nim : J1C108036
Abstract
The concept of biodiversity is widely used but poorly defined. Although there exist formal definitions, they are so broad and vague that their long –term effectiveness in environmental management is questionable. Some countries interpret conservation of biodiversity so rigorously that all development can be blocked by the prospect of the extinction or loss of critical habitat of any single species – it seems unlikely that growth and industrial expansion are resolved.
Inroduction
Biodiversity has emerged as a scientific topic with a high degree of social prominence and consequently of political importance. To the extent that scientists wish to see programs to conserve biodiversity implemented, they must be aware of the political aspects of problem and be prepared to make compromises that are necessary whwn one enters into the political arena.
Conservationists face similar issues- just as campaigns against cruelty to animals often deal more with the human appeal of the animal than with its actual suffering, so species loss is often seen more in terns of the attractiveness of the species to humans than any biological factors. This is a practical reality that we have to address, and if we hope to occomplish the kind of conservation goals that many scientists support, we need to understand how to integrate these with the often irrational processes that go the formulation of public policy.
Why Focus On Biodiversity ?
The current public emphase on biodiversity is fairly new, and it is interesting to consider how the concept developed. During the past half-century or so there has been a growing awareness of the importance of natural ecosystems and a desire to conserve rather than simply exploit our environment. The concept probably goes back to foresters and game managers like Aldo Leopold ( 1933 ) but came to the public attention with popular book like Fairfield Osborn’s “Our Plundered Planet ” ( 1948 ).
The problem with all this is that extinction is a natural phenomenon which occurs even in the absence of human pressure, and evolutionary history is a record of species being wiped out by natural occurrences or being superseded by better adapted life forms ( Example, the replacement of dinosaurus by warm-blooded mammals ).
The transition form conserving species to conserving biodiversity is a confusing one, and even in the scientific literature it is not always clear what is meant. However, given the social importance and prominence of biodiversity, it is vital that scientists be able to communicate with the public about what is happen and what the consequences of our actions or inaction in this field are likely to be.
Why Conserve biodiversity ?
Although the question may seem like heresy to an ecologist, we cannot take it for granted that all sectors of society see value in biodiversity. Quite the contrary, humans often deriberately reduce biodiversity to achieve their goals. In many parts of the globe fields or richly varied plant types have been replaced by vast uniform fields of maize, wheat, and other valued crops.
In almost every case where undesirable species are removed or suppressed no effort is made to consider the impact on biodiversity. Healthy crops or abundant fish are considered far more important than maintaining the diversity of insect fauna or marine mammal populations. The unappealing nature of many vital organisms, such as the vast variety of marine worms, does not contribute to public appreciation of their roles. So it cannot be taken for granted that everyone supports biodiversity, and conservation may at times encounter surprising resistance.
Types of biodiversity
There are many different kinds of definition that have been devised for biodiversity, but only three main categories will be considered here. One is genetic diversity, which can refer to the diversity of genes within a single species as well as between species. Another is taxonomic diversity, based of course on the different taxa contained within an ecosystem. The third is functional diversity, which recognizes the variety of roles that different organisms- including the separate life stages of individual species- play in the ecosystem.
The concept of genetic diversity also applies between populations, since species replacement in response to inveronmental change usually indicates that the replacement species is genetically better suited to the changed conditions. We tend to think of these changes as different, especially when the replacement is a previously rare or exotic species, but the underlying idea that under changed conditions there is likely to be a shift to a population better suited to the changed conditions is fundamentally the same whether they come from the same of different species.
Taxonomic diversity is probably the most widely recognized from of biodiversity, but it may also be the least meaningful. It can be defined in many ways, but basically in involves identifying the number of different taxa ( usually at the species level ) and possibly weighting them by the abundance of individuals. Calculations of taxonomic biodiversity tend to be limited by the taxonomic expertise available, especially at lower trophic levels – whales are easy to classify, but nematode taxonomists are in short supply. There is a tendency to lump some of the more confusing taxa together at the genus or higher level, which introduces a degree of arbitrariness to the calculations.
