Biodiversity

Biodiversity

Biodiversity: Basics, Threats, Conservation efforts

• The word “biodiversity” is an abbreviated version of “biological diversity”.
• The Convention on Biological Diversity defines biodiversity as: “the variability among living organisms from all sources including, inter alia, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are a part; this includes diversity within species, between species, and of ecosystems.”
• Thus, Biodiversity refers to the variety of forms - the different plants, animals and micro-organisms.
• It also includes the genes they contain and the ecosystem they form.
• It deals essentially with dynamic processes and increases when new genetic variation is produced and decreases on the loss of genetic variation or species extinction.

Types of Biodiversity

There are three distinct levels of biodiversity though all of them are components of a much intricate web.

Genetic Diversity

• It refers to variation of genes within species. This variation can exist between different populations of the same species as well as between individuals within a population.
• Genetic diversity provides organisms and ecosystems with capacity to recuperate after change has occurred.
• Thus Genetic diversity is a level of biodiversity that refers to the total number of genetic characteristics in the genetic makeup of a species. It is distinguished from genetic variability, which describes the tendency of genetic characteristics to vary.
• Genetic diversity plays a great role in the adaptability and survival of a species. A species that has a large degree of genetic diversity among its individuals will have more variations from which to choose the most fitting allele.

Species Diversity

• Species diversity is a measure of the diversity within an ecological community that incorporates both species richness (the number of species in a community) and the evenness of species’ abundance.
• Species diversity can be measured in terms of:
  • Species richness –refers to the number of various species in a defined area.
  • Species abundance – refers to the relative numbers among species. For example, the number of species of plants, animals and microorganisms may be more in an area than that recorded in another area.
  • Taxonomic or phylogenetic diversity – refers to the genetic relationships between different groups of species.
• Species diversity is not evenly distributed across the globe. The overall richness of species is concentrated in equatorial regions and tends to decrease as one move from equatorial to Polar Regions.
• In addition, biodiversity in land ecosystems generally decreases with increasing altitude. The other factors that influence biodiversity are amount of rainfall and nutrient level in soil. In marine ecosystems, species richness tends to be much higher in continental shelves.

Ecosystem Diversity

• It refers to the presence of different types of ecosystems. For instance, the tropical south India with rich species diversity will have altogether different structure compared to the desert ecosystem which has far less number of plant and animal species.
• Likewise, the marine ecosystem although has many types of fishes, yet it differs from the freshwater ecosystem of rivers and lakes in terms of its characteristics. So such variations at ecosystem level are termed as ecosystem diversity.

Functional Diversity 

• Functional diversity refers to the diversity of ecological processes that maintain and are dependent upon the other components of diversity. It includes the many ecological interactions among species e.g. competition, predation, parasitism, mutualism, etc. as well as ecological processes such as nutrient retention and recycling.
• It also includes the varying tempos and intensities of natural disturbances that many species and communities require if they are to persist.

Patterns of Biodiversity

• Biodiversity is not uniform throughout the world but varies with latitude and altitude.
• Favourable environmental conditions favour speciation and make it possible for a larger number of species to exist there, i.e., biodiversity is more in such areas than the others.
• Species diversity decreases from the equator towards the poles. Tropics (latitudinal range of 23.5°S) have more species than temperate or polar areas.
• There are three different hypothesis proposed by scientists for explaining species richness in the Tropical region:
  • Tropical latitude receives more solar energy than temperate regions, which lead to high productivity and high species diversity.
  • Tropical regions have less seasonal variations and have more or less constant environment. This promotes the niche specialization and thus, high species richness.
  • Temperate regions were subjected to glaciations during ice age, while Tropical regions remained undisturbed which led to an increase in the species diversity in this region.

