Climate change is increasing diseases.

They will be widespread and unpredictable.

By

Dr. Nitish Priyadarshi

An outbreak of the Ebola virus has killed 14 people in western Uganda last month. There is no treatment and no vaccine against Ebola, which is transmitted by close personal contact and, depending on the strain, kills up to 90 per cent of those who contract the virus. In recent years, Uganda has been hit with three Ebola outbreaks, the worst of which was in 2000, when more than half of the 425 people infected died.

Cases of Japanese Encephalitis (JE) has gone up to 50 in the Assam State in Eastern India. The areas mostly affected by Japanese Encephalitis are Kamrup, Sivasagar, Dhubri, Morigaon, Darrang and Nalbari. More than 400 people in northern India have died last year from encephalitis, a rare condition that causes inflammation of the brain. Around 347 people have died in Uttar Pradesh, while 54 children have died in the neighbouring state of Bihar. Cases of malaria is increasing every year in the state of Jharkhand, Assam, Orissa, Maharashtra etc.

With over 2,50,000 people testing positive for malaria last year, Orissa topped the chart for reporting the highest number of malaria cases. This was followed by 95,000 cases reported from Chhattisgarh and over 61,000 registered in Madhya Pradesh.

A 1996 report from the London School of Hygiene and Tropical Medicine calculated that, of ten of the world’s most dangerous vector-borne diseases (malaria, schistomiasis, dengue fever, lymphatic filariasis, sleeping sickness, guinea worm, leishmaniasis, river blindness, chagas’ disease and yellow fever), all but one were likely to increase, or in some way change their range as a result of climate change.

In recent years, vector-borne diseases (VBD) have emerged as a serious public health problem in countries of the South-East Asia Region, including India. Many of these, particularly dengue fever, Japanese Encephalitis (JE) and malaria now occur in epidemic form almost on an annual basis causing considerable morbidity and mortality. Dengue is spreading rapidly to newer areas, with outbreaks occurring more frequently and explosively. Chikungunya has re-emerged in India after a gap of more than three decades affecting many states.

Asia spans tropical and temperate regions. Plasmodium falciparum and P. vivax malaria, dengue fever, dengue haemorrhagic fever, and schistosomiasis are endemic in parts of tropical Asia. In the past 100 years, mean surface temperatures have increased by 0.3–0.8 °C across the continent and are projected to rise by 0.4–4.5 °C by 2070.

An increase in temperature, rainfall and humidity in some months in the Northwest Frontier Province of Pakistan has been associated with an increase in the incidence of  P. falciparum malaria. In north-east Punjab, malaria epidemics increase fivefold in the year following an El Niño event, while in Sri Lanka the risk of malaria epidemics increases fourfold during an El Niño year. In Punjab, epidemics are associated with above-normal precipitation, and in Sri Lanka, with below-normal precipitation.

According to WHO, many countries in Asia experienced unusually high levels of dengue and/or dengue haemorrhagic fever in 1998, the activity being higher than in any other year. Changes in weather patterns, such as El Niño events, may be major contributing factors, since laboratory experiments have demonstrated that the incubation period of dengue 2 virus could be reduced from 12 days at 30 °C to 7 days at 32–35 °C in Aedes aegypti .

Public health officials often use the term tropical diseases to refer collectively to a list of infectious diseases that are found primarily in developing countries. These include malaria, schistosomiasis, dengue, trypanosomiasis, leprosy, cholera, and leishmaniasis, among others. Many of these diseases are spread by insect vectors, and all of them disproportionately affect the world's poor. Malaria is the most severe of these, with the World Health Organization estimating that the disease causes about 250 million episodes of acute illness and perhaps 880,000 deaths annually.

The most widespread and severe climate-sensitive vector-borne disease in South America is malaria. Studies have shown that unusually dry conditions (for example, those caused by weather related to the El Niño–Southern Oscillation phenomenon in the northern part of the continent) are accompanied or followed by increases in the incidence of the disease. This has been documented in Colombia and Venezuela.