Perhaps the most important form of biodiversity is functional diversity, the kind of diversity that ensures that every task that needs doing within an ecosystem gets done. It doesn’t help to have thousands of species of herbivores in a system if there are no primary producers to feed them and no detritivores to clean up after them. But there major difficulties in defining functional diversity, no least of which is difining what the various functions are and who is capable of carrying them out.
Generalised niche theory
The niche is classically associated with existing populations ( Hutchinson 1957 ) and strict Hutchinsonians reject the concept of an empty niche, which by definition is not associated with any existing organisms. This is however a valuable concept in understanding biodiversity, so it is worth exploring. The potential niche of a population is the range of inveronmental conditions in which it can persist, the actual niche is the range in which it is currently found ( often called the realized niche ), and an empty niche represents an environment which could in principle support a population of some sort but currently does not.
A diverse ecosystem is usually one in which the niches are closely packed, in which every room is occupied by a different family to stretch the analogy ( Christiansen and Fenchel 1977 ). Invasion by a super-competitor which can expel many of the native species from their niches, in effect taking over an entire apartment, greatly reduces the diversity of the community. But what are consequences of this for ecosystem function.
While the idea of defining biodiversity in terms of niches rather than species is speculative, and it will certainly not sit well with some of the classical interpretations of the niche, it offers a potential formalism for investigating biodiversity under conditions of environmental change that may have some advantages over functional biodiversity, since it may be easier to identify changes in the possible niche structure of a changed environment than changes in functional requirements.
Triage
No matter how we choose to define biodiversity, our ability to conserve it is limited. Aside from the inevitability of natural extinction, there are forces beyond the control of the scientific community or environmental agencies which force us admit that some battles cannot be won. The changes of restraining the exploding human population, industrialization, and consequent loss of natural habitat are nil ( Ehrlich 1971 ).
The concept of triage was developed by Baron Dominique –Jean Larrey (1832). Napoleon’s cheaf surgeon, and is still used today in medical situations where the need for medical attention exceed the resources available. Basically it consists of directing care to those patient who are seriously at risk but are likely to be saved by medical attention. The “ walking wounded ” who are likely to recover in any case and those who are too seriously injured to have a good chance of recovery constitute the other two branches of the triage system and receive minimal treatment.
The concept of triage is similar to the use of cost effectiveness criteria in economics. A battlefield physician confronting three casualties and evaluating the probable outcomes of treating them might conclude that one patient needs treatment to save his eyesight- another will probably die anyway, but whit a small chance of recovery with treatment – and the third is bleeding to death, but medical care would probably save his life.
Setting value on species
One of the hardest part of conservation is trying to decide where to direct one’s limited effort and resources, and this is especially hard when the outcome is likely to be extinction is a factor that upsets both scientists and laymen, and for the scientific community the prospect of losing a species before we learn about it is doubly distressing. Even so, we have to balance our priorities carefully to make wise choises.
At the top of any list of factors that make a species a good candidate for public support is charisma. Some animals capture the public attention and will always lead the campaign for conservation, regardless of biological concerns. A second factor that again may not correspond to the priorities of scientists, nor of many environmentalists, is the value of a species to man. There has been tremendous concern about the depletion of stocks of Atlantic cod ( Gadus morhua) in recent years, but the endangered status of the barndoor skate (Raja laevis), a species of virtually no commercial importance, passed virtually unnoticed (Casey and Myers 1998)
However, there are many technical issues about the ecological roles that plants and animals play which probably have to be worked out within he scientific community. Some species truly have unique and essential ecological functions, ranging from the common earthworm up to the mighty polar bear, and it is relatively easy to make a case for their conservation.
Obstacles to conservation
There are many obstacle that makenthe life of a conservationist hard, and it is important to understand the rationale behind resistance to conservation efforts. Although scientists tend to view all species and habitats with the enthusiasm that a thirst for knowledge generates, this attitude is not widely share, and often the environments that most intrigue the scientific community, such as marsh lands, generate little excitement among the population at large.
While the case of the endangered fly in California may seem extreme, there are many cases where conservation efforts engender enormous secondary costs, either by lessening support in general for conservation or sometimes by need for financial support to affected communities. The government of the United States and California do not offer compensation to developers whose projects are blocked by habitat concerns, but in countries like India, where protected elephant species can destroy crops, villages, and human lives, the costs and liabilities must be viewed as a governmental responsibility (Bist 2002). Other endangered species, such as some of the great apes and whales, are traditional food sources for native communities.
