How does a change in the landscape affect the life of the streams and life in them?
A sudden gust of wind and a few bright red leaves of a grand Elaeocarpus break free, only to be unhurriedly carried away in the clear waters of the stream flowing by. Unlike trees where the young leaves are red and turn green, the leaves of the Elaeocarpus, a species of wild rudraksh, turn a bright red as they age, sprinkling the brown leaf litter of many a rainforest floor with its colour. A journey that started as a bud attached to a branch has now reached its final stage; detached and sailing away past massive buttresses of other Elaeocarps, wild mango and jamun, in the rainforests of the Anamalais. As they set sail, away from their branches, they are joined by others; walnut-like seeds of the same tree. They float past stream rubies defending their favourite perches, past Danios and spotted barbs in the water, past rounded rocks and overhanging bridges, past whistling thrushes and sallying flycatchers, past tumultuous rapids and scarlet impatiens, to gently settle in the arms of a calm pool.
Somewhere in the same landscape — not far — a sudden gust drops a few bright red leaves from another majestic elaeocarp. The stream flowing by is subdued and silent, unlike its gurgling neighbour a few miles away. The bright red leaves go with the flow, but there are no stream rubies here, nor sallying flycatchers. Harsh light streams through the sparse vegetation, in contrast to the soft, dappled light that a rainforest canopy allows. Far fewer rounded rocks remain; many now resting alongside roads as barriers. The water is slightly coloured, too, sluggish and slow to respond. The journey ends abruptly, as the stream disappears into a swamp in massive tea fields. Those few bright red leaves lend the only colour in a depressingly monotonous green ocean of tea, clogged in a mat of rushes and swamp vegetation. To understand the decay of streams, one has only to walk along a few in tea plantations.
Character of their own
Wherever they flow, streams have a character of their own. Whether in the mighty Himalayas or the equally impressive hills of peninsular India, from roaring rapids and rolling cascades to gurgling brooks, a stream is a strand that weaves life together. And fragmentation due to tea and coffee plantations sever the strand, converting fast-flowing streams to marshes and swamps. Vital meanders are straightened to drain away what appears to be excess water, but this in turn only leads to increased erosion and flooding. This is the decay of a stream, and the plantation landscapes of the Western Ghats are riddled with such streams. Most streams that originate and flow through these areas end up being dammed, diverted, mined and polluted. Their gentle meanders are straightened, their laughter silenced; their only solace being a few isolated rainforest fragments and protected forests of sanctuaries and reserves miles downstream.
How do landscape transformations affect the life of the streams and the life in the streams? Our recent study on the Asian small-clawed otter, the smallest of the world’s 13 otter species, threw up some pointers. In India, these otters are elusive mammals mostly restricted to the hill streams of the Western Ghats, the Himalaya and the North-east. For our study in the Valparai plateau of the Anamalai hills, we walked along numerous perennial streams flowing through the tea and coffee landscape, looking for evidence of otters. At first, the only glimmers of hope in the streams running through the stunted ocean of tea were the occasional grey wagtail or a flitting stream glory damselfly. Still, camera trap photographs and spraints (droppings) revealed that otters were using these streams. Coffee plantations with their shade trees, being more similar to forest, fared slightly better than tea for otters, despite the release of insufficiently-treated coffee wastewater into already-depleted streams. What was crucial for streams and otters were, however, the few patches of rainforest that had survived the onslaught of plantations. Retaining these strips of natural vegetation to regenerate along streams can help revive stream health and water quality, and prevent erosion and loss of wildlife habitat. It is in these strips that streams can still hum a part of their original tune.
Towering trees, an occasional herd of elephants crashing through and the sound of great hornbills in the canopy were constant reminders that much of the Valparai landscape was once like this. One early morning in April, in the adjoining Anamalai Tiger Reserve, we watched a pack of dholes frolicking in the shallow waters of a stream. They had killed a sambar the previous evening and had returned to finish the remains.
A couple of hours later, walking further upstream, we glimpsed our first small-clawed otter. Too stunned to react, we watched it disappear into a rock crevice. All these months of walking along streams had finally paid off, however short-lived. Not wanting to surprise it any further, we quickly moved on, walking upstream towards our destination; an obscure waypoint marked on the GPS. We had barely arrived and were yet to recover from having seen the otter when we heard a growl that could only have come from a tiger! Moments later, the forest exploded with the alarm calls of lion-tailed monkeys in the canopy. We watched as a tiger walked down to the stream for a quick drink. The stripes of orange and black disappeared as suddenly as they had appeared, the cacophony was soon transferred to the neighbouring valley, and tranquillity reigned once again.
Most natural systems are resilient in nature and if allowed to recover, these streams too can perform vital ecological functions in modified landscapes and support a substantial amount of biodiversity. Native riparian vegetation binds the soil together and prevents erosion. Restoration of streams and riparian ecosystems in modified landscapes also help in reducing conflicts and providing habitats for native species of both flora and fauna. It also helps in reviving corridors for movement of large mammals like elephants and gaur. The fact that otters and other animals still use streams in plantations is hope enough that all is not lost in this blind dash towards development.
The writer is a Masters student of wildlife biology and conservation from the National Centre for Biological Sciences, Bangalore, currently working with Nature Conservation Foundation, Mysore. E-mail: [email protected]