সেউজী ধৰণী
Impact of Climate Change on
Agriculture
Compiled and edited by
Munu
Devi *
The word ‘climate’ means the average weather conditions over
a number of years. When we talk about climate change, we mean the unusual
changes in the Earth’s weather patterns that have happened over the last 100
years.
In the past, some scientists thought
that changes to the climate were just part of the Earth’s natural climate
cycle, but it is now clear that it isn't that simple. Today, most climate
experts believe that climate change is a
complex phenomenon, and its full-scale impacts are hard to
predict far in advance. An extensive literature has developed on the impacts of
climate change on agriculture focusing primarily on the vulnerability of the
sector. These literature showed that the degree of vulnerability of the
agricultural sector to climate change is contingent on a wide range of local
environmental and management factors. However, the general consensus is that
changes in temperature and precipitation will result in changes in land and
water regimes that will subsequently affect agricultural productivity.
Why is climate change happening?
Studies across
the globe have clearly demonstrated that increased human induced activities are
the primary drivers of increased concentration of Green House Gases and
resultant increase in temperature and variability in rainfall pattern
experienced by most of the regions. Of all the Green House gases 72% is Carbon
di-oxide, 18% is Methane and 9% Nitrous oxide. Global atmospheric concentration
of carbon di-oxide has increased from about 378 ppm in 2005 to 395 ppm in
January 2013. According to the Inter Governmental Panel for Climate Change, the
three main causes of the increase in Green House Gases observed over the past
century have been fossil fuels, land use and agriculture. Agriculture itself is
responsible for an estimated one third of global warming and climate change.
Agricultural activities release significant amount of Green House Gases into
the atmosphere. Emissions from this sector are primarily methane and nitrous
oxide. The largest shares of emissions originate from agricultural soils
(nitrous oxide) and fermentation (the natural digestive processes of
ruminants such as cattle and sheep) associated with livestock and rice
production (methane). Green House Gas emissions from agriculture are expected
to rise because of increased food demand for growing and more prosperous
populations able to afford more varied diets with higher shares of meat and
dairy products. This shift will also lead to increased pressure on forests from
agricultural expansion. Emissions from both fertilizers and livestock are
expected to continue to increase significantly by 2020.
Potential
impacts of climate change
The climate change is causing havoc
to the agricultural production and causing serious concern on food security of
many countries including India. Climate change will have a range of direct and
indirect impacts on agriculture and the people. According to the findings of Inter
Governmental Panel for Climate Change, wheat yields would fall by 5-10% with
every increase of 10C and over all crop yields could decrease up to
30% in South East Asia by the mid 21st century. Agricultural
productivity of India could experience 40% reduction by 2080. There will be
around 40% reduction in agricultural productivity in India by 2080 as the
temperature rise will affect the wheat production in the country. There is possibility
of loss of 4-5 million tons in wheat production in future with every rise of 10C
temperature throughout the growing period. The projected increase in climate
change will result in greater instability in food production and threaten
livelihood security of farmers. Changes in temperature and rainfall could have detrimental
effect on quality of cereals, fruits, aromatic and medicinal plants with
resultant implications on their prices and trade. Plant pathogens and insect
populations are highly dependent upon
temperature and humidity. According to Food and Agricultural Organization
(FAO), climate change is likely to trigger a risk of hunger in India by
affecting cereal production. Climate change will have profound effect on vector
borne viral diseases, for example- yellow mosaic virus in peas and soybean.
Reduction in rainfall and increase in temperature will reduce the production of
spices like black pepper, turmeric and ginger. Due to unequal distribution of
rainfall, there is occurrence of drought and also flood, and as a result
production of horticultural crops drastically reduced. In Orissa, there was
large plantation of Jackfruit which gave good yield every year. However, due to
unequal distribution of rainfall and high temperature during the last few years
the jackfruit production has been reduced drastically. Higher temperature
causes small stomatal opening and thick epidermal wax layer of plant. Elevated
carbon di- oxide will also adversely affect on nectar production. High humidity
and high temperature increases the post harvest loss of horticultural crops.
Changes in climatic conditions will
have significant influence on livestock production. Due to the increased
temperature, the milk production of our country will be reduced by 1.6 million
tons by 2020. The decline in milk production will be higher in cross breeds
followed by Buffalo and indigenous cattle. If the present increased trend of
Green House Gases is not restricted it is expected that there will be rise of
2-30C by the end of 2050, and this will adversely affect poultry
health and production including egg and meat production.
