PRAGATI PRAVA
The clarion call for a return to nature for support and sustenance – the World Environment Day theme this year – is a rallying cry at a time climate change poses the single biggest threat to sustainable development. The need of the hour is to establish channels of communication with the environment and keep a track of its general health. This is possible through indicator species, say scientists, which help us diagnose the symptoms of failing ecological health and teach us to remain alert to the subtle signals of nature…
At one time coal miners kept birds trapped in cages that sent out signals ahead of the emission of toxic gases from mines. The birds served as a warning system that alerted miners to the unsafe levels of gas building up inside a mine and prompted them to take action to prevent a catastrophe. Ahead of World Environment Day, June 5, Sunday POST speaks to scientists and environmentalists on nature’s own indicators, often called “bio-indicators” or “indicator species”, that signify the state of the environment, track a possible disease outbreak, and also monitor pollution and climate change in general. Scientists assert that we need to keep our senses alert for receiving the subtle signals of nature.
The theme of World Environment Day this year is ‘Connecting People to Nature’, a collective effort that reflects humanity’s urge to go back to nature for sustenance and support and understand its mysterious ways of functioning, said zoologist Pratyush P Mohapatra.
Explaining the term indicator species, the Zoological Survey of India scientist said an indicator species is an organism whose presence, absence or abundance reflects a specific environmental condition. For example, presence of tigers in the wild signifies a healthy forest.
Burning bright
Being the supreme predator and placed on the top of the ecological pyramid in the Indian forest ecosystem, tigers choose as their habitats forest areas that have a thriving population of herbivores such as deer, wild buffaloes, antelopes and boars. The near-disappearance of tigers from jungles indicates that our forest ecosystems are fast deteriorating, added Mohapatra.
A member of the International Union for Conservation of Nature’s (IUCN) Viper Specialist Group, Mohapatra said: “Tigers are considered the ‘umbrella species’ by conservationists because saving tigers implies saving the a whole ecosystem. In India, both the Centre and state governments are expending significant efforts to protect this endangered species from extinction, because in the name of tigers we can save many other animals that live in forest patches where tigers exist today – mainly tiger reserves. We should double up the collective effort to protect tigers because in order to save the big cat in a forest ecosystem we need a good prey base for it. Maintaining a good prey base means ensuring sufficient food for predators, a well-maintained water table and adequate rainfall. So tiger protection translates into direct ecological conservation.”
Sushil Kumar Dutta, a retired professor at the Indian Institute of Science, said: “Te He added here are plenty of bio-indicators. Starting from microbes, plants and insects right down to mammals there are examples that indicate the health of a natural habitat.
Dutta, who specialises in zoology and herpetology, explained how many species serve as bio-indicators. They are:
Dragon flies: These brightly-coloured insects are found hovering over ponds, lakes, streams, open areas and crop fields. Dragonflies are best suited for evaluating water quality and other environmental changes. If at a place you spot hundreds of dragonflies you can conclude that it is a healthy habitat. A sudden reduction or complete disappearance of the species indicates that the water bodies are contaminated and the surroundings polluted. Delicate and dainty dragonflies are precious to a particular ecosystem.
Butterflies: These colourful fluttering darlings are not only an attractive addition to a flower garden; they act as a vital wildlife indicator. They can tell almost everything we need to know about the health of an ecosystem. Butterflies react extremely quickly to even minor changes in the environment and biodiversity. They provide an early warning for subsequent depletion of wildlife. They are found in areas where there is an abundance of flowering plants and their disappearance point to the negative impact of climate change.
Moths: This insect is an important indicator of a forest ecosystem’s health. If they are found in abundance in a particular forest, it indicates that there are plenty of mango, jackfruit and palm trees as the insects feed on those fruits when they are ripe. If you spot a swarm of moths at a particular patch on the ground inside a forest, it implies that a specific wild animal has urinated there and it is indicative of the presence of the particular wild animal inside the forest. Moths throng on the ground to feed on the salt content of animal urine.
Vultures: Vultures show an early indication of contamination in the environment. The endangered birds are mostly victims of diclofenac, an anti-inflammatory drug used by farmers and veterinarians to ease pain in cattle. Vultures eat the remains of the drugged animals and suffer kidney failure and visceral gout, which prove fatal for them. Further, being scavengers, the birds eat from garbage dumps, which are mostly contaminated. Hence the disappearance of the species is an indicator that a particular habitat is contaminated. More than 97 per cent of vultures have disappeared from India’s skies over the past 15 years.
Parrots: If you spot a good number of these green beauties, you can conclude that you are in a healthy habitat. They stay inside tree holes and feed on insects. Their presence indicates that a particular area maintains biodiversity with a number of trees, insects and water bodies.
Mosquitoes: Being a bad indicator, abundance of mosquitoes in a particular area implies that the habitat has already been destroyed and the water bodies contaminated.
