Dust storms and associated clouds like the one that recently threatened to cross the Tasman damage health and cause billions of dollars of economic harm around the world
When New Zealanders were recently told a 2300-kilometre dust cloud was heading across the Tasman after striking Sydney, Canberra and other parts of eastern Australia, it was a potent reminder of the power and reach of one of nature’s most underrated hazards.
In the end, any remnants of the cloud that may have touched New Zealand had negligible impact, but for millions of people in Australia and other parts of the world the outcome of sand and dust storms (SDS) is not so fortunate, damaging health and incurring billions of dollars in costs.
SDS are wind erosion events typically associated with dryland regions, although they can occur in most environments and their impacts are frequently experienced outside drylands because material can be carried thousands of kilometres, regularly across international boundaries.
While SDS do not feature prominently in disaster literature and do not result in the damage to infrastructure associated with earthquakes and hurricanes, they are hazards in numerous ways and their cumulative effects are significant because they occur more commonly than most other types of hazard.
They are gaining increasing attention at a global policy level, with the United Nations General Assembly adopting resolutions to combat them and acknowledging they represent a severe impediment to the sustainable development of affected developing countries and the wellbeing of their peoples.
The largest areas with high SDS activity are in desert regions of the northern hemisphere, mainly in a broad dust belt that extends from West Africa across the Middle East to South, Central and Northeast Asia. The Sahara is widely agreed to be the world’s largest dust-producing region.
Drylands in the southern hemisphere generally emit less dust, although prominent concentrations of wind erosion occur in Central Australia, Southern Africa and the Atacama Desert and Patagonia in South America. These produce significant local impacts, as does the North American Great Basin, but are relatively minor on a global scale. Dust from South America, however, is regularly transported to Antarctica.
Most dust emissions come from natural sources, with human activity’s contribution subject to debate. Estimates range from 50 percent to insignificant, with a 2012 calculation of 25 percent adopted by the United Nations Environment Programme and the United Nations Convention to Combat Desertification.
But human activity may also affect emissions indirectly, particularly through climate change. This is an important potential driver of future wind erosion and SDS, especially via more extreme wind events, greater frequency of droughts and increased aridity in some areas.
The minimal damage SDS cause to infrastructure in impact regions can lead people to assume there is little or no cost, but costs are created by clean-up, loss of production and health consequences due to decreased air quality. SDS can disrupt many sectors of an economy, including manufacturing, transport, tourism, and retail and wholesale.
Source region damage typically takes the form of soil and sand loss and associated loss of nutrients, fertiliser, seeds and organic matter, including soil carbon. Erosion preferentially removes the finest particles, which is detrimental to soil structure and in turn reduces moisture storage. Combined, such degradation reduces productivity and potentially decreases the income of land holders and users.
Additional source region costs might include damage to infrastructure such as irrigation and water systems, destruction of telegraph poles, fences and walls, loss of livestock and forage for livestock, sandblasting of crops, and road cleaning.
Impact region costs depend on many factors, the main being the level of economic activity in the region and the number of economic sectors affected.
A single severe SDS in 2011 was estimated to have cost New South Wales alone A$320 million, with the cost to neighbouring Queensland, also impacted, not estimated.
Research shows that households face the highest SDS costs, because of cleaning interiors and exteriors and repairs to and maintenance of buildings and vehicles.
Dust in the atmosphere also has implications for human health due to its biological, chemical and physical properties. Exposure can result in conjunctivitis and dermatological disorders, while inhalation can cause respiratory illnesses such as silicosis (or desert lung syndrome) and trigger asthma, bronchitis, chronic obstructive pulmonary disease and emphysema. Particle size is the main determinant of where dust comes to rest in the respiratory tract once inhaled.
SDS can present transport dangers and increase accidents in the air and on the ground. Poor visibility is a frequent cause, sometimes in combination with the adverse mechanical effects of dust. For these reasons, airports, and on occasion roads and ports, are frequently closed during intense SDS. With aircraft usually grounded, and flights cancelled, delayed or diverted, airlines face increased costs and lost income. Aircraft that do fly in dusty conditions require more maintenance and replacement costs of mechanical equipment are higher.
For most economies, the impact on the road system can be a significant cost, with road closures because of poor visibility and dust or sand on the road surface, accidents due to surface or visibility conditions, and reduced transport requirements as a flow-on effect of reduced activities in other sectors such as the construction industry.
As well as being affected by transport issues, the manufacturing sector is impacted if dust or sand enters a facility. For instance, electronic component manufacturers in South Korea observed more faulty products and components on days of high atmospheric particulate matter.
The agricultural sector in impact regions can suffer crop losses because of plant destruction or lower yields and reduced animal production due to livestock deaths or lower yields of meat or milk.
Finally, sand and dust can have serious repercussions for solar power plants, adversely affecting the two main technologies used: photovoltaic (PV) and concentrating solar-thermal power (CSP) systems. Power can be reduced in PV systems typically by 15–30 percent in moderate dust conditions and can reach 100 percent if cementation by water soluble salts occurs due to the combination with dust of dew, very light rain or humidity. CSP systems are even more sensitive to dust accumulation and require greater maintenance to mitigate deposition. Power distribution grid reliability can also be adversely affected, with dust and sand particles frequently carrying an electrical charge that interferes with porcelain insulators on high-voltage lines.
This article is adapted from an online paper for the journal Disasters.