Fauna are
defined as being the animal life of a region or geological period
(8), and they are essential to the survival of the rainforest.
Animals serve an integral role in the ecosystem of the rainforest,
as they interact with all parts of the ecosystem, such as the
flora, soil, air, and water systems. They contribute to the
various
nutrient cycles, the energy cycle, and act as ambassadors for the
jungle to humanity.
With
approximately 500 species of mammals (1), 1600 species of birds
(2), and 1 million species of insects (2) in a 2.5 million square
mile area (1), the Amazon rainforest is considered one of the most
biologically diverse places on the planet. To ensure
the health of the rainforest, we must preserve the health of the
fauna.
Because of the diversity of animal species and the constant
discoveries of yet more species, it is impossible to characterize
the Amazon's fauna by listing all the species.
However, it
is possible to break the fauna of the Amazon into different
categories and know that each category is necessary for the
survival of others. Doran and Safley define soil health as being
"the continued capacity of soil to function as a vital living
system... to sustain biological productivity, promote the quality
of air and water environments, and maintain plant, animal and
human health" (4). This can also be applied to fauna; they are
healthy if they are able to exist as a 'vital living system' and
'sustain biological productivity.' This can also be generalized
to the entire ecosystem. Costanza et al (3) proposed an "ecosystem
health paradigm." Costanza discusses a combined effort of
ecologists and economists to try to create a "unifying concept of
environmental management that would meet the needs felt with
regulatory agencies to adopt a broader set of management goals
than used at the time." (Costanza). Costanza found that an
ecological system is healthy if it is "stable and
sustainable."This is very difficult to measure directly; in fact
it is nearly impossible. Therefore, a proxy must be employed.
The proxy used by ecologists is bioindicators: "... a complex
concept such as ecosystem health cannot be measured as such, but
that it can be approached through a series of indicators, each of
which will measure a certain aspect..." (van Straalen). Thus,
fauna can be very important to monitoring reliably the state of
certain aspects of Amazon Rainforest health.
There are still many important questions to be resolved. For
instance, what is the relationship between species and ecosystem
health? Since one cannot investigate all species, which are the
most important, the key species. Ecological theorists have
proposed answers to the former question. Lawton (1994) tried to
explain an interesting facet of the relationship between
biodiversity, and ecological ability to function properly. If all
species are present and relationships unaffected, then one can be
sure that ecological functions are constant. However, the
presence of all functions does not require the presence of all
species. He proposed 3 models to explain this relationship:
a) Redundant species hypothesis - With a decrease of biodiversity,
ecosystem
functions are unaffected until the point where only a few key
species remain.
If one of these species is lost, the system collapses.
b) Rivet hypothesis - With a decrease of biodiversity,
ecosystem function will
decrease proportionally. This represents a direct correlation
between the two.
c) Idiosyncratic hypothesis - There is no relationship
between biodiversity and
ecosystem functions.
There is some evidence for the redundant species hypothesis. For
example, Nordgren et al (1983) studied the effects of heavy metal
contamination on soil respiration. Species of fungi were killed in
a gradient surrounding the source of the metals. However,
respiration was only affected with an high level of metal (and
therefore a high
loss of species) near the source (Nordgren). In fact, there is a
"general feeling...that functional redundancy indeed plays a
role..." (van Straalen). Nevertheless, despite great efforts
arising from the Rio convention, there is very little empirical
evidence to support
any of Lawton's hypotheses (van Straalen). Still, as Naeem and Li
(1997) put it, biodiversity is "ecological insurance." (Naeem).
Rather than looking at the number of species to show health,
bioindicators can show continuation of attributes.
Sources:
(1)
http://www.pbs.org/journeyintoamazonia/enter.html
(2)
http://www.txdirect.net/sitc/sci-rain.htm
(3) Costanza, R. Norton BG and Haskell BD (eds) (1992) Ecosystem
Health. Island
Press, Washington, D.C.
(4) Doran JW and Safley, M. (1997) Defining and assessing soil
health and
sustainable productivity. In: Pankhurst CE, Doube BM and Bupta
VVSR (eds)
Biological Indicators of Soil Health (pp 1-28). CAB Inernational,
Wallingford.
(5) Lawton, JH (1994) What do species do in ecosystems? Oikos 71:
367-374.
(6) Naeem S, and Li S (1997) Biodiversity enhances ecosystem
reliability. Nature
390: 507-509.
(7) Nordgren A, Baath E and Soderstrom B (1983) Microfungi and
microbial activity
along a heavy metal gradient. Applied and Evironmental
Microbiology. 45:
1829-1837.
(8) The Oxford Dictionary of Natural History. Oxford University
Press, Oxford,
1985.
(9) van Straalen, Nico M (2002) Assessment of soil contamination -
a functional
perspective. Biodegeneration. 13: 41-52.
Ideally, one would be able to monitor the health and
population dynamics of every species in a particular ecosystem.
Naturally, when discussing the Amazon rainforest, this is
impossible. The biodiversity of the rainforest is such that not
only are there vast numbers of species, many of them are very rare
or endemic to the Amazon region. Therefore, in order to
efficiently characterize the fauna of the rainforest, a different
method must be used.
