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Chapter 28
Habitat Loss, Biodiversity, and Conservation
| Required Reading |
Additional
Reading (2-3 Quiz questions from these sources) |
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Links for Enrichment and Further Learning
Student Learning Outcomes. Lessons in this
chapter are intended to help students to:
Study Questions / Quiz Prep. (Consult Required Reading and lecture notes for answers.)
- Evidence in the rocks indicates that Earth has experienced
several, previous mass extinction events. How is the current mass
extinction event different from those of the past?
- In the recent past, and in some cases today, over hunting has
caused the extinction of animals such as the saber-toothed cat,
wooly mammoth, Stellar's sea cow, New England sea mink and the dodo
bird of Mauritius Island. But today, what is the main cause for
species extinctions?
- On the map below, label the top ten countries in terms of total
area of forest cleared in the period between 1990-2000. (You may
consult to following link for a world map:
http://en.wikipedia.org/wiki/World_map .
- Geographically, what is the notable relationship between these
top ten countries and the planetary region of greatest biodiversity?
- About how many square kilometers of tropical rain forest are
being destroyed every year.
- Using the following links, the area of which state in the the
USA most closely matches the area of annual tropical rain forest
destruction?
- On the map above, label Madagascar.
- How much of the original forest remains on the island of
Madagascar?
- Identify one type of animal at risk of extinction on Madagascar.
- On the map above, label Borneo.
- Identify one type of animal at risk of extinction on Borneo.
- On the map above, label Kenya.
- Identify one type of animal at risk of extinction in Kenya and
eastern Africa.
- Identify one type of animal at risk of extinction in Central
America and South America.
- On the map above, label southern California.
- Identify one type of animal at risk of extinction in southern
California.
- What are the main reasons that humans destroy natural habitat?
- Salt cedar is a plant that was recently introduced by humans to
the southwest USA for a variety of reasons. It has since spread out
and now dominates patches of many natural habitats. Be able to
identity a photograph of salt cedar.
- How does salt cedar become a problem to native plants?
- How does salt cedar cause problems for the desert pupfish?
- The brown tree snake was introduced to the islands of Guam and
Hawaii. How did this snake cause problems to the native animals?
- Pampas grass seems pretty enough. Why is this introduced plant
problematic to the native plants of California?
- Sweet fennel and black mustard have been introduced to
California. How do these plants cause problems to the native
ecosystems they invade?
- What is an endemic species?
- The International Union for the Conservation of Nature has
developed a classification scheme for species based on their
probability of extinction. List and define the three levels in this
scheme.
- Refer to Table 28.2. In terms of the number of threatened
species as a percentage of the number of evaluated species, which
groups are at greatest risk from each of the following categories:
1) vertebrates; 2) invertebrates; 3) plants?
- Conservationists realize that they do not have sufficient time
and resources to save all threatened species on the planet. How then
do they recognize and define the most important areas to which they
should devote their limited time and resources?
- What are the three characteristics of a biodiversity hotspot?
- Is there a biodiversity hotspot in California?
- Define: minimum viable population.
- How would the minimum viable population size differ between the
two following groups: 1) invertebrates and annual plants; 2)
vertebrate species?
- Define: minimum dynamic area.
- Refer to figure 28.12. According to this graph, how many large
carnivores could a park with an area of 104 hectares
support?
- Refer to figure 28.12. According to this graph, if we want to
create a park only for populations of 1000 small herbivores, how
many hectares should our park be?
- J. Berger studied 120 populations of free-ranging bighorn sheep
in the American southwest. According to this investigation, what is
the minimum viable population for this species?
- Conservationists have had differential success relocating and
reintroducing black rhinos and white rhinos in Africa. Why so
different?
- Before California Condors could be reintroduced to the wild,
their total numbers had to be increased. How did conservationists
successfully increase the condor populations?
- After being regionally extinct for decades, the gray wolf has
been reintroduced to Yellowstone National Park. What were the
immediate changes that the wolves caused to the Yellowstone
ecosystem?
- The American bald eagle recently was reintroduced to Catalina
Island off the coast of southern California. How can these large
predatory birds possibly find enough food to eat while living on
this small island?
- Refer to Table 28.18. According to this table, how many regions
of the world have protected more than 10% of their land area?
- Below are two pictures that represent the geographic arrangements
of two protected areas. Protected land is shown in black. Both areas
are equal in size. Which is better?
(a) |
(b) |
- In the USA, where are most of the protected lands?
- In the USA, what is the main geographic characteristic shared by
most regions of protected lands?
- What are the three arguments presented by conservationists for
the maintenance of biodiversity?
Biodiversity
A map showing that the tropical zone has the greatest number of species
on the planet.
Habitat Loss
Global distribution of original and remaining forests
History of habitat loss in Madagascar.
A close up view of habitat destruction in Madagascar. The pattern shown
here indicates: 1) clear-cutting the rain forest in order to harvest
timber; and 2) conversion of rain forest to pasture land to support
grazing cattle.
 
