Kolkata: Creatures as little as butterflies and moths are bio-indicators and can be used as an effective tool to monitor the health of our forests, says a new book.
"Of special interest in assessing the health of a forest would be the local species that are found year after year in a limited area at a fixed time of year. Some butterflies and moths are found only in a particular ravine in a forest," writes naturalist Peter Smetacek in "Butterflies on the Roof of the world".
If one could understand why those creatures cannot inhabit other areas, then one would automatically understand why the chosen ravine or hillside is special, he says in the book published by Aleph.
Considered an authority on Indian butterflies and moths, Smetacek has described a dozen species new to science. He also runs the Butterfly Research Centre in Uttarakhand`s Bhimtal.
According to the lepidopterist, one can use the presence or absence of living creatures to indicate the health of their environment as they are bio-indicators.
In the book which demystifies the fascinating world of colourful insects, he gives the example of the Golden Birdwing butterflies found in the western Himalayas.
"If one does not find any Golden Birdwings among them, it means that there is probably no perennial water source in the vicinity. If there are Birdwings, then one can be reasonably certain that there are mature plants of Aristolochia dilatata, which need perennial water, so there must be a spring or stream nearby," says the book.
If the Birdwings begin to disappear from an area, it would mean that the streams are becoming seasonal and the Aristolochia plants are not reaching maturity.
The author explains how butterfly and their larvae are dependent on plants for food and shelter. The survival of plants on the other hand is directly dependent on the presence of water bodies including underground watercourses.
Revealing how insects camouflage themselves to escape predators, Smetacek writes that the Orange Oakleaf butterfly is an exceptionally good mimic of a dry leaf of a certain shape.
The presence of these butterflies is restricted to forests with leaves similar to the shape of their wings.
"In a forest with many trees with similarly shaped leaves, it is difficult to distinguish these butterflies. However, in a pine forest, the dry leaf shape and pattern of the butterfly would actually attract attention, since there would be nothing like it among the pine needles," says the book.
"So if there are many Orange Oakleaf butterflies about, it strongly suggests that the leaf cover or canopy of the trees in that area is undisturbed and dense. The canopy cover is reduced when the leafy branches of trees are lopped for fodder," it says.
Full of personal anecdotes, the book which is a result of spending a lifetime chasing butterflies in meadows and forests concludes that the time is coming when butterflies will help in monitoring our forests.