion . Many valuable species, useful for example in agroforestry have been already degraded as consequence to this unsustainable exploitation. Despite the local importance of these species, they remain mostly wild and thus endangered .
On September 9, 1987, the satellite NOAA-9 took a picture of the Amazon. Onthis picture, Brazilian scientist Alberto Setzer from the National Institute for Space Research (INPE) counted 7,603 artificial forest fires (on this one day) of minimal size of one football field. There were fires on up to 350,000 places during the whole burning season. After 38,539 km² of rainforest disappeared in 1975, 123,646 km² in 1978, 200,724 km² in 1980 and 960,263 km² in 1988 (which is more than twice the size of the state of California), it was obvious that deforestation in the Amazon got out of control .
The fragmentation of the forest has a highly negative effect on biodiversity, forest dynamics, the food chain and various ecosystem processes. Forest fragmentation also interacts with ecological disruptions such as hunting, fires and logging and together they represent an even larger threat for the rainforest biome .
In 2005, parts of the Amazon basin experienced the worst drought in a century and there were hints of a following dry year in 2006. Results of the Woods Hole Research Center show, that the forest in its current state cannot survive three consequent years of drought. In 2010 the Amazon experiences another big drought, in some aspects even more extreme than in 2005. The afflicted area was approximately 3,000,000 km² of forest as compared to 1,900,000 km² in 2005 . In a typical year, the Amazon rainforest absorbs 1.5 billion tonnes of carbon dioxide. During 2005, 5 billion tonnes of CO2 were instead emitted and in 2008 the emissions of CO2 amounted to 8 gigatonnes. During the dry season of 2005 and 2010, large amounts of vegetation were destroyed in the affected areas .
Agricultural expansion and climate change have become significant disturbances in the region. Studies published in journal Nature proved a considerable resistance of the Amazonian forests to mild annual droughts but also show that the interactions between deforestation, fires and drought could lead to losses of stored carbon and to changes in regional precipitation and river flow rates. Although the impacts of increased land use and droughts in the basin may not have exceeded the extent of natural variability of hydrologic and biogeochemical cycles, there are some suggestions of transition into regime of dominating disturbances. Among these suggestions belong changes of hydrologic and energetic cycles in souhter and eastern parts of the Amazon .
Scientists from the Brazilian National Institute Amazonian Research (INPA) claim, that the influence of drought together with the influence of deforestation on the local climate is pushing the rainforest towards a “tipping point” where it could start to disappear irreversibly. They conclude that the forest is on the threshold of changing into savannah or desert, with catastrophic impact on world’s climate .
Figure 2. Forest loss in the Amazon in 2001-2012 (ha/year), data from O Eco (InfoAmazonia.org). Taken from Conservation giant puts $100M into Amazon protected areas (Rhett A. Buttler March 22, 2016), source: mongabay.com
Figure 3. Forest loss in the non-Brazilian Amazon in 2001-2012 (ha/year), data from O Eco (InfoAmazonia.org). Taken from the article “Conservation giant puts $100M into Amazon protected areas” (Rhett A. Buttler March 22, 2016), source: mongabay.com
Hecht, S.B., Cockburn, A., 2010. The Fate of the Forest: Developers, Destroyers, and Defenders of the Amazon, Updated Edition. University of Chicago Press.
authors of the pictures: Jiří Lipenský (JL), Ludvík Bortl (LB), Lukáš Huml (LH), and Alexandr Rollo (AR)
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