Restoring the Ecosystem
of the Kapiriggama Small Tank Cascade System
Background
An ecosystem functions as a unit to provide a range
of ecosystem services that are extremely beneficial to
humans. (See overleaf for more detail.) A village tank
cascade is a centuries-old ecosystem that has provided
villagers living in its surrounds with a suite of life-sustaining
ecosystem services for their daily needs — such as food,
medicines and fuelwood; absorption of carbon, purification
of water; control of erosion and stabilisation of stream
banks.
A range of human induced activities — such as
deforestation, overexploitation, pollution, and the spread of
invasive alien species — has degraded the traditionally rich
Kapiriggama village tank cascade ecosystem (see Brief #1).
There was an urgent need, therefore, to rehabilitate these
tanks and restore the cascade ecosystem to ensure that
the historical benefits that the community enjoyed are
provided again.
The overall goal was to rehabilitate the irrigation system
and restore the cascade ecosystem, with enhanced
biodiversity, to provide adequate and good quality water
for all needs of the community. Specific objectives were
as follows: i) to create awareness about the tank cascade
ecosystem and its services; and ii) to carry out ecosystem
restoration with involvement from the community.
To this end, elements of each tank (see Brief # 1) were
evaluated and actions taken to rehabilitate and restore
these elements.
IUCN Cascade Development Project Information Brief No. 3
What is an ecosystem and what is ecosystem
restoration?
Ecosystems are groups of species that interact with
each other and with the physical environment. Each
ecosystem consists of a variety of different species —
plants, animals and micro-organisms — interdependent
on and interacting with each other in a specific habitat
with a given set of physical variables, to form a natural
unit. Shown in the diagram are the main components of
an ecosystem.
Primary producers: Plants — such as Terminalia
arjuna, lotus and reeds — that use the energy of the
sun to make their own food, through the process of
photosynthesis;
Primary consumers or herbivores: Animals that
eat plants or plant products — such as bees,
grasshoppers whistling ducks and fish;
Secondary consumers or primary carnivores:
Animals that eat herbivores — such as spiders,
dragonflies, cormorants and frogs;
Secondary carnivores: Animals that eat both
herbivores and other carnivores — such as fishing
cats, white-bellied sea eagles and crocodiles; and
Decomposers and detritivores: Detritivores feed on
dead and decaying material and decomposers cause
decay at a microscopic level, releasing nutrients back
into the soil.
The arrows show the energy flow through one simple
food chain.
The dashed arrows show the detritus cycle.
Thus, each organism in the community has a function. All
living organisms in an ecosystem are fitted to share their
physical habitat and to the presence of each other in an
elegant, complex, intertwined web of life.
Although it is the diversity of species and the diversity of
interactions that make for well-functioning ecosystems,
each ecosystem functions as a unit: many parts function
together to provide a whole. Through this smooth
functioning, ecosystems churn out food and fuel for us,
protect us from the floods and famines, purify our waters
and detoxify our soils, sustaining our lives. An ecosystem
sustains itself entirely with energy flow through food
chains and webs, as well as through nutrient recycling.
Damaging even a part of this unit disrupts the whole.
When ecosystems stop functioning smoothly, the
goods and services that they provide decline in quality
and quantity, affecting humans. Conversely, when
one component is improved it influences the whole
ecosystem.
Ecological or ecosystem restoration involves human
intervention to renew and restore degraded, damaged,
or destroyed ecosystems.
Achievements
Creation of awareness
• Four awareness raising programmes were conducted
in three schools in the project area on the importance
of the cascade tank ecosystem and its conservation.
• About 350 students participated in these programmes.
• About 600 books related to the history, ecology,
biodiversity and culture of ancient cascade systems
were donated to the three schools of the project area.
• A herbal garden was established in one of the schools
in the project area.
Community and partner participation
•
•
Eighteen shramadana programmes were carried out.
About 700 villagers from 10 villages participated in the
these activities.
About 110 HSBC staff participated in cascade
ecosystem restoration activities.
