Bay of Bengal
Click here to choose an LME

×
← go back to the LME Portal

LME 34: Bay of Bengal

Bordering countries:

Bangladesh, India, Indonesia, Malaysia, Maldives, Myanmar, Sri Lanka, Thailand

LME total area:

3,657,502 km²

LME overall risk:

This LME falls in the cluster of LMEs that exhibit low to levels of economic development (based on the night light development index) and high pollution from plastic debris.
Based on a combined measure of the Human Development Index and the averaged indicators for fish & fisheries and pollution & ecosystem health modules, the overall risk factor is very high.

Productivity

Chlorophyll-A:

The annual Chlorophyll a concentration (CHL) cycle has a maximum peak (0.253 mg.m^-3) in August and a minimum (0.162 mg.m^-3) during May. The average CHL is 0.211 mg.m^-3. Maximum primary productivity (430 g.C.m^-2.y^-1) occurred during 1998 and minimum primary productivity (288 g.C.m^-2.y^-1) during 2013. There is a statistically insignificant decreasing trend in Chlorophyll of -5.76 % from 2003 through 2013. The average primary productivity is 332 g.C.m^-2.y^-1, which places this LME in Group 4 of 5 categories (with 1 = lowest and 5= highest).

Primary productivity:

Sea Surface Temperature:

From 1957 to 2012, the Bay of Bengal LME #34 has warmed by 0.53°C, thus belonging to Category 3 (moderate warming LME). The steady warming of the Bay of Bengal was modulated by interannual (every 3-to-5 years) variations with a typical magnitude of <0.5°C. The all-time maximum of 1998 occurred simultaneously with other Indian Ocean LMEs and could be linked to the El Niño 1997-1998. Temperature history of the Bay of Bengal is linked to its salinity regime and freshwater discharge of three great rivers, Ganges, Brahmaputra and Irrawaddy. Interannual variability of the Indian monsoon largely determines the river discharge, hence salinity regime and eventually SST variability, in the Bay of Bengal LME.

Fish and Fisheries

The fisheries of the Bay of Bengal LME target a wide range of species, including sardine, anchovy, scad, shad, mackerel, snapper, emperor, grouper, pike-eel, tuna, shark, shrimp, bivalve and other shellfish.

Annual catch:

Catches from commercial and subsistence fishing equal or exceed those from industrial fisheries. During the last decade, several countries have developed offshore fishing for tuna. There are strong indications that the continuous increase in the reported landings, particularly of unidentified fishes is a product of deficiencies in the underlying statistics, rather than improvements in the performance of the fisheries in the LME.

Catch value:

Reported landing rose to about 1.2 million t in 2006 and the value of the reported landing reached a peak of about 5.7 billion US$ (in 2005 real US$) in the recent 5 years (2006 – 2010), but this figure is also questionable.

Marine Trophic Index and Fishing-in-Balance index:

The MTI shows a steady decline over the past 60 years, while the FiB index increased over the same period. Due to the nature of the underlying landings statistics, it is not difficult to draw reliable conclusions from these indices; however, a detailed analysis of the MTI and FiB index of Western India, found that a ‘fishing down’ of the food webs indeed occurs in the region.

Stock status:

The Stock-Catch Status Plots indicate that the number of collapsed and overexploited stocks in the LME is low but on the rise, with over 50% of the reported landings from fully exploited stocks. Again, the questionable quality of the underlying landings statistics must be noted.

Catch from bottom impacting gear:

The percentage of catch from the bottom gear type to the total catch decreased from 17% in 1950 to around 8% in the 1960s. Then, this percentage fluctuated between 10 and 18% in the following years.

Fishing effort:

The total effective effort was below 200 million kW from 1950 to the mid-1990s. Then, it increased sharply to 1,400 million kW in 1996 and it fluctuated around 1,400 million kW in the recent decade.

Primary Production Required:

The primary production required (PPR) to sustain the reported landings in this LME has increased over the years, and reached 20% of the observed primary production in 1998, which may be another indication that the reported landings for this LME is overestimated.

Catch potential projections (under global warming):

Pollution and Ecosystem Health

Pollution

Nutrient ratio, Nitrogen load and Merged Indicator:

Human activities in watersheds are affecting nutrients transported by rivers into LMEs. Large amounts of nutrients (in particular nitrogen load) entering coastal waters of LMEs can result in high biomass algal blooms, leading to hypoxic or anoxic conditions, increased turbidity and changes in community composition, among other effects. In addition, changes in the ratio of nutrients entering LMEs can result in dominance by algal species that have deleterious effects (toxic, clog gills of shellfish, etc.) on ecosystems and humans. An overall nutrient indicator (Merged Nutrient Indicator) based on 2 sub-indicators: Nitrogen Load and Nutrient Ratio (ratio of dissolved Silica to Nitrogen or Phosphorus - the Index of Coastal Eutrophication Potential or ICEP) was calculated.