Elephants: Peaceful existence of jumbos in a habitat is an indication that a particular ecosystem is intact. From the Chandaka elephant sanctuary, the pachyderms stray towards Khuntuni, Athagarh and other places, which indicates a particular place lacks water bodies or trees to feed the wild animals. Due to excessive mining activities in Jharkhand and the other neighbouring places, the animals stray into jungles in Similipal – a relatively safer habitat.
Earthworm: The segmented worms live in swampy areas, lowland forests and open grasslands free from contaminated soil. If we find a good population of earthworms in a place, the soil there is surely free from fertilizers and pesticides.
Frogs: There are frog species belonging to the genus Polypedates and Philautus (bush frogs/tree frogs) in the forests of Similipal, Barbera, Daringbari and Meghasani in Orissa. They live in a forest habitat similar to semi-evergreen forests of the Western Ghats and Northeast India. The presence of such frogs in the forests of Orissa means the state has a similar forest habitat conducive to the survival of these species. However, such habitats are small fragmented patches in our forests. The frogs indicate that once upon a time – may be several thousand years ago – the Eastern Ghats and specifically Orissa was a thriving habitat which has sustained gradual fragmentation due to man-made and environmental factors.
Caecilian species: The presence of caecilian species (a limb-less amphibian) in the forests of Koraput (Deomali hilltops) and Meghasani in the state indicates the existence of a healthy habitat. Furthermore, the presence of a rare limbless skink (lizard) at Banei, Similipal and Meghasani, which prefers to live in loose soil below rocks in moist forest floors, signifies an unpolluted ambience, pointed out Dutta.
Honeybees: Honeybees are an indicator of the abundance of flowering trees and crop fields in a particular area, said Deepak Pani, a green activist, who is generating awareness among tribal communities in Similipal about sustainable honey collection.
Besides, bees have traditionally been viewed as indicators of environmental pollution due to heavy metals, pesticides and radionuclide. Through their high mortality rates honeybees signal the presence of toxic molecules in the air.
President of the Orissa Environment Society, SN Patro said, “The presence of dolphins and crocodiles in a water body indicates that the water is not polluted. Similarly, if you find a high density of birds in a particular area, it signals the presence of clean water bodies and sufficient food – conditions essential for a good habitat.” Patro maintained that animals like cheetah, blackbuck, Indian bison, wild buffalo, Indian wolf, swamp bear, fishing cat, Indian pangolin and eagle are bio-indicators.
According to Prasad Kumar Dash, a botanist with the Orissa Biodiversity Board, “In the event of an undesirable change in the environment because of human activities or the destruction of a biotic system, the indicator species send out alerts from numerous sources in a simplified manner. A variety of effects can be produced on aquatic and terrestrial organisms due to the presence of harmful substances and changes in their habitats.
Dash said plant indicators such as angiosperms, hydrophytes, algae, fungi, bryophytes, lichens and orchids alert us to specific changes in the ecosystem. “While some plants indicate water pollution others alert us to pollutants in the air. Lichens, orchids and bryophytes are found abundantly in a place where the air is clean. Their absence signifies deteriorating air quality like in Bhubaneswar,” added Dash.
If the air is clean, shrubby, hairy and leafy, lichens become abundant. In Khandagiri, a variety of lichens blue, red, green and yellow in colour are found. But in Dhauli, these are not seen as the area is exposed to heavy pollution and high temperature. This resulted from the destruction of wetlands surrounding the area which contributed to further rise in temperatures. However, the presence of a few lichen species, crusty in appearance, is suggestive of a high level of pollution. These are commonly found on pavements, walls and tree barks in urban areas.
While mosses indicate acidic soil, a few species are also indicators of atmospheric metal deposition. Specfic moss species growing on urban trees is an indicator of cadmium air pollution, while some species indicate fresh air quality.
Bryophytes of the genus Hypnum are particularly sensitive to pollutants, especially sulfur dioxide. As a result, most bryophytes are not found in cities and industrial areas.
Multivariate analysis of orchid abundances and environmental parameters reveal three orchid species that could potentially be used as indicators of an ecosystem’s health. Fungi can indicate old-growth forests where an abundance of coarse woody debris exists. Wood-decay fungi are sensitive to intensive forest management. Their diversity correlates with insect diversity and indicates continuum of dead wood.
If the air of a place is badly polluted with sulphur dioxide, green algae may be found there. A few algae varieties are also indicators of water quality. Synecocystis algae, which is found in Bindusagar lake in Bhubaneswar, has turned the water green and indicates pollution. Algae divisions like desmids and diatoms found in the Kedar Gouri pond, however, indicate unpolluted water. Also, plenty of climbers in an area suggests that the ecosystem has good moisture content and that the air is clean, Dash added.