In Asia, dengue fever  and malaria  have been associated with positive temperature and rainfall anomalies, while in Australia arboviral disease outbreaks are most frequently associated with flooding. Urban developments in Asia and the surrounding regions may have a substantial impact on trends in the transmission of dengue fever. In some areas, such as Viet Nam, effects of past civil instability and slow economic growth may also be implicated.

Climate change would directly affect disease transmission by shifting the vector's geographic range and increasing reproductive and biting rates and by shortening the pathogen incubation period. Climate-related increases in sea surface temperature and sea level can lead to higher incidence of water-borne infectious and toxin-related illnesses, such as cholera and shellfish poisoning. Human migration and damage to health infrastructures from the projected increase in climate variability could indirectly contribute to disease transmission. Human susceptibility to infections might be further compounded by malnutrition due to climate stress on agriculture and potential alterations in the human immune system caused by increased flux of ultraviolet radiation.

Of the many scientists who have projected, predicted and warned of the likely health effects of climate change, almost all agree on the basics: they will be widespread and unpredictable, they are likely to be severe, and many, many people across the world will die as a result.

New Scientist magazine reported that ‘human disease is emerging as one of the most sensitive, and distressing indicators of climate change. “It is accepted by virtually all climate scientists that the likely increase in and spread of, potentially fatal diseases is likely to be the single most dangerous threat that climate change poses to human health.

Among the ten most dangerous diseases Malaria is the world’s most prevalent mosquito- borne disease. All experts seem to agree that one effect of climate change will be to increase the range of the malarial mosquito. Destruction of forests to create new human settlements can increase local temperatures by 3–4 °C and at the same time create breeding sites for malaria vectors. These phenomena can have serious consequences on malaria transmission in India, African highlands and other parts of the world.

And it is not just vector-borne diseases that are likely to take advantage of the changing climate. Other infectious killers are likely to enjoy a resurgence too, particularly diseases associated with water supply and sanitation. Climate change could have a major impact on water resources and sanitation by reducing water supply. This could in turn reduce the water available for drinking and washing, and lower the efficiency of local sewerage systems, leading to increased concentration of pathogenic organisms in raw water supplies.

More than 100 pathogens can cause illness if you drink or swim in water contaminated by sewage, including norovirus Norwalk and hepatitis A viruses and bacteria such as E. coli and campylobacter.

Several studies have shown that shifts brought about by climate change make ocean and freshwater environments more susceptible to toxic algae blooms and allow harmful microbes and bacteria to proliferate.

Global Warming will also increase rainfall intensity. Rainfalls will be heavier, triggering sewage overflows, contaminating drinking water and endangering beachgoers. Higher lake and ocean temperatures will cause bacteria, parasites and algal blooms to flourish. Warmer weather and heavier rains also will mean more mosquitoes, which can carry the West Nile virus, malaria and dengue fever. Fresh produce and shellfish are more likely to become contaminated.

Heavier rainfalls are one of the most agreed-upon effects of climate change. The frequency of intense rainfalls has increased notably in the Eastern India, China, Philippines, Korea and Japan.

Flooding may follow heavy rainfall. For developing nations there is evidence of outbreaks following floods. Outbreaks of leptospirosis in Rio de Janeiro (Barcellos and Sabroza 2001) and in the Philippines (Easton 1999) have followed floods. Hepatitis E, malaria and diarrhoeal disease have followed floods in Khartoom (Homeida et al. 1988; Novelli et al. 1988 ). Both acute diarrhoea and acute respiratory disease increased in Nicaragua following Hurricane Mitch and the associated flooding (Campanella 1999).

