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Saturday, January 15, 2011


Greates cave in Vietnam
Some 20 million people visit caves every year. Mammoth Cave inKentucky, USA, alone has 2 million visitors annually. Great Britain has some 20 showcaves, with the most-visited receiving over 500,000 visitors every year. About 650 caves around the world have lighting systems, and many others are used for ‘wild’ cave tours where visitors carry their own lamps. Tourists damage caves and karst directly and indirectly through the infrastructure built for the tourists’ convenience – car parking areas, entrance structures, paths, kiosks, toilets, and hotels. The infrastructure can lead to hydrological changes within the cave systems. 

Land surfaced with concrete or bitumen is far less permeable than natural karst, and the danger is that the feedwaters for stalactites may be dramatically reduced or stopped. Similarly, drains may alter water flow patterns and lead to changes in speleothem deposition. Drainage problems may be in part alleviated by using gravel-surfaced car parks and paths, or by including strips where infiltration may occur. Within caves, paths and stairs may alter the flow of water. Impermeable surfaces made of concrete or steel may divert natural water movement away from flowstones or stream channels, so leading to the drying out of cave formations or to increased sediment transport. These problems are in part overcome by the use of permeable steel, wooden, or aluminium walkways, frequent drains leading to sediment traps, and small barriers to watermovement that approximate the natural flow of water in caves.
The Exotic Cave (Goa Gong) in Pacitan, Indonesia

Cave tourists alter the cave atmosphere by exhaling carbon dioxide in respiration, by their body heat, and by the heat produced by cave lighting. A party of tourists may raise carbon dioxide levels in caves by 200 per cent or more. One person releases between 82 and 116 watts of heat, roughly equivalent to a single incandescent light bulb, which may raise air temperatures by up to 3◦C. A party of tourists in Altamira Cave, Spain, increased air temperature by 2◦C, trebled the carbon dioxide content from 0.4 per cent to 1.2 per cent, and reduced the relative humidity from 90 per cent to 75 per cent. All these changes led to widespread flaking of the cave walls, which affected the prehistoric wall paintings (Gillieson 1996, 242). 

A prolonged increase in carbon dioxide levels in caves can upset the equilibria of speleothems and result in solution, especially in poorly ventilated caves with low concentrations of the calcium ion in drip water (Baker and Genty 1998). Other reported effects of cave tourism include the colonization of green plants (mainly algae, mosses, and ferns) around continuous lighting, which is knows as lampenflora, and a layer of dust on speleothems (lint from clothing, dead skin cells, fungal spores, insects, and inorganic material). 

The cleaning of cave formations removes the dust and lampenflora but also damages the speleothems. A partial solution is to provide plastic mesh walkways at cave entrances and for tourists to wear protective clothing. Recreational cavers may also adversely affect caves (Gillieson 1996, 246–7). They do so by carbide dumping and the marking of walls; the compaction of sediments with its concomitant effects on cave hydrology and fauna; the erosion of rock surfaces in ladder and rope grooves and direct lowering by foot traffic; the introduction of energy sources from mud on clothes and foot residues; the introduction of faeces and urine; the widening of entrances and passages by traffic or by digging; and the performing of cave vandalism and graffiti. The best way of limiting the impact of cave users is through education and the development of minimal-impact codes, which followcave management plans drawn up by speleologists, to ensure responsible conduct (see Glasser and Barber 1995).(Gerrard, 2007)

Sources : Gerrard, John.2007.FUNDAMENTALS OF GEOMORPHOLOGY. New York : Routledge 270 Madison Avenue

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