Mee; Tamil: Illupai); Milletia pinnata (Sinhala: Karanda;
Tamil: Punku/Poona); Limonia acidissima (Sinhala: Divul;
Tamil: Vila maram); Syzygium gardneri (Sinhala: Damba;
Tamil: Nir nawal); Azadirachta indica (Sinhala: Kohomba;
Tamil: Arulundi); Diospyros malabarica (Sinhala: Timbiri;
Tamil :Panichchai); Ficus spp. (Sinhala: Nuga) and Areca
catechu (Sinhala: Puwak; Tamil: Paaku).
Yathuru wala: This is a strip of swamp forest at the toe of the
dam.
• In four tanks, the vegetation of the yathuru wala was
improved by augmenting it with Lasia spinosa (Sinhala:
Kohila; Tamil: No name known) and Ipomoea aquatica
(Sinhala: Kang kung; Tamil: Kang kung kirai), as well as
reeds.
Gasgommana: This is the windbreak of trees that functions
like a catchment forest.
• In eight tanks, the gasgommana was replanted with
the same species, as for the kattakaduwa area except
Areca catechu.
Plant nurseries
• The land for two plant nurseries was donated by two
villagers and maintained for the project duration by
them.
• About 7,500 plants from these nurseries were used in
the process of restoration.
Physical rehabilitation of the tanks
• The tank bed, command area and spill canals were
altered and the tank bunds repaired in various tanks
(see information brief # 5 for details of the process).
Ecosystem restoration of tanks elements
Kattakaduwa (interceptor):
This is the stretch between the tank bund and paddy fields
consisting of three land phases (water hole, marshy land
and dry upland). It acts as a downstream wind barrier,
reduces tank seepage, prevents sodium, magnesium and
iron from entering the paddy land and safeguards the tank
bund.
• The kattakaduwa area was demarcated in 6 tanks
facilitating restoration activities and also for the
conservation, in future, of this element;
• In 12 tanks, the kattakaduwa was replanted and gaps
filled;
• The vegetation in encroached areas of the
kattakaduwa was enriched with economically
important crops such as Areca catechu (Sinhala:
Puwak; Tamil: Paaku);
• Seedlings used for ecological restoration of the
kattakaduawa included Terminalia arjuna (Sinhala:
Kumbuk; Tamil: Marudu); Madhuca longifolia (Sinhala:
Map summarising the restoration work carried out in
the Kapiriggama Cascade
Recommendations for future work
•
•
•
•
•
•
•
•
•
•
Use the newly developed institutional framework to
spearhead restoration and maintenance;
Continue demarcation of tank elements and the
cascade ecosystem;
Maintain existing plant nurseries, a source of plants for
continuing restoration;
Continue tank ecosystem restoration and ensure
maintenance of restored areas;
Set up a long-term study, using schoolchildren, to
assess the biodiversity of the restored areas;
Improve, and if needed, establish legal provisions and a
mechanism to resolve legal issues related to restoration;
Develop a study to value, in hard currency, what has
been done through ecological restoration in terms of
ecosystem services to the community;
The above will allow for linking ecological restoration to
economic activities;
Link restoration to sustainable use; and increase
female participation by sustainable use to cottage
industries.
Explore possibilities of establishing a financing
mechanism for restoration, from contributions by the
beneficiaries of tank ecosystems.
January 2016
Photographs:
Cover: Community members engaged in replanting the
gasgommana in the Massalawa tank, S. M. M. Senavirathna ©
IUCN; page 2 diagram: Devinda Halwalage; page 3: left: IUCN
officers conducting a school awareness raising programme on
biodiversity and ecosystem conservation at Konakumbukwewa
Maha Vidyalaya (Kumudu Herath © IUCN); right, top: community
members participating in a shramadana at Peenagama Tank, S.
M. M. Senavirathna © IUCN; right, bottom: community and HSBC
staff engaged in restoring the kiwul ela at Konakumbukwewa
tank, Kumudu Herath © IUCN; this page, top: map by Darshani
Wijesinghe.
For more information contact
Shamen Vidanage,
Programme Coordinator,
IUCN Sri Lanka Country Office
53, Horton Place, Colombo 7, Sri Lanka
tel: +94-112682418, fax: +94-112682470
email: [email protected]
https://www.iucn.org
Access technical note from here.