Introduction:

A healthy environment is mandatory to for the survival of living things. Without a healthy environment non-living things also can’t exist. To have a healthy environment, a balanced ecosystem is essential. Without a balanced ecosystem, healthy environment is not possible. An ecosystem is a geographical area of a variable size where both living and non-living settings co-exist, interact & affect one another. Ecosystem encompasses all the parts of a living environment, including the plants and animals, and the non-living components, such as water, air and solar energy. Ecosystems can vary greatly in size. Some examples of small ecosystems are tidal pools, a home garden, or the stomach of a cow. Larger ecosystems might encompass lakes, agricultural fields, or stands of forests. Landscape-scale ecosystems encompass larger regions, and may include different terrestrial (land) and aquatic (water) communities. Ultimately, all of Earth's life and its physical environment could be considered to represent an entire ecosystem, known as the biosphere.

Entities of the ecosystem:

An ecosystem is based on two entities. One is living things and another is non-living things. Living things are plant, human being, animals and insects. And non-living things are land, water, temperature, air, rock, solar energy. We can divide the entities of ecosystem in 4 parts.

• Hydrosphere (water)
• Lithosphere (rock & soil)
• Atmosphere (air)
• Biosphere (human & other living organism)

Biosphere can be divided into two parts:

1. Producers are autotrophic photosynthetic organisms. They can produce their own food. In terrestrial ecosystems, producers are predominantly green plants but inn freshwater and marine ecosystems, dominant producers are algae.
2. Consumers are heterotrophic organisms that depend on producers for food. Among 4 types of consumers herbivores feed directly on green plants which are primary consumers. Carnivores feed on other animals and are secondary or tertiary consumers. Omnivores feed on both plants and animals; for example, humans eat both leafy vegetables and beef. Decomposers are organisms of decay and they are mostly bacteria and fungi.

There are some cycles in ecosystem. Without those cycles ecosystem will collapse. Those cycles are:

• Oxygen Cycle
• Hydrological Cycle
• Nitrogen Cycle
• Phosphate Cycle
• Biogeochemical cycle

If single of these cycle breaks down, whole ecosystem will break down.

Energy Flow and food chains in ecosystem:

The sun is the ultimate source of energy for nearly all life. From solar energy producers makes food and this energy flows to others by food chain & food web. Food chains indicate who eats whom in an ecosystem. It represents one path of energy flow through an ecosystem. Ecosystems have numerous interconnected food chains. In a food chain, each level of producer and consumers is a tropic level. Some primary consumers feed on plants and make grazing food chains; others feed on detritus.

Ecosystems in Bangladesh:

Ecosystem of Bangladesh includes all living & non-living things like people, animal, forest, land, river, Bay of Bangle. Bangladesh has a great ecosystem as its floodplains form one of the world's most important wetlands. These wetlands are home to hundreds of species of unique plants, fish, birds and other wildlife. People of Bangladesh are also dependent on these wetlands. These wetlands provide critical habitat for migrating birds and most importantly a source of income and nutrition for millions of people in Bangladesh. The floodplain fishery plays a vital role in cushioning rural poverty and supplying animal protein to the poor and is an integral part of the culture and lifestyle of the Bengali people.

Different ecosystems of Bangladesh:

Ecosystem of Bangladesh can be divided into three types. Three types of ecosystem are:

• Aquatic Ecosystem
• Soil Ecosystem
• Forest Ecosystem

Aquatic Ecosystem:

Bangladesh is a country of river. It has more than 300 rivers. Beside, lots of ponds exist in land area. Again it’s located by the side of Bay of Bangle. That means Bangladesh has a rich aquatic ecosystem. We can divide aquatic ecosystem of Bangladesh into two. They are:

1. Marine
2. Fresh water

Marine ecosystem of Bangladesh:

The location of the landward boundary of the coastal zone is a function of three basic geophysical processes: tidal fluctuations; salinity; and risk for cyclone and storm surges. The coastal zone of Bangladesh, affected by these processes, covers an area of 47,201 km, or 32% of the country, being the landmass of 19 districts. Around 35 million people, representing 29% of the population, live in the coastal zone. Many of the coastal inhabitants are poor, and the population is exposed to both natural disasters and man-made hazards. Climate change and sea-level rise, induced by global warming, also compromise the ecological stability of the coastal zone.