One
such way is the use of bioindicators. Bioindicators are species
that are particularly sensitive to the environment, and provide
information about ecosystem health. Indicator species respond
well respond both to the presence or absence of other species as
well as the presence of pollutants. By studying the population
dynamics or by statistically sampling an indicator species, one
can deduce much information about the rest of the ecosystem’s
health.
There
are three kinds of bioindicators:
a)
compliance
indicators: these verify that maintenance or restoration goals
have been met
b)
diagnostic
indicators: these help the investigation of observed disturbances
c)
early warning
indicators: these reveal the first signs of a disturbance before
most species are affected
In an
attempt to cover all three types of indicators, we selected two
groups of animals to serve as indicator species: bats and
amphibians. Based off scientific papers, it was decided that bats
would serve as good indicator species because they have an
abundance of species, occupy almost every trophic level,
contribute to ecological processes such as seed dispersal and
pollination, and because they select specific habitats.(4) The
first three reasons make them good bioindicators, the last reason
makes them easy to monitor.
Amphibians were selected because they take in nutrients
through their skin, so toxins in the environment build up faster
in their bodies than in other species. For instance, if someone
is using a certain pesticide, we can monitor the frogs of the area
and
test them to see conclusively if a decrease in population is
resulting from exotoxicity. This proves that the pesticide is
having a negative effect and should be removed. Similar
experiments may be done to determine pollution by industries, such
as mining or logging,
or any other possible source of contamination.
There
is a slight difference between bioindicators and key
indicator species. While both of them are useful in deducing
information about their environment, bioindicators tell us
information about the environment through their population numbers
or particular responses to the ecosystem, while key indicator
species are those species that are essential to an ecosystem.
That is, if this species were to disappear, a good part of the
food web (indeed the whole ecosystem) could perish. A good
example of key indicator species is the connection between otter,
sea urchins, and kelp. If the otter were to disappear, there
would be no species to eat the sea urchins, and their populations
would grow as their food source, kelp, would disappear faster and
faster.
As it
applies to the rainforest, however, monitoring key indicator
species to find out information on the ecosystem is not very
efficient. That is, with such biodiversity, it is almost
impossible to find a key indicator species. There are such vast
numbers of species, and the Amazon food web is so complex that if
one species were to disappear, the other species can quickly
adapt. Every species in the Amazon consumes many different
species, and is likewise consumed by many different species,
therefore a key indicator is not readily apparent.
Sources:
(1)
http://www.pbs.org/journeyintoamazonia/enter.html
(2)
http://www.txdirect.net/sitc/sci-rain.htm
(3) Jamil, Kaiser. Bioindicators and Biomarkers of Environmental
Pollution and Risk Assessment. 2001. Science Publishers, Inc.
(4) Medellin, Rodrigo A. (2000). "Bat Diversity and Abundance as
Indicators of Disturbance in Neotropical Rain forests."
Conservation
Biology, 14(6), 1666-1675
(5)
http://www.rainforest-alliance.org/resources/forest-facts.html
Bats as Indicator Species
With increasing human encroachment on the Amazon rainforest
and its diverse faunal constituents, monitoring its impacts on the
habitat and ecosystems becomes proportionally more imperative.
Though satellite imagery, soil sampling, water analysis, and
detailed air sensory may give researchers an idea about the
general health of the
habitat, the information provided by these techniques would not
give a very clear picture of how human encroachment is impacting
the animal life of the rainforest. Due to the sheer mass and
diversity of the rainforest, it would be extremely difficult and
probably
completely unfeasible to attempt to monitor all of the animals
that exist in the Amazon rainforest. Here is where indicator
species come in: due to their inherent
characteristics, preferred habitat and place in the food web,
indicator species are extremely sensitive to the overall health of
the rainforest's ecosystems. By monitoring the progress of these
species over time, researchers are able to easily determine
whether
or not an ecosystem is being affected by unusual or adverse
conditions. One particular type of animal that has been selected
to be a primary indicator species is the bat. Their commonplace
occurrence in every trophic level in the canopy and their relative
immobility by their maintenance of a permanent roosting place,
bats are relatively easy to find in the rainforest. They are also
significant contributors to the ecology of the rainforest, helping
to maintain insect populations, pollinating flowers and dispersing
seeds over broad areas.
Bats are of the order Chiroptera, which is divided up into
18 families, in all totaling 986 known species in the world. They
inhabit most temperate and tropical regions of the globe and are
one of the most numerous forms of mammals on the planet. Only
rodents
have more species than bats. The most obvious and unique
distinctive feature that bats have is the capability of flight.
They are the only mammals who have this capability, which is
granted to them by skin membranes that extend out from the side of
their bodies and their tails to connect their limbs with their
main bodies. The forearms and fingers have been adapted to support
these membranes, with long extended fingers and slender bones. The
entire body of the bat is designed for flight, with flattened
ribs, an extremely well supported shoulder girdle and clavicle,
and a rigid sternum.
