chapter 12 biodiversity: preserving landscapes...history of us forests • 1897 – forest...
TRANSCRIPT
1
Chapter 12
BIODIVERSITY:
PRESERVING
LANDSCAPES
2
OUTLINE
• WORLD FORESTS
DEFORESTATION
OLD GROWTH
HARVEST METHODS
• GRASSLANDS
• PARKS AND PRESERVES
TERRESTRIAL
MARINE
3
WORLD FORESTS
• A FOREST is any area where trees cover more than 10% of the land.
SAVANNAS - trees cover less than 20% of ground
CLOSED CANOPY - tree crowns cover most of ground
• Most remaining forests are in tropical and boreal (taiga) regions.
• Highest rates of forest loss in Africa and South America
• Largest tropical forest is the Amazon
4
WORLD FORESTS ECOLOGICAL SERVICES
• CARBON SINK for carbon dioxide
• MOISTURE from transpiration contributes to
global rainfall. (water cycle)
• OLD GROWTH FORESTS - cover large areas
and have been undisturbed by humans long
enough that trees can live out a natural life
cycle and ecological processes are normal
Home to much of world’s biodiversity,
endangered species and indigenous people
¾ found in Russia, Canada, Brazil,
Indonesia, Papua New Guinea
5
WORLD FORESTS ECOLOGICAL SERVICES
• Habitat for species which creates utilitarian uses:
camping, bird watching, hunting
• Cool air surrounding the forest by
evapotranspiration and shade
• Forests serve as watersheds
• Parts of biogeochemical cycles
(especially: nitrogen/carbon/water)
• Roots reduce runoff and decrease erosion
6
GLOBAL LAND USE
Other: cities, arid
areas, tundra
& wetlands
7
MAJOR FOREST TYPES
8
UTILITARIAN FOREST USES
• WOOD AND PAPER
Developed countries provide less than half of industrial wood, but 80% of consumption.
Paper pulp is 1/5 of all wood consumption.
In developing countries fuel (wood/charcoal) accounts for 1/2 of global wood use.
One quarter of world’s forests are managed for wood production, much of it in single species monoculture forestry.
Many developing countries sell exotic woods (teak, mahogany) to developed countries.
Mining and rangeland use also damage forests
9
FOREST MANAGEMENT
• FOREST MANAGEMENT: science of
maintaining a forest for sustainable harvests
• EVEN-AGED: all trees are same size/age
MONOCULTURE: single species which
increases pests and decreases
biodiversity, usually clearcut
• UNEVEN-AGED: trees are different
ages/sizes, usually different species.
Increases biodiversity, decreases pests &
erosion, trees are selectively cut
10
TROPICAL FORESTS ARE BEING CLEARED
• Tropical forests occupy less than 10% of land
surface but contain half of all species.
• FAO estimates that 12.3 million ha are
deforested every yr, the equivalent of one
football field every second.
11
CAUSES OF DEFORESTATION
• CONVERSION OF FOREST TO AGRICULTURE
Accounts for 2/3 of destruction in tropics
SLASH & BURN – aka: Milpa or Swidden
- cut/burn small areas & use for a few years
then let return to forest
- Slash & Burn can be sustainable if
populations are small and plots are left
alone for many years. Repeated cropping
over time leads to permanent damage.
- Usually multiple crops are grown at the
same time, harvested separately
12
EFFECTS OF DEFORESTATION
• As forests are cleared, plant transpiration and
rainfall decrease.
• This leads to drought & erosion.
• Drought kills more vegetation.
• Fires become more numerous and extensive.
• More of the forest is then lost.
13
FOREST PROTECTION
• Some places are being reforested (U.S. and China have had greatest gains.)
• About 12% of world’s forests are protected.
• With industrialization, countries become developed, deforestation decreases and forests are protected instead for other uses
• DEBT FOR NATURE SWAPS - conservation organizations/banks buy debt obligations, then offer to cancel the debt if the debtor country protects biologically important areas
14
FORESTS HAVE COMPETING USES
• U.S. Forest Service managed for “multiple uses”
but many were conflicting e.g. bird watching and
dirt biking.
• OLD GROWTH FORESTS VS. LOGGING
Less than 10% of old growth forest remains in
U.S. and 80% of that is scheduled to be
logged.
Spotted owl vs. logging jobs
Compromise forest management plan allows
some logging, but protects some prime
habitat. May not be enough to save the salmon
and steelhead trout in northwestern rivers.
15
OLD GROWTH FOREST • Temperate rainforest and the spotted owl.
• 2,000 owl pairs remain in the old growth forests
of the Pacific Northwest.
• Salmon & trout need pristine rivers to spawn
16
HARVEST METHODS
• ALL HARVEST METHODS REQUIRE ROADS
Building roads to remove trees also allows
entry to forest by farmers, miners, hunters.
