Defining Ecological Value
Defining ecological value can be conceptualized as a process. This process of defining an ecological value begins with the identification of the ecological values to be protected, otherwise known as GAE’s. The process is carried out in two parts.
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First, using a strictly ecological perspective, ecological values are identified. In other words, this identification is carried out from the ecological perspective. Secondly, human values that relate to the ecological values are put into consideration (Paustebauch, 2002). The two parts of defining ecological value are analyzed below:
Identification of Ecological Values
The first part is carried out scientifically by identifying the values common to all ecosystems. This is followed by narrowing in on the area of interest.
It should however be noted that only ecologically relevant GAE’s are put into consideration. There is a procedure that should be followed in identifying these relevant GAE’s. This procedure follows the steps below:
Identifying Values Common to All Ecosystems
Values common to all ecosystems are identified. Examples of such values are analyzed below:
- Biodiversity which is basically how many different communities are in the ecosystem and the generic diversity. The more disturbed the ecosystem, the higher the probability of it having a higher biodiversity.
- Ecological function or how the living organisms in that ecosystem interact in a hierarchal way to sustain the cyclic processes in that ecosystem. An ecosystem is said to have functional integrity if it has a population consisting of organisms from various taxa (Paul, 2010).
- Any normally functioning ecosystem has a directional flow of nutrients and energy. This directional flow is designed in such a way that it maintains a balance in the ecosystem. Nutrients and transport processes are therefore common values in all ecosystems (Paul, 2010).
Identification of the Functional Components of Regional Ecosystems
After identification of the values common to all ecosystems, there is need then to identify the functional components of regional ecosystems. It is noted that the basic functional component of any ecosystem is the food web.
This is made putting into consideration the broad interrelationships between the various parts in order to determine the relevance of each species (Glenn, 2006).
For example in a tropical rain forest, the main producers can be the lianas, the consumers are herbivores and carnivores and the decomposers are the detritivores. Such broad categorization makes the task easier in cases where the species are not known. This is for example in complex ecosystems such as those found in countries and regions such as the New Guinea.
Developing a Food Web for the Ecosystem
A food web for the ecosystem is then developed. This shows the feeding preference of each of the species in the ecosystem. Specificity is the key at this step. This is given the fact that there is need to state the function or role played by each species found in the ecosystem and how this affects the others.
Unlike the previous step, this step is organized into more trophic levels. For instance in New Guinea, the producers are lianas, trees and ground canopy. The herbivores are the first consumers in the ecosystem. Omnivores and intermediate predators are intermediate consumers in the ecosystem.
Lastly, terrestrial and arboreal predators are to be found on the periphery of the food web. There are also those species which plays the role of decomposer. According to Glenn (2006), scavengers, detritivores and chemicals are part of the decomposers.
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Determining the Ecologically Relevant Characteristics of the Functional Components
The ecologically relevant characteristics of the functional components in the ecosystem are then determined. This defines the non- trophic attributes which are a critical part of the ecosystem. Examples of such attributes are listed below:
- Shelter or habitat for the species and the source of the shelter
- Source of energy or food for the species in the ecosystem
- The process of distribution of seeds probably through pollination. This shows how plant species are distributed in the ecosystem
- Processes that break down dead matter to release nutrients. This will include the identification of the mechanisms or agents that aid this breaking down of dead matter
Stating the Relevant GAEs
The relevant GAEs are then clearly stated after determining the ecological attributes of every functional component. These are considered as endpoints of a specific ecosystem.
Human Values and Ecological Values
The first procedure in defining ecological values involved the identification of the ecological values of the ecosystem. This was analyzed in detail above.
The next procedure in defining an ecological value is determining how much it conforms to the societal and ecological values (Glenn, 2006). Values touching on issues such as endangered species, valued species, resources and species identified as important in terms of recreation and aesthetic purposes are identified.
This is a participatory phase of the process. Local citizens including the indigenous inhabitants of the area are contacted for purposes of understanding the values placed on ecological resources.
Other sources of societal values can be gleaned from existing literature such as the ones compiled by the International Union for the Conservation of Nature and Natural Resources (herein referred to as IUCN).
It can also be gleaned through interviews with knowledgeable individuals. The ecologically relevant values to be protected here include game species, water sheds and indigenous plants.