Temperature can affect both the distribution of the vector and the effectiveness of pathogen transmission through the vector. Gubler et al. (2001) list a range of possible mechanisms whereby changes in temperature impact on the risk of transmission of vector-borne disease:

1. Increase or decrease in survival of vector
2. Changes in rate of vector population growth
3. Changes in feeding behaviour
4. Changes in susceptibility of vector to pathogens
5. Changes in incubation period of pathogen
6. Changes in seasonality of pathogen transmission

By 2100 it is estimated that average global temperatures will have risen by 1.0–3.5 °C, increasing the likelihood of many vector-borne diseases in new areas. The greatest effect of climate change on transmission is likely to be observed at the extremes of the range of temperatures at which transmission occurs. For many diseases these lie in the range 14–18 °C at the lower end and about 35–40 °C at the upper end. Malaria and dengue fever are among the most important vector-borne diseases in the tropics and subtropics; Lyme disease is the most common vector-borne disease in the USA and Europe. Encephalitis is also becoming a public health concern. Health risks due to climatic changes will differ between countries that have developed health infrastructures and those that do not.

Human settlement patterns in the different regions will influence disease trends. While 70% of the population in South America is urbanized, the proportion in sub-Saharan Africa is less than 45%. Climatic anomalies associated with the El Niño–Southern Oscillation phenomenon and resulting in drought and floods are expected to increase in frequency and intensity. They have been linked to outbreaks of malaria in Africa, Asia and South America. Climate change has far-reaching consequences and touches on all life-support systems. It is therefore a factor that should be placed high among those that affect human health and survival.

Conclusion:

Analyzing the role of climate in the emergence of human infectious diseases will require interdisciplinary cooperation among physicians, climatologists, biologists, and social scientists. Increased disease surveillance, integrated modeling, and use of geographically based data systems will afford more anticipatory measures by the medical community. Understanding the linkages between climatological and ecological change as determinants of disease emergence and redistribution will ultimately help optimize preventive strategies.

References:

Barcellos, C. and Sabroza, P.C. (2001) The place behind the case: leptospirosis risks and associated environmental conditions in a flood-related outbreak in Rio de Janeiro. Cadernos de Saude Publica 17(suppl), 59–67.

Bouma MJ, Dye C, van der Kaay HJ. (1996) Falciparum malaria and climate change in the northwest frontier province of Pakistan. American Journal of Tropical Medicine and Hygiene,  55: 131–137

Bouma MJ et al. (1997) Predicting high-risk years for malaria in Colombia using parameters of El Niño–Southern Oscillation. Tropical Medicine and International Health, 2: 1122–1127.       

Campanella, N. (1999) Infectious diseases and natural disasters: the effects of Hurricane Mitch over Villanueva municipal area, Nicaragua. Public Health Reviews 27, 311–319.

Dengue in the WHO Western Pacific Region.(1998) Weekly epidemiological record, 73(36): 273–277.        

Easton, A. (1999) Leptospirosis in Philippine floods. British Medical Journal 319, 212.

Gubler, D.J., Reiter, P., Ebi, K.L., Yap, W., Nasci, R. and Patz, J.A. (2001) Climate variability and change in the United States: potential impacts on vector- and rodent-borne diseases. Environmental Health Perpectives 109(suppl 2), 223–233.

Homeida, M., Ismail, A.A., El Tom, I., Mahmoud, B. and Ali, H.M. (1988) Resistant malaria and the Sudan floods. Lancet 2, 912.

Novelli, V., El Tohami, T.A., Osundwa, V.M. and Ashong, F. (1988) Floods and resistant malaria. Lancet 2, 1367.

Poveda, G et al.(1999) Climate and ENSO variability associated with vector-borne diseases in Colombia. In: Diaz HF, Markgraf V, eds. El Niño and the Southern Oscillation, multiscale variability and regional impact. Cambridge, Cambridge University Press. 

Watts DM et al. (1987) Effect of temperature on the vector efficiency of Aedes aegypti for dengue 2 virus. American Journal of Tropical Medicine and Hygiene, 1987, 36: 143–152.        

http://onlinelibrary.wiley.com/doi/10.1046/j.1365-2672.94.s1.5.x/full

http://jama.jamanetwork.com/article.aspx?articleid=394508

http://www.searo.who.int/LinkFiles/CDS_vector-borne_diseases_in_India.pdf

http://www.scielosp.org/scielo.php?pid=S0042-96862000000900009&script=sci_arttext&tlng=e

The survival of Agriculture in a destabilized climate

With special reference to India and its Jharkhand State.

