Climate Change refers to any change in climate over time, whether due to natural variability or as a result of human activity. This usage differs from that in the United Nations Framework Convention on Climate Change, which defines "climate change" as: "change in climate which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural variability observed over comparable time periods". In Bangladesh there are four prominent climatic seasons, namely, winter (Dec.-Feb.), Pre-monsoon (March-May), Monsoon (June-Sep.) and Post-monsoon (Oct.-Nov.). The monsoon has its onset during the first week of June and in the first week of October. However, the onset and withdrawal dates vary from year to year.

Bangladesh has a tropical monsoon type climate, with hot and rainy summers and a pronounced dry season in the cooler months. January is the coldest month of the year, with the temperature ranging 13.5°C to 26.5°C, and April the warmest month, with the temperature ranging 33°C and 36°C. In rare cases the temperature goes down less than 50°C but never touches the freezing point. It is evident that, our region has been getting warmer. According to the climatic situation, Bangladesh may be divided into following climatic sub-regions: a) South-eastern zone, b) North-eastern zone, c) Northern part of the northern region, d) North-western zone, e) Western zone, f) South-western zone, and f) South-central zone.

Political Ecology of Sea-level Rise

Sea-level rise potentially impacts human populations (those living in coastal regions and on islands) and the natural environment marine ecosystems). Two main factors contributed to observed sea level rise. The first is thermal expansion: as ocean water warms, it expands. The second is from the contribution of land-based ice due to increased melting. The major store of water on land is found in glaciers and ice sheets.

Sea level rise is expected to continue for centuries. In 2007, the Intergovernmental Panel on Climate Change (IPCC) projected that during the 21st century, sea level will rise another 18 to 59 cm (7.1 to 23 in), but these numbers do not include "uncertainties in climate-carbon cycle feedbacks nor do they include the full effects of changes in ice sheet flow". Statistical data on the human impact of sea-level rise is scarce. A study in the April, 2007 issue of Environment and urbanization reports that 634 million people live in coastal areas within 30 feet (9.1 m) of sea level. The study also reported that about two thirds of the world's cities with over five million people are located in these low-lying coastal areas. The IPCC report of 2007 estimated that accelerated melting of the Himalayan ice caps and the resulting rise in sea levels would likely increase the severity of flooding in the short term during the rainy season and greatly magnify the impact of tidal storm surges during the cyclone season. A sea-level rise of just 400 mm in the Bay of Bengal would put 11 percent of the Bangladesh's coastal land underwater, creating 7-10 million climate refugees.

The effect on Public Health

The variation of humidity, temperature and rainfall is likely to have ample health consequences. High temperature manipulates the reproduction and survival of the infective agent within the vector, thereby further influencing disease diffusion in areas where the vector is previously present. The ecology and transmission dynamics of vector borne disease are complex. Vector borne diseases are transmitted by insects − mosquitoes and ticks that are sensitive to temperature, humidity and rainfall.

Mosquito-borne diseases can spread due to lack of proper faeces management. Survey around 6,000 households (UNICEF Report, 2018) implies, in urban poor areas among the latrines, pit latrine with slab without lid and water-seal is the major one -53%. Pit latrine with slab and water-seal is 13%. Pit latrine with slab without water-seal is 5.9%. Pit latrine with slab and flap without water-seal is 8.1%. Latrine without slab or open pit latrine is 7.3%. Latrine connected with open drain with flush or pouring water is 5%. Flush latrine connected to septic tank is 3.1%. Use of hanging latrines is 3.1%. Pit latrine with ventilation system 1.4%. In general, by reducing fresh water supplies, climate alteration affects sanitation and lowers the efficiency of local sewer systems, leading to amplify concentrations of pathogens in unprocessed water supplies. Later on mosquito larvae gets developed in such places, which may in turn cause mosquito-borne diseases once it bites humans.

Apart from that, numerous diseases that are transmitted by mosquitoes (chikungunya, dengue, and yellow fever), sand flies (leishmaniasis) and ticks (Lyme disease, tick-borne encephalitis) may also be amplified by climate alteration. Prevalence of dengue fever in the capital and elsewhere appears to be a common feature at the advent of the monsoon but there is hardly any effort on the part of the authorities to fight its outbreak. Reports have it that the mosquito-borne disease has lately taken a serious turn in many parts of the country, including Dhaka. In Dhaka alone, there are reports of hundreds of people suffering dengue attack recently, a majority of whom were hospitalized. A local daily quoting sources of the DG Health Services (DGHS) has described the situation as alarming.

Land Ecosystems and Food Security

Climate is not confined to only competing countries or regions. It affects all human beings regardless of race, caste, ethnicity, sex and level of income. It is characterized by increased temperature; alter action in rainfall and seasonal disruption across the globe. True factor is that our heartbeat increases just after hearing a word "war". Such a war continues in our nature that is defined as climate war. South Asian country Bangladesh is globally known as one of the most vulnerable countries to the impacts of global warming and climate calamity. It not only affects human development and biodiversity conservation but also poses a threat to human security with increased frequency of extreme weather events - floods, cyclones, draught, earthquake that are degrading our socio-economic conditions. No country and people know this better than Bangladesh, where millions of people are suffering. Sudden severe catastrophic floods and cyclones have intensified and taking place move frequently owing to increased rainfall in the monsoon. This article clarifies the existing research findings to draw an overview of emerging trends and identified areas of impacts on land ecosystem in Bangladesh due to climatic calamities.

