GLOBAL DEFORESTATION

The Fate of a Renewable Resource

Deforestation

Deforestation is the net reduction of forested area on our planet

One of the greatest forces of global environmental change (mainly over the past 200 years)

Reduced forest cover by human action has a huge impact on global biodiversity

Why We Deforestaion occurs Forests are cleared, degraded and

fragmented by: Timber harvest Conversion to Agriculture Road building Human caused fire Removal for heating and cooking fires Urban development

How Much Forest Do We Have Originally, almost half of the United

States, three-quarters of Canada, almost all of Europe, the plains of the Levant, and much of the rest of the world were forested

Currently about 34 million Km2 of forest remains

What’s Left?

About ½ of our original forests are gone Each year another 13-16 million hectares are

removed (approximately the size of Panama) 22% of the world’s old growth forest remains About ¼ of the world’s land area is still

forested Seven countries including: Russia, Brazil, USA,

Canada, China, Indonesia, Dem.Rep. Congo, account for 60% of the world’s forested land

Frontier Forests of the World

Red = Frontier Forests, 8,000 years ago

Green = Frontier Forests TodayPink = Current non-frontier forests

How Fast is it Disappearing?

Most developed Countries currently have close to zero net deforestation

Deforestation in Europe was largely completed before the end of the 1800s

Most current deforestation currently occurs in the tropic and most severely in poor countries

In Latin America and Asia deforestation rates are about 2% per year

At this rate by 2080 we will have only ¼ our current forested area

Key Definitions Deforestation: The conversion of forest to another land use or the long-

term reduction of the tree canopy cover below a 10 percent threshold. Deforestation implies the long-term or permanent loss of forest cover and its transformation into another land use.

Primary forest: is a forest that has never been logged and has developed following natural disturbances and under natural processes, regardless of its age.

Secondary forests: are forests regenerating largely through natural processes after significant human or natural disturbance, and which differ from primary forests in forest composition and/or canopy structure.

Disturbed forests: Any forest type that has in its interior significant areas of disturbance by people, including clearing, felling for wood extraction, anthropogenic fires, road construction, etc.

Frontier forests:  large, ecologically intact, and relatively undisturbed forests that support the natural range of species and forest functions (WRI definition).

Forest plantation is one established by planting or/and seeding in the process of afforestation or reforestation. It consists of introduced species or, in some cases, indigenous species.

Importance of Forests

Forest Products In many poor areas wood is still commonly used for

cooking. Building materials Furniture Pulp and paper products (including cardboard and

cellulose) Source of numerous non-wood products, including

bark, dyes, fibers, gums, incense, latexes, oils, resins, shellac, tanning compounds & waxes.  Fruits, nuts and berries are harvested as food. Maple syrup is an example of a unique non-wood product from the sap of the maple tree.

Ecosystem Services

Influences climate: captures carbon, reduces atmospheric CO2, involved with hydrologic cycle

Where forests are cut increased erosion and flooding may be issues and may result in ultimately a drier climate

Protection of soil and nutrients Foster biodiversity (loss of potentially

valuable species for medicine or agriculture)

Tropical Deforestation

about 100,000 km2 are deforested each year, and another 100,000 km2 are degraded

Estimates are constantly improving, based on satellite imagery

Causes of deforestation in the Amazon Cattle ranches 65-70% Small-scale, subsistence agriculture 20-25% Large-scale, commercial agriculture 5-10% Logging, legal and illegal 2-3% Fires, mining, urbanization, road construction,

dams 1-2%

The State of Tropical Forests In many countries the rate of

deforestation is accelerating. For example, most of the forested areas

of Bangladesh, India, the Philippines, Sri Lanka and parts of Brazil's rain forest could be gone by the end of the century.

Brazil contains about 3.5 million km2 of tropical forest. This is equivalent to 30% of the world's total

Biodiversity and the Amazon Amazonia has been characterized as the

"single richest region of the tropical biome." A single hectare of rain forest near Manaus

yielded 235 tree species over 5 cm in diameter and 179 species over 15 cm in diameter.

There are 2000 known species of fish in the waters of the Amazon Basin. This is eight times the number found in the Mississippi River system and 10 times the number found in all of Europe.

The Impact of Roads

Roads usually accompany timber harvest, in order to move logs to sawmills and markets. 

Even when tree harvest is highly selective, and much of the forest remains, it has been found that the roads themselves have numerous adverse side-effects

As forests become more open through thinning, they become drier, and more susceptible to fire

In wet areas roads become pathways for surface runoff, and carry sediments into streams, destroying aquatic life

Culverts installed where roads cross rivers often block fish passage

roads allow hunters and poachers much greater access, resulting in the large and very serious bushmeat trade

Forest fragmentation by roads in Central Africa. This study shows that 42% of forest area in the six countries is within 10 km of a road and more than 90% is within 50 km of a road

Forest Management and RecoveryRotation Harvest:the goal typically is to maximize annual

harvest while ensuring that the area harvested is consistent with forest regrowth rates and total area under management

Results in a second harvest of the same forest plot after some 60-100 years. 

The length of time between successive harvests of a forest is called the rotation length

Forest Management and RecoveryMultiple Use:Forests on federal and state lands are usually

managed according to multiple use principles

This means that in addition to forest harvest, the land is available for recreation and maintains a healthy forest ecosystem

Managing to protect biodiversity and to restore pre-settlement conditions are relatively recent goals

Forest Management and RecoveryIndigenous Use:Forests may be used by indigenous people

for: subsistence hunting forest harvest as a place to live

Forest Management and Recovery If left to nature forests will re-establish

themselves This process is called Succession and

typically takes from 50-200 years depending on tree growth rate

Tropical forest are very vulnerable as they are difficult to rehabilitate. Soil is quick to be leached of nutrients and may be lost through erosion

Restoration Vs Rehabilitation Forest restoration may seek to restore

the system to a near-natural or completely natural state, or to restore many aspects of the structure and function of an undisturbed forest

The latter is usually referred to as rehabilitation, to emphasize that the desired endpoint is not necessarily that of pre-settlement conditions

Forest Management and Fire Fire is suppressed in many forest ecosystems to:

Protect valuable commercial wood Protect human homes in or adjacent to forest Protect old growth ecosystems

In many cases fire is positive to a forest ecosystem

Some trees require fire to reproduce (jack pine) Other trees require thinning of the understory to

repopulate (Oak) Fire suppression created a build up of dry fuel This increases the intensity of a forest fire and

may cause greater ecosystem damage