ENV 301: Environmental Science

tubacitychiropractorManagement

Nov 8, 2013 (3 years and 7 months ago)

64 views

1

Chapter 12


Human Impact on Resources and Ecosystems

Copyright
©
The McGraw
-
Hill Companies, Inc. Permission required for reproduction or display.


ENV 301: Environmental Science

A Study of Interrelationships


Discussion notes: Scott M. Graves


Text:
Enger

Smith

Ninth Edition

Human Impact on Resources and Ecosystems

Chapter 12

3

Chapter Outline


Historical Basis of Pollution


Resource Utilization


Mineral Resources


Ecosystem Modification


Forests


Rangelands


Wilderness


Aquatic


Managing Ecosystems for Wildlife


Extinction

4

Changing Role of Human Impact


As human population grew, and tools
became more advanced, the impact a single
human could have on surroundings
increased.


Environmental modifications allowed larger,
dense human populations to arise.


Nearly all earth’s surface has been affected
in some way by human activity.

5

Historical Basis of Pollution


Pollution

Anything released into the
environment that affects an organism’s
survival and reproduction.


Two primary factors affect the amount of
damage done by pollution:


Size of the population


Level of technological development

6

Historical Basis of Pollution


When the human population was small, waste
products were generally
biodegradable
.


Human
-
caused pollution is produced when
waste is generated faster than it can be
degraded, especially as people began to
congregate and establish cities.


Throughout history, humans fought
ecosystem degradation with technology.


Short
-
term solutions.

7

Renewable and Nonrenewable Resources


Natural Resources

Structures and
processes humans can use, but not create.


Renewable

Can be formed or
regenerated by natural processes.


Soil, Vegetation, Wildlife


Non
-
Renewable

Not replaced by natural
processes, or, rate of replacement is
ineffective.


Minerals, Fossil fuels

8

Costs Associated With Resource Utilization


Economic

Monetary costs necessary to
exploit the resource.


Energy

Energy expended exploiting the
resource.


Environmental

Environmental effect of
resource exploitation (often deferred).

9

Mineral Resources


Major form of nonrenewable resource.


Distribution is not uniform.


Many deposits have already been exploited.


North America consumes >30% of world minerals.


Steps in Mineral Utilization


Exploitation


Mining


Refining


Transportation


Manufacturing

10

Recycling of Mineral Materials


Many minerals are not actually consumed,
but only temporarily held.


In many industries, cost of purchasing
recycled raw materials is higher than the cost
of purchasing virgin materials.


More costly to produce products from
recycled material than virgin materials.


Historically, monetary cost for energy has
been low, thus no incentive to recycle.

11

Utilization and Modification of

Terrestrial Ecosystems


Natural ecosystems have greater biodiversity
than human
-
managed ecosystems.


Impact of Agriculture on Natural Ecosystems


40% of world’s land surface converted to
cropland and permanent pasture.


Most productive natural ecosystems are the
first to be modified by humans.


Pressures to modify the environment are
greatest in areas with high population
density.

12

Managing Forest Ecosystems


1/2 of U.S., 3/4 of Canada, and almost all of
Europe was originally forested.


Because of increasing human population
growth, forested areas are under increasing
pressure to provide wood products and
agricultural land.


Efficient methods of harvest and
transportation are important to reduce
economic cost of using forest resources.

13

Economic and Energy Costs


Major
Economic Costs

of Utilizing Forests:


Purchasing or leasing land.


Paying for equipment and labor.


Building roads


Major
Energy Costs

of Utilizing Forests:


Harvesting


Transportation

14

Environmental Costs


Modern forest management practices involve
a compromise that allows economic
exploitation while maintaining some of the
environmental values of the forest.


Forested areas effectively reduce erosion.


Loss of soil (nutrients) reduces soil fertility.


Road building in forests increases erosion.


Forest areas modify climate, and provide
recreational opportunities as well.

15

Environmental Implication of Harvesting


Clear Cutting

Removal of all trees in an
area. Economical but increases erosion,
especially on steep slopes.


Patch
-
Work Clear Cutting

Clear cutting in
small, unconnected patches; preserves
biodiversity.


Selective Harvesting

Single
-
tree
harvesting. Not as economical, but reduces
ecosystem damage.

16

Plantation Forestry


Many lumber companies maintain forest
plantations as crops and manage them in the
same way farmers manage crops.


Plant single species, even
-
aged forests of
fast growing hybrid trees.


Competing species are controlled by fire
and insects controlled by spraying.


Mature rate as low as 20 years (vs. 100).


Quality of lumber reduced.


Low species diversity and wildlife value.

17

Special Concerns About Tropical Deforestation


Tropical forests have greater species diversity
than any other ecosystem.


Not easy to regenerate after logging due to
poor soil characteristics.


Deforestation Concerns


Significantly reduces species diversity.


Impacts climate via lowered transpiration.


CO
2

trap

Increased global warming.


Human population pressure is greatest in
tropics, and still increasing.

18

Managing Rangeland Ecosystems


Rangelands

Lands too dry to support
crops, but received enough precipitation to
support grasses and drought
-
resistant
shrubs.


