Land and Water Use

Part 2

Forestry

Ecological Services1. Providing wildlife habitat2. Carbon sinks3. Affecting local climate patterns4. Purifying air and water5. Reducing soil erosion6. Providing energy and nutrient

cycling

Tree Plantations Large, managed commercial farm

with uniformly aged trees of one species

Tree Plantations Primary uses

Trees harvested by clearcutting

Tree Plantations Species choice

1. 2. 3.

Tree Plantations

Pros Cons

Easy to harvest Economical More wood

production

Little biodiversity Damage to

wetlands Much smaller

food webs Little decaying

wood

Old-Growth Forests Have not been seriously impacted by

humans Much biodiversity

Old-Growth Forests Depletion increases risk of climate

change High economic value, but mature

slowly Mahogany, oak

Old-Growth Forests

Forest Fires Each forest is unique

Number of fires Frequency of fires

Changes in Forest Fires Wild fire frequency has increased (4X

average 1970-1986) Area burned has increased (7X

previous) Wild fire season lengthened by 78

days

Reasons for Changes Appears to be linked to spring and

summer temperatures

Fire management has changed

Crown Fires Occurs where no fires

have occurred in long time

Extremely hot Burn entire tree Hop from tree to tree Kills wildlife, increases

soil erosion, destroys structures

Yellowstone 1988

Ground Fires Occur underground and burn partially

decayed leaves Common in peat bogs Difficult to detect and extinguish Summer 2008 - Pocosin Lakes National

Wildlife Refuge

Surface Fires Burns undergrowth

and leaf litter. Kills seedlings and

small trees Releases minerals

back into soil Stimulates

germination Control pathogens

and insects

Controlling Fires Prevention

Prescribed burning

Deforestation Conversion of forested areas to non-

forested areas

Deforestation Natural causes

Human reasons

Results of Deforestation

Methods to Manage and Harvest Selective cutting Strip cutting Clear-cutting

Clear Cutting

Pros Cons

Practical method for trees that require full or moderate sunlight

Genetically improved – resist disease, grow faster

Increased economic returns

Produces high yield of timber

Provides jobs

Reduces recreational value of the land

Causes soil erosion, water pollution, flooding on steeply sloped surfaces

Reduces biodiversity Decaying wood is

absent

Effect on Hydrologic Cycle Decreased evapotranspiration Lessens downwind precipitation Increased runoff to rivers/ocean

Causes of Deforestation1. Growing number of poor

2. “Open-access property rights”

3. Entrepreneurs

Forest Management Forests cover 1/3 world land surface

Most forests in N. America, S. America, Russia

Forests cover 1/3 of US 2/3 nonfederal

Forest Management Forest Service

1905 Agency of USDA Manages public land in national forests

and grasslands (193 million acres)Logging, farming, recreation, hunting,

fishing, mining, oil/gas extraction, livestock grazing