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Chapter
Three : Impacts
With
the natural environment of a subtropical island, Taiwan
is very vulnerable to the impacts of climate change. In
particular, the impacts would include sea-level rise, lack
of water resources, primary industries, public health, ecosystems,
etc. The direct impacts of sea-level rise would be the flooding
of coastal lands, coastal erosion, and retreat of coastal
front. Coastal communities would face the problems of relocation
and subsequent social adaptation. The impacts on water resources
would include the increase in frequency and extent of droughts,
lack of water resources, and impacts on people's livelihood
and industrial development. On the other hand, the increase
in CO2 concentration would enhance photosynthesis of plants
and promote forest and agricultural growth. However, it
would also promote the growth of pests and propagation of
disease vectors.
3.1
Sea-level Rise
1.
Damages from sea-level rise
Sea-level rise will affect land use in coastal areas of
Taiwan, including agriculture, livestock farming, forestry,
salt pan, aquatic farming, mining, tourism, commercial and
fishing ports, residence, cementery, industrial areas, nuclear
and thermal power plants, airports, coastal transportation
facilities, ecological protection areas, drainage and tide-defense
facilities, oil and natural gas exploration, etc. The economic
impacts of sea-level rise will mainly come from the loss
from societal costs, including:
(1) Direct loss of land and capital from the retreat of
coastal line and tidal surges ;
(2) Costs of all protection, mitigation and response measures
to reduce the loss described above; and
(3) Loss of construction and development opportunities from
sea-level rise. In addition, sea-level rise will increase
flooding and seawater intrusion, thus worsening damages
to coastal areas. It will also destroy existing fish farms,
salt pans, and wetlands, affecting people's livelihood and
coastal ecosystems.
2.
Related Research
Regarding the impacts of sea-level rise on the Taiwan region,
flooding scenarios of the Tsang-Wan River delta and the
I-Lan sedimentary plain were modeled for rising levels of
0.5, 1, and 1.5 meters. The results show that flooded areas
in the An-Ping district of Tainan City could reach 30.6%,
50.0%, and 72.5%, respectively, and in the Wu-Jiage area
of I-Lan the flooded areas could reach 13.0%, 27.2%, and
40.2%, respectively. In addition, using the Chia-Nan plains
as a case study, with sea level rises of 1, 2, 3 and 4 meters,
the flooded coastal area of Tainan could reach 119.1, 162.7,
207.4 and 253.1 km2, respectively. The flooded coastal areas
in Chiayi could reach 51.9, 75.8, 99.8, and 121.4 km2, respectively.
Of the lands that could be flooded in Tainan and Chiayi,
most are aquatic farms, salt pans and cultivated lands.
In addition to the potential one-meter rise in sea level
over a hundred years, effects of subsidence in Taiwan make
the problem even more serious. According to investigation
by the Water Resources Bureau, the rate of subsidence in
coastal areas of Tainan and Chiayi is over 1 cm per year.
The combined effect with sea-level rise would be over 1.5
cm per year.
Based on the results of long-term analysis of 14 tide monitoring
stations in Taiwan, during the past 90 years, sea levels
in Keelung and Kaohsiung showed an increasing trend, at
a rate of 0.035 cm and 0.061 cm per year, respectively.
However, sea level at Taichung Port has decreased 0.364
cm per year. Overall, data from the tidal stations indicate
that sea levels in parts of northeast, northwest, and south
have an increasing trend; sea levels in central Taiwan have
an decreasing trend.
An analysis of long-term changes in coastal lines of Taiwan
shows that coastal lines in the north currently remains
stable overall, but erosion is more serious in some parts.
In the past 20 years, coastlines in the southeast have retreated
by 20-50 meters. Furthermore, coasts in central and southern
Taiwan showing signs of erosion in recent years and changes
as the area decreases.
3.2
Water Resources
Based
on data analysis of average annual rainfall in Taiwan between
1953 and1990, the amount of annual rainfall in northern
and eastern Taiwan showed an increasing trend, while it
showed a decreasing trend in central and southern parts.
The number of days of no rain in southern part also has
an increasing trend. It was estimated by the Water Resource
Bureau in 1995 that the amount of runoff rainfall in Taiwan
would decrease in 4% by 2050, and possibly by 4.1% during
the driest year.
Rainfall in Taiwan mainly comes from plum rains and typhoons,
of which the amount of rainfall during typhoon season accounts
for the most. An analysis of rainfall amount in Taiwan during
typhoon seasons in 1994 shows that the percentage of annual
total rainfall from typhoon decreased from southern to northern
parts of Taiwan: over 50% in the southern region, over 40%
in the central region, and about 30% in the northern region.
Thus, the amount of rainfall during typhoon seasons has
significant effects on the water resources in Taiwan.
According to the results of a simulation of river flow changes
by using the WatBal and WLF models in 1997, the river flow
will increase during plentiful water period and decrease
during drought period, thus intensifying flooding and drought
conditions and making disaster prevention even more difficult.
