In this article we will discuss about:- 1. Introduction to Biodiversity 2. Definition of Biodiversity 3. Convention 4. Types 5. Components 6. Threats 7. Loss 8. Hotspots 9. Population Diversity 10. Measurements.
Introduction to Biodiversity:
Human population growth is clearly outstripping the Earth’s non-renewable resources, biological fundaments and Earth’s ability to revive. Ecological degradation and its corollary – biodiversity loss – pose a serious threat to development. Ecologically destructive economic activities are inefficient not merely because of the resulting resource misallocation but also because of the excessive scale of activity levels in relation to the limited availability of natural resources. In order to bring about sustainable resource conservation and management, it is essential to adopt several different approaches for managing our forests and biodiversity.
Future efforts for conservation and management of our natural resources must derive from a set of clear objectives, mechanisms for action and commitment from all stakeholders. Apart from this, halting the process of degradation and species loss requires specialized solutions and an understanding of ecological processes. Protecting biodiversity does not merely involve setting aside chunks of area as reserves.
Instead, all the ecological processes that have maintained the area’s biodiversity such as predation, pollination, parasitism, seed dispersal and herbivory, involving complex interactions between several species of plants and animal needs to be ensured. This is possible only if reserves are large enough to maintain these processes and some of the other crucial links in the web of life.
There is also the need for greater involvement of communities and for models which decentralize of management and conservation roles and responsibilities. Strengthening of information resources is important pertaining to forests, biodiversity – flora and fauna, causative factors for their degradation and major threats.
Data on current status and ongoing losses/gains of biodiversity is very important for successfully implementing conservation strategies. More importantly, laws and policies governing natural resources need to be strengthened to tackle the scale of the problem and the insufficiencies should be addressed with a sense of urgency.
Definition of Biodiversity:
Biodiversity is a modern term which simply means “the variety of life on earth”. This variety can be measured on several different levels. The most widely accepted definition for biodiversity is contained within the Convention on Biological Diversity. ‘Biological diversity’ means the variability among living organisms from all sources including, among other things, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part; this includes diversity within species, between species and of ecosystems.
Estimates of global species diversity vary enormously because it is so difficult to guess how many species there may be in less well explored habitats such as untouched rain forest. Rain forest areas which have been sampled have shown such amazing biodiversity that the mind boggles over how many species there might remain to be discovered in unexplored rain forest areas and microhabitats. According to some biologists, the true numbers of living species on earth are much higher and any range from 3.6 million to more than 100 million.
Ten million is probably nearer the mark. Only 1.4 million species have been named. New species are continually being discovered every year. The number of species present in little- known ecosystems such as the soil beneath our feet and the deep sea can only be guessed at. It has been estimated that the deep sea floor may contain as many as a million undescribed new species. It is absolutely difficult to mention the exact number of species available.
Earth is endowed with enormous biodiversity. About 3,00,000 green plants, 8,00,000 insects, 23,000 fishes, 9,000 birds, 6,500 reptiles, 4,100 mammals and few thousand microbes have been estimated to exist in the world. Biologists estimate that more than half of the species occur in the tropical rain forest on earth.
Many world records of biodiversity have been reported from these natural greenhouse e.g., 425 kinds of trees in one hectare of Brazil’s Atlantic forest and 1,300 butterfly species form a corner of Peru’s Manu National Park. These figures are more than 10 times the number of species found in the comparable sites of World. On other side, McMurdo Dry valley of Antarctica has the poorest and the coldest soils in the world but still provides shelters to spares communities of bacteria, fungi and microscopic invertebrates.
India is one of the 12 mega-biodiversity centers of the world. India is divided into 10 bio-geographic zones and 25 biotic provinces representing all the major ecosystems. India is recognized as a country rich in biodiversity because of its tropical location, varied physical features, altitude and climate.
Various taxa showing the number of species reveals that India has nearly 30 per cent of the world’s endemic flora and 62 per cent of the known amphibian species in the world. According to Zoological Survey of India, nearly 53,430 insects, 5,050 molluscs, 2,546 fishes, 204 amphibians, 456 reptiles, 1,228 birds and 372 mammals are reported from India.