Probabilistic Risk Assessment
Chapter 22 touches on the potential risks faced by the duck population in the Canadian prairies. These are for example risks posed by the use of insecticides. The aerial hazard causing insecticides referred to in this case are the organophosphates, organochloride and pyrethroid insecticides.
The insecticides pose indirect risks in the pothole region by interfering with the ducks’ nesting habitats and food supplies. The insecticides also affect the formation of the eggs early foraging by ducklings. These are the risks that were studied in this chapter (Paustebauch, 2002).
Organophosphate pesticides contain carbaryl and deltametrin as the main ingredients. The chemicals form compounds believed to have negative effects on Saskatchewan (Paul, 2010). It was to be determined which percentage of these compounds caused toxicity and at what levels.
This gave rise to probabilistic studies. Several questions were asked and this further contributed to the probabilistic studies. The questions posed are provided below:
- What was the percentage of invertebrates that died due to aerial toxicity from insecticides in the first 24 hours after spraying?
- What role does gill absorption, ingestion and dermal intake play in mortality cases?
- How much exposure to insecticides leads to mortality among invertebrates?
- In which slough depth is there a probability of more deaths occurring?
- In which slough width is there more deaths after spraying?
The end result or ecologically relevant value to be protected is the micro-invertebrate as it plays an important role as a source of food for the ducks (Glenn, 2006). The conceptual assessment model involves studying ways through which the insecticides reach the sloughs.
They may reach the sloughs for example through wind or water and the exposure concentration distribution. A short time frame of 24 hours is considered and thus sediments and their effects are not studied.
Risks are determined through exposure of micro- invertebrates to determine the levels of concentration that are lethal. Apparently, the amount of insecticide applied determines how much of it gets to the sloughs.
For example, application of insecticides from higher heights on a windy day leads to more of it being spread into the sloughs. Different birds prefer different pond depths with semi- permanent holes having a higher rate of attraction as breeding sites (Glenn, 2006).
This means that if a semi- permanent hole is near a farm, the probability of it getting contaminated by insecticide is very high. This leads to high mortality rates on the part of the species that prefer that habitat. The deeper the slough, the less the mortality rate because of less contamination.
Finally, risk is characterized using the exposure and effect analysis. The first way of doing this is to determine how exposure and effects overlap each other. In this case, two micro- invertebrates are used. These are the mosquito and a water-flea.
They are exposed to different concentrations of deltamethrin at their various toxic levels (Paustebauch, 2002). The result of this was the various probabilities exceeding fifty percent mortality rate for the species.
Application of reliability theory is fundamental in determining the probability of an event occurring or failing to occur. For example, lethal concentrations may lead to more than lethal effects giving erroneous results. The results can be used to make inferences about the other micro- invertebrates in the community using similar characteristics that the ecosystem taxa share.
There is however some inconsistencies between the observations made in the field and those made in the lab. In some instances, values obtained from the lab may differ from the ones obtained from the field probably due to the lab being an artificial environment (Paustebauch, 2002).
This can be overcome through the application of probabilistic assessment procedures. By using the quantitative results, one can determine whether the results differ significantly or not and thus repeat the experiment if necessary.
Risk assessment framework is used in exposing different species to varied concentrations of insecticides. This is considering how the insecticide will reach the slough. This could be through seepage, wind dispersal and surface run- off that eventually forms the breeding grounds dependent on factors like humidity, height and frequency of application.
The other way is to quantitatively describe the effect of a chemical at different concentrations. A toxicological benchmark of 50% is used and different chemicals are used on different species at their lethal levels (Glenn, 2006). These are then plotted on a table to determine which species are tolerant to which chemicals and at what level.
The ecological values in this case are the invertebrates and the prairie nesting ducks (Paustebauch, 2002). The societal values include how farmers value their crops. The question is: can they let their crops be destroyed by grasshoppers just to protect the birds?
We have to interview the farmers to know how far they would go in protecting their crops. The ecological values in case one include all the endangered organisms constituting the ecosystems of various forests. The societal values in the case are how much the indigenous people value the forests.
Glenn, S. (2006). Ecological risk assessment. NY: CRC Press.
Paul, E. H. (2010). Environmental and economic sustainability. NY: CRC Press.
Paustebauch, D. J. (2002). Human and ecological risk assessment. NY: John Wiley Publishers.