Friday, October 17, 2008

Terrestrial Sequestration

“The best time to plant a tree was 20 years ago. The second best time is now.” Anonymous

Published Oct. 14, 2008

Trees play a key role in the environment's natural landscape due to their ability to prevent erosion.

The Spanish Government says it will plant 45 million trees over the next four years to counter desertification caused by global warming. The massive tree–planting scheme aims to reduce the amount of carbon dioxide (CO2) in the atmosphere, the cause of global warming.

It estimates that in the long term, the trees could absorb more than 3.5 million tonnes of CO2 emissions.

Soils contain carbon in the form of organic matter. When organic matter is exposed to oxygen in the atmosphere, the carbon in the organic matter combines with the oxygen to produce carbon dioxide, contributing to the greenhouse effect and global warming.

Organic matter is being lost from soils for a number of reasons. These include long—term changes in land management practices, changing soil management techniques, and changes in rainfall patterns and rising temperatures.

Soil respiration is the main pathway through which carbon is transferred from soil into the atmosphere, with an estimated 50—75 Gt carbon released each year. This is approximately 10 times the amount of carbon released from fossil fuel combustion. The large amount of carbon stored in soils means that small changes in soil respiration rate could have a huge impact on atmospheric CO2.

Carbon also moves from the terrestrial to the marine environment and can impact the ecology of both areas. This also affects the global carbon cycle, which is important for climate change studies.

The polar regions, especially the Arctic, are very sensitive indicators of climate change, The UN’s Intergovernmental Panel on Climate Change has shown that these regions are highly vulnerable to rising temperatures and predicted that the Arctic would be virtually ice—free in the summer months by 2070.

Arctic soils are believed to hold 30 percent or more of all the carbon stored in soils worldwide, and thawing permafrost may release additional greenhouse gases that would further accelerate global warming.

Wind, especially high wind, is one of the mechanisms researchers refer to as a 'forcing,' since it can drive other conditions such as erosion. Wind generates waves, and high waves can cause further coastal erosion.#1

Alaska has seen increased coastal erosion, melting of permafrost, dying forests and shrinking sea ice, all widely conceded to be the result of warming temperatures.

In the last 50 years, Native communities that were once transient have settled in coastal areas where there is access to hunting, fishing, and transportation. Coastal communities have used sea walls and other man—made barriers to hold back erosion. These measures have worked to an extent, but as areas of open water become larger, wave and wind effects also increase and eat away at these temporary solutions.

Recent warming has degraded large sections of permafrost, with pockets of soil collapsing as the ice within it melts. The results include buckled highways, destabilized houses, and "drunken forests" of trees that lean at wild angles. Warming induced changes in tundra vegetation and plant life threaten caribou, reindeer and migratory bird populations. Loss of sea ice and wildlife also makes indigenous life in the Arctic increasingly difficult, endangering an entire way of life.

Rising temperatures cause sea level rise in two ways. Because water expands as it gets warmer, the upper layers of the ocean are expected to expand. Also, the heat is causing glaciers in Greenland, North America and the Antarctic to melt, releasing water trapped for at least tens of thousands of years.

Glacial melting can accelerate itself. As melting begins, torrents of water flow off and underneath the glacier, acting as a lubricant and accelerating its slide toward the sea. ’Once that starts melting, it’s like Vaseline under it.’

An important unresolved question is how the delicate balance of life in the Arctic will respond to such a rapid warming, Will we see, for example, accelerated coastal erosion, or increased methane emissions, or faster shrub encroachment into tundra regions if sea ice continues to retreat rapidly?

The polar bear population is expected to decline by 30 percent in the next 35 to 50 years due to disappearing habitat induced by global warming.

#1 Coastal Erosion

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