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Subjects
and Functions |
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Implementation of Policies,
Plans and Programmes in respect of Environment
& Natural Resources
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Forests and Forestry
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Exploitation and Sale
of Mineral Sands
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Environmental protection
and management
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Strict Natural Reserves,
National Parks, Game Sancturies, Wildlife,
Elephant and Buffalo Kraal
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Protection and Conservation
of Fauna & Flora
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Conservation of river
catchments and Major reservoirs
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Conservation and development
of Natural Resources.
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Meteorological Service
& Research
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Marine Pollution Prevention
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Impacts
of Climate Change in Sri Lanka |
Impacts on the agricultural
sector
Extreme
events of rise in temperature and changes in
rainfall
patterns will have adverse impacts on agricultural
production in Sri Lanka. The changed rainfall
scenario suggests an increase in amplitude of
rainfall extremes causing adverse environmental
impacts. Frequent floods will lead to increased
soil erosion, landslides, and damage to agriculture
through flooding of low-lying areas. Temperature
and moisture changes will also force farmers
to change the cropping patterns that have so
far been tuned to traditional climates. |
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It
is estimated that even a 1 oC warming would necessitate
major adjustment of the finely tuned crop calendar.
According to climate scenarios produced by the Commonwealth
Scientific and Industrial Research Organization (CSIRO)
for Sri Lanka, temperature changes are significant
for the year 2070. The increase in mean temperature
would increase the maxima of the existing temperature
cycle. It is reasonable to assume that these changes
will manifest themselves in the frequency of warmer
spells, warmer months, and warmer seasons. In warm,
semi-arid regions, deficiency of moisture would be
a major constraint.
Vidanage and Abeygunawardena used crop–climate
relationships developed by Seshu and Cady (1983) [Response
of Rice to Solar Radiation and Temperature Estimated
from International Yield Trials. In Crop Science 24:
649–654] to estimate the changes in paddy output
at each level. Calculations were done separately for
the yala and maha seasons. Based on the analysis for
2010, overall paddy production will be reduced by
5.9% if temperature increases by 0.5 oC. This will
reduce the GNP at current prices by 0.2%. Although
the status of water resources in the country in 2010
changes, it is not expected that paddy production
will change drastically. This is because about 65%
of paddy land is irrigated; minor impacts can be overcome
through water storage in reservoir systems. The economic
value of the change in paddy output under the low
temperature scenario is estimated to be about Rs 171
million, while for the high temperature scenario it
is about Rs 823 million.
Goonasena carried out similar studies for coconut
and soyabean production in Sri Lanka. The results
show a continuous increase in coconut production up
to 2010, while the soyabean yield increases by 1.4%
in the maha season under the low climate change scenario.
However, in the medium and high climate change scenarios,
yields drop by 2%–3%. The yields drop substantially
in the year 2070. The results of the above crop studies
should, however, be used with caution as they do not
take into account the full range of impacts likely
to be encountered under the changed climatic conditions.
Except for tea, most of the other cropping activities
(e.g., coarse grain, legumes, vegetables, and potato)
are likely to be affected adversely. The highest negative
impact is estimated for two components: coarse grain
and coconut production. It is reasonable to expect
such adverse effects. For example, coarse grain is
produced in the country under rain-fed conditions,
and on marginal lands. No irrigation facilities are
available for these crops and any changes in rainfall,
temperature rise, pests and diseases, and natural
calamities, will have impact directly on these crops.
Coconut production will be affected similarly. Table
1 [ADB, 1994] outlines the economic assessment of
the impact of global warming on agriculture in Sri
Lanka for the year 2010.
The tea industry in Sri Lanka is its main source
of foreign exchange and a significant source of income
for labourers. Tea yield is greatly influenced by
weather, especially by drought and heavy rains which
cause soil losses. An increase in the frequency of
droughts and extreme rainfall
events could result in a decline in tea yield, which
would be the greatest in regions below 600 metres
(Wijeratne 1996) [Vulnerability of Sri Lanka tea production
to global climate change. Water, Air, and Soil Pollution
92: 87-94]. Furthermore, the vulnerability of Sri
Lanka’s tea industry to climate change would
have spillover effects in terms of greater economic,
social, and environmental problems.
Impacts on the forestry sector
The climate change scenarios predicted for Sri Lanka
indicate significant changes in temperature and precipitation
by the year 2070. It can be assumed that the boundaries
of existing forests would change and hence would have
impacts on timber production, biological diversity,
recreational opportunities, and watersheds. The hydrological
cycles influenced by forests would also get affected.
With a likely increase in extreme events like droughts,
the incidence of forest fires may also increase. The
rise in temperature could increase the population
of insects, and the incidence of diseases that damage
forests. The present loss of mangroves could be aggravated
by climate impacts such as increase in rainfall
due to increased intensity of monsoon circulation,
and increased flooding from storm surges. Even a 20
cm sea level rise would lead to submergence of some
mangroves, which are at low elevation.
