Environment & Ecology: Biodiversity

Categories
Environment & Ecology
Published
05-Feb-2020

Biodiversity

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.

Rhinos to be re-introduced in Uttarakhand

Context

The Uttarakhand State Wildlife Board has cleared a proposal by the Wildlife Institute of India (WII) to introduce rhinoceroses in the Corbett Tiger Reserve (CTR) to boost tourism and revive the habits of species that survive on low-height grass.

About

According to officials, around 10 rhinos will be brought in CTR in the first phase and subsequently, 10 more would be added.
Experts claim that protecting these rhinos from poaching will be the only challenge for the state’s forest department staff after the move.
The geographical terrain and environmental conditions in CTR are suitable for rhinos.
The ideal sites chosen in Corbett are valley habitats bounded on either side by the lower Himalayas (north), Shivalik Hills (south) and the Ramganga Reservoir (east), which would also act as natural barriers to rhino movement outside these area, thereby minimising conflict with people.

Benefits from this move-

According to wildlife experts, rhinos reduce the size of elephant grass by eating it.
This would mean that species that thrive on lower-height grass — Hog Deer, Cheetal, Sambar and Swamp Deer, among others — would also be encouraged.
According to WII experts, the rhino’s range was once continuous across the flood plains of the Indus, Ganges and the Brahmaputra, but today, it is limited to small fragmented pockets in India and Nepal as a result of anthropogenic pressures.
Re-introduction into habitats in its historic range would not only create safety-net populations for the species but also restore their ecological role in these faunally-degraded habitats.

About One-horn Rhino-

The Indian rhinoceros also called the greater one-horned rhinoceros and great Indian rhinoceros, is a rhinocerosspecies native to the Indian subcontinent.
It is listed as Vulnerableon the IUCN Red List.
The Indian rhinoceros once ranged throughout the entire stretch of the Indo-Gangetic Plain, but excessive hunting and agricultural development reduced its range drastically to 11 sites in northern Indiaand southern Nepal.
It inhabits the alluvialgrasslands of the Terai and the Brahmaputra basin.
The Indian rhinoceros is regionally extinct in Pakistan.
There are about 2,600 rhinos in India, with more than 90% of the population concentrated in Assam’s Kaziranga National Park. Outside Kaziranga, rhinos are found in West Bengal, Uttar Pradesh, and Bihar.
Kaziranga National Park in Assam, India, holds about 70% of the world population. This is worrisome for two reasons – the park may have reached its carrying capacity and might not be able to support any more rhinos; and the entire species’ population could decimated because by a disease outbreak, natural disaster, or another acute threat.

About Jim Corbett National Park-

It is the oldest national park in India and was established in 1936 as Hailey National Park to protect the endangered Bengal tiger.
It is located in Nainital district and Pauri Garhwal district of Uttarakhand and was named after Jim Corbett, a well known hunter and naturalist.
The park was the first to come under the Project Tigerinitiative in 1973.

Indian Rhino Vision 2020-

It is an ambitious effort to attain a wild population of at least 3,000 greater one-horned rhinos spread over seven protected areas in the Indian state of Assam by the year 2020.
IRF has partnered with the Assam Forest Department, the Bodoland Territorial Council, the World Wide Fund for Nature (WWF), and the US Fish & Wildlife Service to address the threats facing Indian rhinos.

Why India needs a Project Dolphin

Context

The government is planning to launch a programme called “Project Dolphin”, along the lines of “Project Tiger” to enhance the population of these dolphins

About

About the Gangetic river dolphin

The Gangetic river dolphins can only live in freshwater, are blind and catch their prey in a unique manner, using ultrasonic sound waves.
The Gangetic river dolphins were officially discovered in 1801 and are one of the oldest creatures in the world along with some species of turtles, crocodiles and sharks, according to the World Wildlife Fund (WWF).
They once lived in the Ganges-Brahmaputra-Meghna and Karnaphuli-Sangu river systems of Nepal, India, and Bangladesh, but are now mostly extinct from many of its early distribution ranges, as per WWF.
In 2009, the Gangetic dolphin was declared India’s National Aquatic animal. Gangetic dolphin has been notified by the Assam as the state aquatic animal too.
It is placed under the “endangered” category by the International Union for Conservation of Nature (IUCN).
They are distributed across seven states in India: Assam, Uttar Pradesh, Madhya Pradesh, Rajasthan, Bihar, Jharkhand and West Bengal.
Their numbers have dwindled in the last few decades mainly because of direct killing, habitat fragmentation by dams and barrages and indiscriminate fishing.

Efforts made in India to protect the dolphins?

Setting up of the Conservation Action Plan for the Gangetic Dolphin (2010-2020), which has identified threats to Gangetic dolphins and impact of river traffic, irrigation canals and depletion of prey-base on dolphin populations.
Gangetic dolphins have been included in Schedule -I of the Wildlife Protection Act, 1972, which means they have the highest degree of protection against hunting.
They are also one among the 21 species identified under the centrally sponsored scheme, “Development of Wildlife Habitat”.