Lead to increased erosion, soil compaction, increased runoff of sediment into rivers
Sedimentation of rivers reduces biodiversity and decreases spawning
• CLEAR CUTTING – most popular with logging companies.
• Every tree in an area is cut regardless of size
• Increases erosion and decimates habitat
• Loss of recreational space
• Can be replanted or go through succession
17
HARVEST METHODS
• SHELTERWOOD HARVESTING - mature trees are removed in a series of two or more cuts
• STRIP CUTTING - all the trees in a narrow corridor are harvested
• COPPICING – leaving stumps to regenerate (a few species can do this: oak, maple, ash)
• SEED TREE CUTTING – clear cutting but leaves a few trees to reproduce and drop seeds
• SELECTIVE CUTTING - only a small percentage of the mature trees are taken in each 10 to 20 year rotation (best method environmentally)
18
HARVESTING – CLEAR CUTTING
Clear cutting (removal of all trees) in Washington’s
Gifford Pinchot National Forest.
19
SELECTIVE HARVEST
COPPICING STRIP CUTTING
SHELTERWOOD HARVEST
20
LOGGING ON PUBLIC LANDS?
• Some are calling for an end to all logging on
public lands.
Lands provide ECOLOGICAL SERVICES such
as clean water, rivers for fish, irrigation,
recreation. Worth $224 billion.
Federal government builds roads, manages
forests, fights fires and then sells the timber
to logging companies for less than their
costs. This is a subsidy for the logging
industry. Worth $4 billion.
21
HISTORY OF US FORESTS
• 1897 – Forest Management Act – created
Forest Reserves for timber, mining & grazing
• 1905 – US Forestry Service forest reserves
are now national forests
• 1960 – Multiple Use Sustained Yield Act
replaced FMA. Requires forests to be
managed for lumber, recreation and wildlife
• USFS sells logging rights to timber
companies (highly subsidized)
22
LOGGING ON PUBLIC LANDS?
• Timber companies claim logging produces
jobs, supports rural communities, keeps forests
healthy.
• Roads on public lands are another controversy.
Economists argue it opens up land for
motorized recreation and industrial uses.
Wildlife supporters see it as disruptive.
• Clinton protected 23.7 million ha of wilderness
from roads; Bush overturned this and ordered
expedited logging and mining. Obama
protected additional lands.... Trump?
23
FIRE MANAGEMENT
24
FIRE MANAGEMENT
• U.S. adopted a policy of aggressive fire control
in the 1930s.
• Recent studies indicate many biological
communities are fire-adapted and require
periodic burning for regeneration.
• Eliminating fires has caused woody debris to
accumulate over the years. Fires are now larger
and more severe.
• 40 million Americans now live in areas of high
wildfire risk.
• Collection of debris and small prescribed fires
can prevent large scale fires
25
ECOSYSTEM MANAGEMENT
• Ecosystem management attempts to integrate
sustainable ecological, economic, and social
goals in a unified systems approach.
Managing across whole landscapes over ecological time
scales
Considering human needs and promoting sustainable
economic development
Maintaining biological diversity and ecosystem processes
Utilizing cooperative institutional arrangements
Generating meaningful stakeholder and public
involvement and facilitating collective decision making
Adapting management over time based on conscious
experimentation and routine monitoring.
26
SUSTAINABLE FORESTRY
• Consumers can make better choices &
demand sustainable products
Home Depot – all wood is sustainably
raised and managed
Staples uses 30% recycled paper in many
of their products
• Forests can be used sustainably for other
products: nuts, fruits, mushrooms, latex
(rubber) and chicle (gum) that doesn’t
remove the trees
27
GRASSLANDS
• Occupy about 1/4 of world’s land surface
(prairies, savannas, steppes, open woodlands)
• Frequently converted to cropland, urban areas, or other human use
• More threatened plants in rangelands than in any other American biome
• Can be used sustainably
PASTORALISTS move their animals to adjust to variations in rainfall and seasonal conditions. Reducing negative impact on land
28
RANGELAND vs PASTURE
• RANGELANDS - have natural vegetation
managed by grazing, usually dry/poor for
agriculture
• PASTURES - have forage that is adapted for
livestock and managed, by seeding, mowing,
fertilization and irrigation.
• OVERGRAZING – results from too many
animals on the land for too long a period of
time. Plant roots die and soil compaction
occurs. Often overgrazed areas lead to
DESERTIFICATION
29
OVERGRAZING
• 15% of US livestock feed on native grasslands.
• 90% of US grain crop (corn, alfalfa, oats) is used to feed livestock
• 75% of rangelands in the world are degraded; one-third of that is due to overgrazing.
• 55% of U.S. public lands are in poor condition due to overgrazing.
• Grazing fees charged for use of public lands are below market value and represent a hidden subsidy to ranchers.