Biodiversity Hotspots

• Norman Myers, a British Ecologist, developed the concept of Hot spots in 1988 to designate priority areas for in situ conservation. According to him, the hot spots are the richest and the most threatened reservoirs of biodiversity on the earth.
• To qualify as a biodiversity hotspot, a region must meet two strict criteria:
  • It must have at least 1,500 vascular plants as endemics — which are to say, it must have a high percentage of plant life found nowhere else on the planet. A hotspot, in other words, is irreplaceable.
  • It must have 30% or less of its original natural vegetation. In other words, it must be threatened.

Biodiversity Hotspots in India

The Eastern Himalayas Hot Spot

• The eastern Himalayas are the region encompassing Bhutan, northeastern India, and southern, central and eastern Nepal. The region is geologically young and shows high altitudinal variation.
• The abrupt rise of the Himalayan Mountains from less than 500 meters to more than 8,000 meters results in a diversity of ecosystems that range from alluvial grasslands and subtropical broad leaf forests along the foot hills to temperate broad leaf forests in the mid hills, mixed conifer and conifer forests in the higher hills, and alpine meadows above the tree line.

Indo-Burma

• The Indo-Burma region encompasses several countries.
• It is spread out from Eastern Bangladesh to Malaysia and includes North-Eastern India south of Brahmputra River, Myanmar, the southern part of china’s Yunnan province, Lao people’s Democratic Republic, Combodia, Vietnam and Thailand.

Western Ghats and Sri Lanka

• Western Ghats, also known as the “Sahyadri Hills” econompasses the mountain forests in the southwestern parts of India and highlands of southwestern Sri Lanka.
• The entire extent of hotspot was originally about, 82,500 square kms, but due to tremendous population pressure, now only 12,445 square km or 6.8% is in pristine condition.
• The wide variation of rainfall patterns in the Western Ghats, coupled with the region’s complex geography, produces a great variety of vegetation types.
• These include scrub forests in the low-Lying rainshadow areas and the planes, deciduous and tropical rainforests up to about 1,500 meters, and a unique mosaic of montane forests and rolling grasslands above 1,500 meters.
• In Sri Lanka diversity includes dry evergreen forests to dipterocarpus dominated rainforests to tropical montane cloud forest.

THREATS TO BIODIVERSITY

Threat to biodiversity stems mainly from: habitat fragmentation, degradation and loss; shrinking genetic diversity; invasive alien species; declining forest resource base; climate change and desertification; over exploitation of resources; impact of development projects; and impact of pollution.

Causes of Biodiversity losses (‘The Evil Quartet’)

• Habitat loss and fragmentation: Habitat of various organisms are altered or destroyed by uncontrolled and unsustainable human activities such as deforestation, slash, and burn agricultural, mining and urbanization. This results in the breaking up of the habitat into small species, which effects the movement of migratory animals and also, decreases the genetic exchange between populations leading to a declination of species. E.g.
  • Tropical rain forests (loss from 14% to 6%). Thousands hectares of rain forests is being lost within hours.
  • The Amazon rain forest is being cut for cultivating soya beans or for conversion of grasslands for cattle.
  • Due to fragmentation, animals requiring large territories and migratory animals are badly affected.
• Over-exploitation: Due to over-hunting and over-exploitation of various plants and animals by humans, many species have become endangered or extinct. Many species like Stellar’s sea cow, Passenger pigeon etc. are extinct due to over-exploitation.
• Alien species invasions: Accidental or intentional introduction of non-native species into a habitat has led to the declination or extinction of indigenous species. Alien species cause decline or extinction of indigenous species. E.g.
  • The Nile Perch introduced in Lake Victoria (East Africa) caused extinction of more than 200 species of native fish, cichlid fish in the lake.
  • Invasive weed species like carrot grass (Parthenium), Lantana and water hyacinth (Eicchornia) caused damage to our native species.
  • The illegal introduction of the African Catfish (Clarias gariepinus) for aquaculture is posing a threat to the indigenous catfishes in our rivers.
• Co-extinction: In a native habitat, one species is connected to the other in an intricate network. The extinction of one species causes the extinction of other species, which is associated with it in an obligatory way. E.g.
• • Extinction of the parasites when the host in extinct.
  • Co-evolved plant-pollinator mutualism where extinction of one leads to the extinction of the other