The Indian flora is mainly concentrated in four hotspots of floristic diversity viz. Himalayas, Western Ghats (and Sri Lanka), NE India and Andaman Islands (Indo-Burma) and Nicobar Islands (Sundaland), which are identified amongst the thirty four global diversity hotspots. The recent group wise list of species in India and world recorded by Botanical Survey of India.
Biodiversity Conservation Efforts:
At International level, several organizations took initiative to conserve global biodiversity since early 1970s. United Nations Environmental Programme (UNEP) was formulated by 113 member countries under the hood of United Nations on 5 June 1972 in Stockholm (Sweden). Through this work plan, different countries enacted laws on environment protection from time to time and these laws paved the way for biodiversity
conservation as well.
A global strategy for dealing with all aspects of biodiversity was prepared by the World Resources Institute (WRI), UNEP, FAO and IUCN. The detailed strategy was put forth at the United Nations Conference on Environment and Development 1992. The World Summit on Sustainable Development held in Johannesburg (South Africa) in 2002 formulated the guidelines for biodiversity conservation under a long-term development programme all over the globe.
The Convention on Biological Diversity:
The Convention on Biological Diversity (CBD), one of the key agreements adopted during the Earth Summit 1992, is the first comprehensive global agreement which was related to all aspects of biodiversity. The CBD has membership of 192 countries, sets out commitments for maintaining the world’s ecological underpinnings, while pursuing economic development.
The Convention, while reaffirming sovereign rights of nations over their biological resources, establishes three main goals – conservation of biological diversity, sustainable use of its components and the fair and equitable sharing of the benefits arising out of the use of genetic resources.
The year 1992 was a historical moment in the struggle for conserving the world’s natural heritage which had set off the creation of many large protected areas. The 4th World Parks Congress was held in Caracas, Venezuela in February 1992 organized by the World Conservation Union (IUCN), the global alliance for conservation and wise use of natural resources.
The world parks congress adopted the “Caracas Action Plan” with recommendations for strategic actions for protected areas creation and management over the decade from 1992 to 2002, calling for special attention to enhancing the capacity to manage marine protected areas and to include them as major components of national system plans.
The Caracas congress devoted much of its attention to the need to build constituencies, involve major interest groups in planning and management, enhance revenue generation and financing and assess and quantify the benefits protected areas provide.
The United Nations Conference on Environment and Development or “Earth Summit” in Rio de Janeiro, Brazil was the largest-ever meeting of world leaders and a historic set of agreements was signed, including the CBD, which was the first global agreement on the integral conservation and sustainable use of biological diversity. The CBD was signed at the Earth Summit by over 150 Governments, and since then, more than 175 countries have ratified the agreement.
The significance of the CBD was not only the commitment of almost all the countries of the world to promote biodiversity conservation, but for the first time in history, a funding mechanism was established that could at least launch a serious initiative for establishing biodiversity conservation programmes in countries that for compliance, would have to rely heavily on external financing and technical assistance.
Launched in 1991 as an experimental financing facility, the Global Environment Facility (GEF) was restructured after the Earth Summit for the financing of a number of environmental issues among which biodiversity conservation is of primary importance. Two years after the Earth Summit, the IUCN published a “Guide to the Convention on Biological Diversity” which provides a solid basis on how to work with the CBD.
Types of Biodiversity:
Biological diversity is usually considered at three different levels:
i. Genetic diversity.
ii. Species diversity.
iii. Ecosystem diversity.
i. Genetic Diversity:
Genetic diversity refers to the variation of genes within species or variation between individuals of the same species. This includes genetic variation between individuals in a single population, as well as variations between different populations of the same species.
Genetic diversity can be measured using a variety of DNA-based and other techniques. New genetic variation is produced in populations of organisms that can reproduce sexually by recombination and in individuals by gene and chromosome mutations.
The large differences in the amount and distribution of genetic variation can be attributed in part to the enormous variety and complexity of habitats, and the different ways organisms obtain their living. One estimate is that there are 10,000,000,000 different genes distributed across the world’s biota, though they do not all make an identical contribution to overall genetic diversity.
In particular, those genes which control fundamental biochemical processes are strongly conserved across different species groups (or taxa) and generally show little variation. Other more specialized genes display a greater degree of variation.
ii. Species Diversity:
Species diversity refers to the variety of species in a given region or area. This can either be determined by counting the number of different species present, or by determining taxonomic diversity. Taxonomic diversity is more precise and considers the relationship of species to each other.