It is observed that the fishing
zones and fish production in the India’s coastal area are declining gradually
over the years. It may be due to sea level rise, increase of salinity at
coastal belt, frequent cyclone and change in the oceanic current pattern. The
dry fish export from our country is also declining in the recent years which
are also indicative of downward trend of fish production in the Indian coast. A
survey by FAO also revealed that around 100 important fish species have
disappeared from the country’s water territory in the Bay of Bengal over the
last couple of decades.
Predicted effects of
climate change on agriculture
Although there will be
gain in some crops in some region of the world, the overall impact of climate
change on agriculture are expected to be negative and hence, threatening global
food security. Various workers tried to predict impact of climate changes on
agriculture since many years. Each year scientists learn more about how climate
change is likely to affect agriculture sector and most agree that certain consequences are likely to
occur if current trends continue.
In
table 1 some such predicted effects of climate change on agriculture are
furnished. In addition to this some selected research findings on impact of
climate change on rice and wheat production in India are furnished in Table 2.
Table1. Predicted effects of climate change on agriculture over
the next 50 years
|
Climatic element
|
Expected changes by
2050's
|
Confidence in
prediction
|
Effects on agriculture
|
|
CO2
|
Increase from 360 ppm
to 450 - 600 ppm (2005 levels now at 379 ppm)
|
Very high
|
Good for crops:
increased photosynthesis; reduced water use
|
|
Temperature
|
Rise by 1-2oC.
Winters warming more than summers. Increased frequency of heat waves
|
High
|
Faster, shorter,
earlier growing seasons, range moving north and to higher altitudes, heat
stress risk, increased evapotranspiration
|
|
Precipitation
|
Seasonal changes by ±
10%
|
Low
|
Impacts on drought
risk' soil workability, water logging irrigation supply, transpiration
|
|
Storminess
|
Increased wind speeds,
especially in north. More intense rainfall events.
|
Very low
|
Lodging, soil erosion,
reduced infiltration of rainfall
|
|
Variability
|
Increases across most
climatic variables. Predictions uncertain
|
Very low
|
Changing risk of
damaging events (heat waves, frost, droughts floods) which effect crops and
timing of farm operations
|
Source: Climate change
and Agriculture, MAFF (2000)
Table
2 Impact of Climate Change on rice and wheat production in India
|
Crop
|
Observations
|
Reference
|
|
Rice
|
Studies conducted by Saseendran et al (2000) showed
that in Kerala :-
·
An
increase in CO2 concentration led to yield increase of rice and
also enhanced water-use efficiency.
· For increasing temperature up to 5°C, there is a
continuous decline in rice yield. For every 1°C rise, the yield fell by about
6 per cent.
· The physiological effect of ambient CO2 at 2°C
compensated for yield losses at 425 ppm CO2.
|
Saseendran, A. S. K., Singh, K. K.,
Rathore, L. S., Singh, S. V., and Sinha, S. K. (2000), “Effects of Climate
Change on Rice Production in the Tropical Humid Climate of Karala, India,” Climatic
Change, 44, pp. 495–514.
|
|
Achanta, A. N. (1993) observed
that
· for
irrigated rice, yields in Pantnagar district of Uttarakhand under doubled CO2
levels and increased temperature, would be positive in the absence of
nutrient and water limitations
|
Achanta, A. N. (1993), “An
Assessment of the Potential Impact of Global Warming on Indian Rice
Production,” in A. N. Achanta (ed.), The Climate Change Agenda: An Indian
Perspective, Tata Energy Research Insitute, New Delhi.
|
|
|
By Using the ORYZA1
model to simulate rice yields under current and future climates Mohandass, S et
al (1995) predicted that
· An increase in rice production mainly because in the main
season, crops’ enhanced CO2 levels more than offset the negative
effects of increased temperatures.
· Though large decreases were predicted for second-season
crops at many of the locations due to high temperatures, the relatively low
proportion of total rice produced in this season meant that its overall
effect on rice production was small.
|
Mohandass,
S., Kareem, A. A., Ranganathan, T. B., and Jeyaraman, S. (1995), “Rice
Production in India Under Current and Future Climates,” in R. B. Matthews, M.
J. Kropff, D. Bachelet and H. H. Laar van (eds.), Modeling the Impact of
Climate Change on Rice Production in Asia, CAB International, U. K., pp.