Invasive Species

Definition

• Invasive species also called introduced species, alien species, or exotic species, any non-native species that significantly modifies or disrupts the ecosystems it colonizes.
• Such species may arrive in new areas through natural migration, but they are often introduced by the activities of other species.
• Human activities, such as those involved in global commerce and the pet trade, are considered to be the most common ways invasive plants, animals, microbes, and other organisms are transported to new habitats.
• The most common characteristics of invasive species are rapid reproduction and growth, high dispersal ability, ability to survive on various food types and in a wide range of environmental conditions and the ability to adapt physiologically to new conditions, called phenotypic plasticity.

What are their impacts?

• The direct threats of invasive species include preying on native species, outcompeting native species for food or other resources, causing or carrying disease, and preventing native species from reproducing or killing a native species’ young.
• There are indirect threats of invasive species as well. Invasive species can change the food web in an ecosystem by destroying or replacing native food sources. The invasive species may provide little to no food value for wildlife. Invasive species can also alter the abundance or diversity of species that are important habitat for native wildlife.
• Invasive alien species are a major driver of biodiversity loss. In fact, an analysis of the IUCN Red List shows that they are the second most common threat associated with species that have gone completely extinct, and are the most common threat associated with extinctions of amphibians, reptiles and mammals.
  • An example is the Micronesian Kingfisher Todiramphus cinnamominus which was endemic to the island of Guam, but following predation by invasive alien snakes (Brown tree snake Boiga irregularis) it became Extinct in the Wild in 1986 when the last remaining wild birds were taken into captivity for captive breeding. In fact the Brown tree snake has caused much extinction on Guam, including the local extinction of over half of Guam’s native bird and lizard species as well as two out of three of Guam’s native bat species.
• Invasive alien species can also lead to changes in the structure and composition of ecosystems leading to significant detrimental impacts to ecosystem services, affecting economies and human wellbeing.
  • For example the Water Hyacinth Eichhornia Crassipes, a native to South America is spreading across Africa, Asia, Oceania and North America. It is a fast growing floating aquatic plant forming dense mats on the water surface, limiting oxygen and preventing sunlight reaching the water column. Infestations have led to reduced fisheries, blocked navigation routes, increased cases of vector borne diseases, reduced hydropower capacity and affecting access to water.

Invasive Species in India

Some Commonly Found Alien Species:

• African apple snail (Achatina fulica): The most invasive among all alien fauna in India, this mollusc was first reported in the Andaman and Nicobar Islands. It is now found across country and is threatening the habitat of several native species.
• Papaya Mealy Bug (Paracoccus marginatus): Native of Mexico and Central America, it is believed to have destroyed huge crops of papaya in Assam, West Bengal and Tamil Nadu.
• Cotton Mealy Bug (Phenacoccus solenopsis): Native to North America, it has severely affected cotton crops in Deccan.
• Amazon sailfen catfish (Pterygoplichthys pardalis): This species is responsible for destroying the fish population in the wetlands of Kolkata.

Effects of Loss of Bio-Diversity

• Loss of cultural diversity: The loss of both genetic and ecosystem diversities result in a loss of cultural diversity. As new strains and systems are introduced, they result in an overall change, the extinction of many species embedded in religion, mythology and folklore etc.
• Ecosystem breakdown: The loss of a species can have deleterious effects on the remaining species in an ecosystem. The loss of even one species can ruin an entire forest ecosystem of plants and animals.
• Food insecurity: Reduced biodiversity means millions of people face a future where food supplies are more vulnerable to pests and disease and where water is in irregular or short supply.
• Economic impact: The loss of plant species also means the loss of unknown economic potential, as extinct plants can hardly be harvested for food crops, fibers, medicines, and other products that forests, especially rainforests, provide.