Land degradation in Bangladesh

Land is the basic natural resource that provides habitat and sustenance for living organisms, as well as being a major focus of economic activities. Degradation of land refers to loss of its potential production capability as a result of degradation of soil quality and also its loss for effective use. In Bangladesh, the topsoil degrades due to natural processes and human activities.

 

The functional capabilities of soil deteriorate from activities related to agriculture, forestry, and industry. On the other hand, urban sprawling and infrastructure development cause loss of available land. Natural events such as cyclones and floods cause land loss, and can also deteriorate functional capabilities of soil. Soil degradation in the coastal area results from unplanned land use, as well as intrusion of saline water. Therefore, solving or minimizing land degradation problems should be based on multi-sectored, multi-layered, yet integrated approaches.

 

Bangladesh has a total land surface of 12.31 million hectares, of which presently 7.85 million hectares are under agriculture (BARC 2001). It accommodates more than 130 million people. This amounts to an average of 27 percentile of land and 17 percentile of cultivable land per head. Moreover, due to population growth, this share of land per capita is shrinking every year making the resource base for agriculture, forest and wetlands more vulnerable and marginalized. For example, in 1983-84, there was 20.0 million ha of total cultivable land, which dropped to 17.5 million ha in 1997. On average we are losing nearly 82,000 ha of land each year. This is mainly due to conversion of land into urban, peri-urban, industrial uses, and construction of roads, embankment. Competition between forest and agriculture, fisheries and agriculture are also responsible for some conversions (e.g., Chokoria Sundarban of Cox’s Bazar district and its adjacent areas).

 

Different types of land degradation and their extent in Bangladesh

 

Types of land degradation	Areas (in mha) affected by different degrees of degradation				Total area (mha)
	Light	Moderate	Strong	Extreme
1. Water erosion - Bank erosion	0.1 -	0.3 1.7	1.3 -	- -	1.7 1.7
2. Wind erosion	-	-	-	-	-
3. Soil fertility decline - P deficient (for HYV rice) - P deficient (for Upland crops) - K deficient (for HYV rice) - K deficient (for Upland crops) - S deficient (for HYV rice) - S deficient (for Upland crops) Soil organic matter depletion	3.8   5.3   3.1   4.0   2.1   4.4   4.1   1.94	4.2   3.2   2.5   3.4   5.4   3.3   4.6   1.56	-   -   -   -   -   -   -   4.05	-   -	8.0   8.5   5.6   7.4   7.5   7.7   8.7   7.55
4. Water logging	0.69	0.008	-	-	0.7
5. Salinization	0.29	0.43	0.12	-	0.84
6. Pan formation	-	2.82	-	-	2.82
7. Acidification	-	0.06	-	-	0.06
8. Lowering of water table	-	-	-	-	-
9. Active floord palin	-	-	-	-	1.53
10. Deforestation	-	0.3	-	-	0.3
11. Barind	-	-	-	-	0.773

 

 

The estimates of the extent of land degradation in Bangladesh are that over 6.0 million ha falls below the minimum threshold for sustainable cultivation. In drier parts of Bangladesh, low soil fertility is recognized to be at the root of the land degradation spiral leading to desertification. Land degradation in Bangladesh may be considered as temporary or permanent lowering of the productive capacity of land. Natural processes that lead to land degradation in Bangladesh can be considered part of the ongoing land formation process. During 1983-84 and 1997 period, an 11% decline in total cultivable area, and specifically a 14% decline in cultivated area, has been observed.

 

Further evidence of land degradation is shown on satellite imagery which indicates a definite change in vegetation cover and soil moisture through many of the western regions of Bangladesh including Rajshahi, Kushtia, northwestern Jessore, Pabna, western Bogra and southern Dinajpur. These affected areas are known as the Barind Tract, a largely monocultural area with shrinking wetlands, notably the Chalan Beel wetlands. Human intervention from densely populated adjoining regions (around the national average of 900 persons per km2) makes these areas vulnerable.