The coastline is 710 km long, composed of the interface of various ecological and economic systems, including mangroves, estuaries, islands, accreted land, beaches, a peninsula, rural settlements, urban and industrial areas, and ports. The territorial, contiguous and exclusive economic zones extend 12, 18 and 200 nautical miles respectively out into the Bay of Bengal. The continental shelf reaches a breadth of 350 nautical miles. It is characterized by low salinity; predominantly muddy, sandy or muddy-sand bottom conditions and high freshwater and sediment discharge. So far, 475 fish species of 133 genera, 5 spp. of marine turtles, 24 shrimp spp. of 5 families, 50 spp. of crabs, 301 spp. of marine mollusks, and some 20 spp. of seaweed have been recorded here. However, the ecology and distribution of most of these species are almost unknown.

Lentic water ecosystems (standing water) cover around 3% of the coastal zone area. In combination with lotic water systems (running water), they support an extremely rich and diverse fish fauna: 260 spp. of indigenous freshwater, bony fish belonging to 145 genera and 55 families have been recorded so far. In addition, these ecosystems support a very large population of commercially important freshwater shrimp.

Freshwater:

Bangladesh is a land of river. It was more than 300 rivers and lots of ponds. So it has a large freshwater ecosystem. We can divide freshwater ecosystem of Bangladesh in three basic types:

• Lentic: slow-moving water, including pools, ponds and lakes.
• Lotic: rapidly-moving water, for example streams and rivers.
• Wetlands: areas where the soil is saturated or inundated for at least part of the time.

The majority of the natural ecosystems of Bangladesh are wetlands. Intricate networks of rivers that drain into and inundate Bangladesh have created many riverine ecosystems in the country. The haors in the north-eastern parts of Bangladesh are probably the most complex of seasonally inundated wetlands. They switch between a vast basin of water during the monsoon and a well-networked system of smaller wetlands including biecls and khals in the summer. Surface water is the most severely impacted natural resource in the country.The haor basin is known for its rich biodiversity. There is little doubt that the seasonally inundated wetlands are amongst the most productive ecosystems. Among the whole haors are Considering the ecological value of the haor, the Tanguar haor has been declared a Ramsar site and an Ecologically Critical Area. The largest haor in the country is Hakaluki Haor, which extends over 18,000ha during the rainy season, and consists of more than 80 inter-connected beels. The rich fish resources of Hakaluki support one of the largest inland fisheries in the country. Tanguar is an important “mother fisheries area”, where many species breed during the rainy season.

Soil ecosystem in Bangladesh:

Before knowing about the soil ecosystem we should know about what is soil. Soil is the product of organism and climate acting on rocks. It is a complex, intimate mixture of minerals, organic matter, and organisms. Many kind of organisms (e.g. plants, microbes, vertebrate and invertebrate animals) are part of soil ecosystem. Plants are the ultimate source of carbon, which is a critical structural component of soil and source energy fueling the processes that occur with in the soils. Understanding the role of the soil in the farm ecosystem, knowing how to manage the land, are critical and difficult tasks facing the organic farmer.

Soil ecosystem of Bangladesh refers to the micro animals live in the soil and how they interact themselves. In undisturbed soil, leaves and other organic debris accumulate on the where they broken down by the decomposers. Aerobic bacteria and certain small animals begin the process. These organisms are joined by fungi, mites, springtails, small insects, other arthropods and earthworms assist the process by consuming, mixing and transporting materials. Biological activity is greatest when the soil is worm. Rhizophere organisms like plants roots leak or exude a large number of organic substances and continually slough off root caps into the soil. The most group of larger soil organisms are earthworms. Earthworm performs the final task of mummification the conversion of decomposed organic matter to stable human colloids. In the process of borrowing, earthworms mix the subsoil with the topsoil and deposit their nutrient-rich castings on or near the soil surface. The presence of a large earthworm population indicates good soil fertility. Mites are the most abundant of the soil arthropods. Most mites are beneficial, feeding on micro-organisms and other small animals.

Forest ecosystem in Bangladesh:

A forest ecosystem is a natural unit consisting of mostly plants, animals and micro-organisms in forest area and functions together with all of non-living physical factors of the environment. Logically, trees are an important component of forest research but the wide variety of other life forms and abiotic components in most forests means that other elements, such as wildlife or soil nutrients are often the focal point. Among forest ecosystems of Bangladesh, Sundorban is major. The Sundarban, covering about one million ha in the delta of the rivers Ganga, Brahmaputra and Meghna at the point where it merges with the Bay of Bengal, is the single largest block of tidal halophytic mangrove forest in the world shared between Bangladesh (62%) and India (38%), which supports a large, biodiversity-rich unique ecosystem. With its array of trees and wildlife the forest is a showpiece of natural history. It is also a center of economic activities, such as extraction of timber, fishing and collection of honey. The area of Sundarban experiences a subtropical monsoonal climate with an annual rainfall of 1600-1800 mm and severe cyclonic storms. Enormous amount of sediments carried by the three rivers contribute to its expansion and dynamics. Salinity gradients change over a wide range of spatial and temporal scales. The Sundarban is intersected by a complex network of tidal waterways, mudflats and small islands of salt-tolerant mangrove forests, and presents an excellent example of ongoing ecological processes. The area is known for its wide range of flora and fauna. The most famous among these are the man-eating Royal Bengal Tigers, but numerous species of birds, spotted deer, crocodiles and snakes also inhabit it. The mangroves have been extensively exploited over centuries for timber, fish and prawns, honey, fodder, or converted for paddy and aquaculture and now it faces the serious challenges for its existence. Javan rhino, wild buffalo, hog deer, and barking deer are already extinct from the area. While conservation efforts have focused on wildlife, particularly tiger, through creation of several sanctuaries and a biosphere reserve, reduced freshwater inflows are a serious threat as salinity is rising. Heritiera fomes (from which Sundarban derives its name), Nypa fruticans and Phoenix paludosa are declining rapidly.

