Chapter Six (also chapter 3 and 4)
Sustaining Biodiversity: the Ecosystem Approach
Geog415
Dr Ye
Biological diversity (Biodiversity): earth’s variety of genes, species, ecosystems, and ecosystem
processes
• Genetic diversity: the variety of genetic material within a species or a population
• Species diversity: the number of species present in a different habitat
• Ecological diversity: the variety of terrestrial and aquatic ecosystems found in an area or on
the earth
• Functional diversity: the biological and chemical processes such as energy flow and matter
cycling needed for the survival of species, communities, and ecosystems.
Earth’s major
biomes
Climate and Biomes
Latitude and elevation have a
similar impact on vegetation
distribution
Ecological Succession: the gradual change in species composition of a given area (during succession
some species colonize an area and their population become more numerous, whereas population of
other species decline and may even disappear
1. Primary succession: gradual establishment of biotic communities on essentially lifeless ground where
there is no soil in a terrestrial community or no bottom sediment in an aquatic community.
2. Secondary succession: a series of communities with different species
can develop in places containing soil or bottom sediment.
Climax community: dominated by a few
long-lived plant species and is in balance
with its environment
Human’s Impact on Biodiversity
We disturbed or degraded about half to 84% of the
earth’s surface (excluding Antarctica and
Greenland) by filling in wetlands, and converting
grassland and forests to crop fields and urban
areas
In U.S. at least 95% of virgin forests in the lower 48
states have logged for lumber and converted to
agriculture, housing, industry, 98% of tallgrass
prairie in the Midwest and Great Plains have
disappeared, and 99% of California’s native
grassland and 85% of its original redwood
forests are gone. More than half of country’s
wetland have been destroyed.
Aquatic biodiversity has been degraded. 27% of the
world’s diverse coral reefs have been severely
damaged or eliminated. ¾ of the world’s 200
commercially valuable marine fish species are
either over-fished or fished to their estimated
sustainable yield.
Why should we care about biodiversity?
Usefulness to us and other species
Values:
Intrinsic value: components of biodiversity,
regardless of their usefulness to us
Instrumental value: usefulness to us
(1) Use value: benefit u in the form of
economical goods and services,
ecological services, recreation, scientific
information and preserving options for
such use in the future
(2) nonuse values: existence value (redwood
forest, wilderness or endangered species,
even if we will never see it or get direct
use from it); Aesthetic value (people
appreciate a tree, a forest, a wild species,
a vista because of its beauty); bequest
value (willingness of some people to pay
to protect some forms of natural capital for
use by future generations.
Public land in US
More than 1/3 of U.S. land consists of publicly owned national forests, resource lands,
parks, wildlife refuges, and protected wilderness areas (no nation has set aside as much
of its land for public use, resource extraction, enjoyment, and wildlife as has the U.S.)
Federal government manages roughly 35% of the country’s land that belongs to every
American. About 93% of this federal public land is in Alaska, and another 22% is in
western states.
Land Management systems:
National Forest System: 155 forests and 22 grasslands managed by the U.S. Forest
Service (USFS) and are used for logging, mining, livestock grazing, farming, oil and gas
extraction, recreation, hunting, fishing, and conservation of wetland, soil, and wildlife
resources.
National Resource Lands: managed by the Bureau of Land Management (BLM) and used
primarily for mining, oil, and gas extraction, and livestock grazing.
National Wildlife Refuges: 542 places, managed by U.S. Fish and Wildlife Service
(USFWS). Protect habitats and breeding areas for waterfowls and big games to provide
a harvestable supply for hunters, a few protected endangered species from extinction.
Permitted activities in most refugees including hunting, trapping, fishing, oil and gas
development, mining, logging, grazing, some military activities and farming.
National Park Systems: managed by National Park Services (NPS) include 56 major parks
and 331 national recreation areas, monuments, memorials, battlefields, historic sites,
parkways, trails, rivers, seashores, and lakeshores. Only camping, hiking, sport fishing,
and boating can take place in the national parks, but sport hunting, mining and oil and
gas drilling is allowed in National Recreation Areas.
National Wilderness Preservation system: most restricted public lands of 630 road less
areas. There areas lie within the national parks, national wildlife refugees, national
forests, and national resource lands, and are managed by agencies in charge of these
lands. Most of there areas a re open only for recreational activities such as hiking,
sport fishing, camping, and no motorized boating.
Controversy of Public Land Management:
Most conservation biologists, environmental economists, and many free market
economists believe the 4 principles should govern the public land
1.
Protecting biodiversity, wildlife habitats, and the ecological functioning of
public land ecosystems should be the primary goal
2.
No one should receive subsidies or tax breaks for using or extracting
resources in public lands (a user pay approach)
3.
The American people deserve fair compensation for the use of their
property
4.
