Saturday , 22 September 2018

Lessons for Goa from dust storm

Nandkumar Kamat

Dust is defined scientifically as solid particles having diameters of less than 500 micrometers. Smaller dust particles of size 2.5 to 10 micrometers create public health problems. Dust originates from various natural sources like loose soil lifted by wind and ejecta thrown up by volcanic eruptions. Dust may also contain anthropogenic particles and fibres.

Why Goa doesn’t have any dust storm recorded in history? Were our ancestors wise to raise high density coconut plantations along the coast from Terekhol to Galjibaga followed by rows of bamboo groves and protect dozens of giant Ficus trees in all the coastal and subcoastal villages? Did they do it intentionally as a shield, a buffer, an insurance against heavy cyclonic winds and dust storms? With most of the coastal coconut plantations and bamboo groves currently thinned out, the natural anti storm coastal shield of Goa has weakened.

What if a dust storm similar to one which hit north India hits coastal and midland Goa? Most of the coastal structures in Goa are not resistant to wind speed above 120 kilometres per hour. Local architecture has never factored in the effects and impacts of dust storms and need to insulate the houses from dust being blown inside. Dust particles being spread during the storm in human breathing zone are dangerous and cause what is known as ‘dust pneumonia’.

According to IMD, the north Indian dust storms were caused by “a western disturbance-induced cyclonic circulation, high moisture brought by easterly winds, and the recent spell of unusually high temperatures” leading to a series of storm clouds. Already the Arabian Sea and entire west coast is showered by thousands of tons of sand particles from Middle East’s deserts. Satellites clearly show these long dust trails from Iranian desert touching India’s west coast. More aridity and higher temperature in deserts of Saudi Arabia, Syria, Iraq, Iran means more sand getting transported towards India. These are continental drivers of suspended particles.

What about the local drivers that create arid and desert like conditions? Unsustainable urbanisation and landscape fragmentation, removal of tree cover, fragmentation of green belts, terracing of hills for constructions, conversion of open grasslands, creation of artificial ‘heat islands’, reduction of natural heat sinks like lakes, ponds, reservoirs are creating perfect conditions for inviting the dreaded dust storms. These factors are very common along rapidly industrialising west coast corridor linking Roha to Mangalore. And we should worry more about heavy metal containing dust from exposed mining area from Advalpale to Rivona. If heavy winds blow over it from east to west then no coastal town would be spared from the ‘red dust storm’.  If Goa remains shielded so far it is only because of the cooling effect provided by Western Ghats vegetation from Sattari to Cotigao.

The microenvironmental effect of the Western Ghats forests neutralising the dust storm conditions has not been investigated. The satellite pictures indicate that these forests along foothills are also facing water stress and may not provide the necessary capacitance in future as temperature rises. Soil moisture stress would cause gradual desertification of forest areas of the foothills of Western Ghats. When we consider the thinning of protective coastal vegetation, Goa would be much more vulnerable to dust storms.

The north Indian dust storm was a freakish, once in 20 to 50 years incident precipitated by higher temperature in eastern Rajasthan. What we need is a very warm sea and a gradient of higher temperature around Goa in rain shadow areas to build ideal conditions to invite a dust storm. According to microbiologist Dale Griffin, of US Geological Survey, Earth circulates annually about 500 million and 5 billion tons of dust every year. These particles are teeming with bacteria.

Localised dust storms are known in Goa but these are restricted in time and space. The first lesson to be learnt from the recent north Indian dust storm is – increase the number of heat sinks in Goa by undertaking massive tree plantation drives along the roads and launch urban forestry projects in all towns. Only those species of trees which are resistant to high wind velocity and provide large canopies which act as dust traps need to be planted instead of those which serve only aesthetic and ornamental purpose.

The second lesson is: landscape engineering would be required to prevent aridity and desertification. The 2000 kilometres long Khazan embankments in eight talukas could be converted into wind barriers and dust traps by raising rows of coconut trees. One kilometre of bund can accommodate 1000 coconut trees in two parallel rows. So Goa can launch a Khazan bundh coconut plantation drive to plant two million coconut trees. Khazan landscape engineering with coconut trees would protect the hinterland from fierce winds. Bamboos don’t need much maintenance and a thick, healthy grove can break the force of the wind. So, if long corridors of Bamboo are raised in countryside after studying the local wind circulation a permanent cushion would be provided against storms.

The third lesson is – restore surface sinks of heat – undertake desiltation, deepening and ecorestoration of old lakes, ponds, tanks, reservoirs to provide more natural heat sinks. If nothing is done, more than primary impact of the dust storm, the diseases spread by dust may bring more serious public health disaster.

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