 

The land degradation section of this chapter deals with causes of land degradation, both in terms of deterioration of soil quality and loss of land. It also highlights state and impacts of degradation, along with policy and program responses. There are several issues related to land degradation that intersect with other concerns.

 

Pressures
There are many driving forces compelling people in Bangladesh to over-exploit natural resources like land. The main ones are the poverty with rapid population growth, improper land use, absence of a land use policy, and ineffective implementation of existing laws and guidelines. Unplanned agricultural practices, and encroachment on forest areas for agriculture and settlements, also put pressure on scarce land resources. Unplanned or inadequate rural infrastructure development and the growing demands of increasing urbanization are also devouring productive land. The level of landdegradation and its extent vary seasonally and yearly, by region, as well as the pressures on land are not always the same either. Natural processes that lead to land degradation in Bangladesh can be considered part of the ongoing land formation process.

 

The upliftment and deposition processes that led particularly to formation of land in the regions of Sylhet, Chittagong, Barind and Madhupur continued during the period of the Miocene, Pliocene and Pleistocene ages. Throughout the Pleistocene time up to the present, the rivers have been depositing heavy sediments to build up the country’s flat alluvial plain, although the processes of erosion and deposition have not been similar all along. There are a few studies on recent sedimentation and erosion that show these processes have been aggravated by human interventions such as encroachment for settlement and improper agricultural practices. Land degradations caused by nature are often balanced by formations of new land. Deterioration of soil quality and land loss due to human intervention may not always be reversible. If the pressures on land are considered in a regionwise manner, the following picture emerges: Land degradation in the Chittagong Hill Tracts (CHT) is occurring mainly due to rapid changes in demographic patterns, development of roadways and other physical infrastructure.

 

Jhum cultivation, the traditional community-based agricultural method practiced by the indigenous people of the CHT, is one of the major causes of land degradation. The Madhupur forest area has almost been denuded due to deforestation and has further been aggravated by many other factors such as its closeness to the capital city, improvement of road communication leading to displacement of population, urbanization and industrialization. This land, a Pleistocene terrace, is naturally raised and flood-free, therefore, it is attractive for infrastructural development.

 

The land in the area has further been degraded by the development activities related to building of the Jamuna Multipurpose Bridge. Land degradation in the Barind Tract is caused mainly due to over exploitation of biomass from agricultural lands and unscientific cultivation of HYV rice through groundwater irrigation. The process has been aggravated by irregular rainfall; and insignificant water flow in the adjacent rivers that normally play a vital role in replenishing soil fertility and recharging groundwater. Degradation of soil quality in the floodplains is mainly attributed to improper use of chemical fertilizers and pesticides to boost agricultural production. Siltation in the floodplains also contributes towards degradation of land due to flashflood and sediments accumulated from riverbank erosion. Dispersed industrial growth and uncontrolled discharges of their untreated effluent in the nearby rivers deteriorate the quality of land and soil.

 

Land degradation in the coastal areas of Bangladesh is a result of recurring cyclones and storm surges, which inundate the land. Practice of shrimp cultivation round the year is ultimately increasing the salinity of the degraded soil. Intrusion of saline water in the dry season is attributed to the low flow in the river system. Human interference and waterborne action are the two most important land degradation processes in Bangladesh. Table 1.1 presents driving forces and pressures, state, impacts related to land degradation
and responses to address the problems.

 

Table 1.1 Pressures, State, Impacts and Responses of Land Degradation

 

Human Activities
Improper Cultivation in Hill Slopes, Terrace Land and Piedmont Plains Shifting cultivation on the hills, locally known as “Jhum”, is a common practice among the tribal communities in the greater Chittagong Hill Tracts. Traditionally Jhum cultivation is a slash-and-burn process where a certain area is cleared and cultivated for 1-2 years, and then abandoned for 5-12 years until the natural fertility of the soil is regained to a useful economic level. In the recent years this traditional agricultural practice is considered as the most inefficient way of using the rich forest lands. Due to increase in the number of population in the CHT region there is a demand on agricultural production, which is putting pressure on cultivable land. As a result, the traditional regeneration time is not being allowed, and the soil is loosing its fertility.

