14 Sep

Biodiversity Basics

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Content

• Definition
• How Is Biodiversity Distributed on EARTH?
• Mega Diverse Countries
• Biodiversity Hotspots
• High Biodiversity WIlderness Area
• Three Levels of Biodiversity
• Factors which Determine the Degree of Diversity
• Significance of Biodiversity
• Endemic Species
• KeyStone Species
• Indicator Species
• FLagShip Species
• Priority Species
• INVASIVE Species
• Speciation
• Measurement of Biodiversity
• Classification of Life Forms

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1) DEFINITION

• Biodiversity is the term popularized by the socio-biologist Edward Wilson to describe the combined diversity at all levels of biological organization.
• Biodiversity is defined as ‘the variability among living organisms from all sources, including terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part; this include diversity within species, between species and of ecosystems‘. (UN Earth Summit).

2) HOW IS BIODIVERSITY DISTRIBUTED ON EARTH?

• The vast majority of all species are found in the tropics, and subtropics, where most of the developing countries are also located. Infact, 50-75% of all species are found in tropical rainforests that account for just 6% of the land areas.
  • The genetic diversity needed to maintain the world’s agricultural system is found mainly in tropics, and sub-tropics. These areas also contain most of the important medicinal plants from which new pharmaceutical products are extracted.
  • In the northern regions, the recurrent ice ages did not permit the flowering of many life forms.
• Variation with altitude: In general biodiversity increases with altitude until a certain threshold and then decreases. This is due to environmental factors such as temperature, air pressure, and precipitation.
  • Many mountain ecosystems show greater biodiversity and higher levels of endemism than adjacent lowlands.
  • Mountain at lower altitudes can support exceptional biodiversity, due to compression of a wide range of ecosystems into a relatively short distance. Mountains also often provide islands of suitable habitat, isolated from unfavourable surrounding lowlands.

3) MEGA DIVERSE COUNTRIES

• The megadiverse country is a term used to refer to the world’s top biodiversity-rich countries. These were identified in 1988 by Conservation International (CI), to promote the awareness for biodiversity conservation among world nations. According to CI, there are 17 of these nations, which are mostly located in the tropical and subtropical region.
• Criteria
  • The principle criterion is endemism, first at the species level and then at higher taxonomic levels such as genus and family. To qualify as a Megadiverse Country, a country must:
    1. Have at least 5,000 of the world’s plants as endemics (native restricted to a certain place)
    2. Have marine ecosystem within its border.
• Purpose of this classification [Raises awareness about biodiversity conservation; complements biodiversity hotspots and HBWA in protection of biodiversity; Demonstrates how a few countries hold a large portion of global biodiversity and therefore have disproportionate political responsibility]

List of 17 megadiverse countries according the conservation international:

• USA
• Mexico
• Brazil
• Venezuela
• Colombia
• Ecuador
• Peru
• Democratic Republic of Congo
• South Africa
• Madagascar
• India
• China
• Malaysia
• Indonesia
• Philippines
• Papua New Guinea
• Australia

4) BIODIVERSITY HOTSPOTS

• Biodiversity hotspots are regions containing exceptional concentrations of plant endemism and experiencing high rates of habitat loss.
• Of the total 35/36 globally identified biodiversity hotspots India has 4 of them i.e. Eastern Himalayas, Nepal, India; Indo-Burma, India and Myanmar, Western Ghats, India; Sundalands: include Nicobar group of islands (and Indonesia, Malaysia, Singapore, Brunei and Philippines)
• Norman Meyers wrote about the concept in two articles in “The Environmentalist” (1988) & (1990)
• Description: Biodiversity hotspots are a method to identify those regions of the world where attention is needed to address biodiversity loss and to guide investment in conservation.
• To qualify as a biodiversity hotspot on Meyers 2000 edition of the hotspot-map, a region must meet two strict criteria
  1. Plant Endemism: It must contain at least 0.5% of the world’s total or 1500 species of vascular plants as endemics.
  2. Serious Habitat Loss : It has to have lost at least 70% of its primary vegetation.
• Around the world 36 areas qualify under this definition, with some other possible candidates.
• Supported by Conservation International

5) HIGH BIODIVERSITY WILDERNESS AREA 

• The large intact ecosystems of the world that hold significant levels of global biodiversity.
• Approach developed by Conservation International.
• HBWAs consist of 5 of the 24 major wilderness areas that hold globally significant levels of biodiversity.
• The 5 HBWAs are Amazonia, the Congo forest of Central Africa, New Guinea, the Miombo-Mopane woodlands of Southern Africa (including the Okvango delta), Northern American desert complex of northern Mexico and South Western part of USA.
• In the past, the HBWAs were mostly considered to have ‘low vulnerability’ because of their low level of past habitat loss. However, recent analysis suggests that the high cultivation potential of many HBWAs makes them a target for future agri-expansion.

