Fire, Insects, and Climate Change Can Threaten Forest Ecosystems

• Surface fires– Usually burn leaf litter and undergrowth– May provide food in the form of vegetation that sprouts after fire– Help control tree diseases and insects

• Crown fires – Extremely hot: burns whole trees– Kill wildlife– Increase soil erosion

• Introduction of foreign diseases and insects– Accidental - hemlock woolly adelgid– Deliberate

• Global warming– Rising temperatures– Trees more susceptible to diseases and pests– Drier forests: more fires– More greenhouse gases

Harmful Environmental Effects of Deforestation

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

• Deforestation• We have reduced the earth’s original forest

cover by 46% (mostly in the last 60 years)– Tropical forests (cover 6% of earth’s land)• Latin America, Indonesia, and Africa• Contains at least half of world’s species • It is estimated that ½ of remaining rainforests will

be gone in 37-117 years

• Boreal forests• Alaska, Canada, Scandinavia, and Russia

There are other sources of pulp for making trees!

• Hemp – high yield, few pesticides• Kenaf- high yield, few pesticides, fast growing

annual, absorbs more CO2 than trees

• Kudzu• Agricultural residues – wheat, barley,

bamboo, hemp, rice straw

Forests Cover 30% Of US Land Area

• Forests cover more area than in 1920!Forests cover more area than in 1920!• Many old-growth forests that were cleared Many old-growth forests that were cleared

between 1620-1920 have grown backbetween 1620-1920 have grown back• More wood is grown in the US than is cut, and More wood is grown in the US than is cut, and

the total area planted with trees increasesthe total area planted with trees increases• National Forest System= 155 national forests National Forest System= 155 national forests

managed by the US Forest Service- USFSmanaged by the US Forest Service- USFS• BUT, much of the old-growth forests have been BUT, much of the old-growth forests have been

replaced with plantations.replaced with plantations.

Tropical Forests are Disappearing Tropical Forests are Disappearing RapidlyRapidly

• Majority of loss since 1950Majority of loss since 1950• Cover 6% of land’s surfaceCover 6% of land’s surface

Where Is The Loss Occurring?• Africa• SE Asia• SA• Indonesia has lost 72% of its original forest, mostly

from illegal logging• Brazil- has 30% of world’s tropical rainforests, which

covers 60% of Brazil.

• Tropical Deforestation is the main reason that more than 8,000 known tree species are threatened with extinction

Major Causes of the Destruction and Degradation of Tropical Forests

Are Fires Natural in a Rainforest?• NO• Burning is used to clear forest areas• This burning produces patches of forest that dry out

and readily ignite• Wide spread fires in the Amazon basin are changing

weather patterns- raising temperatures, reducing rainfall

• This creates droughts and more likely to burn• This is converting tropical rainforests into tropical

grasslands• Accounts for 20% of CO2 human-related emissions

How Should We Manage and Sustain Forests?

We Can Improve the Management of Forest Fires

• The Smokey Bear educational campaign

• Prescribed fires- planned and monitored

• Allow fires on public lands to burn

• Protect structures in fire-prone areas• by thinning around

• Thin forests in fire-prone areas

• 2003 Healthy Forests Restoration Act– Pros-companies can cut trees, but must clear

brush and fire-prone trees

– Cons- not required to conduct prescribed burns after thinning process, and not

Case Study: deforestation for fuel

• ½ the wood harvested (3/4 in developing countries) is used for fuel

• Charcoal and fuelwood made from wood are used for heating and cooking.

• HAITI- only 2% of forest left, soils have eroded and crops can’t grow.

• This has lead to environmental degradation, poverty, disease, social injustice, crime and violence (a failing state)

How do we solve this problem?

• Establish small plantations of fast-growing fuelwood trees and shrubs

• Have villagers use more fuel-efficient, less-polluting wood stoves, use biogas units that run on methane, use solar ovens and electric hotplates powered by solar/wind.

• Make charcoal from fibers of waste products like sugar cane which burns cleaner