2 Biodiversity and Environmental Conservation – I
Dr Sunil Mittal and Dr Hardeep Kaur
1. Definition, importance of biodiversity and environmental conservation
2. Global, National and Local Dimensions- Historical Evolution of the Subject
3. Values and Uses of Biodiversity
4.Concepts Related to Quantification of Biodiversity
5. Biodiversity, Stability and Resilience- Biodiversity and Ecosystem Services
6. Biodiversity Characterization and Inventorying: Taxonomic Approach
7. Biodiversity Characterization and Inventorying: Cryogenetics Approach
8. Process of Speciation
9.Spatial Patterns of Biodiversity- Aquatic Biodiversity
10.Spatial Patterns of Biodiversity- Terrestrial Biodiversity
11. Microbial Diversity
12. Hotspots of Biodiversity
13. Temporal Patterns of Biodiversity
14. Threats to Biodiversity
15. Biological Invasion
16. Causes of Extinction of Species
2. Definition and importance of biodiversity and environmental conservation
Biodiversity is the divergence of all species on our planet such as different species of plants, animals and micro-organisms, including their gene pool, and different ecosystems. The term was defined as contraction of biological array by E.O. Wilson in 1985.
In other words, biodiversity is the existence of diverse types of ecological habitats, different species and variants of organisms and genes, adapted to different environmental conditions, along with their exchanges and developments.
3. Global, National and Local Dimensions- Historical Evolution of the Subject
Earth was formed 4.5 billion years ago. Initial temperature was 1800 degree Celsius. The temperature dropped to below 100degree Celsius and this lead to condensation of water vapours and opened way to form the primordial soup which formed the 1st organic molecules called RNA molecules. The lipids formed combined with them to form the 1st proto cells. These cells then later formed the 1st organisms similar to the bacteria. Cyanobacteria carried out photosynthesis and produced molecular oxygen which combined with methane in the air. This led to fall in temperature. Anaerobic bacteria went extinct. Around 1.5 billion years ago, 1st eukaryotes evolved. Around 630 million years ago, volcanic eruptions lead to global warming which helped in evolution of algae. The Ediacaran era revealed fossils of multicellular organisms. 542 million years ago phanerozoic era started. This helped in the evolution of the present-day biodiversity. Five major mass extinctions took place during this period. Cambrian period saw a large biodiversity called as the Cambrian explosion and major phyla antropoda, chordates evolved. 450 million years ago ordovician period ended due to global cooling and late Devonian period ended after a long 20 million years. Permian period was the harshest extinction which included volcanic eruption and huge methane production nearly 90 % of life became extinct. The cretaceous period ended nearly 66 million years ago due to volcanic eruptions, hitting of gigantic asteroid with earth leading to 95% of death. The latest epoch known as Anthropocene consists of humans. Humans are blamed to be the main reason for the high rate of extinction of biodiversity. Thus, from a single species which came into existence over 4.5 billion years ago, an estimated 8.7 million species have evolved to populate the planet today. Among them, only about 2 million (14% of terrestrial species and 9% of those from marine environments) species have actually been described and classified by scientists. This tremendous number and variety of species that exist on the planet is referred to as biological diversity or biodiversity.
4. Values and Uses of Biodiversity
The components of biodiversity are interconnected. A change in the composition and abundance of the species that make up an ecosystem can alter the services that can be obtained from the system. In this chapter, we review the types of goods and services that mankind obtains directly and indirectly from biodiversity and its components.
Scheme 1: Values of Biodiversity
5.Concepts Related to Quantification of Biodiversity
Quantification of biodiversity is seen through various concepts. Mainly, the diversity is divided into 2 sub-groups.
A. Taxonomic diversity
B. Other measures of diversity Taxonomic diversity is further divided into
a) Species richness- it is defined as the number of species present in an ecological system. It takes into account only the number and not the abundance of the species.
b) Simpson index- it was introduced in 1949 by Edward H. Simpson to measure the degree of concentration when individuals are classified into types.
c) Shannon–weiner index– It was originally proposed by Claude Shannon to quantify the entropy .The Shannon entropy quantifies the uncertainty (entropy or degree of surprise) associated with this prediction.