It can be measured by counting the number of different taxa (the main categories of classification) present. Aspects of species diversity can be measured in a number of ways.
Most of these ways can be classified into three groups of measurement:
a. Species richness.
b. Species abundance.
c. Taxonomic or phylogenetic diversity.
a. Species Richness:
Measures of species richness count the number of species in a defined area.
b. Species Abundance:
Measures of species abundance sample the relative numbers among species. A typical sample may contain several very common species, a few less common species and numerous rare species. Measures of species diversity that simplify information on species richness and relative abundance into a single index are in extensive use.
c. Taxonomic or Phylogenetic Diversity:
Another approach is to measure taxonomic or phylogenetic diversity, which considers the genetic relationships between different groups of species. These measures are based on analysis which results in a hierarchical classification usually represented by a tree that depicts the branching pattern which is thought to best represent the phylogenetic evolution of the taxa concerned.
On a broad scale, species diversity is not evenly distributed across the globe. The single most obvious pattern in the global distribution of species is that overall species richness is concentrated in equatorial regions and tends to decrease as one move from equatorial to Polar Regions.
In general, there are more species per unit area in the tropics than in temperate regions and far more species in temperate regions than there are in Polar Regions. In addition, diversity in land ecosystems generally decreases with increasing altitude. Other factors which are generally believed to influence diversity on land are rainfall patterns and nutrient levels.
iii. Ecosystem Diversity:
Communities of plants and animals, together with the physical characteristics of their environment (e.g. geology, soil and climate) interlink together as an ecological system, or ecosystem. It is harder to define ecosystem diversity than species or genetic diversity because the boundaries of communities (associations of species) and ecosystems are more fluid.
Ecosystem diversity is more difficult to measure because there are rarely clear boundaries between different ecosystems and they grade into one another. However, if consistent criteria are chosen to define the limits of an ecosystem, then their number and distribution can also be measured.
Ecosystem diversity encompasses the broad differences between ecosystem types, and the diversity of habitats and ecological processes occurring within each ecosystem type. Since the ecosystem concept is dynamic and thus variable, it can be applied at different scales, though for management purposes it is generally used to group broadly similar assemblages of communities, such as temperate rainforests, lakes or coral reefs etc.
Components of Biological Diversity:
Generally, benefits arising from the components of biological diversity can be considered in three major groups:
1. Ecosystem services.
2. Biological resources.
3. Social benefits.
The details of each components of biological diversity with examples are given below:
1. Ecosystem Services:
i. Protection of Water Resources:
The natural vegetation near catchments areas helps to maintain hydrological cycles, regulating and stabilizing water run-off, and act as a buffer against extreme events of flood and drought condition. However, removal of vegetation on these area results in siltation of catchment waterways, loss of water yield and quality and degradation of aquatic habitat.
ii. Soils Formation and Protection:
Biological diversity helps in the formation and maintenance of soil structure and the retention of moisture and nutrient levels including productive capacity of the soil, prevention of landslides, safeguard coastlines and riverbanks and prevent the degradation of coral reefs and riverine and coastal fisheries by siltation. But the loss of biological diversity also contributes to losses such as salinization of soils, leaching of nutrients, accelerated erosion of topsoil and reducing the land’s productivity.
iii. Nutrient Storage and Cycling:
Biological diversity provides the vital function of recycling nutrients. Plants are able to take up nutrients from the soil and these nutrients become basis of food chains, used by a wide range of other life forms.
iv. Pollution Breakdown and Absorption:
Ecosystems and ecological processes play an important role in the breakdown and absorption of many pollutants created by humans and their activities. These include wastes such as sewage, garbage and oil spills. Components of ecosystems from bacteria to higher life forms are involved in these breakdown and assimilative processes.