Ecosystem of urban area:

An ecosystem of urban society consists of several species. Cities are embedded in a larger ecosystem. But like any life supporting system; a city must need basic ecosystem needs. This is accomplished through the connections between city and surrounding environments. Ecosystem of big cities in Bangladesh like Dhaka, Chittagong, Sylhet, Rajshahi includes its population, ponds & rivers, roads & highways, offices & factories, transport and other facilities. People from these areas depend mostly on rural ecosystems for food & other daily necessaries. People from different part of the country come to these areas. Demand for food & housing is increasing. That’s why lots of skyscrapers are being built. As a result quantity of forest area & aquatic area like ponds & rivers are being destroyed.

Ecosystem of rural area:

In rural area of Bangladesh like northern part of the country & other village are totally different from town area. Rural area ecosystem includes its population, fields, plants, cannels & ponds and other biotic and abiotic factors. People in these areas produce food and other crops and supplies the excess of their need. People of rural area mostly depend on agriculture & faming. They destroy forest in order to make house and collect fuel. They also destroy bio-diversity by hunting wild life. Farmers use pesticides that enter in & pollute the environment.

Ecosystem: State of equilibrium ???

If we look see the whole scenario of ecosystem in Bangladesh, we will find a misbalanced situation. People are migrating to cities more and more. But cities don’t have enough ability to provide shelter, food & cloth. As a result skyscrapers and slums are being made. Also cities can’t provide everyone’s livelihood. As a result number of crime is increasing. People are becoming more dishonest. So a particular class of people is becoming rich. They don’t care other people. Again number of factories & vehicles are increasing. These factories & vehicles increase carbon-di-oxide in atmosphere. As a result temperature is getting high.

In rural area, ecosystem is not in balance too. Number of land is becoming less. Productivity of land is going down. People are cutting down the forests. The nestling place of bird & living place of wildlife are being destroyed. Many species have already faced extinction. Many more species are on the way to extinction. Chemicals and pesticides that are used in agriculture contaminates with river & pond water. As a result water gets polluted and people suffer from different disease and often die if they use polluted water.

Climate of Bangladesh is changing. It’s becoming a threat to us. Most damaging effects of climate change are floods, salinity intrusion, and droughts that are found to drastically affect crop productivity almost every year. Due to climate change, fresh water will become scare, sea water level is rising, river banks are wearing down, chance to earthquake have increased.

Considering all these factors, we can say that ecosystem in Bangladesh is not in state of equilibrium.

Conclusion:

It is well recognized to both the scientific and negotiating community that Bangladesh would be one of the most adversely affected country to climate change. Low economic strength, inadequate infrastructure, low level of social development, lack of institutional capacity, and a higher dependency on the natural resource base make the country more vulnerable to climate stimuli (including both variability as well as extreme events). That’s why we need to restore the state of equilibrium in our ecosystem. State of equilibrium in ecosystem is needed to have a healthy environment and sustainable future. We can do restore the state of equilibrium in our ecosystem by doing followings:

• Ensuring sustainability
• Having stewardship
• Using sound science

The ecosystem concept is the heart of managing sustainability. When we try to safeguard species or manage living resource so that they are sustainable, we must focus on the ecosystem and make sure that it continues to function. The strategic goals and objectives of future coping mechanisms are to reduce unfavorable effects of climate change including variability and extreme events and promote sustainable development. Future coping strategies and mechanisms are suggested based on existing process and practices keeping main essence of adaptation science which is a process to adjust with adverse situation of climate change. Sharing knowledge and experiences of existing situation is a great way for stewardship. Development of techniques for transferring knowledge and experiences from one area/ecosystem is also necessary. If stewardship & application of science doesn’t work together, it’s not possible to make future sustainable and restore state of equilibrium in ecosystem.