Other measures are
a) Species diversity-It is represented as the number of species a community consists of. The effective number of species refers to the number of equally abundant species needed to obtain the same mean proportional species abundance as that observed in the dataset of interest. It depends mainly on climatic conditions.
b) Ecosystem diversity- describes the aggregation of and interaction of species with one another and deals with the variations in ecosystems within a geographical location and its overall impact on human existence and the environment especially during stress conditions.
c) Genetic diversity- is the total number of genetic characteristics in the genetic makeup of a species and is distinguished from genetic variability, which describes the tendency of genetic characteristics to vary. The magnitude of variation increases along with size and environmental parameters.
Whittaker (1965) also divided the diversity into 3 classes.
i. α-Diversity- It tells the species diversity in a given community and depends upon species richness and evenness.
ii. β-Diversity- It describes a range of communities formed due to replacement of species. This situation arises due to the presence of different microhabitats, niches and environmental conditions.
iii. γ -Diversity- It describes diversity of habitat over a total land escape or geographical area.
6. Biodiversity, Stability and Resilience- Biodiversity and Ecosystem Services
The various anthropogenic activities have resulted in loss of biodiversity and high rate of extinction of rare species. It is anticipated that this trend will continue in coming decades, if quick steps would not be taken up for biodiversity and environmental conservation. Biodiversity loss can threaten the equilibrium of the ecosystem services on which humans depend for their survival. For example, plant species are the primary producers in the food chain and all animals depend on them for their food supply. As primary production reflects the rate at which carbon dioxide (a greenhouse gas) is removed from the atmosphere, this also decides the availability of food and rates of climate change. Globally climate change has raised the concern on sustainable development to achieve a stable system. Stability is meant by a system having low variability (i.e., little deviation from its average state) despite fluctuating environmental conditions. This is also termed the resistance of a system. Resilience is indicated by the ability of an ecosystem to return to its usual state following a disorder or other disturbance.
7. Biodiversity Characterization and Inventorying: Taxonomic Approach
Taxonomy is the way of recognizing different species under defined categories and orders of classification. Mayr (1969) defines it as “Taxonomy is the theory and practice of classifying organisms”. Taxonomy has four components:
i) The classification
ii) The nomenclature
iii) Circumscriptions or descriptions
iv) Identification aids
Taxonomic hierarchy is pivotal for its value in characterizing species diversity. It provides a reference scheme that documents the summary, storage and retrieval of information about all organisms. In addition to this, the hierarchy also provides a natural system, and elucidate presumed pathway of evolution and the pattern of resemblances or divergence among the organisms.
8. Biodiversity Characterization and Inventorying: Cryogenetics Approach
Cryopreservation is the technique currently available to ensure the safe and cost-efficient long-term conservation of species. Materials such as cells, tissues, gametes, oocytes, DNA samples etc. are stored in a genetic databank for future use. There are two types of techniques: classical and new cryopreservation techniques. Classical techniques involve freeze-induced dehydration, whereas new techniques are based on vitrification. Classical cryopreservation techniques involve low cooling down to a defined pre-freezing temperature, followed by rapid immersion in liquid nitrogen. Vitrification based procedures offer practical advantages as compare to classical freezing techniques. Like ultra-rapid freezing, they are more appropriate for complex organs (shoot tips, embryos), which contain a variety of cell types, each with unique requirements under conditions of freeze- induced dehydration. A successful protocol for long-term conservation of two endangered plants viz. Mantisia spathulata and M. wengeri has been devised through cryopreservation of immature seeds (Das Bhowmik et al., 2011). In case of poultry, as many as 30% of poultry breeds are threatened with extinction and 9% have already gone extinct. A good technique of cell culture and freezing methods will give a broad perspective for unlimited storage of genetic recourses, which in the future can be useful for the restoration of extinct species/breeds (Sawicka et al., 2011). Cryopreservation is an effective method used in the conservation of poultry breeds.
