Landscape fragmentation & biodiversity conservation
Landscape dynamics in Meghalya
The comparative status of the forest cover of Meghalaya during 1980 to 1995 has been shown in table 2. The forest cover of Meghalaya has been decreased during this time period. The exact figures of the total forest cover in 1980 could not be ascertained because of the more cloud cover 769.95 sqkm (3.43%). The forest cover of Meghalya has been decreased during 1980-1995. The trend of forest cover shows that during 1980-89 maximum deforestation has been done. However, the negative trends during 1989-1995 shows that the deforestation process has slowed down (Fig. 2).
The degradational activities viz. shifting cultivation clear felling of forests for timber and mining has altered the natural landscape to a great extent. This has resulted in fragmentation of the landscape and loss of many endemic species of the state (Haridasan and Rao, 1985). There has been significant increase in landscape variability during 1980 – 1995. The land transformations result in the alternation of natural habitats. These changes have brought in impacts like fragmentation, loss of biodiversity and degradation of sites. Spatial presentation of landscape dynamics can be used to infer disturbance regimes horizontally. Higher land cover dynamics has been observed in Garo hills showing more alternations in the landscape during the study period. For example unique plant species such as Cycas pectinata and in the states of Arunachal Pradesh, Meghalaya, Sikkim and Manipur do possess nearly undisturbed forests due to least biotic interference (Fig. 3).
Table 1: Expected loss in the Biodiversity value
|| No. of Samples
|| Species Diversity
|| Total No. of Species
|| Economically Important Species
|| Medicinally Important Species
|| Endemic Species
The zone of ecological influences along and around road and settlements respectively was observed to regulate diversity. It was also observed that diversity is more at medium disturbance level. Accordingly, diversity is lower in the absence of disturbance as well in the presence of too much of disturbance. Landscape analysis concentrates on spatial arrangement of patches, their quality, juxtaposition and the proportion of habitat types that influence and modify the behavior of species populations and communities (Lidicker, 1995). Landscape analysis is an important component in determining the diversity of life forms since most of the ecological patterns and processes have unique shaping factors. Fragmentation is related to connectivity and corridors in wildlife science (Lyon, 1983; Kamat, 1986). Patchiness occasionally results in higher species diversity (Pickett and Rogers, 1995). Because of increased fragmentation, patch size and the edge effect is reduced, which in turn has reduced the species richness. Behera (2000) attempted to validate the findings and observed that fragmentation has got significant impact on species diversity.
The nature of forest fragmentation in these landscapes is mainly attributed due to shifting cultivation, elicit felling, deforestation for creating agricultural lands (Khan et al., 1997). Evidence of retrogressive trend, which has set in the community structure due to prevailing nature of fragmentation in the forested landscape. The study identified four general factors leading to forest fragmentation in this area – jhum cultivation, human population pressures industrial logging and weak government policies. It increases the porosity leading to fragmentation at longer timeframe. It has been an ideal case to test the hypothesis of decrease in plant species richness with the degree of fragmentation. It may also be concluded that slow fragmentation produces a decreasing trend in plant species diversity as revealed from the study. Shifting cultivation in this landscape led to retrogressive pattern of plant species. This study may provide baseline information in simulating various effects relating to forest fragmentation and its depressing effects in plant diversity for various planning and decision-making purposes.
The degraded and barren areas were found to least rich biologically. The biological richness maps very well reflects the distribution and status of biodiversity in the region. The areas of high Biological richness occur in Namdapha National Park and border areas of Lower Subansiri, West Kameng, East Siang and Lohit District of Arunachal pradesh. In Assam southern part of Tinsukia district, parts of Cachar and North Cachar hills show high Biological richness. The geographical locations with high biological richness in Manipur are Chingpi in Churachandpur, Dzuku & Maram in Senapati, Tegnopaul area in Chandel and northern inaccessible hills of Tamenglong district. Important bio-rich sites identified in Meghalaya State are Nokrek Biosphere reserve and Balphakram National Park, parts of Khasi hills and Jaintia hills. High altitude inaccessible hills Tuensang, Phek, Mon and Kohima district in Nagaland are also biologically rich. The biodiversity rich spots in Sikkim are Pangthang, Rumtek, Rongli, Lachen, Namprikdang, and mountains nearby Mangan, Rabangla, Bakhim, and Dentam and Varse areas. The prime reasons for declining of biodiversity in Meghalaya, Manipur, Mizoram, Nagaland and Tripura are shifting cultivation. Aruncahal Pradesh is affected mainly near roads and settlements. Permanent cultivation and tea gardens dominate Assam being in the valley region. It was observed that the higher biological richness occurred in more complex terrain and sub-tropical evergreen belt, which possess more species diversity and intermediate level of disturbance.
Fig. 3: Forest Cover Map of North East India