In terms of water resources management, it could create
problems of inadequate allocation and the need to develop
larger storage volumes, etc.
3.3
Industries
1.
Agriculture
In terms of agricultural products, according to a 1995 study
in Taiwan, a doubling of CO2 concentrations would affect
cucumber, rice and other crops. Furthermore, with changes
in rainfall and distribution as a result of temperature
rise, corn production could decrease by 10-20% and wheat
by 7-8%. Although global warming could increase growing
season and crop production, an increase in energy costs
as a result of global energy control measures would directly
affect crop production in Taiwan. The study shows that crop
areas for sugar cane, corn, rice, and sorghum would decrease
significantly, while those for tea crops would increase.
The overall, crop area in Taiwan would show a decreasing
trend.
2.
Fisheries
Weather in Taiwan changes with the El Nino phenomenon, and
the Japan Current and other minor and mainland coastal currents
also change accordingly, causing fisheries production to
vary widely. Eleven months after the start of the El Nino
phenomenon, surface water temperature in the southern sea
of Taiwan increased by 0.5oC-2oC, and the production
of young fish of the Engralididae family dropped by over
a half. The primary fish catch of Japanese enchovy (Encraulis
joponica) was replaced by other types of enchovy (Encracicholina
heteroba and E punctifer). In addition, eel fingerlings
(Anguilla jopnica) spawn in the western part of the Mariana
Islands in the Pacific Ocean, drift to the east and north
with the northern equator current after hatching, and the
continental shelf close to Taiwan becomes an eel corridor.
In 1997, productivity in the eel corridor reduced significantly
because of weakened El Nino but recovered again in 1998.
On the other hand, mullets travel south every year along
the mainland coast to the southwest coast of Taiwan to spawn
during midwinter, consisting of an important fishery in
Taiwan. As a result of climate change, if the warm water
brought by the Japanese Current prevents the southward flow
along the mainland coast, mullets would not be able to travel
south to spawn and decrease in production. In 1998, the
catch of 160,000 mullets was much less than the annual average
of 1.5 to 3 million. This is a result of the continuing
warming of water temperature around Taiwan, preventing mullets
to travel south to spawn and even causing migration to northern
Taiwan for spawning. In addition, Taiwan has the second
largest tuna industry in the world. The occurrences of El
Nino/La Nina have impacts on the tuna fishing grounds and
catch in the western Pacific Ocean. During El Nino, ocean
temperature in tropical western Pacific Ocean decreased,
causing tuna fishing grounds in Taiwan to move about 5,600
kilometers eastward and resulting in lower production. During
La Nina, tuna fishing grounds concentrated toward western
Pacific Ocean and resulted in increased production. Tuna
production in Taiwan increased significantly in 1999, causing
fish price to drop.
3.
Aquaculture
Direct impacts of sea-level rise on aquaculture include
clam farms located in inter-tidal area and sea-eroded platform.
Their production grounds and acreage could be impacted,
and there could be changes in their growth, maturity, and
spawning ecology, with changes in spawning period and shortening
of growth period. Indirect impacts are harder to predict.
Coastal subsidence due to overuse of groundwater would intensify
the effect of sea-level rise on nearby coast. There's clear
impact of water temperature on fish and marine ecosystem,
including physiology, metabolism, behavior and distribution
of fish. An increase of 10oC in water temperature could
increase biochemical reaction in fish by 6-10 folds; if
the temperature changes by 2oC, it could change the
reproductive season of fish, and higher temperature could
cause fish to spawn early. If future climate change moves
the warm belt north, it could also change the geographical
distribution of fish species in Taiwan.
4.
Livestock Production
Livestock industry in Taiwan consists mainly of pig and
poultry, with cattle as secondary. For pigs, if the temperature
rises one degree above their optimum growth temperature,
feed intake would decrease by 5%, and activity would decrease
by 7.5%. Livestock growth and reproductive ability and temperature
are closely related. When the temperature increases to 27oC,
the estrus cycle of milk cows would be prolonged, estrus
signs weakened, estrus period shortened, the gestation rate
would decrease, and fetal death rate would increase. Another
study confirmed that in Taiwan the conception rate of milk
cow and temperature are closely related. For poultry, with
increasing temperature, its maturity delays, and its body
weight, laying rate, egg weight, protein quality, and feed
intake all decrease. This would result in increasing nitrogen
and phosphorous content in feces.
5.
Macroeconomic
A 1996 study by Mendelsohn used the scenario of 2.5oC
rise in temperature, 8% increase in average rainfall, atmospheric
CO2 concentration of 550ppm, and sea-level rise of 44 cm
to assess the impacts of climate change on 20 countries
in the Pacific region, including Taiwan. The loss from the
impacts was estimated to be USD 37 billion per year. The
impacts included market and non-market categories: market
category covered agriculture, coast, energy, forestry and
tourism, and non-market category covered aesthetics, ecosystem
and health. The study found that the impacts of climate
change on the market is smaller, averaging about 0.1% of
the GDP. The larger effects of climate change are non-market
impacts, but the level of impact is highly uncertain. For
developed countries, the impacts may be within tolerable
range, but for developing countries, the loss from impacts
could consist of a high percentage of the GDP. According
to estimates by Mendelsohn, the loss for Taiwan could reach
USD 1.3 billion per year, about 0.6% of the GDP.