Wildlife are usually introduced species.


19

Environmental Costs of Utilizing Rangelands


Management techniques and selective
grazing of animals may lead to the
elimination of non
-
preferred species.


Important to regulate number of livestock on
rangelands, especially in dry areas.


Desertification

Process of converting arid
and semi
-
arid land to desert.


Over
-
grazing


Firewood cutting


20

21

Wilderness and Remote Areas


Many areas in the world have had minimal
human impact.


Some are remote and may have harsh
environmental conditions.


Wilderness Act (1964)

Wilderness:



“An area where the earth and its
community of life are un
-
trampled by
man, where man himself is a visitor
who does not remain.”

22

Managing Aquatic Ecosystems


Aquatic ecosystems divided into:


Freshwater, Brackish, Marine


Environmental costs related to utilizing
marine ecosystems fall into two categories:


Over
-
fishing


Environmental effects of harvesting


UN estimates 70% of world’s marine
fisheries are over
-
exploited.


Capacity should be reduced by 30%.

23

24

Managing Aquatic Ecosystems


Coastal regions are most productive regions
of the oceans.


Sunlight penetration

shallow

warm


Nutrient deposition from land


Wind/wave action stirs nutrients


Fishing pressure and pollution are greatest in
these areas.


Trawls

nets dragged along bottom.


Large by
-
catch


Disturbs seafloor

25

Environmental Costs Associated with
Utilizing Freshwater Ecosystems


Two primary human alterations:


Water Quality


Erosion, toxic run
-
off


Exotic Species

Introduced species


Humans have great access to freshwater
ecosystems.


Many North American freshwater fisheries
are primarily managed for sport fishery.


Fisheries managers must balance:


Sport fisheries


Commercial harvesters

26

Aquaculture


Fish farming is becoming increasingly
important as a source of fish production.


Currently, about 60% of all aquaculture
production is from freshwater systems.


Problems


Nutrient overloads


Escape into natural waters


Land conversion

27

Managing Ecosystems For Wildlife


Habitat Analysis and Management


Animals have highly specific habitat
requirements that change throughout the year.


Once habitat requirements are understood,
steps can be taken to alter habitat and
improve species success.


Fire to eliminate poor habitats.


Kirtland Warblers

Jack Pine stands.


Encourage growth of certain plant species.

28

Population Assessment and Management


Wildlife managers use population censuses to
check if populations are within appropriate
levels.


With suitable habitat and protection, most wild
animals can maintain a sizeable population.


But high reproductive capacities and/or heavy
protection can cause very large populations.


Whitetail Deer in Eastern U.S.


Elephants in Zimbabwe

29

Population Assessment and Management


Wildlife management often involves harvesting
for sport and meat.


Hunting regulation is crucial.


Seasons usually occur in the fall to take
advantage of surplus animals.



When populations get too small, artificial
introductions can be implemented.


Native species for augmentation.


Non
-
native species for empty niches.

30

Managing a Wildlife Population

31

Predator and Competitor Control


At one time it was believed populations of
game species could be increased if
predators were controlled.


Still used in some situations.


But, in many cases, human modification of
habitat has a greater impact than natural
predation.


Many species do require refuges where
they are protected from competing species
or human influence.

32

Migratory Waterfowl Management


Migratory birds can travel thousands of
kilometers.


North in spring to reproduce.


South in fall to escape cold temperatures.


International agreements necessary to
maintain appropriate habitat.


Canada


United States


Mexico

33

Extinction and Loss of Biodiversity


Small, dispersed populations are more prone
to extinction.


Successful breeding more difficult.


Local weather conditions can severely
impact population size.

34

Human
-
Accelerated Extinction


Wherever humans have become the dominant
organisms, extinctions have occurred.


Food


Animals Parts


Pest Status


Habitat Alteration


Most Important Cause


Habitat Fragmentation

35

36

Why Worry About Extinction ?


Useful to Humans
:


Medical

Less than 1% of tropical
rainforest plant species have been tested
for pharmaceutical use.


Food Resources


Ecological

Species play specific roles in
ecosystem function.


Ethical

Animals have a fundamental right to
exist.

37

Extinction Prevention


Endangered

Very low populations, could
become extinct in very near future.


Threatened

Still exist in large numbers in
current range, but are declining in most
areas.


Could become extinct if a critical
environmental factor is changed.

38

Extinction Prevention


Most extinction prevention interest occurs in
developed countries. Most vulnerable
species already eliminated.


Less
-
developed and developing countries
have both highest population growth and the
majority of the world’s species.


More concerned with immediate needs of
food and shelter than long
-
range issues
such as species extinction.

39

Endangered Species Act (1973)


Gave U.S. government jurisdiction over
threatened and endangered species.


Directs that no activity by a government
agency should lead to the extinction of an
endangered species.


Directs government agencies to use
whatever means necessary to preserve the
species in question.

40

Chapter Summary


Historical Basis of Pollution


Resource Utilization


Mineral Resources


Ecosystem Modification


Forests


Rangelands


Wilderness


Aquatic


Managing Ecosystems for Wildlife


Extinction

41