Biodiversity threat through exotic species monitoring and management using Remotely Sensed data and GIS techniques - A case study of Banni (Kachchh) Gujarat, India  K L N Sastry Scientist, FED/FLPG/RESA, Space Applications Centre (ISRO), Ambavadi vistar (PO), JodpurTekra, Ahmedabad - 380 015. Ph: 079-6914026 (O), 7485271 ®, FAX: 079-6762735 Email: klnsastry@hotmail.com P.S. Thakker, Ravi Jadhav Introduction Natural grassland is a plant community in which the dominant species are perennial grasses, there are few or no shrubs and trees are absent or less in numbers. Usually associated with the dominant grasses are less abundant grass species and variety of other herbaceous plants, both annual and perennial types, which at certain times of the year give a characteristic aspect to the plant community. To be presented at 6th Annual International Conference - MAP INDIA 2003 during 28-31 January, 2003 at New delhi. Grassland is one of the numbers of seral phases of vegetation. The vegetation structure is dynamic rather than static. One ecological association follows upon, and grows in consequence of, its predecessor in a well-marked and orderly sequence. One association therefore acts as a nursery to its immediate successor. This series of successional phases, from the first to the last, is referred to as the "sere", grassland forming one characteristic phase of that sere. The development of the sere may be arrested at any given point if environmental conditions are such that further development is retarded. The sere may thus end at a sub-climax rather than at its climax stage, e.g. in semi-arid areas the natural vegetation may be steppe or open grassland with no trees of any kind. In areas of higher rainfall forest is the climax. In regions of high rainfall, the tendency to revert toward forest is particularly marked and confronts the pioneer with difficult problems of stock and pasture management. Continued under-stocking will allow a normal reversion, first to weeds, and then to shrubs and scrubs, habitual overgrazing will tend to weaken the sward so that the establishment of weeds is made easier. Many of the large grassland areas, such as the prairies and plains of North America, the pampas of South America, the steppes of Asia and the Veld of Africa are believed to be of great antiquity and are climax formations determined by soil and climate. Other grasslands are of more recent origin and have replaced forests that have been destroyed mainly by cutting and fire; these have been maintained largely through grazing animals. True grasslands exist in most part of the world where the rainfall is not sufficient to produce thick forest, and yet sufficiently high to prevent the creation of a desert. The great grasslands once covered nearly half of the earth's land surface, from the rolling Prairies of North America to the great Savannahs of Africa and the vast Steppes of Eurasia. Generally speaking, grassland have few, scattered, small sized trees to break the drying winds. Most of these areas go through periodic drought conditions. As a result, majority of plants of these regions lives more " in " the soil than above it. Just under the surface there is a tangled map of roots and rhizomes. Some grassroots grow down to the depths of a meter into the soil, while the tap roots of other soft stemmed plants may penetrate to five meter in their search for water and nourishment. Importance of Grassland When we talk about grassland, we have to first consider the main component, that goes to form the bulk of the grassland, that is grass. Of all, the grasses are the most important to man. All our food stuff like corn, wheat, oats, rye, barley, and rice, sugarcane are grasses. Bamboo's are also grasses. Although, the great importance of grasslands lies in providing sustenance, grasses also serve humanity in other ways. Grass may be used for building homes and furniture (walls, thatch, matting, brooms) lawns, sports fields and as components of some cosmetics and medicines. Grassland provides crucial grazing land and pastures for the domestic and migrated livestock, which forms important livelihood for majority of the population of Banni and surrounding districts. The milching capacity and overall health of the cattle, is an indicator of grassland quality. From these grasslands large quantity of forage grass is collected annually by cutting, and storing it in grass godowns for the droughts. However, free grazing can deteriorate these grasslands, for which only controlled " rotational grazing " is useful. Introduced Species : Introduction of non-native species (also known as "alien" or "exotic" species), deliberately or accidentally, has been a major threat to biological diversity worldwide as the introduced species have often flourished at the cost of the local species. India's Biodiversity, too, has been affected by introduction of alien species. Several exotic animals and plants introduced in the Andaman and Nicobar Islands are posing a threat to the local species of fauna and flora. Animal husbandry, an occupation of majority of Indian farmers, is directly dependent upon grassland for sustenance and it contributes a significant 5 to 6% towards India's national income (The State of India's Environment 1984-85).
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