2. Ecology
Is the scientific study
of the relations that
living organisms have
with respect to each
other and their
natural environment.
Variables of interest
to ecologists include
the composition,
distribution, amount
(biomass), number,
and changing states
of organisms within
and among
ecosystems.
3. Ecosystems
Ecosystems are
hierarchical systems
that are organized
into a graded series
of regularly
interacting and semi-
independent parts
(e.g., species) that
aggregate into
higher orders of
complex integrated
wholes.
4. Ecosystems
Ecosystems create biophysical feedback
mechanisms between living (biotic) and
nonliving (abiotic) components of the planet.
These feedback loops regulate and sustain
local communities, continental climate systems,
and global biogeochemical cycles.
5. Human ecology
Ecology is a human science as
well. There are many practical
applications of ecology in
conservation biology, wetland
management, natural resource
management (agriculture,
forestry, fisheries), city planning
(urban ecology), community
health, economics, basic and
applied science and human
social interaction (human
ecology).
Ecosystems sustain every life-
supporting function on the
planet, including climate
regulation, water filtration, soil
formation (pedogenesis), food,
fibers, medicines, erosion control,
and many other natural features
of scientific, historical
6. Human ecology
Human ecology and
human behavior are
the two key factors
that determine the
transmission of human
infectious diseases.
When the cycle of
transmission includes
mosquitoes, ticks, rode
nts or other
intermediaries, their
ecology and behavior
are also critical.
7. When multiple species
are involved, the levels
of complexity are even
greater. Lastly, the
virulence of the
pathogen, the
susceptibility of its
vectors and hosts, the
immunity of those hosts
and the collective
immunity of the host
populations all
contribute to the force
of transmission. The
significance of climate
factors can only be
assessed in the
perspective of this
daunting complexity.
8. Human ecology as a science
Climate and weather are often invoked as the
dominant parameters in transmission, but their
true significance can only be assessed in the
perspective of this daunting complexity.
Moreover, the key parameters – temperature,
rainfall and humidity – cannot be viewed
independently. The effects of temperature are
modified by humidity. The daily range of each
may be more significant than the daily mean.
Brief periods of atypical heat or cold can be
more significant than long-term averages.
Heavy storms can have a different impact than
light prolonged rainfall. One year’s events may
have a significant impact on subsequent years.
9. Climate and current distributions of disease
The distribution of many diseases coincides
with certain climate patterns, but in many
cases the reverse does not hold true. For
example, malaria disappeared
“spontaneously” from large areas of
Western Europe and North America after
the mid-1800s, precisely the period when
the current warming trend began (Reiter
2001).