Forest Resources

Types of timber harvesting & sustainable management

What types of forests are there?

Old-growth forest: Original forests that have not been disturbed for logging, road building, or development• Sometimes called primary,

ancient, virgin, or primeval forests

• 36% of world’s forest• High biodiversity

Second-growth forest:

Area which has re-grown after a major disturbance such as fire, insect, or timber harvest

60% of world’s forest

Happens by natural “succession” -small shrubs and trees followed by the larger trees

Forests Vary in Their Make-up, Age, and Origins

Tree plantation (tree farm): Planted stands of a particular tree species that are maintained, harvested, and replanted• Typically used for paper or particle board

Forests Vary in Their Make-up, Age, and Origins

What are forests good for?

Estimated annual value:

Economic services

$1.8 trillion

Ecological services

$4.7 trillion

Three major tree harvesting methods:• Selective cutting• Clear-cutting• Strip cutting• Seed tree/shelterwood

How are trees cut?

Selective Cutting:• Mature trees are

harvested individually from diverse forests

• Younger trees left to harvest later

• Reduces crowding• Removes diseased trees• Encourages growth of

younger trees

Selective cutting

Clear-cutting

Clear-cuttingClear-cutting::• Removing all trees Removing all trees

in a single pass.in a single pass.

Clear-cuttingClear-cutting

Clear-cutting

Strip-cutting

Strip-cuttingStrip-cutting::• A type of clear cutting that A type of clear cutting that

involves clear trees along involves clear trees along the contours of the land.the contours of the land.

• Less erosionLess erosion

Other ways forests can be destroyed

Forest fire

Insect damage (mountain pine beetle in BC)

Disease (Dutch elm disease in Ottawa)

Forest fires can either benefit or harm forests• Burn away flammable ground material• Prevent larger, more destructive fires• Release valuable mineral nutrients• Stimulate new forest growth

Fire Can Threaten Forest Ecosystems

Surface fires• Usually burn leaf litter and undergrowth• May provide food in the form of vegetation that sprouts after fire

Crown fires • Extremely hot, burns whole trees, jump from treetop to treetop• Fierce and hard to control

Forest fires continued

Insect damage

Issues in forestry

Human activities have reduced the earth’s forest cover by as much as half.

Deforestation – temporary or permanent removal of large areas of forests• Results from unsustainable cutting of trees

Where is deforestation an issue? Developing countries – used for fuel, wood in tropical

forests used by international logging companies

Developed countries – boreal forests used for timber and paper

Unsustainable Logging is a Major Threat to Forest Ecosystems

Building roads into previously inaccessible forests paves the way for increased erosion, habitat fragmentation, loss of biodiversity, and invasion by non-native species.• For this reason, many federal wilderness areas do

not allow the construction of roads.

We Have Cut Down Almost Half of the World’s Forests

Poor soil in tropical forests

Run-off

Not much can grow after gain

Tropical Forests Are Disappearing Rapidly

Are there solutions?

We can use forests more sustainably by emphasizing:• Economic value of

ecological services• Harvesting trees no

faster than they are replenished

• Protecting old-growth and vulnerable areas