Biodiversity maintains the ecological balance and evolutionary process of the environmental resources and has its spiritual, cultural, aesthetic and recreational values.
The well-being and survival of human population are dependent on millions of species of plants, animals and micro webs.
Particularly, biological diversity is part of human’s livelihood and constitutes resources upon which families, communities and future generations depend. In general, terms biodiversity indicates variation and abundance of species and their habitat.
It also describes the total availability of life on earth. Biodiversity can be divided into three hierarchical categories—genes, species and ecosystem—that describe quite different aspect of living system.
But in this paper only one category that is species diversity is being dealt with, where species diversity refers to the variety of species within a particular region. According to International Union for Conservation of Nature and Natural Resources (IUCN) the global species diversity varies from 2 million to 100 million and 1.4 million have actually been named (Bradbury, 1991).
Biological diversity is being eroded as fast as at any time since the dinosaurs died out some 65 million years ago. Some of the important factors, which have a great impact on biodiversity, are certain natural disasters like flood, earthquake, landslide, storm and so on. Being located on the banks of the great rivers most of the forest areas are prone to flood.
Particularly, North-East India is one of the worst flood affected areas and yet does not have any proper disaster management policy (Singh, 2004). Flood causes 30 per cent of the total economic loss. Being located on the Brahmaputra floodplain some part of Assam state is severely affected by flood.
Domestic cattle, national parks, livestock and valuable human lives are lost. At the same time, India is one of the twelve mega diversity countries of the world. Owing to its varied physical feature, it has about 45,000 species of plants and 75,500 species of animals. Particularly, North-East India is the most important region representing richest zone for communities and species particularly endemic to the region.
Wildlife of North-East India enjoys a reputation not only for its variety or numbers but also for the fact that within this region quite a few species of very- rare animals and birds are found, which have become extinct from other parts of the world (Assam Remote Sensing Application Centre, 1998).
Much of the North-East’s diversity is found in the forest. The average forest cover of North-East India is 69.59 per cent. Highest forest cover is found in the states of Mizoram and Nagaland, which are 86.99 and 85.43 per cent respectively. Assam shows the lowest percentage, which is only 30.20 per cent (Table 1). Again, rapid population growth of the north-eastern states of India poses a tremendous threat to the existing forest cover and the biodiversity of the area.
For example, percentage decadal growth of population of the states Assam, Nagaland and Arunachal Pradesh in the year 1991-2001 is 18.85 per cent, 64.41 per cent and 26.21 per cent respectively. It has a great impact directly or indirectly on the biodiversity and occurrence of flood. Moreover, density of population is also high in some of the north-eastern states, for example in Assam it was 286 per sq. km in the year 1991 and was increased to 340 per sq. km in the year 2001 (Table 2).
Whatever may be the existing situation; some protected areas of comparatively high forest cover are found. These are the reserve forest, wildlife sanctuaries and national parks etc. This area is the abode of most of the forest species of wildlife, some of which are on the verge of extinction.
Moreover, being located on the southern bank of the river Brahmaputra, Kaziranga National Park is one of the worst flood prone areas. This area gets flooded almost every year, sometimes several times in a year, submerging 80 to 90 per cent of the total landmass. Therefore, this paper deals with the relationship among environment, flood and biodiversity in the north-eastern region taking Kaziranga as the case study.
Study Area and Methodology:
Kaziranga National Park, which is 270 km away from Guwahati in the eastern side, is situated in both the districts of Nagaon and Golaghat of Assam. Topographically this area is located between 26°30′ N to 26°45′ N latitude and 98°08′ E to 93°36′ E longitude. The park is bounded by the mighty Brahmaputra on the north and verdant hills of Karbi Anglong on the south. National Highway 37 goes along the southern boundary of the national park.
The terrain of the national park is more or less flat with gentle, almost imperceptible slope from east to west. Alluvial deposits of the river Brahmaputra due to recurrent floods form the soil of the national park. The total area of Kaziranga National Park is 430 sq. km. The climate of the national park is subtropical monsoon type with high humidity.