9. Process of Speciation
The process of speciation is a 2 stage process in which Reproductive Isolating Mechanisms (RIM’s) arise between groups of populations
Stage 1
- gene flow is interrupted between 2 populations
- absence of gene flow allows 2 populations to become genetically differentiated as a consequence of their adaptation to different local conditions (genetic drift also can act here)
- as populations differentiate, RIMs appear because different gene pools are not mutually co-adapted
- reproductive isolation appears primarily in the form of postzygotic RIMs hybrid failure
- these early RIMs are by-product of genetic differentiation, not directly promoted by natural selection yet
Stage 2
- completion of genetic isolation
- reproductive isolation develops mostly in the forms of prezygotic RIMs
- development of prezygotic RIMs is directly promoted by natural selection: alleles favoring intraspecific fertility will be increased over time at the expense of interspecific fertilization alleles
10. Spatial Patterns of Biodiversity- Aquatic Biodiversity
It is assumed that origin of life took place in sea. This makes Marine system the richest bio-diverse habitats which is playing the most important role in the maintenance of other terrestrial biodiversity. The marine plants (including micro-algal species) are responsible of fixing most of the carbon dioxide from the atmosphere and production of 65% of the oxygen. The different zones of sea such as benthic, pelagic, neritic and intertidal zone house different species of animals and plants. The global spatial pattern is concentrated at the Indo- Malay archipelago and from this place, it gradually decreases in all directions. As like terrestrial biodiversity, marine biodiversity also decreases progressively pole wards (i.e. from equator to either pole). However, extreme southern latitude is highly rich in marine biodiversity.
11. Spatial Patterns of Biodiversity- Terrestrial Biodiversity
The conservation scheme may be understood by spatial patterns of biodiversity. Alexander von Humboldt examined spatial patterns of biodiversity through comparisons among elevational and altitudinal gradients. Charles Darwin and Alfred Wallace studied phylo-geographic patterns and speciation and endemism of islands systems. All the studies formulated generalizations of patterns that define decrease of biodiversity from the equator to the poles and the increase of biodiversity with an increase in area studied. Patterns allow authorities to emphasize on high biodiversity areas and define rarity of extremely diverse communities. These patterns provide the opportunity to predict threats of extinction and anthropogenic and natural response to climate change and disturbances.
11. Microbial Diversity
Biodiversity is a unique asset to any country, and needs to be protected for sustainable development. Since past 4 billion years, microorganisms have evolved by exploiting range of survival skills and have thrived all kind of extreme habitats including cold or hot regions, radiation prone, regions under pressure, or salty, acidic and dark places. They have been crowned as the originators of all living forms on the planet. They contribute to almost 50% of the total protoplasm on the planet (Whitman et al., 1998), and by far represent the richest repertoire of molecular and chemical diversity in nature. They are the primary contributors of the food chain and involved in various ecological processes and biogeochemical cycles. In addition they have created their special niche in the ecosystem by virtue of their interspecies and intra-species relationships. There vast diversity is the reason of their involvement as an essential component of a sustainable biosphere. Microbes as the major workforces perform the task of degeneration, recycling of nutrients, production of gases, destruction of waste and pollutants etc. They also have the commercial value for the production of secondary metabolites like antibiotics, hydrogen, methane, bioplastic, and bioremediation of oily sludge, bio wastes. These properties are important for improving environmental and human health. They are the essence of this planet and all life would cease without them. Still, there are many species which are yet to be discovered.
Consequently, microbiology focuses on two areas:
(I) Microbial diversity, including the isolation, identification and quantification of micro-organisms in various habitats;
(II)Microbial activity, that defines, the activities of micro-organisms in their habitats and how their activities contribute to the observed microbial diversity patterns of distributions. These are often studied in the perspective of environmental factors such as temperature, pressure, pH, salinity, the availabilities of water and nutrients, and the sources of energy like carbon and nitrogen. These factors impact microbial activities and play very important roles in determining the limitations of micro-organisms in natural environments.
