ch 10: renewable resource use

planted forests

• occupy ~31% of the earth’s land surface (excluding greenland and antartica)

old-growth forest

• uncut or regrown forest that has not been seriously disturbed by human activities or natural disasters for 200 years or more

• reservoirs of biodiversity because they provide ecological niches for a multitude of wildlife species
  

second-growth forest

• result from secondary ecological succession

• develop after the trees in an area have been removed by human activities

  • ex. clear-cutting for timber, conversion to cropland, natural forces (fires/hurricanes)

tree plantation

• aka tree farm/commercial forest

• managed forest w/ only one or two species of trees that are all the same age

• often grown on land that was cleared of an old/second-growth forest

• usually harvested by clear-cutting when they become commercially valuable

  • land is then replanted and clear-cut in a reg cycle

*when managed properly, produces wood at a rapid rate that supplies most wood used for industrial purposes

*wood is used in papermaking and construction

harms of tree plantations

• occupy 7% of the world’s forest area

• are less biologically diverse/sustainable than old/second-growth forests

• do not provide the amount of wildlife habitat/ecosystem services diverse natural forests do

• repeated cutting and replanting can deplete the nutrients in the plantation’s topsoil

  • hinders regrowth of any type of forest on the land

forests ecosystem services

1. supports energy flow and chemical cycling

2. reduces soil erosion

3. absorbs and releases water

4. purifies water and air

5. influences local and regional climate

6. stores atmospheric carbon

7. provides numerous wildlife habitats

forests economic services

1. fuelwood

2. lumber

3. pulp to make paper

4. mining

5. livestock grazing

6. recreation

7. jobs

logging roads

1. first step is to build roads for access and timber removal

   1. even carefully designed logging roads have harmful effects (topsoil erosion, sediment run-off into waterways, habitat loss, biodiversity loss)

   2. logging roads also open up forests to disturbances from human activities (mining, farming, ranching)

selective cutting

• cutting intermediate-aged or mature trees individually OR in small groups

• leaves the forests largely intact

• allows forest to produce economically valuable trees on a sustainable basis if trees are not removed faster than they can grow back

clear-cutting

• removing all the trees from an area

• most efficient and majorly the most cost-effective way to harvest trees

• provides profits in the shortest time for landowners and timber companies

*causes forest soil erosion, sediment pollution of nearby waterways, losses in biodiversity

*releases stored CO2 into the atmosphere, reduces uptake of CO2 by forests, alters natural carbon cycle

strip cutting

• allows a more sustainable timber yield without widespread destruction

• involves clear-cutting a strip of trees along the contour of the land narrow enough to allow natural forest regeneration within a few years

• after regeneration, loggers cut another strip, and so on

deforestation

• temp or permanent removal of large expanses of forest for agriculture, settlements, other uses

• has eliminated almost half of the earth’s old-growth forest cover

  • majorly occurred within the last 65 years

• WRI predicts that if deforestation rate continues, 40% of the world’s remaining forests (esp tropical) will be logged/converted to other uses within two decades

harms of deforestation

• water pollution and soil degradation from erosion

• acceleration of flooding

• local extinction of specialists species

• habitat loss for native and migrating species

• release of CO2 and loss of CO2 absorption

• can lead to drier conditions that dehydrate topsoil, exposes it to sunlight, allows it to be blown away

  • makes it difficult for a forest to grow back in an area

tropical forests

• absorb and store ~1/3 of the world’s terrestrial carbon emissions

• reducing these forests means reduced CO2 absorption = atmospheric warming/climate change

• water evaporating from trees and vegetation in tropical rainforests determine rainfall percentage in the area

• when loggers here cut one tree, many other trees often fall bc of their shallow roots and network of vines connecting them to the forest’s canopy

logging companies

• often sell land after harvested trees in an area for cattle grazing

  • after a few years, the land is overgrazed

  • ranchers sell the degraded land to farmers who plow it up to plant large crops (soybeans) OR to settlers for small-scale farming

*after a few years of crop growing and erosion from rail, the topsoil is depleted of nutrients, then the process is repeated

tropical deforestation

• is caused by pressures from population growth and poverty push subsistence farmers and the landless poor into tropical forests

  • where they cut or burn trees for firewood or try to grow enough food to survive

• also caused by fuelwood crisis

  • less-developed countries use fuelwood and charcoal made from wood for heating and cooking

*government subsidies can accelerate large-scale logging and livestock overgrazing by reducing the costs of these enterprises.

surface fire

• usually burns only undergrowth and leaf litter on the forest floor

  • kills seedlings and small trees, but spares most mature trees and allows most wild animals to escape

benefits of surface fires

• burn flammable material such as dry brush to help prevent fires that are more destructive.