 

Land degradation (soil loss) due to shifting cultivation

Location	Predominant slope	Soil loss (t/ha/yr)
Khagrachari	60% area under 60% slope	10.10- 67.00
Manikchari	46% area under 40% slope	12.00 – 120.00
Ramgarh	48% area under 40% slope	7.00 – 27.00
Rangamati	53% area under 40% slope	26.00 – 68.00
Raikhali	49% area under 40% slope	53.00 – 27.00
Bandarban	58% area under 60% slope	8.00 – 107.00
Teknaf	56% area under 20% slope	-

 

 

Clearing of natural vegetation for cultivation of pineapple, ginger and turmeric along the slopes has an ill effect, which increases soil erosion in the Sylhet and in the hilly areas of Chittagong. These lands after 5-7 years of cultivation by this method totally degrade to an almost irreversible state, to the extent that it becomes practically unfit for further generations. Rubber plantations on more than 70 per cent of the slopes of Sylhet and Chittagong hills, leads to severe landslides during the heavy monsoon period. The population pressure and scarcity of agricultural land has caused a heavy influx of settlers from the plainlands to the unprotected forestlands of Madhupur and Barind tracts and also to the northern piedmont plains. The topsoil of all these areas is either laid over infertile loamy soils of shallow depth or over heavy compact clays. Clearing of forestland for settlements and unscientific land management for agricultural use accelerate erosion of the topsoil with the runoff from high monsoon rain. In addition, the infertile heavy compact clay is exposed to the surface as a result of the removal of topsoil.

 

Faulty Irrigation
The availability of irrigation water can be a blessing or a curse depending upon how it is used. During the Fourth Five Year Plan (FFYP, 1990-94) a tremendous increase was made in the installation of Shallow Tubewells (STWs) and Deep Tubewells (DTWs) for groundwater irrigation. Most of this irrigation water is being used on relatively impermeable highlands of piedmont plain, meander floodplain and in terrace areas. A very small area is being irrigated in the haor basins by this irrigation system. In the highlands, the cropping pattern is mostly transplanted HYV Boro/Aus followed by rain-fed transplanted Aman, but in the basins broadcast Aman is grown followed the HYV Boro/ Aus varieties. As a result of this irrigation, the land remains inundated in most of the seasons, which keeps an adverse effect on soils because of continued oxygen deprivation in the sub-soils. Chemical changes of soil material forming toxic compounds for plants and constant percolation loss of essential nutrient elements including micronutrients and organic matter.

 

Imbalanced Fertilizer Use
The use of chemical fertilizers is directly linked to farming in irrigated lands. Three types of fertilizers such as Urea, Triple Supper Phosphate (TSP) and Muriate of Potash (MP) and four types of pesticides are commonly use in Bangladesh, which are insecticides, herbicides, fungicides, and rodenticides. The use of nitrogenous fertilizer alone accounted for about 67 per cent of the total fertilizer use, which rose to 88 per cent in 1995. Although there was no significant increase of total chemical fertilizer application. However, significant increase has been observed in use of pesticides, which has serious implication to quality of land and ecosystem.

 

Ploughpan
Transplanted rice covers the widest cultivated areas of Bangladesh, and is grown on medium
highlands and medium lowlands. The soils are puddled in a wet condition for easy transplantation and to prevent percolation loss, but this destroys the soil structure. As a result of ploughing in wet condition, a compact 3-5 cm ploughpan is formed from the pressure of the plough, as well as from the pressure during the transplantation of seedlings. This ploughpan impedes soil drainage, restricts root penetration to deeper levels and the movement of soil moisture from subsoil to the topsoil during the dry season. The resultant loss of soil structure makes the topsoil water resistant and hard, which makes tillage difficult and often makes it unfit for cultivating Rabi crops. Some people argue that if this compacted ploughpan method is not used, transplantation of rice will be affected, but this has not been shown to be true except in the shallow valleys of Madhupur and Barind tract.