12. Hotspots of Biodiversity: Biodiversity Hotspots of India
In 1988, Norman Myers a British biologist coined the term “biodiversity hotspot” as a biogeographic region characterized both by exceptional levels of plant endemism and by serious levels of habitat loss.
Hotspots comprise different regions on Earth which are biologically rich as well as deeply endangered and are characterized by forests and other remnant habitats which have at least 1,500 vascular plants as endemics. Any area with 30% or less of its original natural vegetation left is characterized as a hotspot. In other words, identification of any region as a hotspot depicts the vulnerability of that region. Around the world, 35 areas have been identified as hotspots. These areas acquire only 2.3% of Earth’s land surface, but support more than half of the world’s endemic plant species i.e., species which are unique to specific regions on earth. Approximately 43% of bird, mammal, reptile and amphibian species are characterized as endemic species around the world.
Biodiversity hotspots in India
As per the IUCN criteria, 4 regions in India have been recognized as biodiversity hotspots.
These are:
I. Himalaya: Includes the entire Indian Himalayan region (and that falling in Pakistan, Tibet, Nepal, Bhutan, China and Myanmar)
II. Indo-Burma: Includes entire North-eastern India, except Assam and Andaman group of Islands (and Myanmar, Thailand, Vietnam, Laos, Cambodia and southern China)
III. Sundalands: Includes Nicobar group of Islands (and Indonesia, Malaysia, Singapore, Brunei, Philippines)
IV. Western Ghats and Sri Lanka: Includes entire Western Ghats (and Sri Lanka)
13. Temporal Patterns of Biodiversity: Factors and processes related to biodiversity changes over time from ecological to geological scale.
The background rates of extinction of various species over geological time can be predicted only up to a certain level by the knowledge of patterns of biodiversity over time. For most of the human history on earth, the global biodiversity has been relatively constant except for the last 1,000 years but the history of life is characterized by considerable change. The estimated background rates of extinction for different species have been predicted to be roughly 0.1–1.0 extinctions per million species per year. These measurements for the extinction rates of species have been assessed using the length of species’ lifetimes through the fossil records that range over 0.5–13 million years. This data is mostly derived from the taxa that are abundant and widespread in the fossil record and thus probably underestimate the background extinction rates.
14. Threats to Biodiversity
• Habitat Related (Loss, Degradation, Fragmentation)
• Pollution (Chemical, Light, and Noise)
• Overexploitation
• Invasive Species
• Anthropogenic Climate Change
• Disease (lesser threat to most taxa)
• UV radiation (primarily threat to amphibians
• Synergistic Effects of Threats
• Cascade Effects i.e. creation of a trophic cascading domino-like effect or a series of events within an ecosystem in which the primary extinction of a species triggers a sequence of secondary losses or extinctions of other species.
15. Biological Invasion
Biological invasion is considered to be one of the major threats for global biodiversity. It refers to the introduction of alien species in any region which imposes a threat to native species and ecosystems as these alien species flourish at the cost of these native species.
These species can be exotic or introduced and are mostly competitive, predating or parasitic in nature.
Modes of introduction of these species:
- By deliberate means
- Through import of ornamental species such as Lantana, Eichhornia, etc. By introduction of pests and pathogens for biological control
- During unintentional or accidental trade and international transport eg. Weed Parthenium with wheat crop from US
The degree of impact of bio-invasion is evaluated in a standard and objective manner through simplified protocols such as Invasive Species Environmental Impact Assessement (ISEIA) (Vanderhoeven, S. & Branquart, 2010). This protocol is composed of harmonious sections with different stages of invasion process: probable spread; establishment of natural habitats; influences on native species and ecosystems. These protocols allow classification of species on one of the following three categories of risk:
Category A: (blacklist) includes species with high environmental risks.
Category B: (watch list or alert) includes species with moderate environmental risk based on existing knowledge.
Category C: includes other non-native species, which are not considered a threat to biodiversity and native ecosystems.