Excessive quantities of any pollutant, however, can be detrimental to the integrity of ecosystems and their biota. Some ecosystems, especially wetlands, have qualities that are particularly well suited to breaking down and absorbing pollutants. Natural and artificial wetlands are being used to filter effluents to remove nutrients, heavy metals and suspended solids, reduce the biochemical oxygen demand and destroy potentially harmful microorganisms.
v. Contribution to Climate Stability:
Vegetation influences climate at the macro and micro levels. Growing evidence suggests that undisturbed forest helps to maintain the rainfall in its immediate vicinity by recycling water vapour at a steady rate back into the atmosphere and through the canopy’s effect in promoting atmospheric turbulence. At smaller scales, vegetation has a moderating influence on local climates and may create quite specific micro-climates. Some organisms are dependent on such micro-climates for their existence.
vi. Maintenance of Ecosystems:
Ecosystem relationships resemble a web of connections from one living thing to many other living and non-living things. They not only allow survival, but also maintain a balance between living things and the resources (such as food and shelter) they need to survive. Vegetation is integral to the maintenance of water and humidity levels and is essential for the maintenance of the oxygen/carbon dioxide balance of the atmosphere.
Due to the complex nature of ecosystem relationships, the removal/disturbance of the ecosystem could affect the functioning of other components of the ecosystem. Maintaining natural habitats helps ecosystem functions over a wider area.
2. Biological Resources:
Biodiversity ensures food security. Animals and humans depend on plans for food. People have 7,000 plant species for food. Today only 20 plant species provide 90 per cent of world’s food and just three plant species namely rice, wheat and maize supply more than 50 per cent food.
Therefore only the conservation of biodiversity can ensure global food security for rapid increase human population as well as animal population. One of the important benefits of conservation of biodiversity is the wild plant gene pool which is available to augment the narrow genetic base of these established food crops, providing disease resistance, improved productivity and different environmental tolerances.
People have long used biological resources for medicinal purposes. Natural flora and fauna are the major sources of pharmaceuticals for curing various ailments. The Indian system of Ayurvedic medication is entirely dependent on plant biodiversity. Diverse plants have diverse medicinal value and provide useful drugs. For example, bark of the Cinchona plant contains an alkaloid called quinine which is prescribed by physicians for curing malaria. Some other plant species Rauwolfia, Aconite, Poppy are commonly used in pharmaceutical industries for extracting useful drugs.
iii. Wood Products:
Wood is a basic commodity used worldwide and is still largely harvested from the wild. It is a primary source of fuel, construction and forms the basis for paper production and other industrial uses.
iv. Future Resources:
There is also potential for further development of biotic resources for natural pesticides and other useful products such as fats and oils. The conservation of diversity is also essential for finding effective biological control organisms and for breeding disease resistant species. Genetic engineering of microorganisms promises further advances in the production of new compounds and processes.
3. Social Benefits:
i. Research, Education and Monitoring:
There is still much to learn on how to get better use from biological resources, how to maintain the genetic base of harvested biological resources and how to rehabilitate degraded ecosystems. Natural areas provide excellent living laboratories for such studies, for comparison with other areas under different systems of use and for valuable research into ecology and evolution. Unaltered habitats are often essential for certain research approaches, providing controls against which the changes brought about by different management regimes may be measured and assessed.
Biological diversity is an intrinsic part of many areas for tourism and recreational purposes. People value such areas for a variety of recreational pursuits: film, photographs or literature based on or using wildlife, natural habitats and natural features; bird watching; and ecological field study and other scientific pursuits.
iii. Cultural Values:
The cultural value of biological diversity conservation for present and future generations is an important reason for conserving it today. Human cultures co-evolve with their environment and the conservation of biological diversity can be important for cultural identity. The natural environment provides for many of the inspirational, aesthetic, spiritual and educational needs of people now and in the future.
The aesthetic values of our natural ecosystems and landscapes contribute to the emotional and spiritual well-being of a highly urbanized population. The conservation of biological diversity also has ethical benefits. The presence of a wide range of living organisms reminds people that they are but one interdependent part of Earth.
Aboriginal relationships to the land and sea, and its animals and plants are complex. To the people, the land and sea has a deep spiritual, economic, social, protective and recreational significance. By hunting and gathering, tribal aboriginal people are not only supplementing their diet with food very high in nutritional value; they are also confirming their self- sufficiency and, more importantly, educating their children in relationships to the land and to other aspects of their culture. Biological diversity conservation can contribute to the conservation of aboriginal cultural identity.