• free valuable plant nutrients trapped in slowly decomposing litter and undergrowth.

• release seeds from the cones of tree species such as lodgepole pines and stimulate the germination of other seeds such as those of the giant sequoia.

• help control destructive insects and tree diseases.

crown fire

• extremely hot fire that leaps from treetop to treetop

• burns whole trees

• usually occurs in forests that have not experienced surface fires for several decades

• absence of fire allows dead wood, leaves, flammable ground litter to accumulate

*fires spread rapidly, destroy most vegetation, kill wildlife, increase topsoil erosion, burn/damage buildings and homes

limiting harms of forest fires

1. using prescribed burns to remove small trees and underbrush in high-risk forest areas

2. allow fires on public lands to burn underbrush and smaller trees

3. protect houses and other buildings in fire-prone areas by thinning trees and other vegetation in zone around them, eliminating use of highly flammable construction materials (ex. wood shingles)

4. use drones w/ infrared sensors to detect forest fires and monitor progress in fighting them

sustainable forestry

1. Include ecosystem services of forests in estimates of their economic value

2. Identify and protect highly diverse forest areas

3. Stop logging in old-growth forests

4. Stop clear-cutting on steep slopes

5. Reduce road-building in forests and rely more on selective and strip cutting

6. Leave most standing dead trees and larger fallen trees for wildlife habitat and nutrient cycling

7. Put tree plantations only on deforested and degraded land

8. Certify timber grown by sustainable methods

*phasing out of gov subsidies and tax breaks and into forest-sustaining subsidies and tax breaks

*using alternative fibers from non-tree sources to make paper

*reduces the use of throwaway paper products

grasslands

• cover ~1/4 of the earth’s land surface

• ecosystem services: soil formation, erosion control, chemical cycling, atmospheric carbon dioxide in biomass, and maintenance of biodiversity

rangelands

• unfenced natural grasslands in temperate and tropical climates that supply forage, or vegetation for grazing (grass-eating) and browsing (shrub-eating) animals

pastures

• managed grasslands or fenced meadows often planted with domesticated grasses or other forage crops such as alfalfa and clover

*as long as only the upper portion of the blade is eaten and the lower portion remains in the ground, rangeland grass is a renewable resource that can be grazed repeatedly

*moderate levels of grazing are healthy for grasslands, because removal of mature vegetation stimulates rapid regrowth and encourages greater plant diversity.

overgrazing

• occurs when too many animals graze an area for too long and damage or kill the grasses and their roots exceed the area’s carrying capacity for grazing

*reduces grass cover, exposes topsoil to erosion by water and wind, compacts the soil (lessens its capacity to hold water)

*promotes the invasion of plant species (sagebrush, mesquite, cactus, cheatgrass) which cattle won’t eat

managing grasslands sustainably

• control how many animals are grazing and for how long

rotational grazing

• small groups are confined by portable fencing to one area for a few days and then moved to a new location

• leads to natural restoration by ecological succession

*ranchers can also move cattle around by providing supplemental feed at selected sites and strategically locating watering ponds/tanks and salt blocks

riparian zones

• areas where cattle prefer to graze around ponds and other natural water sources (streams/rivers)

• overgrazing destroys riparian zones

designated wilderness areas

• undisturbed by humans and are protected by federal law from harmful human activities

ecological restoration

1. replanting forests

2. reintroducing keystone native species

3. removing harmful invasive species

4. freeing river flows by removing dams

5. restoring grasslands, coral reefs, wetlands, and stream banks

restoration

• returning a degraded habitat or ecosystem to a condition as similar as possible to its original one

rehabilitation

• turning a degraded ecosystem into a functional or useful ecosystem without trying to restore it to its original condition

*removing pollutants from abandoned industrial sites and replanting trees to reduce soil erosion in clear-cut forests

replacement

• replacing a degraded ecosystem with another type of ecosystem

*a degraded forest could be replaced by a productive pasture or tree plantation

creating artificial ecosystmes

• ex. artificial wetlands have been created in some areas to help reduce flooding and to treat sewage

restoration and rehabilitation

1. dentify the causes of the degradation, such as pollution, farming, overgrazing, mining, or invasive species.

2. Stop the degradation by eliminating or sharply reducing these factors.

3. Reintroduce keystone species to help restore natural ecological processes, such as reintroducing the gray wolf to Yellowstone National Park

4. Protect the area from further degradation to allow natural recovery

sustainable terrestrial biodiversity

1. Plant trees and take care of them

2. Recycle paper and buy recycled paper products

3. Buy sustainably produced wood and wood products and wood substitutes such as recycled plastic furniture and decking

4. Help restore a degraded forest or grassland

5. Landscape your yard with a diversity of native plants