165–81
|
|
|
By using CERES-Rice and ORYZAIN models to study the impact
of climate change on yields of irrigated rice
Aggarwal, P. K., and Mall, R. K. (2002) predicted that
·
The
direct effect of climate change on rice crops in different agro-climatic
regions in India would always be positive irrespective of various
uncertainties.
·
Rice
yields increased between 10.0 and 16.8 per cent in the pessimistic
scenario, depending on the level of management and model used.
·
For the
optimistic scenario these increases were between 3.5 to 33.8 per cent.
·
These
conclusions are highly dependent on the specific thresholds of phenology and
photosynthesis with respect to the change in temperature used in the models.
|
Aggarwal, P. K., and Mall, R. K.
(2002), “Climate Change and Rice Yields in Diverse Agro-Environments of
India: II. Effect of Uncertainties in Scenarios and Crop Models on Impact
Assessment,” Climatic Change, 52, 3, pp. 331–43.
|
|
|
Wheat
|
Aggarwal, P.
K., and Sinha, S. K. (1993) reported that:
·
At 425
ppm CO2 and no rise in temperature, wheat yield (potential,
irrigated and rainfed) increased significantly.
·
In north
India, a 1°C rise had no significant effect on potential yields, but
irrigated and rainfed yields increased in most places.
· A 2°C rise reduced potential wheat yields at most places,
while the effect on irrigated and rainfed productivity varied with location.
The natural climatic variability also had considerable effect on the
magnitude of response to climate change. Evapotranspiration was reduced in
irrigation as well as rainfed environments.
|
Aggarwal, P.
K., and Sinha, S. K. (1993), “Effect of Probable Increase in CO2
and Temperature on Productivity of Wheat in India,” Journal of
Agricultural Meteorology, 48, 5, pp. 811–14
|
|
Attri, S. D.,
and Rathore, L. S. (2003), by using CERES wheat
dynamic simulation model and climate change scenarios observed that
·
An increase in wheat yield between 29–37 per cent and
16–28 per cent under rainfed and irrigated conditions, especially in
different genotypes under a modified climate.
·
A 3°C increase in temperature or more cancelled out the
positive effects of enhanced CO2.
|
Attri, S. D.,
and Rathore, L. S. (2003), “Simulation of Impact of Projected Climate Change
on Wheat in India,” International Journal of Climatology, 23, pp.
693–705
|
|
|
Aggarwal,
P. K. (2009), reported in his Executive Summary,
·
Simulation results indicate that with simple adaptation, a 1°C
increase and associated CO2 increase would not cause any
significant loss to wheat production in India.
·
Benefits of adaptation gradually decrease as temperatures
increase to 5°C.
·
In the absence of adaptation and CO2 fertilisation
benefits, a 1°C increase alone could lead to a loss of 6 million tonnes in
India as a whole in annual wheat production (with respect to current
production). This loss is likely to increase to 27.5 million tonnes at 5°C
increase.
·
Increase in CO2 to 450 ppm is likely to reduce
these losses by 4 to 5 million tonnes at all temperatures.
·
Climate change is also likely to reduce the wheat yield gap,
since both potential yields and current yields are likely to reduce with time
even after taking into account improvement in crop management.
·
Potential yields are likely to decrease much more than current
yields, leading to a reduction in the yield gap.
·
Considering the slow process of bridging yield gaps and the
costs involved in creating an appropriate environment for this, it can be
concluded that global warming will constrain the progress in increasing wheat
production in future, unless some new technologies are introduced.
|
Aggarwal, P.
K. (2009), “Executive Summary,” in P. K. Aggarwal (ed.), Global Climate
Change and Indian Agriculture: Case Studies from the ICAR Network Project,
Indian Agricultural Research Institute Publication, New Delhi
|
Strategies
to mitigate climate change
In the present situation of climate change,
the following mitigation strategies can be helpful to safeguard the agriculture
sector from future turmoil.
· Develop
new varieties of crops which can adapt to the adverse effects of climate change
and give higher yield.
· Strict
aforestation measures
· Efficient
water harvesting and judicious use of water in agriculture.
· Adoption
of organic farming.
· Promote
the use of solar and wind energy.
*SRF,
Deptt of Agrometeorology, Assam Agricultural University,
Mobile.
985435234; e-mail: munuaau@gmail.com
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