3.4
Public Health
The
rise in the earth's surface temperature as a result of climate
change from the greenhouse effect has various impacts for
different regions. In terms of public health, the negative
impacts are larger for tropical and coastal areas. Deficient
water resources as a result of warming or variation of climate
could lead to relocation of residents, and such relocation
could spread infectious diseases and cause an indirect impact
on public health. The degree of indirect impacts by no means
is less than that of direct impacts. Therefore, when considering
the impacts of climate change on public health, both direct
and indirect impacts should be included. Furthermore, some
regional environmental pollution and destruction, such as
suspended particles, loss of topsoil, subsidence and algal
growth, usually would have incremental effects when combined
with the impacts of climate change.
Warming of the climate could increase concentrations of
environmental allergens (such as fungus and pollen), thus
increasing the prevalence and seriousness of asthma and
hay fever sufferers. The portion of children with asthma
in Taiwan has increased from 1.3% in 1974 to 5.08% in 1985,
5.8% in 1991, and 10.79% in 1994. Room dust and fungus are
found to be the main allergens. A study shows that about
45% of children with asthma in the city of Taipei are allergic
to fungus. Climate change could affect the growth of room
dust and fungus and indirectly lead to the occurrence of
allergic illnesses. In addition, a 1995 study found that
climate warming could cause six species of rodents carrying
Hantavirus to proliferate in Taiwan and thus increase the
potential of the disease agents.
In central and southern Taiwan, dengue fever has usually
occurred during summer and autumn. As a result of climate
change, now it has spread to the northern area, and the
occurrence period has lengthened; some cases have even occurred
in December. Such phenomena could worsen with the increased
growth of disease-carrying mosquito caused by warmer temperatures.
According to statistics, in 1988 dengue fever occurrence
in Taiwan peaked in October, decreased in November, and
ended by December. In 1991, domestic cases of dengue fever
concentrated between September and October, decreased in
November and ended by December. Due to warming climate in
1994-1995, four cases were found in southern Taiwan in December
1995, and by 1998, the occurrence extended until January
1999. Based on the trend of warming climate, the threat
of year-round occurrence of dengue fever could happen in
Taiwan.
According to a 1998 study, climate change has direct as
well as indirect impacts on public health. The increase
in death rate from temperature rise is a direct impact,
whereas the proliferation of disease vectors causing the
spread of diseases an indirect impact. The potential direct
impacts of global warming and climate change on human health
include heat stroke and heat exhaustion, and the indirect
impacts are changing the ecology of disease vectors that
endanger human health.
3.5
Ecological Systems
1.
Forest
Due to influences by climate, soil, terrain and biogeographical
location, terrestrial ecosystems in Taiwan are mainly based
on forests. The complex island environments have formed
different types of forests adapting to long-term environmental
conditions, especially the rainfall and temperature characteristics
of the climate. If global climate change occurred by unnatural
causes, it could have various levels of impacts on the condition
and processes of forest ecosystems, resulting in lower productivity
and loss of bio-diversity and also indirectly affecting
its services to human. For example, natural forests in high
altitudes could decline because of inability to adapt, and
species in medium altitudes (especially plant composition)
could lose diversity.
According to the third survey of "Forest Resources
and Land-use in Taiwan" completed by the Forestry Bureau
in 1995, forest cover area in Taiwan is about 2.1 million
hectares, occupying 58.5% of total land area. With the special
geographical condition and fragile geology of Taiwan, combined
with frequent natural disasters, a well-maintained, extensive
forest is needed to protect developments in the plain region.
On the other hand, with rapid economic development, there
are increasing demands for forest products and forest recreation
in Taiwan. Since over 99% of domestic timber demand rely
on imports, quick strategies are needed to increase self-sufficiency
in domestic timber production. In addition, the richness
and diversity of biological resources in forests have valuable
potentials and still require further research. Therefore,
adjusting to developments in forestry management and environmental
conservation worldwide, appropriate revision of forest resource
management in Taiwan is an importance part of our modernization.
2.
Marine Ecology
Climate change will affect ocean temperature and circulation,
thus impacting the ecology of fish and other marine organisms.
A 1995 study in Taiwan shows that water temperature could
affect the physiology, metabolism, behavior, and distribution
of fish. If water temperature increases by 10oC, biochemical
reaction in fish could increase by 6-10 folds. If the temperature
change by 1-2oC, it could change the reproductive season
of fish, usually with lower temperature causing fish to
spawn late and higher temperature causing fish to spawn
early.
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