6) THREE LEVELS OF BIODIVERSITY

a. Genetic diversity

• Genetic diversity refers to variety at the level of genes. It consists of variation of genes in a particular species.
• Significance of genetic diversity
  • High Genetic Diversity -> Higher Adaptability -> Higher chance of survival
• E.g.
  • India has more than 50,000 genetically different strains of rice, and 1,000 varieties of mangoes.
• E.g. of low genetic diversity :
  • Only one species of Asiatic Cheetah survives in the world today and due to inbreeding, this species has lost genetic diversity.
    • Hence Cheetahs are prone to genetic disorders and low reproductive success.
  • Koalas in Europe

b. Species diversity

• Diversity at the species level.
• Species diversity refers to variety of plants and animals’ species present in a community or ecosystem.
• Species differ from one another, markedly in their genetic makeup, do-not interbreed in nature.
• Closely-related species however have in common much of their hereditary characteristics. For instance, about 98.4% of the genes of humans and chimpanzees are the same.
• It is the ratio of one species population over total number of organisms across all species in the given biome.
  • ‘Zero’ would be infinite diversity, and ‘one’ represents only one species present.
• For e.g.
  • Western Ghats have greater amphibian species diversity than the Eastern Ghats.
• Species diversity is high in:
  • Tropical rain forests
  • Coastal zones
• Species diversity is low in:
  • Small isolated islands
  • Polar regions

c. Ecosystem Community Diversity (Ecological Diversity)

• Ecosystem diversity refers to variety of ecosystems found in a given area or region.
• This refers to the different type of habitats. A habitat is the cumulative factor of the climate, vegetation and geography of a region.
• There are several kinds of habitats around the world. Corals, grasslands, wetlands, desert, mangrove and tropical rain forests are example of ecosystems.
• As the environment changes, species best adapted to that environment becomes predominant. Thus, the variety of diversity of species in the ecosystem is influenced by the nature of the ecosystem.
• E.g.
  • India with its deserts, rain forests, mangroves, coral reefs, wetlands, estuaries, and alpine meadows has a greater ecosystem diversity than a Scandinavian country like Norway.

7) FACTORS WHICH DETERMINE THE DEGREE OF DIVERSITY

• Habitat stress: Diversity is low in habitats under any stress like harsh climate or pollution
• Geographical isolation: Diversity is less in isolated regions like an island. If a species in an island disappears, it can’t be easily replaced.
• Dominance by one species: The dominant species consumes a disproportionate share of the resources. This does not allow many species to evolve and flourish.
• Availability of ecological niches: A complex community offers a greater variety of niches than a simple community and promotes greater diversity.
• Edge Effect: Always greater diversity at ecotones or transition areas between ecosystem.
• Geological history: Old and stable ecosystems like rain forests that have not experienced many changes have high diversity. An ecosystem like the Arctic has undergone many changes and this does not allow species to establish themselves.

8) SIGNIFICANCE OF BIODIVERSITY

A) BIODIVERISTY AND FOOD SECURITY

• Biodiversity is the cornerstone of healthy and sustainable food system.
  • It plays a role in protecting pollinators; improving soil fertility; and building resilience of food system to the effects of climate change. It is thus crucial for fighting global hunger.

B) BIODIVERSITY PROVIDES A NUMBER OF NATURAL SERVICES FOR HUMANS

a. Ecosystem Services

• Protection of water resources
• Soil formation and protection
• Nutrient storage and recycling
• Pollution breakdown and absorption
• Contribution to climate stability
• Maintenance of ecosystem
• Recovery from Unpredictable events

b. Biodiversity Services

• Food
• Wood Products
• Ornamental Plants
• Medicinal resources and pharmaceutical drugs
• Breeding stocks, population reservoirs
• Future resources
• Diversity in genes, species and ecosystems

c. Social Services

• Research, education and monitoring
• Recreation and tourism
• Cultural values

9) ENDEMIC SPECIES

• An endemic species is found only in a specific geographical location, and not found anywhere else. A species may be native to an area, but is not endemic to that areas, if it is found elsewhere too.
  • For e.g., the Lion-tailed macaque (Macaca silenus), and the Nilgiri Langur are endemic to the western Ghats of India.