Rainfall is heavy during summer. The average annual rainfall is 1,320 mm. The maximum temperature is 35°C and the minimum temperature is 8.9°C. The hottest months are July and August. The climatic condition is also somewhat changeable during different seasons of the year. To determine the relation among the environment, flood and the biodiversity in the study area, data has been collected from both the primary and secondary sources.
The studied area is visited for two periods, once in the months of July and August that is in the peak of the flood period and once in the month of January that is in the lean season. The primary survey was conducted in four villages, out of which, two villages are located in the transitional zone (that is, villages located between core and the buffer zone) and another two are located in the buffer zone (that is, 1-10 km around the boundary of the national park). A random survey of 120 households that is 30 households from each village of the study area was carried out to collect primary data.
There are three broad categories of vegetation cover, which can be readily recognized in Kaziranga National Park (Table 3). All total 400 species of plants have been recorded so far from the national park. The predominant species among the aquatic vegetation is water hyacinth. Other floating and struggling grasses like different Andropogen spp., Ipomea reptama (Kalmau), Pistia straflotes (Borpuni), Lema paucicostala (Harupuni), (Nymphia spp. (water lilies), and so on make the aquatic vegetation. Savannah formation covers nearly 66 per cent of the total area of the park.
The most common and widely distributed species of grass in the park is Erinthus reveneae, associated with Saccharum arundinecium, Tamarix dioica, Saccharum sponteneum, Imperata cylendrica, Phragmites karka Arindo donex etc. Woodlands are represented by variety of subtypes or different stages of succession and edaphic variations. Some of the important trees found in the park are Ajhar, Mango tree (Megnifera indica). Gold mahur (Delenix regia), Hollock (Tarminalia myriocarpa), Simul (Bombax malabaricum), Dimaru (Ficus spp), and so on.
Different types of mammals, birds, reptiles, amphibian and fishes represent fauna of the Kaziranga National Park. The primary mammals found in the national park are Great Indian one horned rhinoceros and so on. Among the mammals, there are 1,552 Indian one horned rhinoceros in Kaziranga, which comprises two-thirds of the total world’s population. It has 50 per cent of world’s buffalo population and 55 per cent of world’s swamp deer population (Dutta, 1991) (Table 4).
Thirteen species of reptiles are reported from Kaziranga. Out of total 13 reptiles, 7 are snakes, 4 lizards and 2 turtle or tortoises. Again, amphibia is a poorly represented group with only 5 records of species under 3 families. Nearly 87 species of fishes have been recorded from Kaziranga.
Only five are considered to be rare. The number of fish species is not the only important thing, but the quantity, which is very large, is another important aspect in the park. Moreover there are 133 species of invertebrates in the national park. About 268 species of birds have been recorded so far in Kaziranga National Park.
Flood and National Park:
Flood is defined as a relatively higher flow of water in a river than the usual that causes inundation of lowland. During monsoon, these small rivers originating in the Karbi Anglong hills become unbelievably dangerous along with mighty Brahmaputra, which causes flood to the Kaziranga National Park.
The flood of the Brahmaputra can generally be attributed to a host of interrelated natural and anthropogenic factors. The natural factors include heavy monsoonal rains and devastating landslides, easy erodibility of rocks of the northern mountains, steep slopes and high seismicity, while the anthropogenic factors include large scale deforestation in the hilly catchments, practice of shifting cultivation, human intervention in the river system including encroachment in the floodplains, destructions of natural wetlands and poorly managed embankment system.
The floods of Brahmaputra made a quantum leap, especially after the great 1950 earthquake. The cumulative effect of these factors has aggravated the flood situation on the floodplain of the Brahmaputra as well as the Kaziranga National Park.
Usually floodwater rises from the middle of the month of May and it comes in 3-4 waves till October depending on the intensity of the monsoonal rain in the valley. Floodwater reaches a height of 3 to 4 metres at some particular places of the park. Moreover, the floodwater generally remains for 15-20 days or more affecting the wildlife considerably.
Results and Discussion:
Flood season is always considered to be a dreaded period for Kaziranga National Park but the role played by flood in maintaining the park ecosystem is also very important. Therefore, both positive and negative impacts of flood are studied to make a proper assessment of the theme.