Somaratne and Dhanapala (1996) [Potential impact
of global climate change on forest in Sri Lanka. Water,
Air, and Soil Pollution 92:129-135] estimate a decrease
in tropical rainforest of 2-11% and an increase in
tropical dry forest of 7-8%. This study also indicates
that increased temperature and rainfall
would result in a northward shift of tropical wet
forest into areas currently occupied by tropical dry
forest. The most vulnerable forest areas in Sri Lanka
are likely to be the Sinharaja Forest Reserve and
Peak Wilderness Forest Reserve. These changes would
probably lead to the elimination of most Sri Lankan
endemic species.
Impacts on the water resources
Climate change would change the timing, extent,
and distribution of precipitation and run-off, which
is the source of renewable water supply. However,
it may be noted that the existing General Circulation
Models (GCM) do not adequately simulate how hydrology
and water supplies would be affected by climate change.
In Sri Lanka, the wet season rainfall
change in the year 2070 for the high climate change
scenario is estimated to vary between –5% to
+15%. The impact on water resources would depend on
evaporation, timing, extent, and distribution of precipitation,
and other factors affecting run-off. If the increase
in rainfall manifests itself in heavy rainfall events
and is concentrated in fewer days, much of it would
be lost as run-off to the sea. Further, if there is
any increase in extreme drought events, water deficit
areas could worsen. It is, therefore, unclear whether
the indicated rise in rainfall
by the year 2070 would lead to a significant increase
in the availability of water resources. On the other
hand, the demand for water will increase with population
growth, urbanization, and increased economic activity.
Water demands caused by higher average temperatures
may also increase, as would the demand from natural
ecosystems. Climate change will also increase the
overall uncertainties associated with water management
and supply (Gleick, 1992) [Effects of Climate Change
on Shared Fresh Water Resources. In Mintzer, I M,
(ed), Confronting Climate Change: Risks, Implications
and Responses, Cambridge University Press. pp. 127-140].
An increase in extreme rainfall
events as indicated in climate change scenarios would
lead to exacerbation of the existing vulnerability
of infrastructure and communication through increased
flooding and landslides. It could also lead to increased
siltation in reservoirs. Flooding in coastal areas
could also be increased as a result of reduced drainage
due to sea level rise. Rich mangrove belt along the
coast would also be severely affected. When rivers
are diverted at upper stream for irrigation purposes,
freshwater supply to mangroves will be affected, causing
salinity, and stunted growth. This will degrade mangroves,
which provide supplementary incomes to people, are
breeding grounds for fishes, and put up natural protection
against coastal erosion.
Impacts due to the changes in sea level
The coastal region currently supports about 34%
of Sri Lanka’s population and 24% of its land
area. Marine fisheries produced nearly two-thirds
of the animal protein consumed in the country (data
corresponds to 1987–88). Along with the tourist
beaches, marine fisheries and aquaculture account
for a significant proportion of the nation’s
export earnings.
The Sri Lankan country study carried out by ADB (1994)
focused on the coastal region extending from Waikkal
to Galle for assessing the impacts due to the changes
in sea level. It is one of the most populated and
developed coastal regions in the country, with many
large cities such as Negombo, Kalutara, Galle and
Matara besides the capital, Colombo. The total population
in this coastal belt is projected to be 7.4 million
in 2000, 8.4 million in 2010, 11.5 million in 2050,
and 12.2 million in 2070. Over 70% of Sri Lanka’s
tourism infrastructure, its two major commercial ports,
Colombo and Galle, and five fishery harbours and anchorages
are located in this region. The projected increase
in sea level is about 30 cm by 2010, and a further
10 cm by 2070.
Significant erosion is already evident on many of
Sri Lanka’s beaches. This is likely to increase
significantly with accelerated sea level rise. A rise
in sea level would tend to cause a shoreline recession
except where this trend is balanced by the influx
of sediment. In a 30 cm sea level rise scenario, the
study projects a possible shoreline recession of about
30 m and for a 100 cm scenario, the shoreline retreat
is expected to be about 100 m.
A one metre rise in sea level could be expected to
drown most of the coastal wetlands in Sri Lanka. The
tidal range in Sri Lanka is low (less than 72 cm)
and hence even a modest sea level rise could cause
widespread destruction of wetlands. One factor could
be salt-water intrusion. Salt-water intrusion is already
affecting approximately 15,000 hectares of paddy fields
in the Galle district. Sea level rise would also have
adverse effects on infrastructure facilities, such
as ports, harbours, and coast protection structures
like revetments and sea-walls. Table 2 [ADB, 1994]
outlines the estimated costs of sea level rise in
Sri Lanka for the year 2010.