Crops become toxic in warmer world- says study

by

Dr. Nitish Priyadarshi

Department of Environment and Water Management,

J.N. college, Ranchi University, Ranchi, India.

Climate change has been the norm through out the earth’s history. Ice ages have been interspersed with interglacial periods with warmer temperatures. Although the causes of these previous natural changes are not completely understood, there is a growing consensus that human activities are contributing to the current period of climate change. In 1996, the World Meteorological Office/ United Nations Environmental Program’s Inter- governmental Panel on Climate Change (IPCC) cautiously stated: ‘ The balance of evidence suggests a discernible human influence on global climate. In spite of the nay-sayers, by 2001, new evidence and improved understanding led the IPCC to state unequivocally in its Third Assessment Report that, in its Judgement, ‘most of the warming observed over the last 50 years is attributed to human activities.

Climate change is the outcome of the “Global Warming”. It has now started showing its impacts worldwide. Either it is in the form of floods, heavy rain or in a form of drought.

Climate change induced by increasing greenhouse gases is likely to affect crops differently from region to region. For example, average crop yield is expected to drop down to 50% in Pakistan according to the UKMO scenario whereas corn production in Europe is expected to grow up to 25% in optimum hydrologic conditions.
Crops such as these sunflowers can be affected by severe drought conditions in Australia.
Between 1996 and 2003, grain production has stabilized slightly over 1800 millions of tons. In 2000, 2001, 2002 and 2003, grain stocks have been dropping, resulting in a global grain harvest that was short of consumption by 93 millions of tons in 2003.
The earth's average temperature has been rising since the late 1970s, with nine of the 10 warmest years on record occurring since 1995. In 2002, India and the United States suffered sharp harvest reductions because of record temperatures and drought. In 2003 Europe suffered very low rainfall throughout spring and summer, and a record level of heat damaged most crops from the United Kingdom and France in the Western Europe through Ukraine in the East. Bread prices have been rising in several countries in the region.
The 2001 IPCC Third Assessment Report concluded that the poorest countries would be hardest hit, with reductions in crop yields in most tropical and sub-tropical regions due to decreased water availability, and new or changed insect pest incidence. In Africa and Latin America many rainfed crops are near their maximum temperature tolerance, so that yields are likely to fall sharply for even small climate changes; falls in agricultural productivity of up to 30% over the 21st century are projected.
The impacts of global warming have been truly global and extraordinarily varied. The average rise in global temperatures may seem small- 0.76 degrees C since the Industrial Revolution in roughly the mid-18th century, the earth’s average temperature reaching 14.5 degree C in 2005- but this is only an average. The farther one goes from the equator, in northern latitudes in particular, the rise is much higher than the average.

In this article my emphasis will be more on impact on agriculture due to climate change, with special reference to India and its Jharkhand State. India’s agriculture is more dependent on monsoon from the ancient periods. Any change in monsoon trend drastically affects agriculture. Human interference has certainly made the Indian monsoon fickle. Even the increasing temperature is affecting the Indian agriculture. A recent study by the Indian Agriculture Research Institute found that increase in temperature by about 2 degrees C “reduced potential (wheat) grain yields in most regions”, and that “overall, temperature increases are predicted to reduce rice yields”, the impact on rice yields being most in eastern India. even the IPCC, scarcely alarmist, says 0.5 degree C rise in winter temperature would reduce wheat yield by 0.45 tons per hectare in India. And this when Indian agriculture has already pushed into crisis, and 1.5 lakh farmers have committed suicide since 1995.

There has been a major shift in the pattern of rainfall during the south-west monsoon season (from June to September) in recent years. This is one of the findings of an analysis by scientists at the India Meteorology Department’s National climate Centre at Pune.

