Environmental Engineering Reference
In-Depth Information
give a proper diagnosis for the cause of the disease. In other words, doctors
are expected to understand the cause to give the correct solution to the
problem.
The problem facing ecologists, however, becomes more complex when
the patient is the entire natural system.Take, for example, the case of Lyme
disease. It is a serious human ailment especially in the northeastern United
States (Barbour and Fish 1993). It causes debilitating arthritic conditions and
even serious nervous disorders in infected individuals if the disease is not di-
agnosed and treated early on in the infection stage. Lyme disease is transmit-
ted to humans from a species of tick.These ticks normally feed on the blood
of wildlife species such as white-tailed deer (
Odocoileus virginianus
) and deer
mice (
Peromyscus sp.
), but they will feed on humans given the opportunity.
Humans contract Lyme disease locally when the disease-causing spirochete
passes from the tick into the human bloodstream while the tick is obtain-
ing a human blood meal. Immediate symptoms of the disease include a
bulls-eye target rash surrounding the location where the tick obtained its
blood meal, followed by a high fever. One solution is to prescribe antibi-
otics that kill the spirochete after verifying that the patient has contracted
the disease. From a medical standpoint, this is treating the root cause of the
human
disease condition. From an ecological standpoint, however, it is
merely treating the symptom.Antibiotics will never eradicate Lyme disease.
The way to begin controlling Lyme disease on a human or landscape
scale is to understand why ticks, deer, and deer mice populations thrive to-
gether in the semi-rural environment of northeastern United States in the
first place; and why they sustain spirochete populations.This is what ecol-
ogists try to do. However, environmental problems like this are very com-
plex because they are often intertwined with a variety of other
environmental factors and they usually occur on an extraordinarily large
scale. Furthermore, they are often consequent to long-term changes humans
have caused to natural landscapes. In the case of Lyme disease, this involves
interdependencies that carry over many years. For example, the effect of
mass acorn production in a given year is only realized two years later by in-
creased abundances of mice that in turn are hosts for juvenile ticks that in
turn carry Lyme disease.The increase in host abundance means that the ticks
have a higher chance of obtaining the blood meals needed for survival, lead-
ing to increased abundance of the carriers of the disease. It took thirteen
years of field research to identify this causal chain of interdependency and
rule out other potential explanations (Ostfeld et al. 2006).
