Wednesday, December 11, 2019 | ePaper

Climatic Variability

How It Affects 'Human-Ecology' In Coastal Belt

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Shishir Reza :
Bangladesh is an agricultural country. Climate change has emerged as a global concern in the past 20 years. One particular worry is the potential disastrous consequence for agriculture and food security in many parts of the world, especially in developing countries. Crop production is extremely vulnerable to climate change and it has been predicted that climate change will impact negatively on agricultural yield in the 21st century through higher temperatures, more variable rainfall and extreme climate events such as floods, cyclones, droughts and rising sea levels.
Climate change is now recognized as a great issue for agriculture in coastal region of Bangladesh. The major impact of climate change in this region is salinity increasing. Other impacts are drought, low rainfall, very low and high temperature, cyclone frequently occurs. Salinity of soil is increasing day by day as the result of high saline water from sea which is the consequence of sea level rising. It is the serious issue for agriculture, water quality and fresh water fisheries practices in the coastal region. The environmental impacts of salinity are not well recognized and it is only in the last decade that we have become aware of its significance. Salinity is destroying the important part of coastal landscapes. It damages the native species, ecological communities and agricultural lands. The major effects of salinity on the agriculture are poorly understood.
Climate change refers to the rising average surface temperatures on Earth. A scientific consensus says that climate change is primarily caused by the human use of fossil fuels, which releases carbon dioxide and other greenhouse gases into the air. The gases create and trap heat within the atmosphere, which can have a range of effects on ecosystems, including rising sea levels, altering weather patterns and create severe weather events, and droughts that cause landscapes more susceptible to wildfires.
The agriculture sector depends highly on climate because of temperature, solar radiation and precipitation that are the main drivers of crop growth. Though, consideration of the potential impacts of climate change on agriculture should be based not only on mean values of expected climate parameters but also on the frequency, severity and probability of possible extreme events as well as soil condition, spatial and temporal variation, availability of water and agricultural yields should be considered. In addition, warmer condition and decreased rainfall in some parts result droughts that have negative impacts on agriculture. So, extreme rainfall decreases crop yields, particularly through increased flooding. Bangladesh is the most vulnerable country because of its geographical location. The country is dominated by large Ganga-Meghna-Brahmuputra (GBM) river system as well as tide and wave dominated coastal impacts from the Bay of Bengal surface. As a result, the country is influenced by the above mentioned three rivers, which are all part of the Himalaya's drainage system.
Climate change is observed through temperature rise, sea level rise and rainfall changes. IPCC (2001) has predicted global temperatures will increase between 1.80C to 40C by the late 21st century, but BCCAAP (2010) explains the impacts of this (IPPCC predicted results) temperature rise on Bangladesh result in the overflow of river water and sea level rises between 18 to 79 cm as well as the increased coastal flooding and salinity intrusion for the whole coastal area in Bangladesh. So, on the basis of the country's present report on climate pattern and the reports of IPCC and BCCAP, Bangladesh is the most vulnerable country in the South Asian region, because the country is situated in the most tropical cyclone prone area and 6th most vulnerable country to floods.  
Ahmed and Alam (1998) estimate the temperature will annually increase at the rate of 0.050C to 0.030C. Their estimate was that the mean temperature would be rise by 1.30C by the year 2030 and by 2.60C by the year 2075. Winter temperature will increase 1.30C, summer temperature will increase 0.70C by 2030. In addition, winter temperature will increase by 2.10C and summer temperature will increase 1.70C by 2075. GCM models were used for assessing climate vulnerability in Bangladesh in the early 1990s'. The BUP-CEARS-CRU (1994) used GCM modeling and found that the temperature would rise by 0.50C to 0.20C relative to 1991 by the year 2030. Using four GCMs' (CSIR09, CCC, GFDLH, and UKMOH), ADB (1994) reported that, "the temperature would rise by 0.30C for 2010 with a corresponding rise of 1.50C for 2070".
An important issue in coastal areas in Bangladesh is salinity intrusion. The impacts of salinity are increasing day by day due to sea level rise. Because of high salinity levels, it is difficult to cultivate any HYV (High Yielding Variety) crops. Most of the coastal areas are situated in medium highlands, where flooding depth range from 0.3 to 0.9 meter. Type and condition of soil of these areas is suitable for two crops every year. Most land is tidally affected with saline water during high tidal period. Soils are infertile having very low organic matter such as low nitrogen, phosphorus and micronutrients due to salinity problem. However, melting glacier in the northern hemisphere on account of in increasing temperature has predicted at least 0.1-meter sea level rise during 20th century. This is the cause of large frequency of disasters from climate change is increasing in the coastal belt in Bangladesh, as the Bangladesh coast is highly vulnerable to natural disasters. Salinity is a common problem in coastal area of Bangladesh. In dry season the water level drops up to 240 km in western part of Bangladesh is caused severe saline problem in 30 Upazila in Bangladesh. Sea level rise would produce salinity impacts in surface water, ground water and soil. During the pre-monsoon and post monsoon seasons coastal zone of Bangladesh is mostly prone to tropical cyclones and strong storms. The coastal zone of Bangladesh has its extreme vulnerability to cyclones and storm surges, so that the coastal belt is a geographical death trap. The frequency of natural disasters is increasing day by day in the coastal belt from the change of climate pattern such as increasing of temperature, increasing the frequency of cyclonic storm and sea level rising. Salinity intrusion, river erosion and water logging are caused by sea level rise.
