1Y11 Geography

DeforestationDeforestation

Causes and effects

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Aims and objectivesAims and objectives

• 1. What is deforestation?

• 2. Why have tropical rainforest been cleared?

• 3. What are the impacts of deforestation?

• 4. Are there ways to manage the rain forest in a sustainable way?

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Where the forests areWhere the forests are

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• Deforestation is cutting down tress – not just cutting down forests – as we saw last term cutting down trees in the savannah is called that too – even though the savannah can hardly be called a forest.

• Many primary forests in temperate countries have almost disappeared after centuries of logging or land clearance for farming, industry and housing. But it is relatively recently that large scale deforestation has taken place in the tropical forests.

• Meanwhile there are some temperate areas where reforestation is taking place.

• The speed of deforestation has raised alarm with the scientists and conservationists. What are they concerned about?

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What are the scientists and What are the scientists and conservationists concerned about? conservationists concerned about?

• Biodiversity is a major concern. Rainforest are one of the most biologically diverse regions of the world.

• Over a million species of plants and animals are known to live in the forests and millions more are not classified.

• The unique environment of the rainforest allows for such biodiversity to exist. It is a very special place.

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The AmazonThe Amazon• Is a tropical

rainforest, so the climate tend to indicate rain on a daily basis and a steady temperature throughout the year, that is hot but not excessively so – high 20’s rather than mid 30’s degrees C.

• Vegetation see right

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• The Amazon rainforest, world's largest remaining natural resource, represents 54% of the total rainforests left on Earth.

• It covers an area of 6.5 million square kilometres, embracing nine South America countries: Brazil, Colombia, Peru, Venezuela, Ecuador, Bolivia and the Guianas - Guyana, French Guiana and Suriname, or two thirds of the South America continent.

• The uses to which the Amazon is listed as being put included logging, ranching, roads and urban development, large HEP scheme and according to textbook palm oil! No mention of soya farming for cattle feed and biofuels! Palm oil really does not figure, although Malaysian multinationals would love to start as the potential is huge, but thus far it is still on the drawing board. Also according to the textbook, deforestation has been caused by extracting plants for medicinal use! Really? I thought collecting medical supplies was seen as sustainable? (see slides 23-25)

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What are causes of deforestation in What are causes of deforestation in tropical rain forests?tropical rain forests?

• Logging;

• Ranching;

• Farming;

• Road building;

• Mining;

• HEP schemes

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What do the governments think about What do the governments think about it?it?

• Some of the logging is illegal• But in many case the governments encourage it. • Often these are LICs with few ways of raising

money • So the temptation to pay off debts and increase the

standard of living of their people is a hard one to pass up

• What do they gain from allowing deforestation? Revenue from timber, drugs (legal ones) and minerals –

and more recently exports of animal feed (soya) and biofuels (palm oil)

Land to house and feed their increasing population

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Issues that arise with Issues that arise with deforestationdeforestationin the Amazonin the Amazon

• Includes flooding, increase of CO2 in the atmosphere, bare soil looses nutrients (leaching), biodiversity loss and displacement of native Americans

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In additionIn addition•Mining pollutes rives and gold mining

uses mercury which is highly toxic•Roads, to the soya farms for example,

create great scars through rainforest and give easier access and lead to unplanned settlements.

•Loggers only want the valuable trees – this leads to needless destruction of large areas for only few trees.

•Cattle ranching leads to destruction of the rain forest and soil erosion of bare soils.

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So what are the main impacts of So what are the main impacts of increased deforestation?increased deforestation?

• The impact of deforestation on a large scale can be divided in two

• Local Impacts are those that affect the immediate area from where the trees are being removed.

• Worldwide/International Impacts are those aspects which affect everyone everywhere.

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What are the local impacts of What are the local impacts of increased deforestation?increased deforestation?

• Local Climate Change • When an area of rainforest is either cut down or destroyed, there are

various climate changes that happen as a result. The following is a list of the various climate changes with a brief description of why they come about.

• Desiccation of previously moist forest soil • What happens is because of the exposure to the sun, the soil gets

baked and the lack of canopy leaves nothing to prevent the moisture from quickly evaporating into the atmosphere. Thus, previously moist soil becomes dry and cracked.

• Dramatic Increase in Temperature Extremes• Trees provide shade and the shaded area has a moderated

temperature. With shade, the temperature may be 37 degrees Centigrade during the day and 16 degrees at night. With out the shade, temperatures would be much colder during the night and around 54 degrees during the day.

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What are the local impacts of What are the local impacts of increased deforestation?increased deforestation?

• Moist Humid Region Changes to Desert • This is related to the desiccation of previously moist forest

soil. Primarily because of the lack of moisture and the inability to keep moisture, soil that is exposed to the sun will dry and turn into desert sand. Even before that happens, when the soil becomes dry, dust storms become more frequent. At that point, the soil becomes useless.

• Soil Erosion • Deforestation contributes to run-off of rainfall and intensified

soil erosion. Bare ground, with little added humus, increase the rate of sheet and gulley erosion.

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What are the local impacts of What are the local impacts of increased deforestation?increased deforestation?

• Changes in rainfall pattern• The daily rainfall common in many parts of tropical rainfall is

called convection rainfall.• Heavy rainfall in these areas occurs frequently in the

afternoon. Why?• When it rains, the trees intercept much of the water, slowing

its rate of descent, allowing much of it to percolate into the soil as the ground is shaded and so much cooler than the air above. Much of the water that has percolated the soil will be taken in by the roots of trees and shrubs, which will transpire it into the atmosphere in first part of the day when the sky is clear and so the temperature rises. This warm moist air rises in the atmosphere and eventually cools and condenses into clouds in time for the next teatime downpour

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Every morning

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Every Afternoon

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About 4 o’clock nearly every day

animated version of this is on the wiki under the lesson files

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So what happens when the trees are So what happens when the trees are cut down?cut down?

• The shrinking forest cover that there are no longer trees to intercept, retain and transpire precipitation.

• The deforested areas become sources of surface water runoff, which moves much faster than subsurface flows and can cause flash flooding and more localized floods than would occur with the forest cover.

• With decreased evapotranspiration, atmospheric moisture is reduced the regular rainfall is reduced.

• According to one preliminary study, in deforested north and northwest China, the average annual precipitation decreased by one third between the 1950s and the 1980s.

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What are the international impacts of What are the international impacts of increased deforestation?increased deforestation?

• Less Carbon Dioxide and Nitrogen Exchange • The rainforests are important in the carbon dioxide

exchange process. They are second only to oceans as the most important "sink" for atmospheric carbon dioxide. Deforestation may account for as much as 10% of current greenhouse gas emissions. Greenhouse gases are gases in the atmosphere that literally trap heat. There is a theory that as more greenhouse gasses are released into the atmosphere, more heat gets trapped. Thus, there is a global warming trend in which the average temperature becomes progressively higher.

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A summaryA summary

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• Tropical rainforests, which account for only seven percent of the world’s total land mass, harbour as much as half of all known varieties of plants. Experts say that just a four-square-mile area of rainforest may contain as many as 1,500 different types of flowering plants and 750 species of trees, all which have evolved specialized survival mechanisms over the millennia that mankind is just starting to learn how to appropriate for its own purposes.

• Rainforests are a Rich Source of MedicinesScattered pockets of native peoples around the world have known about the healing properties of rainforest plants for centuries and perhaps longer. But only since World War II has the modern world begun to take notice, and scores of drug companies today work in tandem with conservationists, native groups and various governments to find, catalogue and synthesize rainforest plants for their medicinal value.

Medicines and RainforestsMedicines and Rainforests

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• Rainforest Plants Produce Life-saving MedicinesSome 120 prescription drugs sold worldwide today are derived directly from rainforest plants. And according to the U.S. National Cancer Institute, more than two-thirds of all medicines found to have cancer-fighting properties come from rainforest plants. Examples abound. Ingredients obtained and synthesized from a now-extinct periwinkle plant found only in Madagascar (until deforestation wiped it out) have increased the chances of survival for children with leukemia from 20 percent to 80 percent.

• Some of the compounds in rainforest plants are also used to treat malaria, heart disease, bronchitis, hypertension, rheumatism, diabetes, muscle tension, arthritis, glaucoma, dysentery and tuberculosis, among other health problems. And many commercially available anaesthetics, enzymes, hormones, laxatives, cough mixtures, antibiotics and antiseptics are also derived from rainforest plants and herbs.

Medicines and RainforestsMedicines and Rainforests

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• The Untapped Potential of Rainforest MedicinesDespite these success stories, less than one percent of the plants in the world’s tropical rainforests have even been tested for their medicinal properties. Environmentalists and health care advocates alike are keen to protect the world’s remaining rainforests as storehouses for the medicines of the future.

• The Challenge of Preserving Valuable RainforestsBut saving tropical rainforests is no easy task, as poverty-stricken native people try to eke out a living off the lands and many governments throughout the world’s equatorial regions, out of economic desperation as well as greed, allow destructive cattle ranching, farming and logging. As rainforest turns to farm, ranch and clear-cut, some 137 rainforest-dwelling species—plants and animals alike—go extinct every single day, according to noted Harvard biologist Edward O. Wilson. Conservationists worry that as rainforest species disappear, so will many possible cures for life-threatening diseases.

Medicines and RainforestsMedicines and Rainforests

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HomeworkHomework• You have met the issues.• Our Case study will be the Amazon.• Research these questions• Qu 1: What are the main causes of deforestation in the

Amazon? (figures and/or graphs if you can)• Qu 2: What are the main impacts of deforestation in the

Amazon?• Next week, we will look at what can be done about all

this. How the rainforest can be managed, how international objectives like REDD and NGOs such as the Rainforest Alliance try to cope and individual efforts help reduce deforestation and help improve the lives of those living there, by increasing sustainable economic activity.