 

Improper Use of Pesticides
Farmers of Bangladesh are using pesticides since 1957 and at present on an average of 12-15 thousand tons of pesticides is used every year. Insecticide accounts for about 90 per cent of the total consumed pesticide, and is used most for cultivating vegetables and Rabi crops. Although pesticides are used at low levels still they are a cause of land degradation. The pesticides sprayed over standing crops ultimately contaminate the surrounding soil. Research findings show that pesticides applied at the rate of about one kilogram per hectare contaminates the topsoil to a depth of about 30 cm. The pesticides not only destroy harmful insects, but also destroy useful topsoil microbes, which eventually reduce the biological nutrient replenishment of the soil.

 

Over Exploitation of Biomass from the Agricultural Fields
One of the most important causes of land degradation specifically in the Barind tract, is over exploitation of biomass from cultivated fields. The acute energy crisis in various areas leads to all available vegetation being scavenged for firewood and fodder. Due to the reduction of vegetative cover from this withdrawal of biomass silty loam topsoil over low permeability compact heavy clay is lost and topsoil gets inadequate water conservation capability. Therefore, there is considerable runoff due to heavy rainfall during the monsoon. This process of land degradation is also common in other highland and medium highland areas.

 

Unplanned Rural Infrastructure (Road, Embankment, FCD/I)
The rural roadways of the country have been constructed under Upazila or District programs through Upazila or Union Parishads (local level government). Therefore, the road alignment was subject to the influence of local politicians and influential people. A noteworthy feature of this alignment is that it follows the boundaries separating agricultural lands, rather than cutting through them. As a result, the actual length of the roads is often much longer than needed. A significant part of the roadways constructed under the rural road network program fall within the floodplain, with a view to easy road communication during the monsoon season between village to village, villages to markets and villages to some industrial units. Therefore, the road heights had to be kept above flood level, for which a significant portion of agricultural land was acquired for the roadway and the borrow pits along the sides of the roads. The main objectives of the development of flood control drainage and irrigation are to reduce flood hazard, facilitate agricultural productivity and the livelihood of rural households.

 

Urbanization
Urban development is necessary for economic growth, but the present process of urbanization in Bangladesh invariably reduces the amount of good agricultural land. Dhaka city has been growing at the expense of what were dense jackfruit and mango orchards in Savar, Gulshan, Banani and Uttara areas. The expansion of Khulna is reducing the coconut plantations of Phultala and Abhayanagar. These lands were not only good for horticulture, but also for Aus, Transplanted Aman, sugarcane and all kinds of dry land crops. The rapid urban growth of the past two decades has mainly affected potentially triple croppable highlands.

 

Brickfields and Biomass Use
Brick making is a dry season activity that can be started as soon as the monsoon rain stops.
Unfortunately, brick kilns are mostly situated on good agricultural land as brick manufacture needs silty clay loam to silty clay soils with good drainage conditions, which is turning good agricultural land into unproductive lands. Brick kilns are spread all over the country, and are degrading land. Moreover, over 50 per cent of the energy used for firing bricks comes from biomass.

 

Unplanned Industrial Development
Unplanned industrial development is of concern because it often encroaches on fertile land, and industrial effluents not only deteriorate the quality of soils but also affect fisheries. Despite the low level of industrialization, there are many pockets where effluent discharge cause serious harm to crops and fisheries. The rivers Sitalakhya, Buriganga, Karnaphuli and their banks are some of the many examples. There are areas of damage around or downstream of industrial units. Vast effluent discharge by ships has been identified as a major cause of pollution in the Passur river downstream of Mongla port. This has affected both forest and coastal lands in the Sunderbans.