10) KEYSTONE SPECIES

• Keystone species are those species which have disproportionately large effect on the communities in which it occurs. It plays an essential role in the structure, functioning in fact, it determines the ability of a large number of species in the community to survive.
• When a keystone species disappears, it could result in a series of extinction of other species.
• E.g. 1: An example is the wild durian, a tree endemic to the western Ghats.
  • Its fruits attract insects and birds come in to eat insects. Reptiles consume both insects and birds. The tree is also the habitat of monkeys, which eat the fruits, leaves and insects. Even tigers may come to eat the animals that are attracted by all the food in the tree ecosystem.
  • If the wild durian tree is removed from the ecosystem, many of the species will be adversely affected and some may disappear.
• E.g. 2: Wolves
  • If wolves go extinct in an ecosystem, the population of deer and other herbivores will increase exponentially. Due to excessive grazing by the her bivores, many plants may go extinct. Then, the small animals and insects that feed on the plants may disappear.

11) INDICATOR SPECIES

• Indicator species is one whose presence, absence, or abundance reflects a specific environmental condition. They are very sensitive indicators of environmental problems. They give early warning of problems that could potentially affect other species. They are also called sentinel species.
• E.g. Lichen, which is sensitive to the presence of heavy metals or acids in rain. It’s behaviour may indicate that acid rain is falling in the area.
  • Lichens are mutualistic association of fungus and algae or cyanobacterium and occurs as a crusty patch or busy growths on trees, rocks and bare grounds.
  • Lichens are very sensitive to SO2pollution and since industrial revolution a number of their population have become extinct. So, if air is badly polluted by SO2, no lichens may be present.
• Top predators like tigers and snow leopards are also indicator species. Their presence indicates that entire ecosystem is healthy.
• Frogs and other amphibians may also be indicator species

12) FLAGSHIP SPECIES

• A flagship species is a species selected to act as an ambassador, icon or symbol for a defined habitat, issue, campaignorenvironmentalcause.It ischosentoraisesupport forbiodiversityconservationina chosenplace or context. These species have the ability to capture the imagination of public and induce people to support conservation action and/or to donate funds.
• By focusing on, and achieving conservation of that species, the status of many other species which share its habitat – or are vulnerable to the same threats – may be improved.
• They are usually relatively large and considered to be charismatic in western countries.
• They may or may not be keystone species and may or may not be good indicators of biological process.
• E.g.
  • Bengal Tiger
  • Jerdon’s Courser (a CR bird found only in Andhra Pradesh)
• Some limitations
  • May skew the management and conservation priorities in their favour and to detriment of more threatened species.
  • The disappearance of the flagship can have negative impact on the attitude of conservation stakeholders.

13) PRIORITY SPECIES

• It is a WWF term which is solely for the purpose of planning and simple communication.
• For WWF, a priority specie may be either a flagship specie or a keystone specie and is chosen to represent an ecoregion or region.
• A priority specie is reflective of a key threat across that eco-region – such that conservation of the species will contribute significantly to a broader threat mitigation outcome. It is often crucial to the economic and/or spiritual well-being of people within that eco-region.
  • Note: World Wide Fund for Nature was originally called World Wildlife Fund (WWF), a term which is still used in Canada and USA. It is an international NGO founded in 1961 working in the field of biodiversity preservation and the reduction of human impact on environment.
• WWF Priority species of India
  • Asian Elephant (EN)
  • Bengal Tiger (EN)
  • One-horned Rhino (VU)
  • Ganges River Dolphin
  • Snow Leopard
  • Red Panda

14) INVASIVE SPECIES

• Introduction:
  • An alien plant/animal also referred to as exotic, introduced, foreign etc. is one that has been introduced by humans intentionally or otherwise through human agency or accidentally form one region to another.
  • An alien plant/animal that has escaped from its original ecosystem and is reproducing at its own in the regional flora is considered a naturalized species.
  • Those naturalized aliens that become so successful as to spread in the flora/fauna and displace nativebiota orthreaten valued environmental, agricultural orpersonal resourcesbythedamage it causes are considered invasive.
    • To be called invasive, it should also be a threat to the native species of the area by rapidly growing in population. This happens when the invasive species has no predator in the area.

A) ASSESSMENT REPORT ON INVASIVE ALIEN SPECIES AND THEIR CONTROL: BY INTERGOVERNMENTAL PLATFORM ON BIODIVERSITY AND ECOSYSTEM SERVICES (IPBES)

• Human beings have introduced 37,000 alien species, including plants and animals. Of these 3,500 are invasive alien species that have played a key role in 60% of global plant and animal extinction recorded.
• The report has noted that the number of alien species (species introduced to new regions through human activities) has been rising continuously for centuries. But now, they are rising at unprecedented rate, with increased human travel, trade and expansion of global economy.
• E.g.:
  • Water Hyacinth is the world’s most widespread invasive alien species on land.
  • Lantana, a flowering shrub, and the black rat are the second and third most widespread globally.
• Invasive alien species are one of the five major direct drivers of biodiversity loss globally, alongside land and sea use change, direct exploitation of organisms, climate change, and pollution.