16. Causes of Extinction of Species
A. Natural Causes of Extinction
- Climate Change is the major factor responsible for the extinction of species. Climate influence the species existence at large scale. The unpredictable temperature rise or fall and variation in rain fall certainly affect the life cycle of all species. Those which could not keep up with the fluctuating environmental conditions and changing chemical make-up of their surroundings ultimately vanish. This creates a gap in the food chain and makes the survival of dependent species more difficult. Increase in global temperature has invited more epidemics and diseases to the existing plants and animals and pose a threat to their existence.
- Changes in Sea Levels or Currents also contribute to species extinction. These changes are due to melting freshwater. Marine life depends on the high density salted water that sinks and forms the currents. The spread of Ocean floor and its rise also affects sea level. A small rise in the ocean floor may submerge the nearby occupied land. The volcanic activity inside or near sea may dissolve harmful gases in the water, that changes the chemical composition and thus make life difficult for marine organisms.
- Asteroids/Cosmic Radiation- Collision of asteroids with earth surface completely destroys the impact site and the shock is felt all round the world. Such interplanetary objects including the outer space and Sun which are responsible for emission of cosmic radiations. It is hypothesized that excess exposure to cosmic radiation may lead to gene mutation and weakening of gene-pool of species in future.
- Acid Rain- Acid rain forms due to the reaction between rain water and sulphur dioxide and/or nitrogen oxides in the atmosphere. It increases the soil acidity and adversely affects all living forms especially plants. It can also pollute rivers and lakes to a possibly lethal level.
- Disease/Epidemic- Every species on the planet has internal defense mechanisms and the ability to fight diseases. But, due to fluctuating climate certain species are losing their ability to combat diseases. Certain species are turning more prone to diseases and epidemics, which may lead to their subsequent extinction.
- Spread of Invasive Species- Invasive species are a threat to local species of a territory. They compete for the resources that the other species depend on. Once competition gets pronounced, the mechanism of survival of the fittest works and one of the species, usually the natural one, gets kicked off from the territory.
Natural factors that usually work at slow pace contribute a smaller sum towards species extinction, as compared to human factors that are responsible for maximum extinction.
B. Human Causes of Extinction
Human activities occur at a faster rate and cause higher extinction rates. Human activities that are mostly responsible for the present extinction rates are:
- Increased human population
- Destruction/Fragmentation of Habitat
- Pollution
- Climate Change/Global Warming
According to studies done by the international Union for Conservation of Nature and Natural Resources (IUCN), human induced extinctions is not a new phenomenon, but it is becoming much more rapid now.
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Further readings
- Branquart, E., Verreycken, H., Vanderhoeven, S., & Van Rossum, F. (2010). ISEIA, a Belgian non-native species protocol. In Proceedings of the Science Facing Aliens Conference, Brussels (pp. 11-18).
- Das, M., Bhowmik, A. D., Bhaduri, N., Sarkar, K., Ghosh, P., Sinha, S. & Mukhopadhyay, K. (2011). Role of gene–gene/gene–environment interaction in the etiology of eastern Indian ADHD probands. Progress in Neuro-Psychopharmacology and Biological Psychiatry, 35(2), 577-587.
- Hagelkruys, A., Sawicka, A., Rennmayr, M., & Seiser, C. (2011). The biology of HDAC in cancer: the nuclear and epigenetic components. In Histone Deacetylases: the Biology and Clinical Implication (pp. 13-37). Springer Berlin Heidelberg.
- Myers, N. (1988). Threatened biotas:” hot spots” in tropical forests. Environmentalist, 8(3), 187-208.
- Whitman, W. B., Coleman, D. C., & Wiebe, W. J. (1998). Prokaryotes: the unseen majority. Proceedings of the National Academy of Sciences, 95(12), 6578-6583.
- Whittaker, R. H. (1965). Dominance and diversity in land plant communities: numerical relations of species express the importance of competition in community function and evolution. Science, 147(3655), 250-260.