From 1991 to 2009, seven major cyclones have happened and the amount of destruction is much higher than in previous cyclones. For example, SIDR 2007, AILA 2008 had a severe experience in the coastal area of Bangladesh. These big cyclones greatly affected 147 coastal Upazilas in Bangladesh. Government constructed 5107 km of coastal embankments that helped to bring land under rice cultivation. Embankments help to reduce the impacts of salinity in local areas but unstable and unplanned embankments in the coastal area of Bangladesh cannot fully resist intrusion of saline water.
In the coastal area of Bangladesh climate vulnerability is a major concern. The coastal belt of Bangladesh has been delineated based on three criteria, namely the limits of tidal fluctuation, salinity intrusion and cyclonic risk. The coastal belt of Bangladesh is a low lying area, so it is vulnerable to monsoon flooding and storm surges. The IPCC 1st assessment report suggests a comprehensive national coastal plan on the basis of climate change impact, minimizing the risks to the people's lives and maintaining the important coastal ecosystem. Abnormal floods will inundate 30% of the low lying land in Bangladesh and in major flooding period (1988, 1998 & 2004) more than 60% of land has been inundated; the Bangladesh coastal belt faces a major cyclone on an average once per year and tidal surge may up to 6-10m.
Moreover, sea level rise is an important zonal factor for assessing climate change vulnerability in the coasts of Bangladesh. About 65% of the coastal area is affected by seasonal flooding and tidal surge. Most of the central coastal area in Bangladesh is situated in medium high land where flooding depth ranges from 0.3-0.9 meter. Important factors for climate change vulnerability in the coastal area of Bangladesh are sea level rise and tidal surges. Generally sea level rise due to melting of global glacier and increase of temperature. Uncertain rainfall delays transplanting of rice and tidal surges destroy various crops.
In Bangladesh, 90% of the population is rice-eater. In this country, three seasonal rice crop groups are recognized and dominate the cropping pattern throughout the country. Aus, Aman and Boro rice cultivate throughout the year. Aman varieties are broadcast, high yielding variety (HYV) and transplant, varieties of Aus are HYV and local and varieties of Boro are HYV, hybrid and local. About 75% of the total annual cropped area is covered by rice cultivation. Transplant Aman is cultivated all over the country and broadcast Aman is cultivated mostly in south and south-eastern part of the country. Aus is grown in scattered areas in the country. In the pre-monsoon Aus paddy is sown and harvested during the monsoon season. Boro is grown in dry season. Boro paddy is always transplanted and is mainly irrigated. Crop combination is a pattern of cultivating two or more crops in a cropping season. It is a great opportunity for cultivating diverse crops in the same crop land. 2-crop combinations are Aman-Boro, Aman-Aus and Aman-Boro rice. Three crop combinations are Aman-Boro-Aus, Aman-Boro-Jute and Aman-Boro-Pulse. 4 crop combinations are Boro-Aman-Jute-Mustard, Boro-Aman-Mustard-Aus, Aman-Aus-Boro-Tea, Aman-Boro-Jute-Wheat, Aman-Wheat-Boro-Aus, Aman-Boro-Wheat-Aus and Aman-Aus-Maskalai-Boro.
The crop cultivating period is divided into two main seasons: Kaharif and Robi. Crops such as rice, maize, jute etc. which are cultivated during the Kahrif season also called Kahrif crops and which are cultivated during the Rabi season called Rabi crops such as wheat, mustard, chickpea etc. Rabi season starts from November and continues up to April and Kharif season starts from May and lasts until October. A transition season has been also identified which is called Pre-kharif season. This season starts from March-April and lasts until May-June.
The coastal region of Bangladesh covers 29,000 sq. km or about 20% area of the country and the coastal areas cover 30% of the cultivable lands of Bangladesh. Ayers and Haq (2008) stated that the Bangladesh coastal area may be the front line of climate change impact and response in South Asian Countries. The coastal area plays an important role in increasing country's GDP. Ali and Wakatuski (2002) shown that agriculture contributed 32% to the GDP sector for the Bangladesh and 72% of this contribution comes from rice cultivated areas. BBS (2002) declared that the modern varieties of rice covering about 62% of total rice areas that contribute to about 77% of the total rice production in Bangladesh.
A quarter of the population of Bangladesh lives in the coastal area and about 80% people depends on agriculture activities. When Bangladesh could lose 15% of the land and up to 25 million of people could be refugees with a 1-meter sea level rise in coastal area of Bangladesh. This condition may lead to decline in the country's GDP from 57% to 27% through the decreasing of crop production. The actual cause of lower GDF condition is for the decreasing of crop production in the coastal area of the country due to climate change.

(Shishir Reza, Environmental Analyst & Associate Member, Bangladesh Economic Association)

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