Tropical cyclone Ando in the Indian Ocean
The Western Indian Ocean Islands lie between the tropics, with the exception of a small part of Madagascar which falls south of the tropic of Capricorn. They are subject to about ten tropical storms or cyclones each year in the period between November and May (four per year in Madagascar). The sub-region also experiences inter-annual variations in rainfall as well as periodic flooding and droughts.
Although early warning systems are well developed in the Western Indian Ocean Islands, the threat of increased climate variability and of sea level rise, arising from climate change, are issues of priority and concern.
Air pollution in urban areas is emerging as a problem for human health and for the sub-region's ecology. Preventive action is required.
Cyclones-with high winds gusting at over 200 km/hour-demolish lightweight buildings, damage overhead cables, uproot trees, and are a threat to life and property. Cyclones also cause heavy swells in the Western Indian Ocean which in turn cause significant rises in sea levels that affect coastal infrastructures such as roads and settlements, undermine beach stability, and cause vertical scouring of up to two metres (Ragoonaden 1997). The heavy rains resulting from cyclones cause destruction of crops and vegetation, flooding, soil erosion and contamination of freshwater supplies, with risk to humans and to animal life. At the height of a cyclone most outdoor human activity comes to a halt, schools and workplaces close down, emergency shelter has to be found for those whose homes are destroyed or damaged, and calls are issued for community aid programmes.
In the aftermath of a cyclone, communities may be temporarily prevented from returning to normal activity because people, domestic animals, crops, services and buildings have been lost (UNEP 1999). In some cases the damage may be so severe that countries are obliged to seek international relief aid. Madagascar is an example of this (FAO 1984, UNDHA 1994).
The ENSO phenomenon is also a major factor in climate variability in the sub-region, causing floods and droughts. Mauritius, for example, is prone to drought, especially in the dry season, while Madagascar is most affected by desertification, with sandstorms that cause sand dunes to invade the interior along the coast, covering houses and crops (UNEP 1999). In these countries and elsewhere in the sub-region, the pressure of an increasing population is resulting in the use of marginal land close to rivers, of sand dunes and of land reclaimed from the sea for residential and industrial purposes. Conditions in these marginal or reclaimed lands are more precarious than in other areas, and such encroachment puts more people and jobs at risk from the effects of climate change and natural disasters.
Coral reefs in the sub-region are also at risk. In 1997 and 1998, the ENSO phenomenon caused abnormal increases in sea and air temperatures that led to bleaching and death of coral reefs. In Seychelles, more than 80 per cent of coral reefs were lost and, in the same period, a prolonged drought caused temporary closure of the Seychelles Breweries and the Indian Ocean Tuna Company (UNEP 1999).
|Box 2a.3 Cyclone warnings and preparation in Mauritius|
|Source: US Embassy in Maauritius 2001|
Cyclones cannot be controlled, but their impacts on lives, livelihoods, crops and infrastructure can be minimized through adequate preparation and efficient, accurate warnings by meteorological services. For example, Mauritius has a cyclone warning system that was established in the 1950s, at a time when the island's economy was dominated by sugar production (a crop highly vulnerable to the wind and rain damage associated with cyclones). The subsequent rapid growth in the country's population and its economic and agricultural development mean that more people and infrastructure are now at risk from cyclone impacts and the system is used to give a series of warnings allowing for preparations or evacuation (see Box 2a.3). The regional Tropical Cyclone Warning System in the southwest Indian Ocean is also being upgraded and observation and telecommunications systems are being enhanced. Meteorologists and hydrologists are being given advanced training on early warning systems.
Cyclone-proof buildings are becoming a common feature in the sub-region (incidentally creating a demand for building sand which, as it is often dug from beaches, exacerbates erosion and damage to the delicate reef ecology). Wind resistant crops are also being developed on the islands.
Regional programmes can contribute to better protection from and response to crises, but effective intra-regional collaboration is vital to ensure sharing of technical skills, training, information, research, and collaboration in response.