Threats to Gangetic river dolphin

Pollution: It faces a number of threats such as dumping of single-use plastics in water bodies, industrial pollution, and fishing.

Restrictive Flow of Water: The increase in the number of barrages and dams is also affecting their growth as such structures impede the flow of water.

Poaching: Dolphins are also poached for their flesh, fat, and oil, which is used as a prey to catch fish, as an ointment and as a supposed aphrodisiac.

Shipping & Dredging: It is also called a blind dolphin because it doesn’t have an eye lens and uses echolocation to navigate and hunt.

Ocean Deoxygenation

Context

Marine life, fisheries increasingly threatened as the ocean loses oxygen – IUCN report

About

International Union for Conservation of Nature (IUCN) has released a report titled “Ocean deoxygenation: Everyone’s problem”.
The report is the largest peer-reviewed study so far into the causes, impacts and possible solutions to ocean deoxygenation; and was released by IUCN at COP25 to the UNFCCC.
With this report, the scale of damage climate change is wreaking upon the ocean has come into stark focus. As the warming ocean loses oxygen, the delicate balance of marine life is thrown into disarray.
Large areas of the open ocean are increasingly threatened with low levels of dissolved oxygen. It is harming marine ecosystems which were already under stress from ocean warming and acidification.
The potentially dire effects on fisheries and vulnerable coastal communities make the decisions taken at the UN Climate Change Conference (CoP25) even more crucial.
“To drive action towards restoring ocean health” is one of the key themes of IUCN World Conservation Congress in Marseille in 2010.

What is the problem?

Ocean deoxygenation is one of the most pernicious, yet under-reported side-effects of human-induced climate change.
Oxygen loss from warming of oceans has alarming consequences for global oceanic oxygen reserves, which have already reduced by 2% over a period of just 50-years (from 1960 to 2010).
Ocean regions with low oxygen concentrations are expanding, with around 700 sites worldwide now affected by low oxygen conditions – up from only 45 in the 1960s.
In the same period, volume of anoxic waters – areas completely depleted of oxygen – in the global ocean has grown four times.
If situation continues as is, the ocean is expected to lose 3–4% of its oxygen inventory globally by the year 2100.
But impact witnessed at the local level will be far more severe compared to that seen on average at the global level.
For example, impact will be more severe in mid to high latitudes.
Most of the losses are predicted to be concentrated in upper 1000m of the water column, which is the richest in marine biodiversity.

What are the causes?

The primary causes of deoxygenation are:
Eutrophication (increased nutrient run-off from land and sewage pollution).
Nitrogen deposition from burning of fossil fuels.
Widespread impacts from ocean warming.
Ocean oxygen loss is closely related to ocean warming and acidification caused by anthropogenic carbon dioxide emissions and biogeochemical consequences related to anthropogenic fertilization of the ocean.
As the ocean warms, its water hold less oxygen and become more buoyant, resulting in reduced mixing of oxygen-rich water near the surface with the ocean depths, which naturally contain less oxygen.
Nutrient pollution causes oxygen loss in coastal waters. Fertiliser, sewage, animal and aquaculture waste cause excessive growth of algae, which in turn deplete oxygen as they decompose.

What is the impact?

The loss of oxygen from world’s ocean is increasingly threatening fish species and disrupting ecosystems.
Deoxygenation is starting to alter the balance of marine life , favouring low-oxygen tolerant species (e.g. microbes, jellyfish and some squid) at the expense of low-oxygen sensitive ones (many marine species, including most fish).
Some of the ocean’s most productive biomes – which support one fifth of the world’s wild marine fish harvest – are formed by ocean currents carrying nutrient-rich but oxygen-poor water to coasts that line the eastern edges of the world’s ocean basins.
As naturally oxygen-poor systems, these areas are particularly vulnerable to even small changes in ocean oxygen.
Impacts here will ultimately ripple out and affect hundreds of millions of people.
Species groups such as tuna, marlin and sharks are particularly sensitive to low oxygen because of their large size and energy demands.
These species are starting to be driven into increasingly shallow surface layers of oxygen-rich water, making them more vulnerable to overfishing.
Very low ocean oxygen can also affect basic processes like the cycling of elements crucial for life on Earth, such as nitrogen and phosphorous.

What should be done?

There is urgent need to dramatically raise our ambitions to tackle climate change, before human actions irreparably impact and change the conditions favourable for life on earth.
To curb ocean oxygen loss alongside other disastrous impacts of climate change, world leaders must commit to immediate and substantial emission cuts.
There is need to decisively curb greenhouse gas emissions as well as nutrient pollution from agriculture and other sources.