Nitrogen load:

The Nitrogen Load risk level for contemporary (2000) conditions was very high. (level 5 of the five risk categories, where 1 = lowest risk; 5 = highest risk). Based on a “current trends” scenario (Global Orchestration), this remained the same in 2030 and 2050.

Nutrient ratio:

The Nutrient Ratio (ICEP) risk level for contemporary (2000) conditions was very high (5). According to the Global Orchestration scenario, this remained the same in 2030 and 2050.

Merged nutrient indicator:

The risk level for the Merged Nutrient Indicator for contemporary (2000) conditions was very high (5). According to the Global Orchestration scenario, this remained the same in 2030 and 2050.

POPs:

This LME covers the east coast of India, Sri Lanka and the west coast of Malaysia. Five samples at five locations are available. Average concentrations (ng.g^-1 of pellets) were low: 36 (range 2-139 ng.g^-1) for PCBs, 17 (range 1-3 ng.g^-1) for DDTs, and 4.7 (range 3.2-6.2 ng.g^-1) for HCHs. All indicators correspond to risk category 2 of the five risk categories (1 = lowest risk; 5 = highest risk). Higher PCBs concentration at Chennai, India (139 ng.g^-1) may come from old electronic instruments, although the other location shows almost background level. Moderate concentrations of HCHs at a location in Port Dickson, Malaysia (6.2 ng.g^-1 pellet) may suggest current usage of Lindane pesticide. Continuous monitoring and increase in spatial coverage is recommended.

Plastic debris:

Modelled estimates of floating plastic abundance (items km^-2), for both micro-plastic (<4.75 mm) and macro-plastic (>4.75 mm), indicate that this LME is in the group with the highest plastic concentration. Estimates are based on three proxy sources of litter: shipping density, coastal population density and the level of urbanisation within major watersheds, with enhanced run-off. The high values are due to relative importance of these sources in this LME. The abundance of floating plastic in this category is estimated to be on average over 400 times higher that those LMEs with lowest values. There is good evidence from sea-based direct observations and towed nets to support this conclusion.

Ecosystem Health

Mangrove and coral cover:

0.52% of this LME is covered by mangroves (0.52% of this LME is covered by mangroves (US Geological Survey, 2011) and 0.13% by coral reefs (Global Distribution of Coral Reefs, 2010).) and 0.13% by coral reefs (Global Distribution of Coral Reefs, 2010).

Reefs at risk:

This LME has a present (2011) integrated threat index (combining threat from overfishing and destructive fishing, watershed-based and marine-based pollution and damage) of 238. 11% of coral reefs cover is under very high threat, and 26% under high threat (of the 5 possible threat categories, from low to critical). When combined with past thermal stress (between 1998 and 2007), these values increase to 21% and 27% for very high and high threat categories respectively. By year 2030, 23% of coral cover in this LME is predicted to be under very high to critical level of threat from warming and acidification; this proportion increases to 37% by 2050.

Marine Protected Area change:

The Bay of Bengal LME experienced an increase in MPA coverage from 4,354 km² prior to 1983 to 10,687 km² by 2014. This represents an increase of 145%, within the low category of MPA change.

Cumulative Human Impact:

The Bay of Bengal LME experiences an above average overall cumulative human impact (score 4.00; maximum LME score 5.22). It falls in risk category 4 of the five risk categories (1 = lowest risk; 5 = highest risk). This LME is most vulnerable to climate change. Of the 19 individual stressors, three connected to climate change have the highest average impact on the LME: ocean acidification (0.98; maximum in other LMEs was 1.20), UV radiation (0.61; maximum in other LMEs was 0.76), and sea surface temperature (1.59; maximum in other LMEs was 2.16). Other key stressors include commercial shipping, sea level rise, ocean based pollution, pelagic high-bycatch commercial fishing, and all three types of demersal commercial fishing (demersal destructive, non-destructive low-bycatch, and non-destructive high-bycatch).

Ocean Health Index:

The Bay of Bengal LME scores below average on the Ocean Health Index compared to other LMEs (score 62 out of 100; range for other LMEs was 57 to 82). This score indicates that the LME is well below its optimal level of ocean health, although there are some aspects that are doing well. Its score in 2013 increase 2 points compared to the previous year, due in large part to changes in the score for coastal economies. This LME scores lowest on food provision, coastal protection, tourism & recreation, and sense of place goals and highest on artisanal fishing opportunities, coastal economies, and habitat biodiversity goals. It falls in risk category 5 of the five risk categories, which is the highest level of risk (1 = lowest risk; 5 = highest risk).

