Deforestation: Part 2

Yesterday I talked about the causes of deforestation and gave the some background on the problem. Today I’ll be writing about the consequences of it and tomorrow I’ll talk about the solutions.

Among the obvious consequences of deforestation is the loss of living space, not for us obviously, but for animals, the unspoken fors. Seventy percent of the Earth’s land animals and plants reside in forests. But the harm doesn’t stop there. Rain forests help generate rainfall in drought-prone countries elsewhere. Studies have shown that destruction of rain forests in such West African countries as Nigeria, Ghana, and Côte d’Ivoire may have caused two decades of droughts in the interior of Africa, with attendant hardship and famine.

Deforestation also drives climate change. Forest soils are moist, but without protection from sun-blocking tree cover they quickly dry out. Trees also help perpetuate the water cycle by returning water vapor back into the atmosphere. Without trees to fill these roles, many former forest lands can quickly become barren deserts.

Removing trees deprives the forest of portions of its canopy, which blocks the sun’s rays during the day and holds in heat at night. This disruption leads to more extreme temperatures swings that can be harmful to plants and animals.

Deforestation may have catastrophic global effects as well. Trees are natural consumers of carbon dioxide—one of the greenhouse gases whose buildup in the atmosphere contributes to global warming. Destruction of trees not only removes these “carbon sinks,” but tree burning and decomposition pump into the atmosphere even more carbon dioxide, along with methane, another major greenhouse gas.

Fewer forests means larger amounts of greenhouse gases entering the atmosphere—and increased speed and severity of global warming.

There seems to be a catch to this though. Temperatures data were collected from a network of specialized weather stations in forests ranging from Florida to Manitoba and compared results with nearby stations situated in open grassy areas that were used as a proxy for deforested land.

The climate cooling benefits of forests and trees are added as you get closer to the tropics or going north.

Researchers calculated that north of Minnesota, or above 45 degrees latitude, deforestation was associated with an average temperature decrease of 1.5 degrees Fahrenheit.

On the other hand, deforestation south of North Carolina, or below 35 degrees latitude, appeared to cause warming. Statistically insignificant cooling occurred between these two latitudes

Surface temperatures in open, nonforested, high-latitude areas were cooler because these surfaces reflected the sun’s rays, while nearby forested areas absorbed the sun’s heat. At night, without the albedo effect, open land continued to cool faster than forests, which force warm turbulent air from aloft to the ground.

Deforestation in the boreal region, north of 45 degrees latitude, results in a net cooling effect. While cutting down trees releases carbon into the atmosphere, it also increases an area’s reflection of sunlight (its albedo).

Deforestation and forest degradation are both a cause and a result of climate change. Plants absorb carbon dioxide and use it to grow, but when they decay or burn, carbon dioxide is released again. Decaying plants also produce methane, a greenhouse gas more potent than carbon dioxide.

So deforestation and forest degradation are doubly damaging, because greenhouse gases are released (e.g. through forest fires, or using the cut trees as firewood), while at the same time the number of carbon dioxide absorbing trees are reduced. Thirty percent of the carbon dioxide added to the atmosphere over the past 150 years is thought to come from deforestation, but this is a small amount compared to what is still stored in forests. The Canadian and Russian boreal forests alone hold 40 percent of the world’s carbon stocks.

Soil erosion, while a natural process, accelerates with deforestation. Trees and plants act as a natural barrier to slow water as it runs off the land. Roots bind the soil and prevent it from washing away. The absence of vegetation causes the topsoil to erode more quickly. It’s difficult for plants to grow in the less nutritious soil that remains.

Because trees release water vapor into the atmosphere, fewer trees means less rain, which disrupts the water table (or groundwater level). A lowered water table can be devastating for farmers who can’t keep crops alive in such dry soil.

On the other hand, deforestation can also cause flooding. Coastal vegetation lessens the impact of waves and winds associated with a storm surge. Without this vegetation, coastal villages are susceptible to damaging floods. The 2008 cyclone in Mayanmar proved this fact to catastrophic effect. Scientists believe that the removal of coastal mangrove forests over the past decade caused the cyclone to hit with much more force.


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