 

In addition to polluting both water and land, most industrial units have acquired or bought more land than is required. This can be seen in all the district industrial estates, for example, on the other side of the Sitalakhya river along the Dhaka-Chittagong road. In Khulna, a big area has been acquired and part of it has been utilized for industrial units and part remains unutilized. Planned industrialization and land zoning would be appropriate measures to combat this type of
land degradation.

 

Mining of Sand and Gravels from Agricultural Land
Mining of sand from agricultural land is common along the eastern side of the Dhaka-Chittagong road, from Comilla to near Sitakunda, and in the northern piedmont areas of northern Netrokona District. Farmers tend to enjoy the immediate monetary benefit and lease out their land for extracting sand, which is used in glass manufacturing industries or as building material. First, 2-3 feet of topsoil are removed from the land and dumped anywhere available near the site. Sand is extracted to a greater depth. Once the sand is extracted, the new tenant abandons the site and no one is responsible for making the land productive again.

 

The damage is two fold - the land purchased for dumping topsoil is used unproductively, and the land from where sand is extracted remains unutilized for many years. Extraction of pebbles from 2-3 feet below the surface of agric ultural land is a common phenomenon in the northern part of greater Dinajpur and Rangpur Districts. There are many similar examples of wasteful use of land by businessmen. Farmers lease out or sell their land at higher prices for immediate gain, but in fact a portion of farmland is lost from their descendents, and eventually there is an environmental loss to the nation.

 

Land Ownership and Tenure
The present land tenure and commercial approaches do not provide security to farmers. Since Bangladesh is mostly an alluvial delta, there are land formations of different ages from very recent to old alluvium. Soil improvement for sustained crop production in new alluvial land is a long-term process. But the short-term leases that are common do not provide an incentive to farmers to engage in long-term land improvement. There are many other such related problems. Big farmers cannot manage all their parcels of land by themselves. Therefore, in almost all cases owners retain the irrigable lands (even if they cannot manage them all themselves) and lease out the relatively less productive, non-irrigable land. The practice has two adverse effects on agricultural land. Firstly, the landlord’s attitude that the land is less valuable has a negative effect psychologically on the sharecropper in terms of management of the land. Secondly, the sharecropper calculates his short-term benefit when farming the land, rather than thinking of the future for making the land more productive than its present state.

 

Riverbank Erosion and Sedimentation
The most devastating form of waterborne land degradation in Bangladesh is riverbank erosion. Theactive floodplains of the Ganges, the Brahmaputra- Jamuna, the Tista and the Meghna rivers are most susceptible to riverbank eros ion. Moreover, small rivers, particularly in eastern Bangladesh, also erode land, although to a relatively lesser extent than the big rivers.

There are many factors that may be responsible for riverbank erosion. The unique, natural geographic setting, the behavior of an alluvial channel, together with characteristics of the tropical monsoon climate, are mainly responsible for these ravages. An enormous volume of water comes from the melting of ice in the Himalayan range. Besides natural processes, human activities both up and downstream, mainly irrational use of forest and other natural resources, cause further deterioration of the situation. The whole combination of factors creates an ideal situation for producing devastating floods, which cause bank erosion and sedimentation.

 

In the southern part of the country, the riverbank erosions are also severe. Hatia, Sandwip and Bhola islands are severely prone to recurrent bank erosion. The amount of water and sediment carried in the Ganges-Brahmaputra-Meghna (GBM) river system is given in detail in the Water Pollution and Scarcity sections of the report.

 

Deposition of Sandy Over-wash on Agricultural Land
Deposition of sandy materials on agricultural land is frequent in the lower part of the piedmont areas of greater Mymensingh and valleys of Sylhet and Chittagong Hill Tracts. This is the net result of deforestation in the hills of the upper catchment areas. During the monsoon season, when heavy rainfall occurs in the upper hill areas, it causes flash floods in the lower plains. With the runoff, the water carries sandy sediments that spread over agricultural lands. In the areas of the lower foothills, deposits of sandy materials go up to even a few meters, which compels farmers to abandon such land for agriculture purposes.