Exotic species
In speaking of biodiversity we tend to focus uneritically on conservation of species, but there are some species that might arguably be climinated from the biosphere. There is general agreement that certain disease organisms should be eliminated, such as those responsible for smallpox and poliomyelitis, with only a few reservoirs maintained so that if they reappear we can produce vaccines.
There is a common sense that non –native species always reduce biodiversity, but this probably reflects the fact that it is the invaders which do the greats harm that attract the most attention – rabbit in Australia, goat in Galapagos, water hyancinth in American waterways, mosquitoes in Hawaii, zebra mussels in Great Lakes are only few example. Therea are probably many exotic species which fit in well to new environments and may not even be identified as foreign.
Even for recent introductions we need to ask whether the process is reversible – even if it is possible to turn back the clock by removing an invasive species, we need to determine whether the system will return to its previous state. If native species have gone extinct or been severely depleted, they may never recover.
Speciation factories
Some of the attention in biodiversity studies has focused on biodiversity “hotspots”, regions where enormous numbers of distinct species can be found. If or objective is to save many species, then certainly we should focus our attention on areas like tropical rainforests and the Gulf of Thailand where there are far more areas like tropical rainforests and temperate regions. This viewpoint should be looked at critically, and it is not always clear what the presence of many different species means in terms of any reasonable measure of ecosystem performance.
We do not really understand what determines the number of species in an ecosystem, or why some system have many more than others (Hutchinson 1959). Speciation can occur through many mechanisms-island biogeography is just one of many ways in which a species can split into two, as separated subpopulations evolve slightly differently, especially in the presence of any environmental gradient.
This leads us into Pandora’s box of evolutionary theory, and it is difficult to see how we can judge biodiversity without understanding how it aries. The concept of speciation occurring at periods when organisms reach a stage where they can “chose” between alternate life history patterns, the idea that there can be a bifurcation in the optimal strategy, is akin to the theory of punctuated equilibrium (Gould 1980) which remains controversial and wil not be further explored here.
Regime Shifts
Underlying some of questions about ecosystem dynamics and the ways in which biodiversity changes are the possibilities of major alterations, either natural or enthropogenic, in the structure of communities. Such changes have been documented in the fossil record and by studies of fish scales in sediments (Soutar & Isaacs 1969,1974), and there is evidence of recent dramatic changes in the composition of the North Sea community (Lindeboom et al. 1995).
Risk of species loss
One of the most frightening aspects of dealing with biodiversity is the realization that if we fail to conserve some species and it goes extinct, it will be gone forever – there is no chance of recovery. This element of finality is probably one of the reasons why conservation has achieved the social impact it has, and the awareness that manakind has wiped out such impressive creatures as the wolly mammoth (Mammuthus primigenius), the Steller’s sea cow (Hydrodamalis gigas), the dodo (Raphus cucillatus), and the passenger pigeon (Ectopistes migratorius) is alarming evidence that the permanent loss of prized species is possible.
Even when we fully understand the ecological role of a species, we may not be able to judge the consequences of its loss. Surely the earthworm must be one of the most essential members of the terrestrial community, but even though almost all the native earthworms is Canada were apparently eradicated by European species, the impact of this loss seems to have been far less than we might expect (Hogner 1953). Perhaps we know far less about the robustness communities than we think we do.
Summary
Biodiversity is a huge field and this article has touched only a few of its aspects. The underlying message however can be summarized in a few simple statements.
1. Biodiversity is an important concern of scientists, environmental activists, society as a whole, and politicians.
2. Conservation of biodiversity requires communication and cooperation between all of these parties.
3. Concepts of biodiversity must therefore be meaningful to all parties.
This means that scientific community must develop definitions of biodiversity which they ean explain and defend to the general public, and they must also be sensitive to public, and they must also be sensitive to public concerns which may not always mesh with their scientific judgments. Polities is based on compromise usually means giving up something which you value. It is unlikely that we will ever achieve a perfect policy on conservation of biodiversity, but a good policy is better than none.
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