All users or extractors of resources on public lands should be fully
responsible for any environmental damage they cause
Oppositions are from economists, developers, and resource extractors, they
view public lands in terms of their usefulness in providing mineral, timber,
and other resources and their ability to increase short-term economic
growth. They have succeeded in blocking implementation of the 4
principles (received $1 billion a year in subsides to privately owned
mining, fossil fuel extraction, logging, and grazing interests using US
public land).
Stresses on U.S.
Public Parks
•
Biggest problem may
be popularity
– Noise
– Congestion
– Pollution
– Damage or
destruction to
vegetation and
wildlife
•
Repairs needed to
trails and buildings
Managing and Sustaining Forests
Forests: at least 10% tree covered land
It occupies about 30% of the earth’s land
surface (excluding Greenland and
Antarctica)
Types:
1.
old-growth forests: uncut forests or
regenerated forests that have not
been seriously disturbed by human
activities or natural disasters for at
least several hundred years
(Storehouses of biodiversity because
they provide ecological niches for a
multitude of wildlife species-22% of
the world’s forests)
2.
Second-growth forests: a stand of
trees resulting from secondary
ecological succession after the trees
in an area have been removed by
human activities (clear-cutting or
conversion to cropland) or by natural
forces (fire, hurricanes, volcanic
eruption; about 76% world’s forests)
3.
Tree plantation (tree farm): a
managed tract with uniformly aged
trees of one species that are
harvested by clear-cutting as soon as
they become commercially valuable
(5% of the world’s forests and
produce about 1/5 of the world’s
commercial wood)
Forest managements:
Even-aged managements: involves maintaining trees in a given stand at about the same age and size
(industrial forestry), consists of one or two fast growing and economically desirable species that
can be harvested every 6-10 years).
Uneven-aged management: involved maintaining a variety of tree species in a stand with many ages
and sizes, to foster natural regeneration (biologically diverse, long-tem sustainable production of
high-quality timber; selective cutting of individual mature or intermediate-aged trees, and multiple
use of the forests for timber, wildlife, watershed protection, and recreation.
Study suggests that intensive but sustainable management of as little as 1/5 of the world’s forests
(twice size of India) could meet the world’s current and future demand for commercial wood and
fiber.
Deforestation: temporary or permanent removal of large expanses of forests for agriculture or other
uses.
Harmful effects of tree
harvest (build roads for
access and timber
removal):
Increase erosion and
sediment runoff into
waterways, habitat
fragmentation, and
biodiversity loss,
expose forests to
invasion by nonnative
pests, diseases and
wildlife species; opened
access for farmers,
miners, hunters, and
off-road vehicle users,
disqualify the land for
protection as
wilderness
(a) Selective cutting
(b) Clear-cutting
Clear
stream
Muddy stream
Uncut
Cut 1 year ago
(c) Strip cutting
Dirt road
Cut 3–10 years ago
Uncut
Clear stream
Fig. 6-4, p. 116
Natural Capital Degradation: Harmful
Environmental Effects of Deforestation
Fig. 6-5, p. 117
Fig. 6-6, p. 118
Animation: Hubbard brook experiment
Video: Forest fire
Status of the World Forests
Bad news:
1.
During past 800 years, human activities have reduced the earth’s original
forest cover by 20-80%
2.
World’s forests are being cleared and degraded at a rate of 0.3-0.8% a
year, (mostly over tropical rainforests)
Good news:
1.
Total area of many temperate forests in North America and Europe has
increased slightly because of the reforestation from secondary ecological
succession on cleared forest areas and abandoned croplands
2.
Some of the cut areas of tropical forest have increased tree cover from
re-growth and plating of tree plantations
Ecological restoration: the process of repairing damage caused by humans to
the biodiversity and dynamics of natural ecosystems. Examples:
replanting forests, restoring grasslands, restoring wetlands, reclaiming
urban industrial areas (brown fields), reintroducing native species,
removing invasive species, and freeing river flows by removing dams.
Solution: Sustainable Forestry
Solutions: Sustaining Tropical Forests
Solutions: A Model Biosphere Reserve
Biodiversity hot spots: areas rich in plant ant animal species that are
found nowhere else and are in great danger of extinction or serious
ecological disruption.
Sustaining aquatic biodiversity
1.
2.
3.
Greatest marine biodiversity occurs in coral reefs, estuaries, and
the deep-sea floor
Biodiversity is higher near coasts than in the open sea because of
the greater variety of producers, habitats, and nursery areas in
coastal areas.
Biodiversity is higher in the bottom region of the ocean than in the
surface region because of the greater variety of habitats and food
sources on the ocean bottom
Human Activities Are Disrupting and
Degrading Aquatic Habitats
• Major threats to marine systems
– Coastal development
– Overfishing
– Runoff of nonpoint source pollution
– Point source pollution
– Habitat destruction (1/4 coral reefs damaged; bottom habitats
are degraded and destroyed by dredging operations and trawler
boats)
– Introduction of invasive species
– Climate change from human activities
– Pollution of coastal wetlands and estuaries
Solutions: Managing Fisheries