Deforestation and climate change

There has emerged a direct correlation between deforestation and climate change. Deforestation is widely believed to influence local, regional and possibly global climates. Although the relationship between deforestation and climate change is complex, there is a growing consensus that deforestation leads to warmer, drier climates.

Studies have identified forests such as those in the Amazon and Indonesia as carbon sinks. Experts believe that maintaining forests as carbon sinks will make a significant contribution to stabilising atmospheric greenhouse gas concentrations.

Why should I be aware of this?

• Most of the world’s terrestrial carbon is stored in forests.
• Forests cover about 30% of the land surface and hold almost half of the world’s terrestrial carbon.
• Deforestation is expected to release an estimated 87 to 130 billion tonnes of carbon by 2100.
• This is greater than the amount of carbon that would be released by 13 years of global fossil fuel combustion.

How does this affect me?

• The Amazon, which is also the largest remaining expanse of tropical forest in the world, pumps about 7 trillion tons of water per year into the atmosphere via evapotranspiration, providing the vapor that keeps the regional climate humid and rainy.
• The conversion of water to vapor also cools the air.
• Protecting forests will preserve these other climate-stabilizing interactions as well as slowing clear cutting and fires.
• One of the consequences of deforestation is that the carbon originally held in forests is released to the atmosphere, either immediately if the trees are burned, or more slowly as unburned organic matter decays.
• Only a small fraction of the biomass initially held in a forest ends up stored in houses or other long-lasting structures.
• Most of the carbon is released to the atmosphere as carbon dioxide, but small amounts of methane and carbon monoxide may also be released by decomposition or burning.
• Cultivation also oxidizes 25-30% of the organic matter in the upper meter of soil and releases that to the atmosphere.

All about deforestation and climate change

Tropical deforestation includes

• Permanent conversion of forests to croplands and pastures
• Temporary or partial removal of forests for shifting cultivation and selective logging. This is estimated to have released close to 15-35% of annual fossil fuel emissions during the 1990s.

The magnitude of emissions depends on

• The rates of deforestation
• The biomass of the forests deforested
• Other reductions in biomass that result from forest use.

If, in addition to carbon dioxide, one considers the emissions of methane, nitrous oxide, and other chemically reactive gases that result from deforestation and subsequent uses of the land, annual emissions during the 1990s accounted for about 25% of the total anthropogenic emissions of greenhouse gases.

The emissions of carbon from tropical deforestation are determined by two factors:

1. Rates of land-use change (including harvest of wood and other forms of management)
2. Per hectare changes in carbon stocks following deforestation (or harvest).

Changes in carbon stocks vary with

• The type of land use
• The type of ecosystem i.e.tropical moist or tropical dry forest
• The tropical region (Asia, America, or Africa).
• The changes in different reservoirs (living vegetation, soils, woody debris, and wood products) also determines the net flux of carbon between the land and atmosphere.

The major greenhouse gases under human control are

• Carbon dioxide (CO₂)
• Methane (CH₄)
• Ozone (O₃)
• The halocarbons
• Nitrous oxide (N₂O).

Ozone is not directly emitted from human activity but is produced in the atmosphere as a result of emissions of CH₄, carbon monoxide (CO), and nitrogen oxides.

What can I do?

• Advocat stopping or slowing down of deforestation.
• Study and understand the requirement of people living in that area.

CopperBytes

• Every year, 20 million hectares of rainforest — an area the size of England, Wales and Scotland combined — are cut down, releasing millions of tons of carbon emissions into the atmosphere.
• Tropical deforestation releases 1.5 billion tonnes of carbon each year into the atmosphere.
• Deforestation in the tropics accounts for nearly 20 per cent of carbon emissions due to human activities.
• During years of severe drought, tropical rainforest fires can double emissions from tropical forests
• According to the FAO (2001), the highest rates of deforestation (in 106 ha/yr during the 1990s) occurred in Brazil (2.317), India (1.897), Indonesia (1.687), Sudan (1.003), Zambia (0.854), Mexico (0.646), the Democratic Republic of the Congo (0.538), and Myanmar (0.576). These rates are higher than the reported net changes in forest area.
• Per unit area, forests hold 20 to 50 times more carbon in their vegetation than the ecosystems that generally replace them, and this carbon is released to the atmosphere as forests are transformed to other uses.
• A study by the WWF claims that converting the forests and peat swamps of just one Sumatran province into plantations for pulpwood and palm oil is generating more annual greenhouse gas emissions than the Netherlands, and is endangering local elephant and tiger populations.

References

• Confirmed: Deforestation Plays Critical Climate Change Role
• Tropical deforestation as a source of greenhouse gas emissions
• Sumatran deforestation driving climate change and species extinction, report warns

Source

Science And Technology