B) EXAMPLE OF INVASIVE SPECIES

 DOMESTICATED CATS (FELIS CATUS):

• The State of Indian Birds, 2023 have highlighted that cats are a silent bird killer lurking in India’s urban areas. SO along with other threats like industrialization, forest degradation, and climate change, climate change is also a threat for birds in India.
• But, detailed studies are lacking in India. In the USA, where detailed studies have been done, it is estimated that free ranging domestic cats kill billions of birds every year.
  • One study says that cats may be the single greatest source of anthropogenic mortality for the birds and mammals in the USA.
• Worldwide, free ranging domestic cats have caused or contributed to dozens of extinctions of birds species recorded in the IUCN red list.
• Cats are more dangerous than free ranging dogs:
  • As they can climb easily and thus reach the bird habitat.
  • Cat saliva is also more likely to contain bacteria (Pasteurella multocida) that are lethal to birds. So, if the cat attack doesn’t kill the bird, the bacteria does.
  • Cats also maintain a landscape of fear making birds avoid or nesting in these regions.
• Origin of Domestic Cats:
  • Domestic Cats (Felis catus) are the only domesticated species in the family Felidae.
  • Studies show that Wild Cats (Felis sylvestris) were probably first domesticated in West Asiaaround10,000yearsagoandsincethentheyhavespreadtodifferent parts of the world.
  • Today, they are one of the world’s 100 worst invasive alien species.
• Handling Domestic Cats:
  • A popular method in the West has been Trap-Neuter-Return (TNR) policy, whereby stray dogs and cats are trapped, sterilized and returned in the hope that this will reduce their population. But this hasn’t been very successful.

RABBITS IN AUSTRALIA

AFRICAN CATFISH:

• The fish species is not native to India and is originally found in Africa and the middle east.
• It is known to be aggressive feeder, eating even the chicks of waterfowl. It poses a major threat to native fauna.
• The female matures in about 3 years and can bear 10s of thousands of eggs.
• The species has now spread to subcontinent and is found in Cauvery, Ganga, Yamuna and even the streams of western Ghats.
• This was introduced by businessmen for commercial fish cultivation in the National Park as it could adapt to poor quality of water, raised in high densities, and reproduce well in captivity, making it ideal for those looking to sell the fish for food. Though, the cultivation of this specie was banned by Agriculture Ministry in 2000 itself.

RED EARED SLIDER TURTLE IN NORTH-EAST INDIA

• This is a cute American turtle popular as a pet. But it is threatening to invade the natural water bodies across the northeast, home to 21 of the 29 vulnerable native Indian species of freshwater turtles and tortoises.

CARIBBEAN FALSE MUSSEL (MYTILOPSIS SALLEI):

Origin: The Caribbean false mussel is originally from the Atlantic and Pacific coast of South and Central America. They may have travelled to Indian subcontinent via ships (ballast water) and then using small vessels spread to estuaries.

Damage: It is damaging locally important fishery in Kerala, by wiping out native clams and oysters.

 ACHATINA FULICA (AFRICAN APPLE SNAIL)

The snail (a mollusk) is native to coastal areas and islands of east Africa.

It is invasive species across the world. It has a broad diet preference and cause heavy loss to farmers.

In India, it is most invasive of all faunas.

Most invasive of all fauna

It was first reported in A&N island but today it is found all across the country and is threatening habitats of several native species.

C) IN 2017, ZOOLOGICAL SURVEY OF INDIA (ZSI) HAS FOR THE FIRST TIME COME UP WITH LIST OF 157 ALIEN INVASIVE SPECIES IN INDIA

• While invasive plant species have been studied in the past, the animal species was analysed in detail for the first time. Invasive animal species like the plant species pose threat to biodiversity.
• Key Highlights
  1. Of the 157 species 58 are found on land and the remaining 99 in Marine ecosystem.
  2. Of the 58 invasive species on land, 38 are arthropods, 19 of fish, three of Mollusks and birds, one reptile and two mammals.
• Examples of Alien species found on Land (including rivers)
  1. Paracoccus Marginatus (Papaya Mealy Bug)
     • Destroyed crops of Papaya in Assam, WB and TN.
     • Originally from Mexico and Central America
  2. Phenacoccus Solenopsis (Cotton Mealybug)
     • Severely affected cotton crops of deccan
     • Native to North America.
  3. Invasive Fish Species
     • Pterygoplichthys pardalis (Amaxon sailfin Catfish)
       • Destroying fish population in wetlands of Kolkata.
• Examples of Alien Species found in Marine Ecosystem
  1. Tubastrea Cocciea (Orange Cup- Coral)
     • Originated in Indo-east-pacific but has now been reported in the A&N Islands, the Gulf of Kutch, Kerala, and Lakshadweep.

