Environmental Engineering Reference
In-Depth Information
Appendix B: Case Studies
Reviewing case studies is an important part of your preparation for the AP Environmental Science exam and
an important part of your knowledge about global environmental issues. Case studies can help you learn about
environmental concerns by providing you with perspectives on real-world concepts such as laws and treaties.
On the multiple-choice section of the exam, you may be given a set of events and then asked to match the
event with a provided case study. On the free-response section of the exam, you will be asked to write about a
particular case and then asked to provide additional, related examples.
This section of the topic describes several case studies that are common in the AP Environmental Science
course.
Species
Loss of Amphibians
Although the loss of any species or group of species impacts its ecosystem, the loss of amphibians is an espe-
cially important warning sign of the decline of ecosystem health as a whole. Because of their sensitivity to en-
vironmental change and pollution, amphibians (frogs, toads, and salamanders) are considered to be indicator
species, which means declining population indicates likely environmental damage. The numbers of amphibians
are declining globally, and up to 200 species have gone extinct within the past 20 years. In addition to indicat-
ing ecosystem health, amphibians carry out important roles, including controlling insect populations, acting as
a food source for many other species, and providing products for pharmaceuticals such as antibiotics and
painkillers.
Spending portions of their lives in both aquatic and terrestrial ecosystems, amphibians are exposed to a multi-
tude of environmental risks. Major threats come from the loss of habitat due to fragmentation of land, filling in
of wetlands, development of land, and deforestation. Pollution also has a harmful impact on amphibians, as
does disease, overhunting, and the introduction of predators and competitors. Global climate change alters the
temperatures of regions, which can lead to drought and the drying up of standing water pools. Since amphibi-
ans depend on this water to lay eggs and for early stages of life, the loss of these watering pools affects the sur-
vival of a population and, ultimately, a species. Amphibians also require wet skin. Any weakening of the or-
ganisms from events such as long-term drought or increased pollution can devastate a population, making the
organisms more susceptible to fungi, bacteria, parasites, and viruses.
There is no definitive answer to the cause of the global decline in amphibian species, but it is likely due to
some combination of the listed factors working in unison. For example, climate change is warming some envir-
onments, which increases the growth of some fungi, especially the chytrid. This fungus can be lethal for am-
phibians and tends to proliferate in warm temperatures. With the increase in temperatures in many regions and
the expanding reach of the warmer climate, the chytrid fungus has grown exponentially in many areas, killing
many amphibians, and has potentially contributed to the demise of the golden toad in Costa Rica.
No matter the specific reason for decline, the increasing loss of amphibians on a global scale is a warning to
humans that ecosystems are being altered and the environment is changing quickly.