The impacts of climate change on land affects the livelihood of the concerned people in many ways. According to one estimate the impacts of climate change in case of Bangladesh involves 35.8 million (28% of total population) people who are vulnerable to climate change induced SLR, Cyclone, Salinity in coastal zone of the country. Among these 72 offshore islands with an area of 4200 km sq. falls within the impact zone. Based on this estimation about 18 percent households of the Sundarban impact zone will affect a population who are dependent on Sundarban resources (shrimp fry collectors, honey collectors, golpata collectors, shell/crab collectors and medicinal plant collectors). The impact of climate change will affect around 0.5 million household's (family members 2.7 million) whose primary income source is fishing (losing working days because of rough weather in the Bay). It should be noted over 160,000 coastal fishermen and estimated 185,000 shrimp fry collectors are involved in marine fisheries.

The economic losses increase by threefold to a cumulative $129 billion and as high as $5.1 billion per year under more pessimistic climate scenarios-with economic losses rising in later years. Based on this model, the southern coastal regions and the northwestern regions are expected to experience the largest income declines. IPCC estimates that, in Bangladesh, production of rice and wheat might drop by 8% and 32%, respectively, by the year 2050.

Climatic Calamities and Inequality

Urban area is a composite of different subsystems of physical structures and human activities all having links with one another. Intended and unintended human activities taking place within the urban area have profound impacts both within and exterior it. The degradation in the quality of the urban environment is the consequence of economic activities, which may affect the environment, sanitation security and public health either directly or indirectly.

Intensification in the urban population of Bangladesh is more or less centered on the three metropolitan areas of Dhaka, Chittagong and Khulna through rural to urban migration which is currently 55% of total migration. Everyday - due mainly to rural-push migration - thousands of people are migrating to the cities from their rural inhabitants and a huge number of them are heading towards the cities either being destitute by landlessness, impoverization, employment contraction among poor and marginalized, floods, cyclones, river erosion, droughts or being stricken by poverty. Dhaka density stands at an astounding 49,182 per sq. km and Chittagong 16,613 sq. km. UN report, 2016 has mentioned the urban Population Status in Bangladesh: it was 23.8% in 2000; 30.4 % in 2010 and 2016 it is now 34.9%. Day by day it is escalating.

In general, urban poor lives at slums, squatter and low income settlements. As city life is very expensive to fulfill the basic needs, these poor people are bound to search for a dwelling place at the city slums and those who cannot even afford to live in a slum dwelling are living on streets or pavements, in parks, bus or railway stations or other public infrastructures. They are experiencing with kutcha, jhupri, non-sanitary latrine, unhygienic garbage disposal and impure water supply. No sanitation is safe when covered by flood waters, as fecal matter mixes with flood waters and spread everywhere the flood water goes. Dhaka − which has piped sewage network, 2% only of fecal load is treated.

In reality, human health depends on an adequate supply of potable water. By reducing fresh water supplies, climate change affects sanitation and lowers the efficiency of local sewer systems, leading to amplify concentrations of pathogens in unprocessed water supplies. In addition, climate alteration reduces the water availability for drinking and washing. The unforeseen increase in extreme rainfall events, which is associated with the outbreak of diarrheal disease − may overwhelm the public water supply system.

The ecology and transmission dynamics of vector borne disease are complex. Climate change impacts models suggest that the leading changes in the potential for disease transmission will occur at the fringes in terms of both latitude and longitude of the malaria risk areas. Vector borne diseases are transmitted by insects − mosquitoes and ticks that are sensitive to temperature, humidity and rainfall. High temperature manipulates the reproduction and survival of the infective agent within the vector, thereby further influencing disease diffusion in areas where the vector is previously present. Numerous diseases that are transmitted by mosquitoes (chikungunya, dengue, and yellow fever), sand flies (leishmaniasis) and ticks (Lyme disease, tick-borne encephalitis) may also be amplified by climate alteration. The poor who are environmentally or agriculturally displaced, live in urban areas have no capacity, education, financial aptitude to fight against climate induced health insecurity.

Climate Financing

Climate is not confined to only competing countries or regions. It affects all human beings regardless of race, caste, ethnicity, sex and level of income. It is characterized by increased temperature; alter action in rainfall and seasonal disruption across the globe. It is true that our heartbeat increases just after hearing a word "war". Such a war continues in our nature that is defined as climate war.

Loss of coastal land to the sea in the vulnerable zone is currently predicted to reach up to 5% by 2030, 7% by 2050 and 15% by 2080. Scientists predict that, due to tropical cyclones and salinity intrusion into farming lands in coastal areas, environmental refugees will exceed 20 million in the coming future. As a result, their demand for land, water, employment and other public services generate conflict with local residents.

Some foreign and local alliance - world health organization, intergovernmental panel on climate change, Bangladesh poribesh andolon, Bangladesh environment network, Bangladesh environmental lawyers association believe that climate change cannot be mitigated through discussions. To reduce the climatic impacts, we have to take financial initiatives and share technology for adaptation with increase mass awareness to reduce carbon use.

To conclude, what is critical now is to move away from producing 'paper and reports' towards investing human, material and financial resources on the issues at the places where the climate change is upsetting for collective and sustainable Bangladesh.

Shishir Reza is an Environmental Analyst and Matiur Rahman is a research consultant, Human Development Research centre, Dhaka