 

Land degradation by deposition of sandy materials on agricultural land also occurs when there is a breach of embankments and the materials spread over adjoining agricultural land. This kind of local land degradation often occurs in many riverbank embankments, in the Flood Control and Drainage (FCD) and Flood Control Drainage and Irrigation (FCDI) projects. Many of the Flood Control projects that could not be completed in time resulted in spillover from unfinished polders onto adjoining fields during the monsoon season.

 

Salinity
Land with saline soil occurs in the young Meghna estuary floodplain and in the southern part of the Ganges tidal floodplain. Salinity in the coastal areas developed due to continuous accumulation of salt from tidal flooding and salt removal by leaching or washing by rain or inadequate freshwater flushing. Salinity during the dry season mainly develops from the capillary rise of brackish groundwater to the surface. Total salt affected area of the coastal area is 0.83 million hectares.It is reported that upstream withdrawal of the Ganges water has significantly reduced the freshwater discharge, and hence salinity is encroaching gradually deeper into the mainland. As a result, farmlands are being degraded by increased salinity, non-availability of groundwater for irrigation, industry and domestic need.

 

Soil salinity distribution from August to April

 

	Area under different soil salinity class (in
Month	thousand hectares)
	S0	S1	S2	S3	S4
August	287.4	426.4	75.8	41.9	2.0
September	258.6	433.9	93.1	45.9	2.0
October	244.3	426.9	110.4	47.9	4.0
November	215.5	391.7	170.4	45.9	11.0
December	201.2	406.0	162.4	51.9	12.0
January	201.2	384.7	179.8	55.8	12.0
February	172.4	413.5	175.8	57.8	14.0
March	115.0	428.3	210.5	63.8	16.0
April	0.0	287.4	426.4	79.8	39.9

 

Source: Bangladesh:State of the Environment 2001

 

 

About 6.0 M ha, or 43% of the total geographical area is affected by various forms and degree of degradation. About one fourth of the total cultivable land is affected by drought in every year with different intensity. The recovery of such land depends upon its resilience, which, however, may be lost completely if the land is not treated in time with care.

 

Frequent droughts, through its short-lived but recurrent stress, can aggravate the adverse impact and, if not checked properly, can interfere with the natural capacity of land to recover and advance the process of desertification. Agricultural intensification and the increase in irrigated area have led to a number of environmental problems i.e., loss of bio-diversity through the conversion of forest land into agricultural land; abandonment of many indigenous crop varieties in favour of HYV 's leading to irreversible loss of the country's genetic resources; depletion of soil nutrients and organic matter due to intensive cropping; and deprivation of soil from organic content due to use of crop residue as fuel.

 

Summary of estimates of the cost of land degradation in Bangladesh

 

Nature of degradation	Physical quantity of lost output In mt/yr	Taka equivalent / yr (million)	Cost(million) US$/yr	Remarks
Water erosion	Cereal production loss  = 1.06 Nutrient loss                = 1.44	6613.84   25576.46	140.72   544.18
Fertility decline	Cereal production loss  = 4.27 Addl. Inputs                = 1.22	26641.48   21668.88	566.84   461.04
Salanization	Total production loss  = 4.42	27577.25	586.75
Acidification	Total production loss  = 0.09	561.51	11.95
Lowering of water table	-	-		Not assessed
Water logging	-	-		Not assessed

 

Other environmental degradation includes loss of wetland habitats through abstraction and drainage resulting in depletion of aquatic fauna and flora and reduction in water availability to the rural population, increased use of agro-chemicals raising the pollution potentials of surface and ground water.

Source: Bangladesh: State of the Environment 2001, MoEF