Fauna Group Research (Characterization)
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, ecosystemfunctions 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 willdecrease proportionally. This represents a
direct correlation between the two.
c) Idiosyncratic hypothesis - There is no relationship
between biodiversity andecosystem 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 andsustainable 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. Nature390: 507-509.
(7) Nordgren A, Baath E and Soderstrom B (1983) Microfungi
and microbial activityalong 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 functionalperspective. 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:
compliance indicators: these verify that maintenance
or restoration goals have been met
diagnostic indicators: these help the investigation of
observed disturbances
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 <www.press.jhu.edu/books/walkers_mammals_of_the_world/chiroptera/chiroptera.html>
Order Chiroptera, Museum of Zoology, University of Michigan,
23 July 1997 <animaldiversity.ummz.umich.edu/chordata/mammalia/chiroptera.html>
Bat Detectors, Petterson Electronik, <www.batsound.com/psondet.html>
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 BreachScience Publishers. c1992.