Another is that rainfall over Kerala, Chhattisgarh and Jharkhand has been showing a significant decreasing trend, while that over coastal Andhra Pradesh, Rayalaseema, north interior Karnataka, Madhya Maharashtra, Konkan, Goa and Gangetic West Bengal is showing a significant increasing trend. While the contribution of July rainfall to the overall monsoon exhibit a significant increasing trend. The contribution in June and August exhibited a significant increasing trend. The findings are significant in the context of the global phenomenon of climate change. Due to global warming intensity and number of cyclones has increased. In the cyclone seasons of 2006, the number of depressions and cyclonic storms over Bay of Bengal were almost twice the annual average. This is damaging coastal agriculture and livelihoods. Due to global warming there is high influx of water in the Himalayan rivers flowing through Assam, Bihar and West Bengal in eastern India in the form of floods due to melting of Himalayan glaciers associated with heavy rains in the Himalayas. These floods annually destroy millions of tons of crops. This year the world's largest river island Majuli in Assam State of India has been severely hit by flood and erosion. Floodwaters have inundated over 87 villages of the island causing tremendous difficulty to the inhabitants and due to rapid erosion many fertile paddy fields have also been washed away by gushing water.

In year 2008 more than two million people have been marooned by late monsoon floods in 15 of the country's 64 districts, according to the Bangladesh Water Development Board (BWDB). According to a report by the Department of Agricultural Extension (DAE), crops such as Aman (the mainstay of the country's rice production and a staple component of the population's diet), t-Aman (a locally developed hybrid paddy), Aush (a secondary rice crop whose volume is less than half of Aman), jute and vegetables on more than 100,000 hectares of land in the 15 flood-hit districts were submerged. More than 20,000 hectares of Aman and Aus crops in Companiganj, Golapganj, Jaintapur, Kanaighat, Gowainghat, Fenchuganj and Beanibazar Sub-districts have been destroyed in Sylhet and Sunamganj districts, according to agriculture officials.

Few years ago, there were reports coming in of massive forced migration due to persistent droughts in Bundelkhand area in Central India. large lakes had completely dried, water in wells that people use for their daily needs had run down, rivers and tributaries had dried up, thousands of hand pumps had become useless because the groundwater levels had fallen. People had abandoned their cows and other cattle to a dusty death, as they were unable to provide them fodder and water.

Global warming intensifies drought conditions in regions that already face dry conditions, particularly in [ Sub] continental interiors. The IPCC’s report in 2007 says that “increased continental temperatures are expected to lead to greater evaporation and drying, particularly important in dry regions where surface moisture is limited… drought has become more common, especially in the tropics and subtropics, since the 1970s … more intense and larger drought have been observed.

Drought like situation is also threatening Jharkhand State of India where scanty and late arrival of monsoon this year is affecting crops and depletion of ground water. Drought is a recurrent phenomenon in Jharkhand. It affects the livelihoods of the majority of its people, particularly tribals and dalits living in rural areas. Twelve of the 22 districts of the state, covering 43% of the total land area, are covered under the Drought Prone Areas Programme (DPAP).Hunger and starvation deaths are reported almost every year. Jharkhand is one of the richest states in the country in terms of natural resources. However, the rate of growth in agriculture has been one of the slowest in the country both in terms of production and productivity. Almost 90% of the cultivated area is monocropped. Only 9% of the total cropped area is irrigated. Hence the rural population is very vulnerable to rainfall fluctuations.

Jharkhand receives almost 1200-1300 mm of rainfall every year but from last few years the rains are erratic in many areas. The probability of rainfall failures and coefficient of variations is quite high in the last weeks of June-July and in the last weeks of September-October. Hence, drought in the state primarily occurs at the start or end of the kharif season.

This year there was less rain in the month of July. In July, upland crops grow to maturity and seedlings for transplanted rice are established. If there is deficient rain, the upland crop—mainly paddy and maize, which provides food security in August-September— is affected.