Socio-economics

Indicators of demographic trends, economic dependence on ecosystem services, human wellbeing and vulnerability to present-day extreme climate events and projected sea level rise, are assessed for this LME. To compare and rank LMEs, they were classified into five categories of risk (from 1 to 5, corresponding to lowest, low, medium, high and highest risk, respectively) based on the values of the individual indicators. In the case of economic revenues, the LMEs were grouped to 5 classes of revenues from lowest, low, medium, high and highest, as revenues did not translate to risk.

Population:

The coastal area stretches over 874 413 km². A current population of 323 389 thousand in 2010 is projected to increase to 501 774 thousand in 2100, with a density of 370 persons per km² in 2010 reaching 574 per km² by 2100. About 64% of coastal population lives in rural areas, and is projected to increase in share to 67% in 2100.

Coastal poor:

The indigent population makes up 25% of the LME’s coastal dwellers. This LME places in the very high-risk category based on percentage and in the very high-risk category using absolute number of coastal poor (present day estimate).

Revenues and Spatial Wealth Distribution:

Fishing and tourism depend on ecosystem services provided by LMEs. This LME ranks in the very high-revenue category in fishing revenues based on yearly average total ex-vessel price of US 2013 $5 891 million for the period 2001-2010. Fish protein accounts for 32% of the total animal protein consumption of the coastal population. Its yearly average tourism revenue for 2004-2013 of US 2013 $57 951 million places it in the high-revenue category. On average, LME-based tourism income contributes 15% to the national GDPs of the LME coastal states. Spatial distribution of economic activity (e.g. spatial wealth distribution) measured by night-light and population distribution as coarse proxies can range from 0.0000 (totally equal distribution and lowest risk) to 1.0000 (concentrated in 1 place and most inequitable and highest risk). The Night Light Development Index (NLDI) thus indicates the level of spatial economic development, and that for this LME falls in the category with high risk.

Human Development Index:

Using the Human Development Index (HDI) that integrates measures of health, education and income, the present-day LME HDI belongs to the very low HDI and very high-risk category. Based on an HDI of 0.604, this LME has an HDI Gap of 0.396, the difference between present and highest possible HDI (1.000). The HDI Gap measures an overall vulnerability to external events such as disease or extreme climate related events, due to less than perfect health, education, and income levels, and is independent of the harshness of and exposure to specific external shocks.
HDI values are projected to the year 2100 in the contexts of shared socioeconomic development pathways (SSPs). This LME is projected to assume a place in the very low risk category (very high HDI) in 2100 under a sustainable development pathway. Under a fragmented world scenario, the LME is estimated to place in a very high-risk category (very low HDI) because of reduced income levels and increased population values from those in a sustainable development pathway.

Climate-Related Threat Indices:

The Climate-Related Threat Indices utilize the HDI Gaps for present-day and projected 2100 scenarios. The contemporary climate index accounts for deaths and property losses due to storms, flooding and extreme temperatures incurred by coastal states during a 20-year period from 1994 to 2013 as hazard measures, the 2010 coastal population as proxy for exposure, and the present day HDI Gap as vulnerability measure.
The Contemporary Threat Index incorporates a Dependence Factor based on the fish protein contribution to dietary animal protein, and on the mean contribution of LME tourism to the national GDPs of LME coastal states. The HDI Gap and the degree of dependence on LME ecosystem services define the vulnerability of a coastal population. It also includes the average of risk related to extreme climate events, and the risk based on the degrading system states of an LME (e.g. overexploited fisheries, pollution levels, decrease in coastal ecosystem areas).
The 2100 sea level rise threat indices, each computed for the sustainable world and fragmented world development pathways, use the maximum projected sea level rise at the highest level of warming of 8.5 W/m² in 2100 as hazard measure, development pathway-specific 2100 populations in the 10 m × 10 km coast as exposure metrics, and development pathway-specific 2100 HDI Gaps as vulnerability estimates.
Present day climate threat index of this LME is within the very high-risk (very high threat) category. The combined contemporaneous risk due to extreme climate events, degrading LME states and the level of vulnerability of the coastal population, is very high. In a sustainable development scenario, the risk index from sea level rise in 2100 is very low, and increases to very high risk under a fragmented world development pathway.

Governance

Governance architecture:

This LME is served by two Regional Seas Programme initiatives and several transboundary fisheries arrangements only one of which, the BOB IGO, is focussed on the LME. There does not appear to be any agency that is formally mandated to provide transboundary integration for the issues dealt with above. The BOBLME Project may be filling this role in an unofficial capacity. It also supports integration by facilitating and catalyzing cooperative activities and capacity development.
The overall scores for ranking of risk were: