Coastal Ecosystem: Risk Factors for Development and Threats due to Climate Change

Citation: Sen,H.S. & Ghorai Dipankar (2017). Coastal ecosystem: risk factors for development and threats due to climate change. In "Soil Salinity Management in Agriculture: Technological Advances and Applications", S.K.Gupta & Megh R. Goyal (eds). Apple Academic Press, USA, pp. 63-95.

Coastal Ecosystem: Risk Factors for Development and Threats due to Climate Change

H.S. Sen and Dipankar Ghorai

H.S. Sen, Ph D, Former Director, ICAR-Central Research Institute for Jute & Allied Fibres, Barrackpore -700 120, West Bengal, India, Present address: 2/74 Naktala, Kolkata 700 047, West Bengal, India, Phone; +91987418962, Email:hssen.india@gmail.com

 Dipankar Ghorai, Ph D,  Subject Matter Specialist (I/C), Krishi Vigyan Kendra, ICAR-Central Research Institute of Jute & Allied Fibres (ICAR), Burdwan  -713403, West Bengal, India, Phone, +919433122515,

Email: dipankarghoraikvk@gmail.com

1.               INTRODUCTION

In one of its report IFPRI [16] has projected that globally about 1 billion people are ‘absolutely’ or ‘ultra’ poor living on less than US $ 1 a day and about 800 million people are hungry. Although, this level of poverty has decreased marginally overall from 28.6% of the population in 1990 to 18.0% in 2004, large changes in regional disparities in poverty level have been observed during the period, 1990 to 2004, from 39% to 47% in South Asia, 38% to 17% in East Asia & Pacific, 19% to 31% in Sub-Saharan Africa, and 4% to 5% in Latin America and Caribbean. Various risk factors have been identified to affect poverty in different time frames, which are socio-technological constraints including macro-economic imbalances limiting agricultural and related productivity, rising food prices and resource scarcity, climate change and lack of environmental sustainability, lack of infrastructure, ethnic and other social crises, inappropriate mindset for the acceptance of improved technologies, health related issues, etc.

Of all the major ecosystems which factor in agricultural or food production, being at the very base of poverty alleviation program, ‘coastal’ is probably the most important one because of its high potentiality and production of a large number of value added goods, yet confronted with high risk factors due to a multiple of issues, which is the theme of discussion in this paper. Current challenges and management of the coastal ecosystem have been overviewed in Wikipedia [42]. Different countries with coastal boundaries have varying proportion of the total area exposed to the sea, expressed as coastline: total area of the country (km km^-2), some top-most being [43]: Tokelau (10,100), Federal States of Micronesia (8,706), Palau (3,316), Northern Mariana Islands (3,107), Maldives (2,147), Monaco (2,051), Marshall Islands (2,044), Cocos (Keeling) Islands (1,857), Gibraltar (1,846) Macau (1,464), Nauru (1,429), Kiribati (1,409), Saint Martin (1,093), Pitcairn Islands (1,085), Seychelles (1,079),  and Christmas Island (1,030). India, Bangladesh and USA have low coast/ area ratio of 2, 4 and 2, respectively. However, it is not the coast/ area ratio alone but also the total coastline, population density and anthropogenic factors, topography and related soil properties, protection measures undertaken, and natural disasters caused by the sea and through its interaction with climate and under-sea tectonic movement of the earth, that factor in not only to influence the agricultural production but also the nature and extent of vulnerability of the ecosystem per se in a country.

2.               NEED FOR A THRUST

Coastal ecosystems have an economic value beyond their aesthetic benefit supporting human lives and livelihoods. By one estimate [26], the combined global value of goods and services from coastal ecosystems is about US$ 12-14 trillion annually--a figure larger than the United States' Gross Domestic Product worked out in 2004. The problems of livelihood in these areas are compounded manifolds owing to a series of technological, administrative and socio-economic constraints. A holistic look at the interaction matrix of factors, which are interdependent on each other, impacting on the coastal ecosystem is presented schematically in Fig. 1. Unfortunately, at the global level, until very recently, not much serious and concerted attention has been paid for mitigating the problems for sustainable development in the coastal ecosystem. Attempt for improving on the agricultural front, which is the focal theme of this paper, though should be at the central stage from daily livelihood point of view in this ecosystem, is still in the back seat in majority of the areas. This is possibly because of the ‘slow-poisoning kind of effect’ of this sector, arising out of poor agricultural practice and/ or inability for the poor to pay for the commodities as a result of insufficient food production, that normally goes un-noticed among the poverty-stricken mass, vis-à-vis catastrophic effects with heavy toll on lives and properties due to climatic disasters. Exceptions are India, Bangladesh and possibly a few other countries paying concerted attention on the coastal ecosystem for improvement in agricultural front in particular.     

Figure 1. Interaction matrix of factors influencing stability and livelihood of the coastal ecosystem [32]

3.               DEFINITION AND DISTRIBUTION

A coastal ecosystem includes estuaries and coastal waters and lands located at the lower end of drainage basins, where stream and river systems meet the sea and are mixed by tides. The ecosystem includes saline, brackish (mixed saline and fresh) and fresh waters, as well as coastlines and the adjacent lands. Coastal wetlands are commonly called as lagoons, salt marshes or tidelands [38] . According to World Resources Institute [51] coastal areas may be commonly defined as the interface or transition areas between land and sea, including large inland lakes. Coastal areas are diverse in function and form, dynamic, and do not lend themselves well to definition by strict spatial boundaries. Unlike watersheds, there are no exact natural boundaries that unambiguously delineate coastal areas at the global scale.  According to them, the world coastline extends from 350,000-1,000,000 km in length, depending upon how finely the ‘length’ is resolved. More comprehensively, the coastal ecosystem has been defined as representing the transition from terrestrial to marine influences and vice versa by [29]. It comprises not only shoreline ecosystems, but also the upland watersheds draining into coastal waters, and the near shore sub-littoral ecosystems influenced by land-based activities. Functionally, it is a broad interface between land and sea that is strongly influenced by both.

Soils in the coastal ecosystem along with their characteristics have been described comprehensively on a global scale but no attempt has been made to delineate the zones from inlands based on scientific criteria. Estimates made world over have generally been arbitrarily done based on length of the coastline times a fixed distance landward, varying from 50 to 200 km as followed in different countries, from the shore assuming the zone representing coastal ecosystem different from that for inland part of the country. Velayutham et al. [40] for the first time described soil resources and their potentials for different Agro-ecological Sub Regions (AESR) in the coastal ecosystems of India showing total of 10.78 million hectare (M ha) area under this ecosystem (including the islands). Soil in the coastal ecosystem per se does not have separate significance as far as its productivity is concerned unless it is considered in association with other relevant ecological factors describing the ecosystem owing to the latter’s significant influence on threatening its very stability—a fact, unlike any other ecosystem. It should therefore be necessary, in priory, to delineate and characterize the coastal soils in each country based on sound scientific criteria, and alongside consider the relevant ecological factors which render the ecosystem concerned generally fragile in nature due to various risk factors, often complementing with each other, involved for planning for sustainable development with a holistic approach (Fig. 1). The topic is discussed in a series of two sections, the first of which is devoted to the various risk factors including climatic change threatening the stability, and the second one will discuss various issues impacting on productivity in agriculture and finally the integrated coastal area planning towards livelihood security in the ecosystem. 

4.               RISK FACTORS

According to an estimate by Dirk et al. [7], 51% of the world’s coastal ecosystems appear to be at significant risk of degradation from development related activities. Europe, with 86% of the coastline at high or medium risk, and Asia, with 69% in these categories, are the regions most threatened by degradation. Worldwide, nearly three-fourths of marine protected areas within 100 km of continents or major islands appear to be at risk. These were preliminary estimates and lack precision as commented upon by WRI [51]. However, the data suggest already an alarming state towards destabilizing the ecosystem, notwithstanding that the estimate did not even take into consideration other important factors like agricultural and allied developments, deforestation, fishing, population density, and climatic disturbances with significant adverse contribution.  

4.1 Different Coastal Ecosystems

The ‘main’ ecosystems of the coastal areas, besides taking into account about 50-100 km area landward to be designated as coastal plain and utilized mostly by agriculture and allied activities as well as for domicile and a few other occupational purposes, are reefs, salt marshes and the remaining continental shelves The global distribution of major classified into components, like estuaries, macrophyte communities, mangroves, coral reefs, salt marshes and the remaining continental shelves components of the coastal ecosystems. The global distribution of major components is shown in Fig. 2.     

Figure 2. Major wetland areas and world distribution of mangrove swamps and salt marshes (Source: [10] By courtesy of Encyclopaedia Britannica, Inc., copyright 1997; used with permission)

4.2  Salt Marsh

According to Encyclopedia Britannica [10], salt marsh is an area of low, flat, poorly drained ground that is subject to daily or occasional flooding by salt water or brackish water and that is covered with a thick mat of grasses and such grass like plants as sedges and rushes. Salt marshes are common along low seacoasts, inside barrier bars and beaches, in estuaries, and on deltas and are also extensive in deserts and other arid regions that are subject to occasional overflow by water containing a high content of salts. Maritime salt marshes often extend many miles inland and are variably subject to tidal action; inland brackish marshes are found frequently on mineral substrates of alluvial and lacustrine origin. According to Gedan et al. [11] salt marshes provide more ecosystem services to coastal populations than any other environment. Coastal wetlands all over the world have vanished or are threatened in spite of various international agreements and national policies. Losses due to human activities include effects of urbanization, development of tourism resort, industrial pollution, increase of inflow nutrients from the upstream reclaimed lands, changes in hydrology, conversion to aquaculture ponds and some drillings for gas exploitation. In addition, as a transition zone between land and sea, coastal wetlands are particularly vulnerable to sea-level rise caused by both oceanic thermal expansion and the melting of Artic and Antarctic glaciers as consequence of global warming [52]. According to them, the diversity of saltmarsh plant species increases with increasing latitude. This contrasts with mangrove diversity, which is highest in the lower latitudes of the tropics. In Australia, when saltmarshes and mangroves coexist, saltmarshes are typically found at higher elevations where they are inundated less frequently than mangroves. However, this is not always true in an international context. When seagrass beds are found adjacent to saltmarshes and mangroves, many material links and shared plant and animal communities can exist.

OzCoasts [22] reported characterization of salt marsh sediments generally consisting of poorly sorted anoxic sandy silts and clays. Carbonate concentrations are generally low, and concentrations of organic material are generally high. As with salt flats, the sediments may have salinity levels that are much higher than that of seawater. These sediments are also usually anoxic and have large accumulations of iron sulphides. Disturbing these acid sulphate soils can cause sulphuric acid to drain into coastal waterways. Salt marshes are often associated with salt flats or exposed bare areas.

4.3   Salt Flats

Salt flats, or saline supratidal mudflat facies, occur in dry evaporative environments (often in the tropics) that undergo infrequent tidal inundation. Sediments comprise poorly-sorted sandy silts and clays, including mineral deposits, such as gypsum and halite which form crusts. Salt flats tend to be low gradient, and mostly featureless, with a varying degree of algal colonisation, and often with vertically accreting algal mats. They generally occur above mean high water spring, and experience infrequent inundation by king tides. The high salinity levels (surface and ground water) in these environments often preclude the growth of higher vegetation and biota (some infauna and epifauna may occur at lower elevations). Saltflats are habitats for birds, particularly during the wet season [22].

4.4  Coral Reefs

Coral reefs are aragonite structures produced by living organisms. In most reefs the predominant organisms are colonial cnidarians that secrete an exoskeleton of calcium carbonate [44]. Coral reefs are estimated to cover 284,300 square kilometres, with the Indo-Pacific region (including the Red Sea, Indian Ocean, Southeast Asia and the Pacific) accounting for 91.9% of the total (Fig. 3). Southeast Asia accounts for 32.3% of that figure, while the Pacific including Australia accounts for 40.8%. Atlantic and Caribbean coral reefs only account for 7.6% of the world total.

Figure 3. World distribution of coral reef (Source: [44])

Coral reefs are either restricted or absent from the west coast of the Americas, as well as the west coast of Africa. This is due primarily to upwelling and strong cold coastal currents that reduce water temperatures in these areas. Corals are also restricted from off the coastline of South Asia from Pakistan to Bangladesh. They are also restricted along the coast around north-eastern South America and Bangladesh due to the release of vast quantities of freshwater from the Amazon and the Ganges Rivers, respectively. Although corals are found in temperate and tropical waters, shallow water reefs are formed only in a zone extending at most from 30°N to 30°S of the equator.

Coral reefs cover < 0.5% of the ocean floor and 90% of the marine species are directly or indirectly dependent on them [26]. About 20% of coral reefs have been destroyed in the last few decades and an additional 20% or more are severely degraded, particularly in the Caribbean Sea and parts of Southeast Asia. Coral bleaching, which results from rising ocean temperatures caused by climate change is also increasing and further threatens this valuable resource.

A lagoon on the other hand is a body of comparatively shallow salt or brackish water separated from the deeper sea by a shallow or exposed sandbank, coral reef, or similar feature. Thus, the enclosed body of water behind a barrier reef or barrier islands or enclosed by an atoll (an island of coral that encircles a lagoon partially or completely) reef is called a lagoon [45] .

4.5 Mangroves Swamps

A mangrove is a plant and mangal is a plant community and habitat where mangroves thrive. They are found in tropical and sub-tropical tidal areas worldwide, like Africa, Americas (including Caribbeans), South America, Asia, Australasia, and Pacific Islands. The 15 countries having significant areas under mangrove swamp are given in Fig 4. The areas are typically characterized by high degree of salinity and water logging due to tidal inundation. Areas where mangals occur include estuaries and marine shorelines. Plants develop physiological adaptations to overcome the problems of anoxia, high salinity and frequent tidal inundation. About 110 species have been identified as belonging to the mangal. Each species has its own capabilities and solutions to these problems. Small environmental variations within a mangal may lead to greatly differing methods of coping with the environment. Therefore, the mix of species at any location within the intertidal zone is partly determined by the tolerances of individual species to physical conditions, like tidal inundation and salinity, but may also be influenced by other factors such as predation of plant seedlings by crabs. Mangroves protect the coast from erosion, surge storms (especially during hurricanes), and tsunamis. Their massive root system is efficient at dissipating wave energy. Likewise, they slow down tidal water enough that its sediment is deposited as the tide comes in and is not re-suspended when the tide leaves,

Figure 4. The 15 most mangrove-rich countries and their global share (data source: [14]; with permission to use data)

except for fine particles. As a result, mangroves build their own environment. Because of the uniqueness of the mangrove ecosystems and their protection against erosion, they are often the object of conservation programmes including national Biodiversity Action Plans [46].

Mangroves support unique ecosystems, especially on their intricate root systems (Fig. 5). The mesh of mangrove roots produces a quiet marine region for many young organisms. In areas where roots are permanently submerged, they may host a wide variety of organisms, including algae, barnacles, oysters, sponges, and bryozoans, which all require a hard substratum for anchoring while they filter feed. Shrimps and mud lobsters use the muddy bottom as their home. Mangrove crabs improve the nutritional quality of the mangal muds for other bottom feeders by mulching the mangrove leaves. In at least some cases, export of carbon fixed in mangroves is important in coastal food webs. The habitats also host several commercially important species of fish and crustaceans. In Vietnam, Thailand, the Philippines, and India, mangrove plantations are grown in coastal regions for the benefits they provide to coastal fisheries and other uses [46].

Figure 5. Above and below water view at the edge of the mangal (Source: [46])

In the last 50 years, as much as 85% of the mangroves have been lost in Thailand, the Philippines, Pakistan, Panama and Mexico, globally the value being about 50%. An estimated 35% of mangroves have been removed due to shrimp and fish aquaculture, deforestation, and freshwater diversion. In Indonesia alone over 10,000 square kilometers of mangrove forests have been converted into brackish water ponds (called tambaks) for the cultivation of prawns and fish. Valuation of intact tropical mangroves estimated at US$ 1000 per ha drops to US$ 200 per ha due to clearance by shrimp farming [26]. Although some successful restoration efforts have taken place, these are not keeping pace with mangrove destruction.

4.6 Estuaries

 Estuaries are partially enclosed bodies of water along coastlines where fresh water and salt water meet and mix. Most scientists accept the definition given by D.W. Pritchard in 1967 as: "An estuary is a semi-enclosed coastal body of water which has a free connection with the open sea and within which seawater is measurably diluted with fresh water derived from land drainage" [20]. Estuaries act as a transition zone between oceans and continents. Fresh water input from land sources (usually rivers) dilutes the estuary's salt content. An estuary is typically the tidal mouth of a river and is made up of brackish water. Freshwater from the river is prevented from flowing directly into the open sea by one or more land formations, such as peninsulas and barrier islands. Estuaries are often characterized by sedimentation or silt carried in from terrestrial runoff and, frequently, from offshore [21]. The pH, salinity, and water levels of estuaries vary; depending on the river that feeds the estuary and the ocean from which it derives its salinity. An estuary retains many nutrients derived from both land and sea, and it protects water quality. It thus forms an ecosystem that is filled with a rich variety of living organisms.

Estuaries are vital habitats for thousands of marine species, often called the "nurseries of the sea" because the protected environment and abundant food provide an ideal location for fish and shellfish to reproduce. Most commercially important fish species spend some part of their life cycle in estuaries. Besides fish, many species of birds depend on estuaries for food and nesting areas. Marine mammals also use estuaries as feeding grounds and nurseries. All these marine organisms feed in estuaries because a healthy estuary produces between 4 and 10 times as much organic matter as a cornfield of the same size. Estuaries provide a wide range of habitats leading to a great diversity of marine life [20].

According to USAID [39], complicated interconnections exist between the quality, quantity and timing of fresh water inflows and the health of estuaries. All of the goods and services that estuaries provide are threatened when fresh water inflows are changed. Even a small change in the flow of freshwater may affect the fundamental functioning of an estuary, which in turn will have ramifications on the animals and plants, as well as on human populations dependent upon the estuary. In many cases, upstream alterations to the volume, timing and quality of fresh water inflows have resulted in catastrophic destruction of downstream habitats, loss of species and degradation of ecosystems adapted to a certain range of freshwater inflows.

4.7 Macrophytes

A macrophyte represents a group of aquatic plants that grow in or near water and is either emergent, submergent, or floating. In lakes macrophytes provide cover for fish and substrate for aquatic invertebrates, produce oxygen, and act as food for some fish and wildlife. A decline in a macrophyte population may indicate water quality problems. Such problems may be the result of excessive turbidity, herbicides, or salinization. Conversely, overly high nutrient levels may create an overabundance of macrophytes, which may in turn interfere with lake processing [47].

4.8 Remaining Shelf

The Continental shelf is the extended perimeter of each continent and associated coastal plain, and was part of the continent during the glacial periods, but is under sea during interglacial periods such as the current epoch by relatively shallow seas (known as shelf seas) and gulfs. The continental rise is below the slope, but landward of the abyssal plains (Fig. 6). Its gradient is intermediate between the slope and the shelf, of the order of 0.13-2.5. Extending as far as 500 km from the slope, it consists of thick sediments deposited by turbidity currents from the shelf and slope. Sediment cascades down the slope and accumulates as a pile of sediment at the base of the slope, called the continental rise [48].

Figure 6. Continental shelf in relation to ocean [48]

An ‘Ice shelf’ is a thick, floating platform of ice that forms where a glacier or ice sheet flows down to a coastline and onto the ocean surface. Ice shelves are found in Antarctica, Greenland and Canada only. The boundary between the floating ice shelf and the grounded (resting on bedrock) ice that feeds it is called the grounding line. When the grounding line retreats inland, water is added to the ocean and sea level rises. In contrast, for Ross Ice Shelf sea ice is formed on water, is much thinner, and forms throughout the Arctic Ocean. It also is found in the Southern Ocean around the continent of Antarctica [49].

5.               EROSION AND POLLUTION VIS-À-VIS POPULATION GROWTH

5.1 Population Growth as the Driver

The earth is now home to some 6.5 billion people and is projected to have 9 billion by 2050. World population is increasing with time at an accelerated pace and the population will grow even faster along various coastlines and in already densely populated developing countries. The number of people living within 100 km of coastlines will increase by about 35% in 2050 as compared to that in 1995. This type of migration will expose 2.75 billion people to coastal threats from global warming such as sea level rise and stronger hurricanes in addition to other natural disasters like tsunamis [15]. In an estimate [9], the expected change of the population (or population density) from 2000 to 2025 regionwise shows increase in almost each coastal area. The  estimates (population within 100 km of the coastline) show increase by 25% in Asia (except Middle East), 52% in Middle East and North Africa, 81% in Sub-Saharan Africa, 20% in North America, 31% in Central America and Caribbeans, and 32% in each South America and Oceanea, while there may be decrease by 2.5% in Europe. In India, according to the Department of Ocean Development, there are 40 heavily populated areas along the Indian coast [8]. Apart from climate change, which we will discuss hereafter, population growth is possibly the single most factor impacting on damage to properties in the coastal ecosystem. Around the world maximum people die of drowning by storm surge. 

5.2 Sedimentation and Erosion

The dynamics of alluvial landscapes and natural sedimentation patterns that determine the nutrient and energy flows in coastal areas are increasingly being modified by human activities, in particular those that affect water flows (dams, increased water extraction, deviation of rivers) and erosion, especially due to deforestation. This prevents or slows down vertical accretion, thus aggravating salt water intrusion and impairing drainage conditions in riverine, delta or estuarine areas. It reduces or blocks sediment supply to the coast itself, which may give rise to the retreat of the coastline through wave erosion. Beach erosion is a growing problem and affects tourism revenue, especially in island nations. In the Caribbean, as much as 70% of beaches studied over a ten-year period were eroded. Yet, the long-term success of tourism in the region is dependent on excellent beaches, a pristine marine environment, and warm weather.

5.3 Eutrophication, Hypoxia, Dead Zones and Nutrient Cycle

The urban developments are increasingly expanding to fertile agricultural lands and leading to pollution of rivers, estuaries and seas by sewage as well as industrial and agricultural effluents. In turn, this is posing a threat to coastal ecosystems, their biological diversity, environmental regulatory functions and role in generating employment and food. Overuse of fertilizer can result in eutrophication, and in extreme cases, the creation of ‘dead zones’. Dead zones occur when excess nutrients—usually nitrogen and phosphorus—from agriculture or the burning of fossil fuels seep into the water system and fertilize blooms of algae along the coast. As the microscopic plants die and sink to the ocean floor, they feed on bacteria, which consume dissolved oxygen from surrounding waters. This limits oxygen availability for bottom-dwelling organisms and the fish that eat them. In dead zones, huge growths of algae reduce oxygen in the water to levels so low that nothing can live. There are now more than 400 known dead zones in coastal waters worldwide, compared to 305 in the 1990s, according to a study undertaken by the Virginia Institute of Marine Science. Those numbers were up from 162 in the 1980s, 87 in the 1970s, and 49 in the 1960s. In the 1910s, four only dead zones had been identified [19].

The occurrence of hypoxia in shallow coastal and estuarine areas has been increasing worldwide, most likely accelerated by anthropogenic activities. Hypoxia in the Northern Gulf of Mexico, commonly named the 'Gulf Dead Zone', has doubled in size since researchers first mapped it in 1985, leading to very large depletions of marine life in the affected regions [25]. He studied changes in microbial communities as a result of oxygen depletion, the potential contribution of increasing hypoxia to marine production and emission of N₂O and CH₄, and the effect of hypoxic development on methyl mercury formation in bottom sediments at the Gulf of Mexico's Texas-Louisiana Shelf during the summer months.

The World Resources Institute reported that driven by a massive increase in the use of fertilizer, the burning of fossil fuels, and a surge in land clearing and deforestation, the amount of nitrogen available for uptake at any given time has more than doubled since the 1940s. In other words, human activities now contribute more to the global supply of fixed nitrogen each year than natural processes do, with human-generated nitrogen totaling about 210 million metric tons per year, while natural processes contribute about  140 million metric tons (Table 1).

Table 1. Global sources of Biologically Available (Fixed) Nitrogen (Source: [51])

Anthropogenic sources	Annual release of fixed nitrogen (teragram)
Fertilizer	80
Legumes and other plants	40
Fossil fuels	20
Biomass burning	40
Wetland draining	10
Land clearing	20
Total from human sources	210
Total from natural sources, viz. Soil bacteria, algae, lightning, etc.	140

This influx of extra nitrogen has caused serious distortions of the natural nutrient cycle, especially where intensive agriculture and high fossil fuel use coincide. In some parts of northern Europe, for example, forests are receiving 10 times the natural levels of nitrogen from airborne deposition, while coastal rivers in the Northeastern United States and Northern Europe are receiving as much as 20 times the natural amount from both agricultural and airborne sources. Recently, a new class of chemical substances with toxic and persistent properties was detected in the environment - the polyfluorinated compounds (PFCs). At the Institute for Coastal Research, scientific studies were performed on the PFC-contamination of coastal waters, marine mammals and the atmosphere with emphasis on the mechanisms of global transport and distribution of PFCs [5].

6.               CLIMATE CHANGE

6.1 The Generic Issue 

‘Climate change’ is called for any long-term significant change in the expected patterns of average weather of a specific region over an appropriately significant period of time.  A number of factors have been identified which collectively or individually impact on the build-up of greenhouse gases (GHGs, like carbon dioxide, methane and nitrous oxide) that threaten to set the earth inexorably on the path to an unpredictably different climate. The Intergovernmental Panel on Climate Change [17] says from observations since 1961 that the ocean has been absorbing more than 80% of the heat added to the climate system, and that ocean temperatures have increased to depths of at least 3000 m. It has also been predicted that sea surface temperature would increase in the range of about 1-3 °C to result in more frequent coral bleaching events and widespread mortality unless there is thermal adaptation or acclimatisation by corals. According to them, many parts of the planet will be warmer, as a result of which droughts, floods and other forms of extreme weather will become more frequent, threatening food supplies. Plants and animals which cannot adjust will die out. Sea levels would rise and will continue to do so, forcing hundreds of thousands of people in coastal zones to migrate. One of the main GHGs which human populations are adding to the atmosphere, carbon dioxide (CO₂), is increasing rapidly. Around 1750, i.e. at the start of the Industrial Revolution in Europe, there were 280 parts per million (ppm) of CO₂ in the atmosphere. Today the overall amount of GHGs has topped 390 ppm CO₂e (parts per million of carbon dioxide equivalent – all GHGs expressed as a common metric in relation to their warming potential) and the figure is rising by 1.5–2 ppm annually. Reputable scientists believe the earth’s average temperature should not rise by more than 2°C over pre-industrial levels. Among others, the European Union indicated that this is essential to minimize the risk of what the UN Framework Convention on Climate Change (UNFCCC) calls as dangerous climate change and keep the costs of adapting to a warmer world bearable. Scientists say there is a 50% chance of keeping to 2°C if the total GHG concentration remains below 450 ppm [37].

6.1 Effects on Sea Level Rise and Inundation of Land

Coastal areas are prone to threats from natural causes such as tidal surges and sea level rise (Fig. 7). Each year an estimated 46 million people risk flooding from storm surges. Coasts in many countries currently face severe problems of sea level rise as a consequence of climate change, leading to potential impacts on ecosystems and human coastal infrastructure. The worst scenario projects                                                               a sea level rise of 95 cm by the year 2100, with large local differences (resulting from tides, wind and atmospheric pressure patterns, changes in ocean circulation, vertical movements of continents, etc.) in the relative sea level rises [24]. The impacts on sea level rise are therefore expected to be more local than global. The relative change of sea and land is the main factor. Many cities, for instance, even suffer land subsidence as a result of ground water withdrawal. This may be compounded with sea level rise, especially since rates of subsidence may exceed the rate of sea level rise between now and   2100. Under the worst scenario, the majority of the people who would be affected in different countries are China (72 million), Bangladesh (13 million people and loss of 16% of national rice production), and Egypt (6 million people and 12 to 15% loss of agricultural land), while between 0.3% (Venezuela) and 100% (Kiribati and the Marshall Islands) of the population are likely to be affected. In India, potential impacts on 1 m sea level rise might lead to inundation of 5,763 km² of land [23]. According to IPCC, regions especially at risk are low lying areas of North America, Latin America, Africa, populous coastal cities of Europe, crowded delta regions of Asia, like Ganges-Brahmaputra delta facing flood risks from both large rivers and ocean storms, and many small islands, whose very existence is threatened by rising seas. In North America, current preparedness for rising seas, more frequent severe weather, and higher storm surges is low.

The Greenland and West Antarctic ice sheets face substantial melting if the global average temperature rises more than ~2 to ~7°F (1 to 4°C) relative to the period 1990–2000—eventually contributing to an additional sea level rise of ~13 to ~20 ft (4 to 6 m) or more. This would result in the inundation of low lying coastal areas, including parts of many major cities. Even more significant than the direct loss of land caused by the sea rising are the associated indirect factors, including erosion patterns and damage to coastal infrastructure, salinization of wells, sub-optimal functioning of the sewage system of coastal cities (with resulting health impacts), loss of littoral ecosystems                                                                            and loss of biotic resources. In coastal areas, and particularly deltas, factors such as modified ocean circulation patterns (and their impact on building and erosion of the

Figure 7. Global average sea level change (Annually and globally averaged sea level change relative to the average over the period 1986 to 2005; sheds  indicate different data sets used. Source: [17]; used with permission)

coast), climate change in the catchment basin and change in coastal climate, not to mention changes in the frequency of extreme events, should be taken into account.

Destruction of habitats in coastal ecosystem is also caused by natural disasters, such as cyclones, hurricanes, typhoons, volcanism, earthquakes and tsunamis causing colossal losses worldwide [50]. The frequency of natural disasters is increasing with time (Fig. 8), predictably due to climate change, as sea level rise also follows almost the similar trend (Fig. 7). Trenberth [36] argues that higher sea surface temperatures in the Atlantic Ocean and increased water vapour in the lower atmosphere—caused by global warming—are to blame for the past decade’s intense storms. These factors are causing significant physical damage to reefs or move large amounts of bottom material, thus altering habitat, biological diversity, and ecosystem function. There is however no denying of the fact that human induced activities are to a significant extent responsible for climate change accelerating the pace of natural disasters with time resulting in such damages to coastal lives and properties.

Figure 8. Trend of change of cyclonic storms, hurricanes and typhoons with time in different oceans in the world [13]

6.2 Effect on Agriculture

Climate change directly affects sensitive sectors like agriculture, forestry and fishery and thereby the livelihoods of millions of coastal communities [33,35]. Wide array of impacts due to climate change on factors affecting food production has been predicted. One could stipulate the following changes in forcing variables as likely to materialize sometime during the next century [4].

·       A gradual, continuing rise in atmospheric CO₂ concentration entail in increased photosynthetic rates and water-use efficiencies of vegetation and crops, hence increases in organic matter supplies to soils.

·       Minor increases in evapotranspiration in the tropics to major increases in high latitudes caused both by temperature increase and by extension of the growing period.

·       Increases in amount and in variability of rainfall in the tropics; possible decrease in rainfall in a band in the subtropics poleward of the present deserts; and minor increases in amount and variability in temperate and cold regions could take place. Peak rainfall intensities could increase in several regions

·       A gradual sea level rise could cause deeper and longer inundation in river and estuary basins and on levee backslopes, and brackish water inundation leading to encroachment of vegetation that accumulates pyrite in soils near the coast

6.2.1               Low lying coastal soils

 The probable effects on soil characteristics of a gradual eustatic rise in sea level will vary from place to place depending on a number of local and external factors, and interactions between them [1]. In principle, a rising sea level would tend to erode and move back existing coastlines. However, the extent to which this actually happens will depend on the elevation, the resistance of local coastal materials, the degree to which they are defended by sediments provided by river flow or longshore drift, the strength of long shore currents and storm waves, and on human interventions which might prevent or accelerate erosion.

6.2.2               Sediment supply and deltaic aggradation

 In major deltas, such as those of the Ganges-Brahmaputra and the major Chinese rivers, sediment supplies delivered to the estuary will generally be sufficient to offset the effects of a rising sea level. Such deltaic aggradation could decrease, however, under three circumstances:

• where human interventions inland, such as large dams or successful soil conservation programmes, drastically reduce sediment supply to the delta, e.g. the construction of the Aswan high dam in 1964 has led to coastal erosion and increased flooding of lagoon margins in the Nile delta [34];

·       where construction of embankments within the delta interrupts sediment supply to adjoining back swamps, exposing them to submergence by a rise in sea level, e.g. embankments along the lower Mississippi river have cut off sediment supplies to adjoining wetlands which formerly offset land subsidence occurring due to compaction of underlying sediments [6]; and

·       ·where land subsidence occurs due to abstraction of water, natural gas or oil, e.g. as is presently happening in Bangkok and in the northern parts of the Netherlands.

6.2.3 Tidal flooding

In coastal lowlands which are insufficiently defended by sediment supply or embankments, tidal flooding by saline water will tend to penetrate further inland than at present, extending the area of perennially or seasonally saline soils. Where Rhizophora mangrove or Phragmites vegetation invades the area, would over several decades lead to the formation of potential acid sulphate soils. Impedance of drainage from the land by a higher sea level and by the correspondingly higher levels of adjoining estuarine rivers and their levees will also extend the area of perennially or seasonally reduced soils and increase normal inundation depths and durations in river and estuary basins and on levee back slopes. In sites which become perennially wet, soil organic matter contents will tend to increase, resulting eventually in peat formation. On the other hand, where coastal erosion removes an existing barrier of mineral soils or mangrove forest, higher storm surges associated with a rising sea level could allow seawater to destroy existing coastal eustatic peat swamps, which eventually may be replaced by fresh or saltwater lagoons.

6.2.4 Subsidence of land

The probable response of low lying coastal areas to a rise in sea level can be estimated on the basis of the geological and historical evidence of changes that occurred during past periods when sea level was rising eustatically or in response to tectonic or isostatic movements, e.g. around the Southern North Sea [18]; in the Nile delta [34]; on the coastal plain of the Guyanas [3] and in the Musi delta of Sumatera [2]. Contemporary evidence is available in areas where land levels have subsided as a result of recent abstraction of water, natural gas or oil from sediments underlying coastal lowlands. Further studies of such contemporary and palaeo-environments are needed together with location specific studies in order to better understand the change processes, identify appropriate responses and assess their technical, ecological and socio-economic implications [41].

6.2.5 Trend in vegetation growth

Some major and widespread soil changes expected as a result of any global change are positive, especially the gradual increases in soil fertility and physical qualities consequent on increased atmospheric CO₂. The increased productivity and water-use efficiency of crops and vegetation, and the generally similar or somewhat higher rainfall indicated by several global circulation models, not fully counteracted by higher evapotranspiration, would be expected to lead to widespread increases in ground cover, and consequently better protection against runoff and erosion [4].

6.2.6 Changes in soil properties

According to Brinkman and Sombroek [4], major but less widespread soil changes, including greater biological activity and increased extent of periodic reduction in soils, would be expected where permafrost would disappear. In unprotected low lying coastal areas, gradual encroachment of Rhizophora mangroves or Phragmites following more extensive brackish water inundation may give rise to the formation of potential acid sulphate soil layers after several decades. Deeper and longer duration flooding of basins and levee back slopes in adjacent river and estuary plains could lead to more extensive reducing conditions and increased organic matter contents, and locally to peat formation.

Other changes due to climate change (temperature and precipitation) are expected to be relatively well buffered by the mineral composition, the organic matter content or the structural stability of many soils. However, decreases in cover by vegetation or annual or perennial crops, caused by any locally major declines in rainfall not compensated by CO₂ effects, could lead to soil structure degradation and decreased porosity, as well as increased runoff and erosion on sloping sites and by the concomitant more extensive and rapid sedimentation. Changes in options available to land users because of climate change may have similar effects [4].

In most cases, changes in soils by direct human action, on-site or off-site (whether intentional or unintended), are far greater than the direct climate induced effects. Soil management measures designed to optimize the soil's sustained productive capacity would therefore, be generally adequate to counteract any degradation of agricultural land by climate change. Soils of these areas, or other land with a low intensity of management such as semi-natural forests used for extraction of wood and other products, are less readily protected against the effects of climate change but such soils too are threatened less by climate change than by human actions - off-site, such as pollution by acid deposition, or on-site, such as excessive nutrient extraction under very low-input agriculture.

To armor the world's soils against any negative effect of climate change, or against other extremes in external circumstances, such as nutrient depletion or excess (pollution), or drought or high intensity rains, the best that land users could do [4], would be:

·       to manage their soils to give them maximum physical resilience through a stable, heterogeneous pore system by maintaining a closed ground cover as much as possible

·       ·to use an integrated plant nutrient management system to balance the input and off take of nutrients over a cropping cycle or over the years, while maintaining soil nutrient levels low enough to minimize losses and high enough to buffer occasional high demands.

6.2.7 Erosion

Coasts are also exposed to increasing risks due to erosion as a result of climate change and sea level rise [17]. It is an important area influenced by the climate change with rising temperatures leading to rise in the sea’s water mass. In India, the mainland consists of 43% sandy beaches, 11% rocky coast with cliffs, and 46% mud flats and marshy coast [27]. The damages caused by sea erosion in different coastal states in India alone show a staggering annual loss of Rs. 3683.87 million (1US$ = Rs. 65). Various preventive and mitigation measures have been suggested and being adopted are:

·       Structural measures such as  construction of sea wall/ revetment, groynes and off-shore breakwater

§  Non-structural/ soft measures such as artificial nourishment of beaches, vegetation cover and sand bypassing at tidal inlets

Government of India provides assistance for protection of vulnerable coastal states from sea erosion mainly through two schemes, namely (i) Centrally sponsored scheme for protection of critical stretches (through state sector), and (ii) National Coastal Protection Project (NCPP) for protection of the maritime states/ UTs with a view to explore possibilities of funding through external resources or other domestic resources. 

7.               DETERIORATING E-FLOWS IN RIVER GANGA: A CASE STUDY

Ghorai and Sen [12], Sen [28], Sen et al. [30] and Sen and Ghorai [31] raised serious concern over deteriorating water flow in the river Ganga through a long stretch of run within India owing mainly to unplanned anthropological factors arising out of scores of hydro-electric and irrigation projects already commissioned and many others in the pipeline on the river in addition to adverse climate change impacts, a typical example risking the coastal ecosystem in the lower delta across India and Bangladesh. The lower Ganga delta of both India (south of Farakka Barrage) and Bangladesh (south-west) share the same ecology and face threats due to dwindling water diversion via Farakka Barrage and deteriorating water quality of the river in the upstream at different places in India. This being a matter of common concern to both countries there is need for a holistic and focused attention for which the following suggestions were made with immediate effect to seek for a lasting solution [31].

·       There appears to be a need for revisiting the design of the Farakka Barrage, as well as the discharge and distribution norms of water in the interest of the two countries, keeping in view the predicted flow of upstream Ganga water in long- term perspectives, and if necessary, fresh norms to be decided.

·       Predicted flow of water through Ganga-Brahmaputra river system on account of retreat of glaciers and other parametric uncertainties due to climate change needs to be refined with appropriate climate models in deciding the future norms for distribution of water via Farakka Barrage with higher precision in different time scales. 

·       Need for fresh installation of hydro-electric power and irrigation projects in India must be given extremely careful consideration with stringent norms for discharge of river water in the upstream so that ecology of the area is not disturbed.

·       Past hydro-electric power and irrigation projects in the upstream already  commissioned need to be reviewed in terms of the norms for discharge of water decided, and if necessary, to be revised, scientifically so that ecology of the area is not disturbed.

·       Provisions should be mandatory to make impact analysis of the discharge of water from different projects, be it hydro-electric power and irrigation projects or any others, on the ecology of the area for all past and future installations in India.

·       Strict administrative vigilance to be maintained to stop acts of unscrupulous diversion of water forthwith by private agencies in India.

·       Location specific integrated water development and management schemes at strategic points over the entire flow length in different time scales to be prepared and their methods of implementation be worked out, with adequate participation and vigilance from the local inhabitants, to ensure maintaining prescribed water quality throughout the year in India.

·       In India, in particular, impacts of the water flow at different strategic points into lower delta in respect of salinity in soil and water, flow rate, tidal amplitude and fluctuations, sedimentation/ hydrological parameters, navigation through rivers, ground water table depths and qualities, all important components of biodiversity, and any other related parameters should be taken up and monitored with a holistic plan, over minimum five year phases, through a central task force comprising of scientists, NGOs, government officials, local inhabitants, and the same placed in public domain. Similar programmes should be simultaneously planned and taken up by Bangladesh. A core team consisting of key members drawn from both countries should interact and monitor the progress once in each year and suggest for improvement with respect to targets fixed.       

      

 Sen and Ghorai [31] have cautioned that the concerned lower Ganga delta of the two countries is largely coastal and therefore fragile in nature subject to the increasing vagaries due to climatic disasters beyond possibly anybody’s control to prevent. Additional factors originating from the deteriorating E-flows of the Ganga river network water contribute significantly further to the woes of the inhabitants of the area. In conclusion, they remarked that there might be no short-cuts to improve the ecology for sustained livelihood of the inhabitants in this area across the two countries other than ensuring E-flows via Farakka Barrage, for which careful considerations must be given to the suggestions made above. It is fortunate to observe that Government of India has of late taken cognizance of the fact in the interest of the country to limit future hydro-electric and irrigation projects in hand although a holistic approach as envisaged is still warranted in the interest of the entire ecosystem.

8.               SUMMARY

Coastal areas with high population density along with potentially high aesthetic benefit supporting human lives and livelihoods, are confronted with high risk factors on a multiple of issues viz., anthropogenic factors, topography and related soil properties, protection measures required to be undertaken, and natural disasters caused by the sea and through its interaction with climate and under-sea tectonic movement of the earth, among the major ones - influencing agricultural production and vulnerability of the ecosystem per se in a related country. The resultant effect is that the livelihood in the ecosystem remains uncertain and the masses remain poverty-stricken in majority of the countries having reasonably large coastal boundaries due to the lack of concerted efforts to address the risk factors and their interactions in a holistic manner. Soil in the coastal ecosystem per se does not have separate significance as far as its productivity is concerned unless it is considered in association with other relevant ecological factors describing the ecosystem. The chapter presents an overview of the distribution of different coastal components in the world along with analysis of relevant risk factors.

The impact of climate change, being a major risk factor, has been discussed as a generic phenomenon and with special emphasis on predictability of sea level rise, oceanic disasters including cyclones, storms, hurricanes, typhoons and inundation of coastal land in different parts of the world. Its role on different aspects in agriculture particularly in low lying coastal lands and on sediment supply and deltaic aggradation, tidal flooding, subsidence of land, and changes in soil properties is also explained. The influence of climate change on erosion of soil in the coastal areas has been discussed along with important structural and non-structural measures suggested. Finally, a case study on deteriorating water flow in the river Ganga risking the ecosystem in lower delta across India and Bangladesh has been discussed and future lines of action suggested.

KEY WORDS

Climate change

Carbon-dioxide

Coastal ecosystem

Delta

Ecology

Erosion

Inundations

Livelihood

Mangrove ecosystem

Nutrient imbalance

Natural disasters

Low lying soils

Risk factors

River Ganga

Sediment supply

Tidal flooding

REFERENCES

1.     Brammer, H. and Brinkman, R. (1990). Changes in soil resources in response to a gradually rising sea-level. In Chapter 12 (Scharpenseel et al., eds.), 145-156.

2.     Brinkman, R. (1987). Sediments and soils in the Karang Agung area. In Some Aspects of Tidal Swamp Development with Special Reference to the Karang Agung Area, South Sumatra Province (R. Best, R. Brinkman & J.J. van Roon, eds.), pp. 12-22. Mimeo, World Bank, Jakarta.

3.     Brinkman, R. and Pons, L.J. (1968). A Pedo-geomorphological Classification and Map of the Holocene Sediments in the Coastal Plain of the Three Guyanas. Soil Survey Paper No. 4, Soil Survey Institute (Staring Centre), Wageningen. 40 p + separate map.

4.     Brinkman. R. and Sombroek, W.G. (2007). The effects of global change on soil conditions in relation to plant growth and food production. (http://www.fao.org/docrep/W5183E/w5183e05.htm)

5.     Coastal Wiki (2008). Polyfluorinated compounds - a new class of global pollutants in the coastal environment. (http://www.Polyfluorinated compounds PFC - pollutants in coiastal water.htm)

6.     Day, J.W. and Templet, P.H. 1989. Consequences of sea level rise: implications from the Mississippi delta. Coastal Management, 17, 241-257.

7.     Dirk, B., Burke L., McManus, J.  and Spalding, M. (1998). In Reefs at Risk: A Map-Based Indicator of Threats to the World's Coral Reefs, World Resources Institute, USA.

8.     Dubey, M. (1993). Population explosion hits coastal ecosystems. (http://www.indiaenvironmentportal.org.in/node/5370)

9.     Duedall, I.W. and Maul. G.A. (2005). Demography of coastal populations, In Encyclopedia of Coastal Science (M. Schwartz, Ed.), 1211p. Encyclopedia of Earth Sciences Series, Springer, The Netherlands. pp. 368-374.

10.  Encyclopaedia Britannica (2009). Mangrove forest: global distribution.  (http://www.britannica.com/science/world-map/images-videos/Major-wetland-areas-and-worldwide-distribution-of-salt-marshes-and/40)

11.  Gedan, B.K., Silliman, B.R. and Bertness, M.D. (2009). Centuries of human-driven change in salt marsh ecosystems. Annual Review of Marine Science, 1, 117-141.

12.  Ghorai, D. and Sen, H.S. (2014). Living out of Ganga: A Traditional yet Imperiled Livelihood on Bamboo Post Harvest Processing and Emerging Problems of Ganga, In: Our National River Ganga: Lifeline of Millions, Rashmi Sanghi (Ed.), Springer International Publishing Switzerland, pp. 323-338. 

13.  Ghorai, D. and Sen, H.S. (2015). Role of climate change in increasing occurrences of oceanic hazards as a potential threat to coastal ecology. Nat Hazards, 75, 1223-1245.

14.  Giri, C., Ochieng, E., Tieszen, L., Zhu, Z., Singh, A., Loveland, T., Masek, J., Duke, N. (2011) Status and distribution of mangrove forests of the world using earth observation satellite data. Global Ecol Biogeogr, 20,154-159.