15) SPECIATION

Speciation refers to formation of new species due to genetic changes in an existing species. Speciation occurs when a group within a species separates from other members of its species and develops its own characteristics. In the process of a species adapting itself to changing environmental conditions, a new species may emerge.

There are five types of speciation:

Allopatric Speciation: It occurs when a species separates into two separate groups which are isolated from one another. A Physical barrier, such as mountain ranges or a waterway, makes it impossible to breed with one another. Each species develops differently, based on the demand of their unique habitat or the genetic characteristics of the group that are passed to the offsprings.

• • • For e.g.:
      • Four distinct sub-species of the Asian elephant probably emerged due to allotropic speciation.
      • Squirrels and other small mammals on the two sides of Grand Canyons
    • Peripatric Speciation: When small group of individuals break off from the larger group and form a new species. This is called peripatric speciation. Like allopatric speciation, here also, physical barriers make it impossible for members of the group to interbreed with one another.
      • Main difference between Allopatric Speciation and peripatric Speciation is that in peripatric speciation, one group is much smaller than the other.
    • Parapatric Speciation: In this method, a species is spread over large geographical area. Although, it is possible for any member of the species to mate with another member, individual only mate with those in their own geographical region. Like allopatric and peripatric speciation, different habitats influence the development of different species in parapatric speciation. Instead of being separated by a physical barrier, the species are separated by differences in the same environment.
    • Sympatric Speciation: It is controversial. Some scientists don’t believe that it exists. It occurs when there are no physical barriers preventing any members of species from mating with another, and all the members are in close proximity to one another. A new species, perhaps based on a different food source or characteristic, seems to develop spontaneously. The theory is that some individuals become dependent on certain aspects of environment – such as shelter or food source, while others don’t.
      • For e.g., the parasitic great spotted cuckoo, and its magpie host, both native to southern Europe, are considered to be sympatric species.
    • Artificial Speciation: It is creation of new species by people. This is achieved through lab experiments, where scientists mostly research insects like fruit flies.

16) MEASUREMENT OF BIODIVERSITY

• Diversity is a single statistic in which the number of species richness and evenness are compounded. Biodiversity is measured in two components:
  • Species Richness
  • Species Evenness

Species Richness

• • It is the measure of number of species found in a community
    • Alpha Diversity
      • The diversity within a particular area or ecosystem and is usually expressed by the number of species (i.e., species richness) in that system.
    • Beta Diversity
      • It represents differences in species composition among sites (ecosystem).
        • It is something of a bridge from local (alpha) to the regional (gamma) scale. · It can be considered a metric of dissimilarities between sites.
        • It can also be interpreted as rate of accumulation of diversity with an increasing number of sites sampled.
        • In simple terms it is ratio between gamma (regional) and alpha(local) diversities.
      • Gamma Diversity
        • It is the measure of diversity of the entire landscape (regional species pool).

Species Evenness

• • It measures the proportion of species at a given site, e.g. low evenness indicates that only few species dominate the site.

17) CLASSIFICATION OF LIFE FORMS

• Kingdom (Monera, Protista, Fungi, Plantae, Animalia)
• Phylum (For animals) / Division (for plants)
  • Class
  • Order
  • Family
  • Genus
  • Species

 E.g. For tiger

• • Kingdom: Animalia
  • Phylum: Chordata
  • Class: Mammalia
  • Order: Carnivora
  • Family: Felidae
  • Genus: Panthera
  • Species: P. Tigris

 E.g. For Humans

• • Kingdom: Animalia
  • Phylum: Chordata
  • Class: Mammalia
  • Order: Primates
  • Family: Hominidae
    • Members of this family are known as great apes or hominids. Currently it consist of four genera.
      • Pongo (Bornean, Sumtran, and Tapanuli Orangutan); Gorilla (the eastern and western Gorilla); Pan (the Chimpanzee and the bonobo); and Homo (of which only Homo Sapiens remain)
  • Genus: Homo
  • Species: H. sapiens