Lemurs at risk of extinction in Madagascar.
Deforestation in Borneo. As in Madagascar, deforestation progresses as a
wave of destruction moving from the coasts toward the interior.
Orangutans are at risk of extinction on Borneo.
Deforestation in Kenya surrounds islands of protected lands.
Mountain gorillas are at risk of extinction in eastern Africa.
Deforestation in Rondonia, Brazil.
Deforestation in Rondonia, Brazil -- Google Earth.
Jaguars are at risk of extinction in Central America and South America.
Deforestation in Weakley County, Tennessee, USA.
 
Grizzly bear (left) and the gray wolf (right) now are regionally extinct
in nearly all of their former ranges in North America.
Deforestation in Orange County, CA, USA. Endangered Coastal Sage Scrub
habitat inconveniently occupies the most buildable land in Southern
California.
California gnatcatcher at risk of extinction in Southern California.
A truck carries a load of trees removed from a natural forest. The trees
will be used for lumber, paper or fiiber.
  
Products directly produced from harvested trees.
Cattle graze on pastureland made available after clearing away the
original forest.
  
Products directly produced from cattle.
Harvesters collect a crop of wheat in an enormous wheat field. The
farmland was made available after clearing away the original woodland or
natural prairie communities.
  
Products directly produced from harvested fields of grain.
Introduction of Alien Species
California
Plants
 
Salt cedar (above left) is an aggressive plant that crowds out native
plants. Salt cedars are exceptionally active ground water pumps. In
large stands, they can rapidly deplete ground water reserves and cause
ground water levels to drop. This can cause water levels in desert ponds
to drop or disappear altogether. Many desert animals depend on desert
ponds for water, such as the endangered desert pupfish (above right),
local rodents, migratory birds and insects. The draining of these ponds
by salt cedar results in fatal consequences to numerous species of
desert animals.
Finally, salt cedar "leaves" secrete large
amounts of salt. The salt falls to the ground and accumulates, making
the soil too salty for other plants.
Pampas grass. Pampas grass is an aggressive plant that can rapidly
colonize and dominate any suitable territory. Pampas grass seeds are
carried by the wind, helping the species to rapidly spread downwind.
When it does, the diverse, native flora can be quickly replaced by a
monoculture of pampas grass.
Sweet fennel. Sweet fennel is an aggressive plant that tends to dominate
its territory, crowding out native plants and transforming a diverse
ecosystem into a monoculture.
Black mustard. Black mustard spreads rapidly and dominates new
territories. Its success crowds out native plants, resulting in a loss
of biological diversity.
Animals
 
Red fox (left), San Joaquin kit fox (right). The red fox is a larger,
stronger and more aggressive fox when compared to the San Joaquin kit
fox. As a result, the introduction of the red fox has caused native kit
fox populations to decline.
 
German brown trout (left), Golden trout (right). Fishermen periodically
(and illegally) introduce German brown trout into high Sierra lakes. The
brown trout out competes and devours the native golden trout.
Threatened and Endangered Species
Table of threatened and endangered species. Click
here for larger
view.
Biodiversity hotspots. Places around the world where there is: 1) high
species diversity; 2) high species endemism; 3) large impact from human
activities.
Minimum Viable Populations (MVP) and Minimum Dynamic Area (MDA)
This graph indicates that for any given minimum viable population size,
large carnivores require the greatest amount of territory. NOTE: a
hectare is 10,000 square meters (2.47 acres), about the size of two and
a half football fields.
 
Bighorn sheep of the southwest USA (left). At right, the results of a
study of 120 populations of bighorn sheep in the American southwest by
J. Berger. Results indicate that populations of bighorn sheep of less
than 100 tend to go extinct quickly. Populations of 100 or more tend to
persist.
Reintroduction
A black rhinoceros is released into a protected area in South Africa.
Range history of the black rhinoceros. Note that this once free-ranging
species is now restricted to isolated protected areas.
Feeding a California Condor chick using a surrogate puppet. The puppet
is used so that the chick "imprints" on condors and not humans. The
person operating the puppet is hidden from the chick with curtains.
Wildlife biologists release a juvenile condor into a controlled compound
in preparation for final release to the wild. This condor was raised in
captivity in order to better protect young condors and safeguard against
critical losses.
A map showing the location of Yellowstone National Park. Regionally
extinct for decades, the gray wolf was reintroduced to Yellowstone in
1995. Since then the gray wolf population has rapidly increased.
 
On Santa Catalina Island, a wildlife biologist feeds a bald eagle chick
with a puppet. Bald eagles were reintroduced to the island in 1980. Bald
eagles are fish predators and soar above the island's coastal waters in
search of fish. They are experts at using their large talons to snatch
up fish swimming just under the surface.
Habitat Protection
Current estimates of the percentage of land now protected from the
destructive actions of humans.
Maps showing the patterns of protected lands in the USA.
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