This year most of the vegetables have been destroyed either due to uneven rainfall or due to intense un-seasonal hailstorms that damaged the standing crops and vegetables and led to huge losses to farmers. In year 2007 and 2008 also hailstorms destroyed crops. This year situation worsened as most of the green vegetables vanished from the local markets or was too costly to be purchased by the common and poor people.

Palamau district in Jharkhand State of India is reeling under drought due to scanty rainfall. Crops have been destroyed and the region is facing a famine-like situation. It has not only affected the crops but also depleted the ground water and well water forcing people to drink contaminated water.

The Indian Irrigation Commission described Palamau as the driest and probably the poorest district of the province. The frequent draughts and famines or scarcity conditions that have visited this district within the last century support this observation. The district falls within the retreating range of the south-west monsoon and as such rainfall is wholly dependent upon local conditions and local winds which are seldom favourable to the district.

The rainfall in Palamau is not only scanty but very capricious in its distribution. There are, it is true, a large number of rivers and streams in the district, but in most of them the supply of water diminishes rapidly or fails entirely soon after the end of the scanty rains.

It is not only Palamau but other districts are also under threat of drought like conditions including Ranchi district. It is not only the scanty rain but rise in temperature and short period of winter has also affected the crops and vegetables of the state.

Jharkhand is one of the most food-insecure and malnourished states in the country. NSSO (55th round) data reveal that 10.46% of all households in Jharkhand face seasonal food insecurity. Around 2.5% of households face chronic food shortages. Of the families facing food insecurity, 64% face food shortages for two to three months while as many as 28% do not have sufficient food for four to five months. Almost 6% of the food-deficient
households have to go hungry for more than half the year. The incidence of food insecurity is higher among ST and SC families. Assured food supplies exist for only three to four months of the year, after the harvest in late October-early November. Food supplies tend to run short by the end of winter. The starvation period begins by mid-summer (June) and in many cases, continues till the end of October.

Entire Jharkhand has been now declared drought-hit following scanty rainfall. The decision was taken at the meeting of the Advisory Council of the Governor. Earlier, the Council had announced 11 of the 24 districts as drought-hit. In the face of severe drought, it was decided to distribute grains free of cost to BPL (below poverty line) families, besides setting up of grain godowns at district and block headquarters.


If the same condition prevails in coming years situation will be worse as the state lacks proper irrigation facilities and proper storage facilities for grains.

A dry spell has led the Uttar Pradesh government to declare 20 of the state's 70 districts as "drought-hit". According to weather reports, Uttar Pradesh has received only about 128 cm of rainfall since June 1 as against the expected normal rainfall of about 307 cm. In the 20 drought-hit districts, the recorded rainfall was barely 60 cm.

Scanty rainfall in most parts of Uttar Pradesh, will hit agricultural production leading to a shortage of rice in the state, says a government report. According to the report prepared by the state agriculture department, the worst hit would be paddy yield, which is expected to decline by about 60 percent this year. Maize production is also expected to fall 1.15 million tonnes to 900,000 tonnes.
The districts where rainfall has been lowest include Chitrakoot (81 percent below normal), Etah (84 percent below normal) and Rampur (85 percent below normal).
Twenty six of Bihar’s 38 districts were declared drought-hit this year in view of scanty rainfall that has badly hit transplanting of paddy seedlings and affected millions of farmers.

Bihar has recorded a 42 percent rainfall deficit so far this monsoon season. This has hit the transplanting of paddy seedlings.
The state during the period between June 1 and Aug 6 had received just 331.7 mm of rainfall against the average 568.5 mm — a deficiency of 42 percent. It has resulted in 58 percent decline in paddy transplantation. Bihar had targeted sowing of paddy in 8,772,241 acres this year, but the crop could only be planted in only 3,822,967 acres so far.
Uttarakhand State is under drought-like conditions for last six months. 50 per cent of crops damaged in 3216 villages of five districts alone. Rainfall in the months of December, January, February and March has been far below normal, severely affecting winter crops in the hilly areas.

