 Carbon Neutrality » Tree planting
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Tree planting includes not only re-creating natural forests (reforestation) and avoiding deforestation, but also monoculture tree farming on plantations for logging, biodiesel production, or other commercial purposes. The term "reforestation" is nevertheless often applied to monoculture tree farming as well as re-creating natural forests. There is also afforestation, which can produce higher carbon sequestration rates because it means establishing forests particularly on land not previously forested, for example on agricultural lands where baseline carbon levels are comparatively low.
Many environmentalists have criticized the use of forestry carbon offsets as an inadequate substitute for long-term fossil fuel use reduction. In addition, many forestry offset projects have been conceived and/or conducted in ways that are vulnerable to criticism, drawing their net benefits into question.
Significant concern arises from the fact that carbon sequestered in the newly planted trees will be again released as CO2 when the tree dies and decays, thus merely postponing the negative impact of the man-made increase in CO2. The only reason we have a net of oxygen in the atmosphere is that the oxygen producing plankton (and plants) in the ocean are often covered in mud and decay without consuming oxygen in a process called sublimation.
Climate impacts
Trees sequester carbon through photosynthesis, converting carbon dioxide and water into oxygen and plant matter. Hence, forests that grow in area or density will reduce atmospheric CO2 levels. (Carbon is released if a tree or its lumber burns, but as long as the forest is able to grow back, the net result is carbon neutral.) In their 2001 assessment, the IPCC estimated the potential of biological mitigation options (mainly tree planting) is on the order of 100 Gigatonnes of Carbon (cumulative) by 2050, equivalent to about 10% to 20% of projected fossil fuel emissions during that period.
However, the global cooling effect of forests from sequestration is not the only factor to be considered. For example, the planting of new forests may initially release some of the terrain's existing carbon stores into the atmosphere. Specifically, the conversion of peat bogs into oil palm plantations has allegedly made Indonesia the world's third largest producer of greenhouse gases. Compared to less vegetated lands, forests affect climate in three main ways:
• cooling Earth by functioning as carbon sinks
• cooling Earth by evaporating water to the atmosphere and increasing cloudiness
• warming Earth by absorbing a high percentage of sunlight due to the low reflectivity of
forest's dark surfaces. This warming effect is large where evergreen forests(very low
reflectivity) shade snow cover (very high reflectivity).
Some näive tree planting strategies have taken only the first effect into account. A study published in December 2005 combined all these effects and found that tropical forestation has a large net cooling effect, because of increased cloudiness and because of high tropical growth and sequestration rates. Trees grow three times faster in the tropics than in temperate zones; each tree in the rainy tropics removes about 22 kilograms (50 pounds) of carbon dioxide from the atmosphere each year. However, this study found little to no net global cooling from tree planting in temperate climates, where warming due to sunlight absorption by trees counteracts the global cooling effect of carbon sequestration. Furthermore, this study confirmed earlier findings that reforestation of colder regions—where long periods of snow cover, evergreen trees, and slow seqestration rates prevail—results in global warming.
"To plant forests outside of the tropics to mitigate climate change is a waste of time", said Ken Caldeira, a study co-author from the Carnegie Institution. "To prevent climate change, we need to transform our energy system. It is only by transforming our energy system and preserving natural habitat, such as forests, that we can maintain a healthy environment. To prevent climate change, we must focus on effective strategies and not just ‘feel-good’ strategies." His study indicates that one effective strategy is well-planned and executed tree-planting in the tropics. Although trees planted adjacent to buildings and pavement were not addressed by this study, they will cool Earth to the extent that they shade dark pavement, shade windows and dark building surfaces in the summer, sequester carbon, and enhance cloud formation.
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Other sections: Carbon Home | Renewable v. Conservation | Tree Planting | External Links | Carbon Calculators
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