Threats to Biodiversity:
There are several factors for threat to biodiversity and biodiversity loss. Today we are losing two to five species per hour from tropical forests alone. This amounts to a loss of 16 million populations per year or 1800 populations per hour. If the trend of population loss remains continues, about 20 per cent of the total 2,50,000 higher plant species will be lost in the next few decades and another 25 per cent by the end of the 21st century.
i. Habitat Loss and Degradation:
Habitat loss and degradation is considered by conservation biologists to be the primary cause of biodiversity loss. Clearance of vegetation for food production, human settlement and timber leads to degradation of habitat. The destruction of resources leads fragmentation of the area into small segments. Habitat loss, alteration and fragmentation directly affect the species that rely on the habitat that is being changed.
ii. Introductions of Invasive Alien Species:
Invasive species considered second largest threat to biodiversity worldwide. Whether introduced on purpose or accidentally, non-native species can cause severe problems in the ecosystems they invade, from affecting individuals to causing huge changes in ecosystem functioning and the extinction of many species. Virtually all ecosystems worldwide have suffered invasion. In the USA, it is estimated that an economic loss of $79 billion was incurred because of 79 harmful alien species during 1906-91.
In India, ICFRE has identified nearly 75 forest invasive species, out of which 61 are of plants, 12 are fungi and 14 are insects, which are a threat to the natural forest cover of the country. In India, some of the invasive species are Parthenium hysterophours, Eupatorium adenophorum, Eupatorium odoratum, Mikania microantha, Ageratum conyzoides and Galinsoga poarviflora which have already caused a huge loss to the local biodiversity. In Indian flora, about 40 per cent of the species are alien of which 25 per cent are invasive.
iii. Over-Exploitation of Natural Resources:
Exploitation of biodiversity occurs for food, construction, industrial products, pet trade, fashion, traditional medicines etc. Selective removals of an individual species can imbalance ecosystems and all other organisms within them.
iv. Pollution and Diseases:
Pollution is currently poisoning all forms of life, both on land and water, and contributing to climate change. Any chemical in the wrong place or at the wrong concentration can be considered a pollutant. Transport, industry, construction, extraction, power generation etc. contribute pollutants to the air, land and water.
These chemicals can directly affect biodiversity or lead to chemical imbalances in the environment that ultimately kill individuals, species and habitats. There are thousands of pollutants circulating through the earth’s ecosystems, and many of these materials have significant, large-scale impacts on forests and aquatic ecosystems. Acid precipitation and pollution can also disrupt ecological processes.
v. Human-Induced Climate Change:
Human induced climate changes are due to emissions of greenhouse gases when fossil fuels are burnt. This can lead to a change in the abundance and distribution of individual species around the globe and will affect the crops we grow, cause a rise in sea levels and problems to many coastal ecosystems. In addition, the climate is becoming more unpredictable and extreme devastating events occur.
Habitat destruction is responsible for the extinction of thousands of flora and fauna each year. The forest area harboring about 50 per cent of the global species will be reduced to a tenth or less by 2020 AD. The forest area has already been reduced to 55 per cent of its original cover and is being further reduced at a rate of more than 1,00,000 sq km per year.
According to IUCN, if the current trend of species loss remains continue and no measure were taken, 25 per cent of the World’s species may be lost by 2050 AD. IUCN has reported that 70 per cent of plant species are under global threat along with a number of animal species.
Loss of Biodiversity:
Extinction is a fact of life. Species have been evolving and dying out ever since the origin of life. One has to look at the fossil record to prove the fact. It has been estimated that surviving species constitute about 1 per cent of the species that have ever lived.
However, species are now becoming extinct at an alarming rate, almost entirely as a direct result of human activities. Previous mass extinctions evident in the geological record are thought to have been brought about mainly by massive climatic or environmental shifts. Mass extinctions as a direct consequence of the activities of a single species are unprecedented in geological history.
The loss of species in tropical ecosystems such as the rain forests, is extremely well- publicized and of great concern. However, equally worrying is the loss of habitat and species closer to home. Predictions and estimates of future species losses calculate that a quarter of all species on earth are likely to be extinct, or on the way to extinction within 30 years.
Another predicts that within 100 years, three quarters of all species will either be extinct, or in populations so small that they can be described as “the living dead”. It must be emphasized that these are only predictions and based on modeling. The only possible conclusion is that unless human populations are substantially reduced, it is inevitable that biodiversity will suffer further major losses.
