Global Warming and Its effect in Bihar

Annual Conference 2007, Royal Geographical Society, London Session key: CCRG-session 2
29-31 August, 2007 Paper-2

GLOBAL WARMING AND CHANGING LAND USE PATTERNS IN BIHAR PLAINS, INDIA

Nupur Bose1, A.K.Ghosh2. K.R.P.Singh3, Rajiv K.Sinha4
1Department of Geography, A.N.College, Patna, India
2 Department of Environment and Water Management, A.N.College, Patna
3 remote sensing Application Centre, Patna, India
4 Department of Environmental Engineering, Griffith university, Brisbane, Australia


ABSTRACT-
The densely populated fluvial plain of Bihar is sustained by its agro-based economy. Its land use patterns are largely determined by its abundant fresh water resources augmented by monsoon rainfall. This study was aimed to find the quantum of changes in land use in the region, and identifying the visible, recorded physical causes for these changes. The methodology was based on image processing techniques of IRS-WiFS Sensor satellite imageries of March 1984 and December 2004. Comparative analysis of areas under major land use types was done. References of topographical sheets were obtained to corroborate the findings with ground realities. There was significant reduction in areas under crop cultivation and wetlands, while forest and plantation cover increased by almost 20%. Fallow lands registered a sharp increase. Sandy stretches, bereft of any significant plant cover, also had larger areal spread. The study revealed concomitant reductions in spatio-temporal surface water configurations and sharp recession of Himalayan ice cover within the time span of eighteen years. Though neotectonics have been attributed to changes in the river flow systems, the stark evidence of global warming in the form of gradual shrinking of the perennial sources of water of the region's drainage system cannot be ignored.


INTRODUCTION-
In Bihar, rapid changes in surface water bodies and channel flows have been noted on two satellite imageries obtained in the spring season, covering a time span of last two decades. There are contradictory trends in eastern and western parts of the state - the former showing expansion of surface water and the latter revealing rapid shrinkage of the same. Corresponding changes in seasonal land use indicate the increasing primacy of hitherto unimportant factors of the changing Man-Environment relationship in the state.
The nature of land use in Bihar has been traditionally dependent upon varying conditions of relief, rainfall, soil fertility, water availability, population density patterns, transport, communication, and access to markets. Generally, although over 80% of the total land is devoted to primary activities, inter-regional variations exist

PHYSICAL ASPECTS AFFECTING LANDUSE -
The reorganized State of Bihar is located within Mid Gangetic valley. Bihar covers an area of 94,163 sq. km. and possesses a rich network of surface drainage lines, both from the northern Himalayan ranges and southern plateaus. Basically a part of the mid-Ganga Plains, most of the study area was formed during the late Palaeogene-Neogene times, and is related to the upheaval of the Himalayas vis a vis flexural down warp of the Indian lithosphere under the supracrustal load of the Himalayas [Wadia, 1961]1. Bihar Plains lie on a highly active seismic belt, seismicity being greater towards the north. The western part of the study area is geologically proved to be uplifting in the upstream area, with the result that the general slope is tilting to the south-east2. This is gradually contributing to the draining out of the tectonic sags and surface depressions in the west towards east and south-east.

The hydro-geological framework of the region gets reflected in the numerous channel flows, the wetlands and other fluvial features. The plains are also subject to frequent channel avulsions, flooding, and resultant sedimentation3. These events have influenced the patterns of wetlands, most of which originate from the meandering streams. The rivers appear to be aggrading, thereby increasing the annual overspills, more so in the east4. The surface is composed of calcareous alluvium in north-west, non-calcareous soil in the north-east, and forest and hill soils in the plateau rim of the south5.
Climatic variations, resultant rainfall distribution and water availability also impact Bihar’s land use. In North Bihar, annual inundation is common, while drought-like conditions prevail in the south. The Himalayan ice caps and glaciers feed the innumerable south flowing streams, and along wit the monsoon rains, contribute to high fertility of Bihar Plains. Supply of water is also affected by hydrological changes, where determinations of channel conditions due to excessive aggradations, itself the result of an increase in the quantities of sediment carried by the major tributaries of the Ganga have occurred6. Hence, any change in the factors affecting surface water availability impacts the pattern of land use. This study refers to the dry period of December-March, when demand for water availability is highest.