• Ranchers claim that without a viable ranch economy, western lands would be further subdivided.
30
NEW GRAZING METHODS
• ROTATIONAL GRAZING - encloses livestock in
a small area for a short time within a movable
electric fence to force them to eat vegetation
evenly and fertilize (manure) the area evenly.
• Can raise wild species such as bison or elk,
which forage more efficiently and fend off
predators, diseases and pests better than cattle
• Grazing multiple species together is beneficial
as each eats a different type or part of the plant.
31
PARKS AND PRESERVES 12% OF EARTH’S LAND AREA IS PROTECTED.
32
PARKS AND PRESERVES
• In the developing world, some parks exist only
on paper because they do not have money for
staff and management.
• Brazil has the largest protected area 19% of its
land. With more than 25% of the world’s
tropical forests, Brazil is especially important to
biodiversity.
• US has 16% of its land in “protected” status.
2/3 is sustainable use public lands
33
PRESERVES NOT SAFE FROM
EXPLOITATION
• Excessive stock grazing in Greece
• Dam building in Columbia
• Oil drilling in the Amazon
• Mining & Logging – in Peru
• Coral reefs in Palau damaged by dynamite
fishing
• Eggs from endangered sea turtles are taken by
hunters in Indonesia
• Overuse by the public – Yellowstone, Zion,
Grand Canyon – very popular, but create issues
34
OVERUSE OF NATIONAL PARKS IN U.S.
• Entertainment trumped nature protection.
• Fire suppression resulted in large fires.
• Traffic congestion
• Surrounding areas clear cut or mined
• Air pollution and smog
• Parks are profitable, but do not get to keep the money they generate.
35
HISTORY OF US NATIONAL PARKS
• 1872 – President Grant established first
national park in the world – Yellowstone
• 1912 – US National Park System was created
• 1916 – National Park Service (Dept. of
Interior) was created. Stephen Mather was
first director.
• Currently there are 388 parks ranging from
national parks to historic sites, to memorials
and recreation areas
36
WILDERNESS AREAS
• Areas of undeveloped land, undisturbed by
human activities that people can visit but can
not inhabit.
• 1964 – Wilderness Act – allows public areas to
be protected
WILDLIFE REFUGES
• 1901 – Theodore Roosevelt – started the
National Refuge System. 545 now exist.
• Managed for multiple use (camping, hiking,
fishing, hunting, mining, etc.)
• Arctic National Wildlife Refuge (ANWR) in
Alaska has been debated for oil drilling
37
WORLD CONSERVATION STRATEGY
• Developed by the IUCN
Has 3 objectives:
Maintain essential ecological processes and
life support systems
Preserve genetic diversity essential to
improving cultivated plants and domestic
animals
Ensure that utilization of wild species and
ecosystems is sustainable.
38
MARINE ECOSYSTEMS NEED PROTECTION
• Global fish stocks are becoming depleted and biologists are calling for protected areas where species can be sheltered.
20% of nearshore territory should be marine refuge area.
Refuge can replenish nearby areas.
• Coral reefs are threatened by rising temperatures, destructive fishing, coral mining and sediment runoff.
If conditions persist, all will be gone in 50 years.
39
MARINE ECOSYSTEMS NEED PROTECTION
• Australia has the largest marine reserve in the
Great Barrier Reef.
• The U.S. 13 underwater parks such as the
Northwest Hawaiian Islands National Monument
and the Florida Keys
40
CONSERVATION & ECONOMIC
DEVELOPMENT
• Struggle to save ecosystems cannot be divorced from struggle to meet human needs.
ECOTOURISM - tourism that is ecologically and socially sustainable
NATIVE PEOPLE have valuable ecological knowledge that can be used in ecosystem management.
UNESCO initiated “Man and Biosphere” program (MAB) calling for the establishment of BIOSPHERE RESERVES, protected areas divided into zones with different purposes.
41
A MODEL BIOSPHERE RESERVE
42
SIZE & DESIGN OF NATURE PRESERVES
• SLOSS debate - Is it
better to have Single
Large Or Several
Small reserves?
• Edge effects
• Corridors of natural
habitat essential
43
SIZE & DESIGN OF NATURE PRESERVES
• One of the reasons that large preserves are
considered better than small reserves is that
they have more CORE HABITAT, area deep
within the interior of the habitat that has better
conditions for specialized species.
As human disturbance fragments the
ecosystem, habitat is broken into
increasingly isolated islands with less core
and more edge, supporting fewer species.
44
LANDSCAPE ECOLOGY
• LANDSCAPE ECOLOGY - science that
examines the relationship between spatial
patterns and ecological processes such as
species movement or survival
Variables:
- Habitat size
- Shape
- Relative amount of core and edge
- Kinds of land cover surrounding habitat
45
HOW SMALL CAN A HABITAT BE?