Loss of an individual species can have various different effects on the remaining species in an ecosystem. These effects depend upon the how important the species is in the ecosystem. Some species can be removed without apparent effect, while removal of others may have enormous effects on the remaining species. Species such as these are termed “keystone” species.
Some species are more vulnerable to extinction than others and these include:
i. Species at the Top of Food Chains:
Large carnivores usually require fairly extensive territories in order to provide them with sufficient prey. As human populations increasingly encroach on wild areas and as habitats shrink in extent, the number of carnivores which can be accommodated in the area also decreases. These animals may also pose a threat to people, as populations expand into wilder areas inhabited by large carnivores. Protective measures, including elimination of offending animals in the area, further reduces numbers.
ii. Endemic Local Species:
Endemic species found only in one geographical area with a very limited distribution. These are very vulnerable to local habitat disturbance or human development.
iii. Species with Chronically Small Populations:
If populations become too small, then simply finding a mate, or interbreeding, can become serious problems.
iv. Migratory Species:
Species which need suitable habitats to feed and rest in widely spaced locations (which are often traditional and ‘wired’ into behaviour patterns) are very vulnerable to loss of these ‘way stations’.
v. Species with Exceptionally Complex Life Cycles:
If completion of a particular lifecycle requires several different elements to be in place at very specific times, then the species is vulnerable if there is disruption of any single element in the cycle.
vi. Specialist Species:
Species with very narrow requirements such as a single specific food source, e.g. a particular plant species.
The concept of biodiversity hotspots was drafted by British ecologist Norman Myers in 1988 as a means to address the dilemma of identifying the areas most important for preserving species. Myers recognized that despite their relatively small sizes, certain ecosystems account for a high percentage of global biodiversity. Many of these same areas face tremendous pressure from logging, agriculture, hunting and climate change.
Myers reasoned that a prudent conservation strategy would be to target money and research at those regions where these threats are greatest to the greatest number of species. In the mid-1990s, together with partners at Conservation International, Myers ironed out a formula for hotspot designation – The region must support at least 1,500 plant species found nowhere else in the world and it must have lost at least 70 per cent of its original habitat.
Hotspots are generally defined as fragile area rich in biodiversity with high degree of endemism and higher incidence of rare and threatened species. Preliminary efforts were limited only to vascular plants present in 18 hotspots of the world. The number of hotspots has been increased to 25, out of these India has two hotspots i.e., Eastern Himalaya (Indo-Burma) and the Western Ghats. They are estimated to have about 7,000 and 2,180 endemic species of plants respectively.
The selection of any area as hotspot should have the following:
i. An area must contain at least 0.5 per cent or 1,500 of the world’s 300,000 plant species as endemics.
ii. A second determinant of hotspots status applied only after an area has met the plants criterion the degree of threat through habitat loss.
iii. A hotspot should have lost 70 per cent or more of its primary vegetation and form of habitat contains the most endemic species.
Around the world, 25 areas qualify as biodiversity hotspots under this definition, with nine others possible candidates. The biodiversity hotspots hold especially high numbers of endemic species, yet their combined area of remaining habitat covers only 2.3 per cent of the Earth’s land surface. Each hotspot faces extreme threats and has already lost at least 70 per cent of its original natural vegetation. Over 50 per cent of the world’s plant species and 42 per cent of all terrestrial vertebrate species are endemic to the 34 biodiversity hotspots.
Eleven hotspots have already lost at least 90 per cent vegetation and three have lost 95 per cent vegetation. Among the hotspots which are under greatest threat of extinction of species and habitats are termed as “hottest hotspots”. Eight hotspots have been identified as “hottest hotspots”. The failure to protect the hotspots would result in the loss of nearly 50 per cent of Earth’s plants and terrestrial vertebrates.
There are four key components of population diversity:
(i) Population Richness.
(ii) Population Size.
(iii) Population Distribution.
(iv) Genetic Differentiation of Populations.
(i) Population Richness:
Population richness is the number of populations of a species in a given area, which depends on the criteria used to delineate population boundaries. When the focus is on ecosystem services, it is proposed using as a criterion the spatial disjunctions in the services provided by conspecific individuals occupying a heterogeneous environment. If the required data are unavailable, standard genetic or demographic approaches would be the next best option.
