Impact of Coal Mining on Vegetation: A Case Study in Jaintia Hills ...

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IMPACT OF COAL MINING ON VEGETATION: A CASE STUDY IN JAINTIA HILLS DISTRICT OF MEGHALAYA, INDIA5. General Discussion andConclusions5.1. Discussion and ConclusionsJaintia Hills district <strong>of</strong> Meghalaya has a total coal deposit <strong>of</strong> about 40 million tonnes. The district hasbeen most extensively exploited for coal. Although only 7 percent coal deposits are found in thedistrict, it contributes more than 74 percent <strong>of</strong> the total coal production in Meghalaya. The coalfields<strong>of</strong> the Jaintia Hills district are small and highly dispersed. <strong>Coal</strong> is mostly found in Bapung, Lakadong,Jarain-Shkentalang, Lumshnong, Malwar-Musiang-Lamare, Sutnga, Ioksi, Chyrmang and Mutang.The unscientific extraction <strong>of</strong> coal in unorganized sector is going on since long and the area affectedby coal mining is increasing day by day.Due to extensive coal mining, large areas <strong>of</strong> the district have been turned into degraded land, creatingunfavourable habitat conditions for plants and animals. <strong>Mining</strong> <strong>of</strong> coal has caused massive damage tothe landscape and biological communities. It was found that the number <strong>of</strong> tree and shrub speciesdecreased due to mining. The unfavourable habitat conditions prevailing in the coal-mined areas havereduced the chances <strong>of</strong> regeneration <strong>of</strong> many a species, thereby reducing the number <strong>of</strong> species in themined areas. Although the number <strong>of</strong> trees and shrubs have decreased, the number <strong>of</strong> herbaceousspecies colonizing the mined areas were found to be higher than in unmined areas. Similarobservations were made by several workers in the coal mining areas in different parts <strong>of</strong> the world(Cornwell, 1971; Fyles et al., 1985; Game et al., 1982; Singh and Jha, 1987; Jha and Singh, 1990).The density <strong>of</strong> tree species decreased considerably in the mined areas. The density <strong>of</strong> the shrub speciesdid not vary much. Lyngdoh (1995) and Das Gupta (1999) in Jaintia Hills, and Sarma (2002) in GaroHills district <strong>of</strong> the state had similar observations. This could be due to the better ability <strong>of</strong> herbs toadapt to the disturbed sites. Some herbaceous species invaded the newly created habitats. Nepentheskhasiana was documented from the mined areas (Figure 5.1). Meghalaya is the only home for thisendangered species. Due to indiscriminate mining throughout the district this rare species is highlythreatened.Figure 5.1: The Nepenthes khasiana (pitcher plant), an endangered species, threateneddue to indiscriminate mining.65
IMPACT OF COAL MINING ON VEGETATION: A CASE STUDY IN JAINTIA HILLS DISTRICT OF MEGHALAYA, INDIAThe Khasi pine, Pinus kesiya was the dominant tree species in the study area. The high importancevalue index <strong>of</strong> Pinus kesiya in mining areas suggests its ability to grow in the disturbed environments.The importance value index <strong>of</strong> Schima wallichii was next to Pinus kesiya, which indicates thedegraded environment <strong>of</strong> the area. The dominant shrub species in the mined areas were Eupatoriumadenophorum, Melastoma nepalensis and Lantana camara. The dominant herbaceous species in themining area was Paspalum orbiculare, which suggests that it can multiply rapidly in the disturbedenvironments. The characteristics <strong>of</strong> this perennial grass by virtue <strong>of</strong> its stolon and rooting at eachnode can bind the soil particles, making the soil more stable. This grass plays an important role in soilstabilization. This is in agreement with the findings <strong>of</strong> Ries and H<strong>of</strong>man (1983), who observed thatperennial grasses were well-suited to grow on the mine spoils.Dominance-diversity curves for the mined sites resembled with broken-stick series model. This couldbe attributed to the lesser number <strong>of</strong> species occurring in these stressed environments where conditionsare not favourable for plant growth. Species diversity was low on these sites, but the species that growhere appear to have developed tolerance.Shannon-Weaver index <strong>of</strong> diversity for tree species was much lower in the mined areas compre tocontrol. This suggests dominance <strong>of</strong> one or two species in the mined area. The Shannon-Weaverdiversity index for the shrub species was lower in the mined areas than the control. There were notmany differences in the diversity <strong>of</strong> herbaceous vegetation in both the areas. The diversity index forherbaceous species increased with mining proximities suggesting that mining operation favouredcolonization <strong>of</strong> certain species in the newly created habitats. Similar observation was made byLyngdoh (1995), Das Gupta (1999) and Sarma (2002).The trees <strong>of</strong> medium girth class (55-95cm) dominated the mined areas. Unmined area had moreindividuals <strong>of</strong> lower girth class (15-35cm) even though trees <strong>of</strong> all girth classes were present in thearea. In unmined areas, it was found that density <strong>of</strong> smaller and middle sized trees was higher than theold trees. This indicates a stable tree population structure. Such population structure is represented bya normal case and suggests that the forest is growing and would continue to exist. However, in themined areas, the tree density in all the girth classes was extremely low and did not follow any standarddensity diameter population curve. This has been due to rampant and random clearing <strong>of</strong> forest areasfor mining purpose that has led to drastic change in tree population structure. Such a trend inpopulation structure does not indicate the continued existence <strong>of</strong> the forest.The basal area in the unmined areas was found lower than the mined area. This was due to thedominance <strong>of</strong> low girth class trees, which had regenerated in the unmined area. The higher basal areain the mined areas could be attributed to the existence <strong>of</strong> bigger trees. Bigger trees are normally sparedduring mining operations by the miners. This indicates the removal <strong>of</strong> younger trees during miningactivities. Such a trend leads to the failure <strong>of</strong> the community to generate back. Paijman (1970) andParthasarathi and Karthikeyan (1997) made similar observations in New Guinea and India,respectively.In the unmined area both trees and shrubs showed contagious distribution pattern. All species in themined areas showed contagious pattern <strong>of</strong> distribution. The contagious distribution pattern <strong>of</strong> speciesindicated the mosaiced structure <strong>of</strong> the forest stand. The contagious <strong>of</strong> the species suggests theincrease in patchiness <strong>of</strong> the natural vegetation due to mining. This is in agreement with the findings <strong>of</strong>66
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Impact of Coal Mining on Vegetation: A Case Study in Jaintia Hills ...

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