15.  Goudarzi, S. (2006). Flocking to the coast: world’s population migrating into danger. (http://www.livescience.com/environment/060718_map_settle.html)

16.  IFPRI (2007).  2020 Conference, held at Beizing, China, 17-19 Oct 2007 (http://www.ifpri.org/2020ChinaConference/index.htm)

17.  IPCC (2014). Climate Change 2014. Synthesis Report — Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, R.K. Pachauri and L.A. Meyer (eds.)]. IPCC, Geneva, Switzerland, 151 pp.

18.  Jelgersma, S. (1988). A future sea-level rise: its impacts on coastal lowlands. In Geology and Urban Development, Atlas of Urban Geology, Vol. 1, UN-ESCAP,  61-81.

19.  Minard. A. (2008). Dead zones multiplying fast, coastal water study says. (http://www.Dead Zones Multiplying Fast.htm)

20.  Narragansett Bay Commission. (2009) (http://omp.gso.uri.edu/ompweb/doee/science/descript/asia.htm)

21.  New World Encyclopedia (2008). Estuary (http://www.newworldencyclopedia.org/entry/Estuary)

22.  OzCoasts. (2009). Saltmarsh and Saltflat Areas. (http://www.ozcoasts.org.au/indicators/changes_saltmarsh_area.jsp)

23.  Pacahuri, R.K. (2208^a). Climate change—Implications for India, presented New Delhi, 25 Apr 2008 (http://164.100.24.209/newls/bureau/lectureseries/pachauri.pdf)

24.  Pachauri, R.K. (2008^b). Climate change: what's next? Managing the interconnected challenges of climate change, energy security, ecosystems and water. Presented in International Conference, held at ETH University, Zurich, 6 Nov 2008, (http://www.clubofrome.org/eng/meetings/winterthur_2008)

25.  Portier, R. J. (2003). Trends in Soil Science, Technology and Legislation in the USA. Journal of Soils and Sediments, 3, 257.

26.  Poyya, M. G. and Balachandran, N. (2008). Strategies for conserving ecosystem services to restore coastal habitats. Paper presented in UNDP-PTEI Conference on “Restoration of Coastal Habitats”, held at Mahabalipuram, Tamil Nadu, 20-21 Aug 2008.

27.  SAARC Disaster Management Centre, New Delhi (2009). Coastal & sea erosion. (http://www..saarc.sdmc.nic.in/coast.asp)

28.  Sen, H.S. (2010). Drying up of River Ganga: an issue of common concern to both India and Bangladesh, Curr. Sci., 99, 725-727.

29.  Sen, H.S., Bandyopadhyay, B.K., Maji B., Bal A.R. and Yadav, J.S.P. (2000). Management of coastal agro-ecosystem. In Natural Resource Management for Agricultural Production in India (Eds. J.S.P. Yadav & G.B. Singh), Indian Society of Soil Science, New Delhi, 925-1022,.

30.  Sen, H.S., Burman, D. and Mandal, S. (2012).  Improving the Rural Livelihoods in the Ganges Delta through Integrated, Diversified Cropping and Aquaculture, and through Better Use of Flood or Salt Affected Areas, Lap Lambert Academic Publishing, GmbH & Co. KG, Germany, 61p.

31.  Sen, H.S. and Ghorai, D. (2014). Ensuring environmental water flows in the river Ganga for sustainable ecology in the lower delta across India and Bangladesh. Yojana, 14-19.

32.  Sen, H.S., Sahoo, N., Sinhababu, D.P., Saha Sanjoy and Behera, K.S. (2011). Improving agricultural productivity through diversified farming and enhancing livelihood security in coastal ecosystem with special reference to India. Oryza, 48, 1-21. 

33.  Sinha, S.K. and Swaminathan, M.S. (1991). Deforestation, climate change, and sustainable nutrition security: a case study for India. Climate Change, 19, 201–209.

34.  Stanley, D.J. (1988). Subsidence in Northeastern Nile delta: rapid rates, possible causes, and consequences. Science, 240, 497-500.

35.  Swaminathan, M.S. (1996). Sustainable Agriculture: Towards Food Security. Konark Publishers Pvt. Ltd, Delhi, India.

36.  Trenberth, K. (2005). Uncertainty in hurricanes and global warming. Science, 308, 1753–1754.

37.  United Nations Environment Program (2008). What is climate change? (http://www.unep.org/themes/climatechange/whatis/index.asp)

38.  US Fish & Wildlife Service (2009). Coastal programme (http://www.fws.gov/coastal)

39.  USAID (2007). Estuarine ecosystems. (http://www.usaid.gov/our_work/environment/water/estuarine.html)

40.  Velayutham, M., Sarkar, D., Reddy, R.S., Natarajan, A., Shiva Prasad, C.R., Challa, O., Harindranath, C.S., Shyampura, R.L., Sharma, J.P. and Bhattacharya, T. (1998). Soil resources and their potentials in coastal areas of India. Paper presented in “Frontiers of Research and its Application in Coastal Agriculture”, Fifth National Seminar of Indian Society of Coastal Agricultural Research, held at Gujarat Agricultural University, Navsari, Gujarat, 16-20 Sep 1998.

41.  Warrick, R. and Farmer, G. (1990). The greenhouse effect, climatic change and rising sea level: implications for development. Transaction of Institute Br. Geography, 15, 5-20.

42.  Wikipedia (2015^a). Coastal management. (http://en.wikipedia.org/wiki/Coastal_management)

43.  Wikipedia (2015^b). List of countries by length of coastline. (http://en.wikipedia.org/wiki/List_of_countries_by_length_of_coastline)

44.  Wikipedia (2015^c). Coral reef. (http://en.wikipedia.org/wiki/Coral_reef)

45.  Wikipedia (2015^d). Lagoon. (http://en.wikipedia.org/wiki/Lagoon)

46.  Wikipedia (2015^e). Mangrove. (http://en.wikipedia.org/wiki/Mangrove) 

47.  Wikipedia (2015^f). Macrophyte. (http://en.wikipedia.org/wiki/Macrophyte)

48.  Wikipedia (2015^g). Continental shelf. (http://en.wikipedia.org/wiki/Continental_shelf)

49.  Wikipedia (2015^h) . Ice shelf. (http://en.wikipedia.org/wiki/Ice_shelf)

50.  Wikipedia (2015ⁱ). List of natural disasters by death toll. (http://en.wikipedia.org/wiki/List_of_natural_disasters_by_death_toll)

51.  World Resources Institute (2006). Environment information portal (http://www.Nutrient Overload Unbalancing the Global Nitrogen Cycle.htm)

52.  Zeng, T.Q.,  Peter Cowell, J. and Deanne, H. (2009). Predicting climate change impacts on salt Marsh and mangrove distribution: GIS fuzzy set methods. (http://www.coastgis.org/cgis06/Papers/Zeng_Cowell_Hickey.pdf)