World Geo 3200/3202March 2011

Outcomes4.6.1 Compare the terms clear-cutting and selective

cutting. (k)4.6.2 Compare the advantages and disadvantages

of each approach to the harvesting of timber. (k)4.6.3 Examine major threats to forest resources. (a)4.6.4 Examine strategies for a sustainable forestry.

(a)4.6.5 Evaluate a position taken on a given argument

about timber harvesting. (i)4.6.6 Infer a relationship between climate and the

extent of forest cover. (a)4.6.7 Analyze global patterns in the depletion of

forest resources. (a)

Impact of Climate on Forests There are many aspects of climate that

impact on forest development, some are discussed here, while you will investigate others through your readings.

PrecipitationForests require a large amount of water. 

Consequently, one of the greatest factors that determine whether a forest will grow in a region is amount of precipitation.

A). Tropical areas with high rainfall have tropical rain forests. 

B). Tropical areas that have discontinuous rainfall have savannahs because there is not enough water to support trees and a forest. 

SeasonsTemperate regions of the world often have

deciduous trees to help them deal with the lack of water availability in winter.  Some regions have dry seasons and they have deciduous trees even though it does not get "cold." 

Seasons The type of trees and forest present in a region

is determined by the climate. 

Trees have adapted to climate just as animals have. 

For example, the needle leaf trees of the coniferous forests are adapted to deal with winter and the lack of available water in winter.  Both the tropical regions of the world and the sub arctic regions of the world have evergreen trees.

Diversity Colder regions tend to have less biodiversity

(The number of different species in a given habitat) while tropical regions tend to have greater biodiversity. 

The same is true of trees. 

Tropical forests tend to be a blend of many different species, while coniferous forests tend to be "pure stands" of one type of tree.

Work Time!!!!!!Read pgs. 162- 163 and answer #’s 1-4

DeforestationApproximately one-third of the earth's land

masses are covered in forest. 

The forest provides much for nature and mankind. 

Biodiversity, habitats for animals, food for animals, air purification and water retention are some of the values of our worlds forests. 

Man has always made use of the forests and the trees for things like recreation, building materials, home heat and paper.

DeforestationFor many decades we have used the forest

without regard for the sustainability of forests. 

Will coming generations have a forest to rely on? 

Are we allowing deforestation to occur at a rate faster than it can replace itself?

DeforestationThe clearance of

forest by cutting and or burning.

Why are we using so much forest resource?

Some reasons for extensive deforestation include:

expanding needs in agriculture; urbanization; mining operations; hydroelectric operations;

ExamplesIn Africa forests are being cleared to make room

for subsistence farming to support the growing population.

Latin America has cleared forests for major hydroelectric projects to provide stable electrical supplies to an increasing number of people.  Large scale cattle ranches and urbanization have also been the cause of deforestation in Latin America.

Asia's growing population means that more forest is cleared for housing and for agricultural land to feed the people.

In the activities section  of this lesson you will use a world map showing deforestation trends.  It is important that you be able to interpret this type of map as shown on p. 164 figure 10.2.

Assigned Work Read "deforestation" p. 163 Complete questions 5-7 p. 163-164

Clear cutting and Strip CuttingClear Cutting: is a

form of forest harvesting that removes all trees from an area.  Marketable trees and undesired trees alike are cleared and the land is left uncovered. 

Strip cutting: is actually a variation on clear cutting where strips of forest are left between the clear cut areas.

Selective cuttingSelective cutting:

is a form of forest harvesting that removes only the desired trees and leaves the other trees in place.  Immature trees, undesired species and underbrush is all left intact. 

Clear cutting vs. Selective CuttingClear cutting has the advantage of being

economical and safe whereas selective cutting has the advantage of leaving the ecosystem intact. 

There have been raging debates over the type of cutting that should occur in the forest industry. 

Sustainable ForestrySustainable Forestry: is simple and complex. 

The basic idea is simple.  If we cut trees faster than they grow back, we will run out of trees. 

However, as the world's population increases so does the demand for forestry products and so does the demand for forestry land to be converted to housing, mining, and hydro-electricity projects.

Sustainable ForestryIn the past we have looked at the forest as an

endless resource.  Now we realize we must manage the forest for the forestry industry and many other things. 

Biodiversity, hunting, hiking, camping, habitat protection and many other things are all considerations.

Sustainable Forestry and the Systems Model If we look at sustainable forestry from a

"Systems Model" perspective we can see that we have three options:

1) Improve what we input into forestry (replanting & seedlings)

2) Improve processes like: i. road construction ii. harvesting techniques iii. environmental protection actions iv. reducing losses (use all of the tree)

3) Reduce the need of output product i.  Recycle ii. Use of alternate building materials

Clear Cutting Controversy

Clear Cutting ControversyA bitter debate over cutting B.C.'s old-

growth forests

The war in the Clayoquot woods is over

Protesters leave Clayoquot Sound