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| A view of Bharathapuzha (Image Credit: Wiki Media Commons/ Jjvellara) |
Implement urgent conservation efforts or the
rich and endemic fish wealth in the largest river in the Western Ghats of
Kerala will remain only on papers, warns a new assessment on the threats to the
fish diversity in the Bharathapuzha River, locally known as River Nila.
Through a survey on all the four major
tributaries of the Bharathapuzha River system - Gayathripuzha, Chitturpuzha,
Kalpathipuzha and Thoothapuzha – the study recorded 117 species of fishes in
Nila with the highest species richness from the stretch between Parali to
Purathur estuary. Among this, 33 are found only in Western Ghats and three are
found only in Bharathapuzha River system.
A group of researchers including A
Bijukumar, Department of Aquatic Biology and Fisheries, University of Kerala,
Siby Philip from Department of Zoology, Nirmalagiri College, Koothuparamba,
Anvar Ali and Rajeev Raghavan from Conservation Research Group, St Albert’s
College, Kochi and S Sushama from Department of Zoology, NSS College Ottapalam
carried out the study which is published in the Journal of Threatened Taxa.
Top Ten Threats to River Nila
Despite the richness, the river system of River Nila is under threat from human interference, says the study which is published
in the Journal of Threatened Taxa. “Several anthropogenic stressors including
deforestation and loss of riparian cover, dams and other impoundments,
pollution, sand mining, non-native species, climate change and destructive
fishing practices are threatening the fish diversity of Bharathapuzha River
system”, it says.
Threat
#1: Sand mining
Most notorious, most widely known but most
rampant, despite being regulated (encouraged ?) by the il-legal machinery. If
we number the threat based on the calamity it brings, this one goes to top. The
study marks the region between Pattambi and Thiunavaya as the superhot stretch
of legal and illegal sand mining. Studies conducted by CESS in 1997 itself has
shown that the rate of sand mining is way too above the rate of sand generation
in Nila. For many fishes in Nila, Sand is the
breeding substrate, and is the single crucial link that supports the aquatic
food web. With the indiscriminate sand mining, it is just a matter of time for
fishes like Glossogobius giuris and Sicyopterus griseus to vanish from Nila
forever, warns the study.
Threat
#2: Dams and impoundments
Known fact: Big dams are a major threat to
the rich and endemic fish diversity of Nila, since they change the turbulence
of the river causing high sedimentation and other problems. Lesser Known fact:
Dozens of smaller check damk dams across Nila are also doing the
same. Bigger dams are fixed in number so far – Nila has 11 irrigation dams.
Impoundments are still proliferating, turning out to be a lesser noticed diversity
killer in Nila. It has severely affected the movement of certain fish species
and is believed to be a reason for the near absence of eels in the river
system.
Threat
#3: Pesticide pollution
When it comes to a River system like Nila,
don’t think it is just the factories that are pushing chemicals to the water. River
basin dependent extensive agriculture and plantations are also contributing
their fair share to polluting this blood line of middle Kerala. Chemical
fertilizers, pesticides, chemical nutrients, weedicides, you name it. The
resulting eutrophication- the facilitation of aquatic plant growth which in
turn decreases the available oxygen in the water, killing the aquatic fauna- is
a major issue, especially from Chamravattom to Purakkad, says the study.
Threat
#4: Urban sewage
Read Pattambi. According to the study, the
town of Pattambi which falls under the Palakkad District of the state of Kerala
is a major source of urban sewage which pollutes the river extensively, taking
over the pollutant cocktail made by the agro-pollutants. “The urban sewage canals directly open into the
river, through which the municipal waste is dumped. Such large scale pollution
not only degrades the habitat but also causes endocrine disruptions and several
other physiological imbalances in fish including breeding failure which could
ultimately lead to their extirpation”, says the study.
Threat
#5: Deforestation
According to the study, deforestation in
its catchment areas like Mangalam, Nelliyampathy, Walayar, Malampuzha,
Nellipuzha, Dhoni and Kalladikode is a major threat. The loss of natural native
vegetation has triggered the invasion by exotic plants. Not only that the
fishes loose a food resource, the high sedimentation rate due to deforestation
is changing the natural composition of the river bed. It makes survival
difficult for many endemic loaches in the river since they use the pebbles in the
river bed for breeding.
Threat
#6: Lime stone mining
Lime stone mining is rampant in certain
areas of the catchment of the river, says the study. This is especially
prominent in Malampuzha, part of the Kalpathipuzha tributary. The study claims
that the lime stone mining in the catchment areas is leading to pollution and
siltation in the stream. Apart from triggering an unnatural rise in the
silicate content in the water, the dumping of mining debris also damages
smaller streams in the system like Seemanthinipuzha.
Threat
#7: Alien species
The study has spotted at least six
non-native fish species in Nila. While three of them were non-native to Indian
rivers, three were from the Gangetic plains. Though the Indian major carps were
introduced as part of aquaculture, considered as a success, the study was able
to spot them from lower reaches of the river, revealing that they have
proliferated though the river beyond their actual reservoirs. Such
proliferation of non-native species often wipes out native species in the fight
for resources. Species foreign to India like the Nile Tilapia and Mozambique Tilapia
were also spotted from Nila, showing that the alien invasion is possibly stifling
the endemic fish fauna of the river. However, the surprise factor was that the
study reportedly failed to fetch another notorious alien species – African catfish- which is a known diversity killer in Western Ghats Rivers.
Threat
#8: Climate change
Studies conducted in 2010 and 2011 discovered
that the temperature in the Bharathapuzha basin has been on the rise for a 36
year period from 1969 to 2005. Moreover, rainfall data shows that the Nila
watershed gets less rainfall than the state average. Though the temperature
rise is often cited as an impact of climate change phenomenon and the
increasing anthropogenic pressure in the river banks of the Nila, its effect on
the biodiversity of the river system is scarcely studied.
Threat
#9: Aquarium fish trade
Comes in many colours –state supported as well
as clandestine. This greed trade is especially wiping away endemic and
beautiful fishes like Miss Kerala (Sahyadri
denisoni) and Mesonoemacheilus
remadevii, the latter being found only in river system in Silent Valley
which is part of the Bharathapuzha River System. As per a recent study, Miss
Kerala has been found to be collected in massive amounts from Thoothappuzha
tributary for pet trade.
Threat
#10: Destructive fishing practices
Last, but not the least, as always. Poisoning,
use of mesh nets and dynamiting – small effort, good catch. Though traditional
fishermen abstain from practices like dynamiting, it is raising a major threat
to the fish diversity in the tributaries where the traditional fishermen are
lesser in number, warns the study.
Action
Time: Conservation Points to save Nila
- Prioritizing integrated watershed programmes.
- No more new medium or big dams, cautious about new check dam
proposals.
- Channelize district River Management Fund to Eco restoration
of stretches of Nila.
- Regulation of sand mining has been proved to be futile. So
finding an eco-friendly alternative to sand is the only option left. But that will be like legalizing marijuana- you have to
first convince the cartels before you convince the government. (They will have
to take it, since the sand is running out and the weed is on the rise).
- Beg people not to use pesticides or agro-chemicals near the
river bed cultivations (otherwise also).
- Regulate large scale riverbed cultivation.
- Establishing Aquatic Biodiversity Management Zones (ABMZ) to
conserve river stretches known to shelter endemic and rare fishes.
- Regulate the
greed pet trade
and destructive fishing practices, not to say dynamiting.
- Above all, let people know – ask them, request them, beg
them, threaten them – You may go the extreme since water is the life blood of
the green earth, as River Nila is for Kerala.