(ii) Population Size:
Data about the number of individuals per population provide an indication of the frequency distribution of population sizes. Absolute numbers would be the most useful, but, owing to the difficulty of obtaining such information, orders of magnitude or some other representative measure might be more appropriate.
It is important to document the distribution of population sizes to determine whether a species is characterized by, for example, a single large population and many small populations, or several similarly sized populations. This distribution has implications, not only for species conservation, but also for the contribution that each population makes to the functioning of ecosystems and raises the important issue of how variability in the number of individuals in a given population affects functionality.
(iii) Population Distribution:
The third component of population diversity is the spatial distribution of the populations under study. The important measures here are the extent of the populations relative to their maximum possible extent in a defined area and population dispersion. Focusing on maximum possible extent facilitates comparisons between species with large geographical ranges and those with relatively restricted ranges.
Geographical range is a measure of the maximum area in which a species can provide a given service. Population dispersion is a measure of the spatial aggregation of populations and how this can affect the delivery of services over a given area. For example, the services provided by fish populations might be extremely localized owing to natural (e.g., shorelines) or anthropogenic boundaries (e.g., regional fisheries) and the adaptation of populations to a narrow range of environmental variability.
(iv) Genetic Differentiation of Populations:
The final component of population diversity is genetic differentiation within and among populations. From both conservation and ecosystem service perspectives, more genetic variation within populations might confer greater resilience in the face of environmental change such as the possible stabilizing influence of genetic diversity in key tree species enabling forests to track climate change.
Genetic differentiation among populations can be associated with different types or levels of a given ecosystem service. Perhaps the most important ecosystem service in which study of genetic differentiation of populations is crucial in maintaining or augmenting crop yields, which depends on genetic material that often is only available from populations of wild relatives of crops.
Measurement of Biodiversity:
In spite of many tools and data sources, biodiversity remains difficult to quantify precisely. But precise answers are seldom needed to devise an effective understanding of where biodiversity is, how it is changing over space and time, the drivers responsible for such change, the consequences of such change for ecosystem services and human well-being and the response options available.
Ideally, to assess the conditions and trends of biodiversity either globally or sub-globally, it is necessary to measure the abundance of all organisms over space and time, using taxonomy (such as the number of species), functional traits, and the interactions among species that affect their dynamics and function (predation, parasitism, competition and facilitation such as pollination, for instance, and how strongly such interactions affect ecosystems).
Even more important would be to estimate turnover of biodiversity, not just point estimates in space or time. Currently, it is not possible to do this with much accuracy because the data are lacking. Even for the taxonomic component of biodiversity, where information is the best, considerable uncertainty remains about the true extent and changes in taxonomic diversity.
Ecological indicators are scientific constructs that use quantitative data to measure aspects of biodiversity, ecosystem condition, services, or drivers of change, but no single ecological indicator captures all the dimensions of biodiversity.
Diversity, which is synonymous with heterogeneity, comprises species richness and evenness. Indices that combine both richness and evenness (heterogeneity) into a single value are diversity indices. The total number of species in a community is referred to as species richness while species evenness or equitability explains as to how species abundance is distributed among species. Diversity has emerged as the most widely used criterion to assess the conservation potential and ecological value of a site.
The Heterogeneity or Diversity will be measured by Simpson’s Diversity Index that is commonly referred to as the dominance measure and Shannon-Wiener Diversity Index, which is also referred to as the information statistic index.
s = number of species
Pi = proportion of species i in the community
As a measure of species richness, the number of species in a community or sample will be calculated using Jackknife Index (J) and first Chao Index (C) which is the estimator of species richness.
S = Number of species found when all sample plots are pooled
P = Number of plots sampled
k = Number of species that occur in only one sample plot (unique)
a = Number of species that are represented by a single individual (singletons)
b = Number of species that are represented by two individuals (doubletons)
Species Evenness or Equitability:
Evenness measures attempts to quantify unequal representation against a hypothetical community in which all species are equally common. The Evenness or Equitability (E) will be quantified by expressing Simpson’s index or Shannon index.
Simpsons Measure of Evenness (E) = (1/D) x (1/S)
D = Simpson’s Diversity Index
S = Number of species found when all sample plots are pooled
Shannon – Wieners Equitability or Evenness (J) = H / log(S)
H = Shannon-Wiener’s Diversity Index
S = Number of species found when all sample plots are pooled