Md Rashed Chowdhury
Based on the climate model projections, it is evident that the Sundarbans area will face a 2-3° C rise in temperature during the 2050s. Projected sea-level rise is 0.5 m by the 2050s, which would inundate approximately 491 sq.-km (11 per cent) of the Sundarbans (Bangladesh part). In addition to changing climate, the inter-annual variability of El Niño-Southern Oscillation (ENSO) will further aggravate the problems because of its important correlations with the variability of rainfall, temperatures, sea-level, lightning, and forest fires.
According to IPCC-AR5 RCP8.5 (IPCC-AR5: Intergovernmental Panel on Climate Change-Fifth Assessment Report; RCPs: Representative Concentration Pathways), it is clear that the mean summer temperature in Bangladesh will increase by 1° C in the 2030s. The winter temperature will rise slightly higher than 1° C. The same RCP8.5 indicates that in the 2050s the mean summer temperature will increase by 1.5-2° C and winter temperature will increase by 2.5-3° C. This rise will particularly affect the south-west region (Sundarbans area) of Bangladesh. Apart from the temperature change, future rainfall projections also show an increasing trend during the monsoon, especially in July and August. However, as compared to temperature, the rainfall increase is considerably low. This lower increase of rainfall and higher increase in temperature will create a high demand/competition at a higher evapotranspiration [evapotranspiration (ET) is the sum of evaporation and plant transpiration from the Earth's land and ocean surface to the atmosphere] environment by the 2050s, and this will ultimately seriously affect many sectors of livelihood including agriculture, fisheries, and livestock. Among others, the negative impacts on the physiology of fish will be noticeable. Because oxygen transport to tissues will be limited at higher temperatures, and this constraint in physiology will result in changes in distribution, recruitment, and abundance. Depending on the species, the area it occupies may expand, shrink, or be relocated. These changes will include increases, decreases, and shifts in the distribution of the Sundarbans fish including marine fish, with some areas experiencing gains and others losses.
Bangladesh has a long coastline where the impacts of climate change occur at medium-term and long-term scales. The sea-level may rise and there may be changes in the occurrence of frequency and intensity of storm surges. Recently the country experienced tropical cyclones (TCs) Sidr and Aila, indicating that climate change (as a result of past changes in greenhouse gas concentration) is already impacting it and future climate change will further aggravate this bleak situation. Although there will be stronger TCs in the Bay of Bengal, the total number is not expected to vary very much.
The country's coastal forests such as mangroves and coastal plantations, including charland plantations, will be at the forefront of impacts of climate change. Sea rise due to high temperature may submerge coastal forests and settlements, resulting in climate refugees. In winter, high evapotranspiration combined with low water flow will increase the salinity of the forest soil and coastal waters. These conditions adversely affect freshwater dependent floral and faunal species, in particular, and forest productivity and biodiversity in general. This will eventually shift the character of forest boundaries and vegetation as the species that provide dense canopy cover will be replaced by non-woody shrubs and bushes.
In addition to longer time-scale climate change, the other major issue that needs to be seriously addressed is the inter-annual variability El Ninõ-Southern Oscillation (ENSO). Bangladesh is particularly dry during strong El Niño years (El Niño is the warm phase of ENSO) and wet during strong La Niña years (La Ninã is the cold phase of ENSO). One of the biggest El Niño-related threat is forest fire (i.e., Sundarbans fires in 2016). Forest fires threaten many ecologically important areas, including habitats for rare species like tigers, and the smoke they give off is a serious threat to local people's health. Also, more lightning strikes are expected to occur during El Niño year (i.e., lightning strikes in 2016). So, clearly, improved longer-term climate change projection, combined with a future ENSO event, is essential to develop real-time response plans in the forestry sector of Bangladesh.
IMPORTANCE OF CLIMATE INFORMATION FOR ADAPTATION: Climate change-induced natural hazards, such as cyclones, storms, floods, salinity, and drought may affect a country's forest ecosystems, which may result in consequences for forest-dependent communities. However, like any other natural systems, forest ecosystems are generally able to tolerate some level of climate change and so will continue to persist in short-term as they have done in past. In long-term, whether their resilience will be sufficient enough to tolerate future anthropogenic climate change is not known.
Using climate change, including adaptation, as a driver to undertake activities with multiple benefits can catalyse progress in achieving a country's sustainable development goals. Many countries are starting to take concrete action towards adaptation to climate change. Such action needs to be expanded and integrated into national and sectoral planning to ensure that sustainable development and adaptation are mutually enhanced (see http://unfccc.int/press/ fact_sheets/items/4985.php).
Climate-change-based information has the following advantages on a longer time-scale adaptation planning:
n Helps enhance the scientific basis for decision-making for adaptation
n Strengthening methods and tools for the assessment of adaptation
n Education, training and public awareness on adaptation, including for young people
n Individual and institutional capacity-building
n Technology development and transfer; and promotion of local coping strategies
n Appropriate legislation and regulatory frameworks, which promote adaptive-friendly action
n An adaptive planning process that covers different time-scales and levels (e.g. national, regional) and sectors
RECOMMENDATIONS FOR IMPROVEMENT: Future vulnerability depends not only on climate change, but also on development pathways. The implementation of adaptation needs to be integrated into national and international sustainable development priorities, as well as into national and sectoral development plans in Bangladesh.
Bangladesh has already started to take concrete action towards adaptation to climate change. However, such action needs to be expanded and integrated into national and sectoral planning to ensure that sustainable development and adaptation are mutually enhanced.
Sustainable forest management opportunities have the potential to significantly improve the institutional capacity of Forest Department (FD) field staff and local community organisations for biodiversity conservation, forest restoration, and bio-energy. This management strategy in densely populated countries, such as Bangladesh would have substantial socio-environmental and economic benefits for local communities, who are mainly subsistence farmers and labourers. It is also important to improve our understanding of emissions from fires in the region, which would ultimately help improve climate models. It will also contribute to initiatives like the United Nations Collaborative 'Reducing Emissions from Deforestation & Forest Degradation' program.
The numbers of El Niño/La Niña events have increased considerably from 1981-2016 and this increasing trend will probably continue. From our review, we are fairly con?dent that ENSO variations will continue to occur and in?uence global climate in the coming decades and centuries. The recent CMIP5 models have improved their ability to simulate El Niño teleconnections and, therefore, climate change projection combined with a future ENSO event provided an improved result for capacity building efforts in the forestry sector of Bangladesh.
It is very essential to adopt a comprehensive approach with the following key elements: (i) regular monitoring the relationship of observed climate variability and change within Bangladesh and in the basins outside Bangladesh, (ii) establishing the potential for probabilistic forecasting of the key seasonal ENSO features from the regional and global datasets, and (iii) assessing and establishing linkages of key climate information and forecasts and the impacts in terms people can understand and respond to. Bangladesh Forest Department should, therefore, strive to regularly monitor the global and regional impacts of climate variability and change for consistent and reliable input for forest management in Bangladesh.
Dr. Md Rashed Chowdhury is Principal Research Scientist, Pacific ENSO Applications Climate Center (PEAC), Joint Institute for Marine and tmospheric Research, University of Hawaii at Manoa.