SOCIO-ECONOMIC ASPECTS AFFECTING LANDUSE -
The economy of the reorganized Bihar is underdeveloped and heavily dependent on agriculture. Bihar has the lowest per capita income in India - below Rs. 5000/- as against the national per capita income of Rs. 10,254/- [1993-1994]. Bihar is also densely populated. As per 2001 census, there were 82,998,509 persons, which is about 8.08% of the population of the country, with a density of 881 persons/sq.km7.
The pressure of population have forced deforestation and decrement of the area under orchards and pasture Hence, the land use pattern has a long chronology of being dominated by agricultural production. Traditional agricultural practices are based on near-total dependence on monsoons, with very little land allocated to other activities. Agriculture is the main stay of the rural people of the state, which provides direct and indirect employment to around 77.35% of the total work force of the state and contributes 87% of the Net State Domestic Product. Agriculture, combined with Animal Husbandry, are characterised by low productivity due to traditional practices, inadequate capital formation, low investment, inadequate irrigation According to the Agricultural census, the total number of operational holdings was 75,77,251, 79% of which were of less than 2 acres.


CROPPING PATTERN IN BIHAR [1980s]
Source: Bihar through figures, 1986, Govt. of Bihar, India


Cropping Pattern:
Paddy is the principal food crop of the state and accounts for about 46.66% of the total gross cropped area, followed by wheat (27.93%) and pulses (9.13%). Similarly, the area under cash crops and oilseeds account for 5.89% and 1.88% respectively.
The physical bases of location, configuration, drainage, soil, sub-surface strata, temperature and precipitation with access to water supplies, define the limits of the biotic potentialities of the land. The human bases including the extent of occupancy, population density, social and economic institutions, along with accessibility to markets, transport and communication, control the extent to which the resources of the land are utilized8.

Land Use Pattern:
Bihar has an agro-based economy. As per records, land use pattern in Bihar stresses on primary activities with 78.97 lakh hectares out of total geographical area of 93.60 lakh hectares in 1997-98, under crops. 22.33 lakh hectares were given to multiple cropping, and net sown area was 56.6 lakh hectares. Only 6.22 lakh hectares of forest cover remained in the decade of the nineties. Bihar Plains are almost immune to this category. In the decade of the eighties, they constituted 6.58% of the land cover in Bihar. Altered natural vegetation comprising of dry deciduous forests now survive in areas having less than 1200 mm. rain in the rims of the Highlands in south Bihar. High rainfall of over 1500 mm.permit the growth of moist deciduous forests in the Dun and Someshwar ranges in the north-west and Saharsa and Purnea Districts in the north-east. The area under miscellaneous crops, groves and pastures totalled to 2.53 lakh hectares9. Fallow lands and barren segments are found in the drier parts of the state. The nature of land use in Bihar is dependent upon varying conditions of rainfall, soil fertility, water availability, population density, transport and access to markets. Hence, while eastern Bihar is usually intensively cultivated, the water bodies and swampy conditions inhibit year-round cultivation in the northern part


LAND USE IN BIHAR [1997-98]



PURPOSE OF STUDY
The satellite imageries revealed that the changes in surface land use patterns have taken place too rapidly to assign the cause of these changes solely to neotectonism. The spatio-temporal impact of global warming on economic activities, particularly on agriculture, needed to be assessed. The aim of this study was, therefore, to consider the extent of changes in the areal spread of major land use categories in Bihar in the dry seasons [December –March] in 1984 and 2004, and to seek explanation of these changes especially in the context of evidences of global warming.

METHODOLOGY
Remote sensing techniques have been used to observe and analyze the changes in the land use of Bihar Plains, its geographical location being between 21058’10” N and 27031’15”N latitudes, between 82019’50”E to 89017’40”E longitudes. Two satellite imageries of IRS-WiFS Sensor [Indian Remote Sensing – Wide field Sensor] of March 1984 and December 2004 were studied. The image processing was done on ERDAS-Imagine Version 8.3. FCC was classified, and the classified images were recoded to generate the desired results. The image resolution is of 80 meters. Changes in pixels were calculated. Upon superposition of the physical map of Bihar over the images, comparative picture of the changing trends in the state was highlighted, and subject to analyses and explanations. Limited GT ( Ground Truth ) data were collected for the image processing
SOI [Survey of India Topographical sheets were referred to corroborate the findings. State Boundary was digitized as Vector to know the extent of the study area. The vector was changed in the form of raster to get the statistical value of the spatial extent of crop cover.
Field study of Kabar Tal wetland [ a proposed RAMSAR Site] in Begusarai District, was also undertaken to verify shrinkage of wetlands particularly in north Bihar10.
Interviews with local population, for perception of changes in normal temperature and rainfall variations, land use and surface water availability, were conducted.
The interpretation of the land use changes was based on the observation of the images of two years, obtained in March 1984 and December 2004. Pixel calculations were used to identify important land use categories, which have direct influence on the state’s economy, and may not agree with the land use data collected manually by authorities. These are –