Madhya Pradesh state of central India is going to witness the worst drought of the century due to the scanty rainfall in as many as 37 districts following which it has declared them drought-affected.
Due to scanty rainfall, as many as 37 districts of the state were declared drought-affected. The districts which were declared drought-affected are Alirajpur, Ashok Nagar, Anuppur, Barwani, Bhind, Balaghat, Burhanpur, Chhatarpur, Dewas, Dindori, Datia, Damoh, Guna, Gwalior, Jhabua, Jabalpur, Katni, Khandwa, Morena, Mandla, Narsinghpur, Panna, Ratlam, Raisen, Rewa, Satna, Sidhi, Singrauli, Shahdol, Sagar, Sehore, Shivpuri, Sheopur Kalan, Shajapur, Tikamgarh, Umaria and Vidisha.

Drought like conditions is prevailing in most parts of Northern India. According to William Cline, a senior fellow at the Center for Global Development (CGD) and the Peterson Institute for International Economics, “India is among the most adversely affected with losses of 30-40% (in agriculture productivity) depending upon whether higher carbon dioxide provides a significant fertilization effect.”He noted that in the southern parts of India, damage will be substantial and similar to that in other countries also located close to equator. In these locations, where temperatures are already at high levels, an increase in temperature will surpass crop tolerance levels. In North India, the unusual increase in rainfall combined with higher temperature could result in a higher decline in productivity than one would expect from where it is located relative to equator. Cline finds that agricultural production in developing countries may fall between 10 and 25 percent, and if global warming progresses unabated, India's agricultural capacity could fall as much as 40 percent.
Poverty in South Asia is still largely rural. About 70% of South Asia’s population lives in rural areas, and it accounts for about 75% of the poor. Most of the rural poor depend on agriculture for their livelihood. Agriculture employs about 60% of the labor force in South Asia and contributes 22% of regional GDP. The Green Revolution of 1970s and 1980s substantially increased food grain productivity and increased rural wages. Recent agricultural growth in South Asia, however, is less than 3% and is far below the growth rates of other economic sectors.

Prime Minister of India Manmohan Singh said that the country was facing a drought threat. India's vital monsoon rains have been 29 percent below normal since the beginning of the June-September season, hurting crops such as rice and sugarcane and triggering a sharp rise in food prices. "We are staring at the prospect of an impending drought,".

Since agriculture constitutes a much larger fraction of GDP in developing countries, even a small percentage loss in agricultural productivity would impose a larger proportionate income loss in a developing country than in an industrial country.

A study published in Science suggest that, due to climate change, "southern Africa could lose more than 30% of its main crop, maize, by 2030. In South Asia losses of many regional staples, such as rice, millet and maize could top 10%".

Drought obviously leads to water stress in plants. Heat waves, on the other hand, are acute episodes which, if the temperature is high enough, above 40 degree C for instance, lead to wilting and death, because of structural damage to essential proteins. The problem is that plants react by closing their stomata when subjected to water stress, so shutting down on transpiration and conserving water. But rather as the body would overheat dangerously if it shut its pores to prevent sweating, so in a plant the shutting of the stomata will cause internal temperatures to rise and may well cause permanent damage, if not death. According to a report temperatures above 45 degree C will damage most plants if lasting for half-an-hour or more. High soil temperatures will also damage roots and prevent nutrient uptake.

David Pimental from the college of Agriculture and Life Sciences, Cornell University, points out that each crop has its optimum temperature and length of growing season for maximum yields. Rice generally grows best when temperatures are between 30 degree C and 33 degree C, yet it will still ‘fruit’ and generally produce as long as temperatures do not fall below 18 degree C. Some varieties will tolerate temperatures rising to as high as 40 degree C. In contrast potatoes do badly if temperature rise above 28 degree C and do best when they lie between 15 and 20 degree C. higher soil temperatures will increase the rate of oxidation and hence loss of nutrients and organic matter. Less organic matter means less soil organisms such as earthworms and insects that do so much to improve the ground. Hence global warming and temperature rises could have a deleterious effect on the main cereal crops.