Another highly unique characteristic of bats are their
employment of echolocation for nocturnal orientation. Vocal sounds
emitted through the nose or mouth by a bat in flight bounces off
surrounding objects, effectively giving them a sensory system
analogous to radar. This extra sense allows bats to avoid running
into obstacles at night and to detect the position of flying
insects or other potential food sources.
Bats generally tend to roost in a permanent shelter,
consistently returning to the same place to rest. Shelters can
include cages, trees, crevices, and even buildings. These
relatively secure areas are where bats hibernate when conditions
are
unfavorable, such as a climactic change or reduction in food
supply. During hibernation their body temperatures drop
significantly, reflecting a marked decrease in metabolism and
oxygen consumption. Temperatures and metabolism return to their
normal states immediately following the reawakening of the bats.
A common method of characterizing bats is differentiating
them by their distinct diets. Because of the overall species
diversity of bats, these diets spread over a large range of food
sources. Many can be characterized as follows:
- Insectivorous:
- most insect food obtained by flying
- most will eat some fruit
- largest and most diverse group of bats
- Fruit-eating:
- feed almost exclusively on fruit
- will eat some green vegetation
- sometime work together in groups
- live in tropical environments where fruit is
constantly ripening
- Flower-feeding:
- diet consists mainly of pollen and nectar
- will eat some insects found in flowers
- mainly tropic and subtropical bats
- Carnivorous:
- prey on frogs, birds, lizards, small mammals,
other bats
- extremely varied diet
- Fish-eating:
- catch fish near or at the water surface
All of the above types of bat can be found in the Amazon
rainforest, making them an exceptionally good indicator species,
since they are affected by multiple factors due to their reliance
on a diverse amount of food resources. Due to the large biomass
and
abundance of life in the rainforest, the Amazon is an especially
ideal environment for large colonies and an assorted number of bat
species that can be monitored at all different levels of the
canopy.
Sources:
Order
Chiroptera: Bats. John Hopkins University Press, 1997
Bats
Order Chiroptera, Museum of Zoology, University of Michigan, 23
July 1997
Order Chiroptera
Bat Detectors, Petterson Electronik,
batsound.com
William F. Laurence, "The Future of the Brazilian Amazon,"
Science
Magazine, 19 January 2001.
Amphibians
Why monitor amphibians?
The relevant defining characteristic of amphibians that
sets them apart from other creatures is the fact that they absorb
a great deal of chemicals through their skin as well as through
the thin, moist linings of their mouth and throat. This makes
them especially
sensitive to pollution present in the environment. In addition to
their wide distribution and large numbers throughout the
rainforest, they make an ideal set of animals for the monitoring
of toxin levels in the rainforest. They also constitute a large
enough food base for predators and a large enough controlling
force for insects and other
animals that any disruption in the population numbers of this
group of animals is likely to cause upheaval in the Amazonian food
web.
How will
they be monitored in the Amazon?
Due to the extensive nature of the Amazon Rainforest and
the limited budget and number of personnel involved with the
project, monitoring will consist of what will be essentially "hot
spot" checks. These will consist of blood tests on randomly
selected
animals in areas of concern to determine the exact degree to which
the ecosystem is being polluted. Additional tests, such as gross
anatomical observations for deformities and chemical testing for
behavioral abnormalities will be conducted to determine the
nonlethal synergistic effects of the polluting chemicals on the
amphibians2,3.
"Areas of concern" will consist of areas of the rainforest where
it is believed that pollution is, or could become a major problem
for the overall ecosystem's health. These include industrial
waste dumping sites, farmland drainage areas (pesticide runoff),
and any other site deemed threatened by pollution. Monitoring
actual
population numbers will not be necessary unless the toxins present
are severe enough in their effects to cause significant mortality
rates.
Miscellaneous Chemicals of Possible Importance to the Project
(copper
from mining, etc.)4
CHEMICAL SPECIE LIFE STAGE
CONCENTRATION (mg/L) PERIOD OF EXPOSURE (hours)
Copper Oxychloride Xenopus
dose of
0.007-0.008% 48
Copper Sulfate Xenopus laevis
1.7
48
Ethyl Acetate Xenopus laevis 3-4 weeks
180
48
Saccharin Xenopus laevis embryo
17.94
(17.60-18.30) mg/mL 96
Anthracene Rana pipiens embryo
0.065
24
(after 30 min exposure to sunlight)
0.25 24
(after 5 hrs exposure to sunlight)
Flouranthene Rana pipiens embryo
0.09
24
Carbaryl Xenopus laevis embryo
4.7
(3.9-5.6) 24
Works Cited:
1) Tyning, Thomas F. Stokes Nature Guides: A Guide to Amphibians
and
Reptiles. Little, Brown and Company. c1990.
2) Devillers, J. and Exbrayat, J. M. Exotoxicity of Chemicals to
Amphibians. Garden and Breach Science Publishers. c1992.
3) Cockell, Charles S. Ecosystems, Evolution, and Ultraviolet
Radiation. Springer-Verlag. c2001.
4) Devillers, J., Exbrayat J. M. Exotoxicity of Chemical to
Amphibians. Garden and Breach
Science Publishers. c1992.