1. Wetlands.
2. Forests – this included the area under plantation.
3. Cropped land
4. Fallow land – These are marginal lands whose prospects for use increase with adequate availability of water and other agricultural inputs like better seeds and fertilizers
5. Area under Sand deposits and cloud cover
6. Unclassified land – That which has not been classified, either because the scientists are not aware what is lying in those areas, or because of the fact that the specific area falls beyond the purview of this study.

FINDINGS –
Although both March and December are dry months, surface water availability and sown area coverage are generally more in December as this follows the post monsoon period. By March, winter crops near harvest time in the plains, thereby covering much of the agricultural lands.
This study reveals a changed scenario, in which rivers, wetlands, agricultural land and land under forests exhibit a dynamism that is a harbinger of changes in agricultural trends, and in turn, the state’s economy. Reduction in pixels representing water bodies between the 1984 and 2004 images indicates decrease in areas of water bodies in the western part of the state. Massive sedimentation in the December 2004 image is revealed in the Ghagra-Gandak Interfluve in the north western segment, so much so that the channel flow of the lower Gandak river is almost obliterated. Declining wetlands were noted even in the piedmont north and the adjacent marshy terrain. However, towards the north-east, surface water increased spatially. The Kosi fan and its downstream section revealed an almost 8% increase in surface water area, this being due to the heavy silt load of the river and resultant spillage by the river. A historically flood-prone area, northern Bihar’s topography is characterized by abandoned meanders and channel avulsions. But a comparative study reveals that surface water availability in the dry periods of the two years declined by around 40% in west Bihar and increase by approximately 10% in the east.10 , and declined by -43.40% for the state as a whole. Kabar Tal, a bird Sanctuary in central-east Bihar, covered 6786 hectares in March 1984, but 20 years later, it shrunk to 6043 hectares, the shrinkage being on its western flanks. To the east of these clusters of wetlands, an increase in surface water configuration was noted.
The area under forests is officially stated to be decreasing. However, in this study, interpretation of the satellite imagery included all types of green cover, forests and plantations. The continuous vegetation belt along the northern rim of the platean in south Bihar stood almost obliterated in the second image. Only Munger hill forests, near the southern bank of the Ganga river, was least affected. There was a simultaneous accumulation of swampy tracts and water bodies in the nearby areas that could have attributed to the continuity of this forest zone.
The enhanced figure of forested land, therefore, bears testimony to the rising importance of plantation farming which itself indicates a subtle shift from cereal farming to commercial cropping activity. Since the cropping pattern has historically been dominated by paddy, this shift may be regarded as the farmer’s adaptation to the changing environment of decreasing water resources.
The 1984 image reveals a dominance of cropped area over the Bihar Plains, except in the south-east where most of the flat surface has been left fallow in the dry month of March. Of the total agricultural land, 59.27% was under cultivation. The latter image revealed reduction in pixels in this category of land use, the percentage of agricultural land now being reduced to 54.16%. Also a marginal decrease in the combined categories of agricultural land [cropped land and fallow land] by 80.05 hectares was noted. Significant increase in area under fallow land by approximately 2303 hectares [a 12.35% increase] in the second image of December is suggestive of the fact that changing surface water availability influenced area under crops.
Of greater importance and relevance to changing land use structure was the land under sand. The role of cloud cover becomes minimized if the period of the images studied, is considered. Sand deposits spread by over 40% from the 1984 base year, and included sedimentation of fertile tracts, particularly in north Bihar. Unclassified land increased in cover by 338.6 hectares, registering a 64% expansion beyond its 1984 area.