In temperate latitudes crops need at least 250 millimeters of rain a year and in the tropics 500 millimeters. However, it is not just the amount of precipitation, but when the bulk of it occurs that is important. Global warming will undoubtedly play havoc with a crop’s specific needs, both through increasing surface temperatures, which itself will lead to a greater likelihood of water stress on vegetation because of enhanced evaporation from soils and through distorting rainfall patterns. A failure of the monsoon spells disaster for India as does just a small decline in the amount of rain over the semi-arid countries of the Sahel.

Global warming is not only affecting the production of the crops but also making some of the crops toxic. According to an Australian scientist, Staples such as cassava on which millions of people depend become more toxic and produce much smaller yields in a world with higher carbon dioxide levels and more drought.

A team of Monash University in Melbourne tested cassava and sorghum under a series of climate change scenarios, with particular focus on different CO2 levels, to study the effect on plant nutritional quality and yield. Both species belong to a group of plants that produce chemicals called cyanogenic glycosides, which break down to release poisonous cyanide gas if the leaves are crushed or chewed.
Around 10 percent of all plants and 60 percent of crop species produce cyanogenic glycosides.
The team grew cassava and sorghum at three different levels of CO2; just below today's current levels at about 360 parts per million in the atmosphere, at about 550 ppm and about double at 710 pm.
It was found that at double current CO2 levels, the level of toxin was much higher while protein levels fell.
The ability of people and herbivores, such as cattle, to break down the cyanide depends largely on eating sufficient protein.
Anyone largely reliant on cassava for food, particularly during drought, would be especially at risk of cyanide poisoning.
The group looked at a type of sorghum commonly fed to cattle in Australia and Africa and found it became less toxic at the highest CO2 level. But under drought conditions, leaf toxin levels rose.

Within the context of the modern industrialized farming, global warming and warmer temperatures with mild winters in temperate zones will lead to a surge in pathogens and pests. Not only will some pests be able to take advantage of rising temperatures to spread to higher latitudes and altitudes, but also to increase their rate of reproduction by adding an additional generation. During the growing season some insect pests can produce 500 progeny per female every two weeks and as many as 3,000 in a single generation. In general, losses to insects and mites are higher in warmer regions of the world.

According to the United Nations, agricultural mismanagement has damaged more than 552 million hectares – 38 percent of today’s cultivated area- since World War 2 and that overall, between 5 and 10 million hectares a year are currently being lost. Just 100 years at that rate would leave the world with but a patch of the land for agriculture that it has today.

Reference:

Bunyard, P. 1999. A hunger world. The Ecologist, v.29, no.2, pp.86-91.

Runeckles, V.C. 2002. Air pollution and climate change. In air pollution and plant life, second edition, eds. J.N.b. Bell and M. Treshow. Wiley, USA.

“The roots of Global Warming” a report published by Delhi Platform in year 2008.

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http://www.thaindian.com/newsportal/business/26-bihar-districts-declared-drought-hit-lead_100230110.html
http://en.wikipedia.org/wiki/Climate_change_and_agriculture
http://74.125.93.132/search?q=cache:vqTmwwbX0bQJ:www.imf.org/external/pubs/ft/fandd/2008/03/pdf/cline.pdf+global+warming+and+agriculture+cline&cd=1&hl=en&ct=clnk&gl=in
http://web.worldbank.org/WBSITE/EXTERNAL/COUNTRIES/SOUTHASIAEXT/0,,contentMDK:21571064~pagePK:146736~piPK:146830~theSitePK:223547,00.html
http://timesofindia.indiatimes.com/news/india/MP-to-witness-worst-drought-says-CM-Chouhan/articleshow/4909762.cms
http://www.redorbit.com/news/science/1660279/global_warming_37_percent_cause_of_droughts/index.html?source=r_science
http://uk.reuters.com/article/idUKTRE55S2KY20090629?pageNumber=3&virtualBrandChannel=0