CHANGES IN MAJOR LAND USE CATEGORIES IN BIHAR
[Based on March 1984 & December 2004 remote sensing images]

Land use types
1984 March
[Fig. in Hectares]
2004 December
[Fig. in Hectares]
Change
[in %]
Wetlands
4023.91
2409.86
- 40.11
Forests [includes plantations]
4812.63
5773.54
19.96
Cropped Area
27148.52
24764.96
- 8.78
Fallow
18653.12
20956.63
12.35
Sand [includes cloud cover/haze]
978.53
1373.12
40.32
Unclassified land
521.52
860.12
64.93
TOTAL
56138.23
56138.23



















ANALYSIS OF THE CHANGES –
The study area is an established sedimentation sink and geologically volatile. The high sediment load during the monsoons and frequent spillage in the Ganga and its tributaries normally lead to changes in channel configurations and choking up of wetlands. In north and west Bihar, this is further influenced by neotectonic changes in local slope conditions.. The general slope of the region is tilting to the south-east. But response of each region to sedimentological adjustments and neotectonics is different in magnitude11, this being partly reflected in the land usage of the state. This accounts for sediment and sand deposit increases in the northern-eastern agricultural land between Himalayan foothills and the Ganga.
The above fact was augmented by dramatic changes in the snow cover of the Nepal Himalayas and the Greater Himalayan range that feed the perennial southward-flowing tributaries. InMarch1984, the Himalayan snow belt extended from the vicinity of the upper tract of the Gandak river eastwards in a wider swathe to form the sources of the Sapt Kosi river system. All the mountain streams bore water even in this warm dry month, and the surface depressions were adequately full, thereby supporting a larger area under crop cultivation. Sedimentation was most evident in the upstream area of the Kosi floodplain. The second imagery revealed altered surface drainage, with a visible, considerable disappearance of Himalayan ice cover north and north-west of the fluvial plains. Only the north-eastern ranges feeding the Kosi river network retained their ice cover.
Lesser availability of surface water, therefore, accounted for decline in the seasonal cropping intensity in west and central Bihar and contributed to a larger spread of land left fallow. Conversely, in eastern Bihar, the shrinking wetlands gave way to new arable lands in their outer confines.

CONCLUSION-
Depleting ice covers and glacial recession are having direct impact on the quantum of water and detritus in the perennial Himalayan streams upon which land use patterns have evolved. The Second Bihar State Irrigation Commission, 1994, stated that within Bihar, the river basins already had a shortfall of water availability. This marked depletion does not auger well for the state, for it has already set in motion a series of reactions as exemplified in this study, that are bound to have cataclysmic effects on it’s ecological balance, and in turn, on the economic and social fabric of the state.
Also, the “Interlinking of Rivers” Project of the Govt. of India envisages alteration of the entire nation’s drainage pattern. The Himalayan streams are perennial, snow-fed channels that bring a huge volume of water and load of detritus onto the north Bihar Plains. The right-bank streams drain a huge area south of the Ganga, and overspill their banks during the monsoons. Hence, this flood-prone drainage network, supplemented with adequate monsoon rains ranging between 80-120 cms. per annum, enabled Bihar to meet the textbook definition of “a water-surplus state”. Tragically, this situation is altered in several parts of Bihar today. Dried up riverbeds and truncated flows, along with changes in the area under RABI or winter crop, are the most visible features in the river basins. The emerging environmental constraints would, therefore, come in the way of successful implementation of the interlinking of the rivers in Bihar that fall within the broad framework of this mega-project. Reorganized Bihar has only two precious resources left to cushion its economy – it’s fresh water resources and it’s arable land - which must be conserved for a more balanced regional development.

REFERENCES –

Wadia, D.N. (1961). Geology of India. Macmillan, London.
Geological Survey of India Sp. Publication 31; Bihar-Nepal earthquake, 1993, 14-19, 62-80.
Sinha, R., (1996), Channel avulsion and floodplain structure in the Gandak-Kosi interfan, north Bihar rivers, India. Zeitschrift fur Geomorphologie , 103, 249-268
Ahmad, E. (1971). The Ganga - A Study In River Geography. Geographer, Vol XVIII,; Aligarh Muslim University, India.
Singh, R.P., & Kumar, A. (1970). Monograph of Bihar. Bharati Bhawan, Patna.
Jain, V and Sinha, R. (1996). Monitoring Fluvial Hazards from Space: a Case Study of North Bihar Plains, India. www.GeospatialToday-Articles.htm ; accessed on 20/02/04
8.Census of India –Bihar, 2001
ibid.
Bihar through figures, 2000.
Ghosh, A.K., Bose, N., Singh, K.R.P., & Sinha, R.K. Study of Spatio-Temporal Changes in the Wetlands of North Bihar through Remote Sensing [2004], Proceedings of 12th. International Soil Conservation Organization Conference, Brisbane.