Like a bolt out of the blue
South Africa receives around 25 million lightning strikes a year, and Piet Retief is the ‘Lightning Capital’ of SA. While there’s not much that foresters can do to prevent lightning strikes, there’s plenty they can do to make sure they are well prepared to douse the resulting fires. GAYNOR LAWSON reports …
According to the South African Weather Service (SAWS), South Africa is the southern hemisphere’s highest risk country in terms of lightning-related deaths and injuries (following India and the USA in global terms), with an estimated 25 million strikes hitting the ground each year. Lightning causes millions of Rands’ worth of damage to property and livestock. Global warming is making matters worse, with higher temperatures, longer dry seasons and less rainfall in high-risk areas.
Direct lightning strikes in timber plantations generally do not damage more than one or two individual trees at a time, but when those trees are large, mature pines grown for saw timber, the value of the loss is quite significant – especially when there are multiple strikes over the summer storm season.
However it is the fire that results from a lightning strike that does the real damage. This is where foresters need to be well prepared to douse lightning fires quickly before they get a chance to spread.
What is lightning?
Basically, lightning is a massive, naturally-generated spark of electricity. In the early stages of a storm, air acts as an insulator between positive and negative charges present in the clouds and between clouds and the ground. If there is sufficient development of opposite charges, this insulating capacity fails, resulting in an extremely hot and fast discharge of electricity - lightning. This temporarily balances the charged areas of the atmosphere until opposite charges build up again. Lightning can heat the atmosphere to temperatures five times hotter than the sun, causing the air to quickly expand and vibrate, creating the distinctive accompanying rumbling of thunder.
Where and when does it occur?
Lightning is most likely to strike tall trees in open areas or near bodies of water, on high ground, or close to buildings with electrical wiring and plumbing. According to satellite observations, it occurs more frequently over land than over the sea, with Equatorial Africa being the most high-frequency lightning zone in the world. Locally, SAWS rates Piet Retief as the country’s lightning capital, with the highest density of strikes per square kilometre (as recorded between 2006 and 2018), and a flash density of 16,9 per square kilometre per annum. Carolina, also in Mpumalanga, is close behind with a strike density of 15,6. Generally speaking, the Eastern Escarpment and its adjacent regions have flash densities in excess of 12 flashes per km² annually. The most high-risk period for these regions is the end of October/beginning of November, with random storms occurring while conditions are still dry after winter.
How much of an issue for insurers is lightning?
Pierre Bekker, CEO of short-term insurers Safire Insurance, which has been offering cover to the forestry sector since 1987 through the Safire Crop Protection Co-operative, says: “In terms of damage to plantations, lightning has a minimal impact - it will generally take out a single tree. It’s the resultant fire that causes the damage.” Safire Crop offers plantation clients cover for ‘defined events’ including fire, lightning and explosions. “If adequate measures are in place, such as properly managed fire breaks and a fast-acting response crew, and if there isn’t too much wind with the storm and lightning, the rain that usually accompanies a storm helps curb the spread of the fire. It’s when it’s a dry storm, which is less common, that it’s a problem.”
Lightning nevertheless presents commercial and domestic insurers with a major headache. For Safire, lightning is the most expensive cause of claims - on average 18% more costly than an average burglary claim - and is the basis for over 5% of total claims paid out in the past 15 years. Last year, 10.3% of property claims from the company’s general short-term clients was for damage caused by lightning.
“It’s second on the list of causes of claims after motor vehicle accidents,” comments Bekker, “especially for farmers insured by our specialist dairy product, both in terms of severity of the incident and frequency of claims. Very seldom do we have claims for timber damaged by lightning, but much more often for cattle and other livestock or game animals, pumps and household items such as computers and TVs.”
When there’s bad weather, cattle tend to group together so that a single strike can kill several animals. Also, as farming becomes more high-tech, tractors and harvesters with their sensitive electronics are vulnerable and often have to be completely written off, resulting in high costs to the insurer. Also at risk are camera towers in plantations, largely because of their height. “It can be expensive if the fire-monitoring equipment and solar panels are taken out,” Bekker adds, “and often with lightning claims it’s hard to differentiate between actual lightning damage and damage from the power surge.”
Are there influencing factors?
Dr Ronald Heath, Director: Research & Protection at Forestry South Africa says “Lightning is similar to any point ignition. The fire intensity and rate of spread is determined by factors such as fuel load, fuel type and moisture, ambient temperature, relative humidity and geography”. People are far more dangerous than lightning; they are the most common cause of wildfires, whether intentionally or accidentally. A recent study revealed that 96% of American wildfires severe enough to threaten residential areas were caused by human actions (discarded cigarettes, rubbish left to burn unattended, arson). Also, human-caused fires are often deliberately placed for maximum impact.
“Malicious fires (arson) are frequently set in severe weather conditions and quite often at the bottom of a slope with the prevailing wind and in multiple places,” says Simon Thomas, Operations Manager & Fire Protection Officer of KZNFPA. “This will result in a very fast spread over multiple ignition sites resulting in maximum damage. Containing these types of fires is very difficult. The problem with lightning fires in the early part of the summer rainfall season (so-called dry storms), is that multiple ignitions can occur over a large area, once again making these fires difficult to contain. The difference is that often these strikes occur on high areas and not necessarily at the bottom of a slope, which results in the slower spread of these fires.”
Is there salvage value?
“Usually when a tree is directly stuck by lightning, it results in significant stem damage. Generally, the stem is not utilisable no matter the size,” says Dr Heath. In the bigger picture, a single tree does not cause financial loss. It’s once a runaway fire develops as a result of the lightning strike and sweeps through a plantation that the loss becomes significant. Is it all bad news though? It depends. The main contributing factor is whether a salvage operation can be carried out or not. The extent of the damage and the intended use of the timber are major deciding factors. In the case of chips or pulping some timber can still be produced but at a higher cost. Burned pine needs to be harvested as quickly as possible to avoid blue staining that sets in after a fire, reducing the quality of the product being produced at the sawmills. It also depends on the current market value of the timber type, and the size and age of the tree(s). Young trees tend to suffer worse fire damage so there is unlikely to be any salvage value.
Risk management measures
Speedy response to a fire threat is vital in curtailing the spread and extent of the damage (and potential risk to the lives of responders). Manned fire towers are commonplace across the world but the human factor is a weakness: inactivity and boredom lead to sleepiness and lack of attention. The FireHawk digital fire detection system, developed locally almost 30 years ago, is popular with the larger corporate growers as well as clients in Chile, Brazil, Ghana and Malawi. But it is relatively costly. Is there an alternative for smaller growers?
“We developed Dtect as a web-based lightning detection system specifically for foresters, who face unique challenges,” says Willem Oosthuizen. Dtect was inspired by a request from Mondi for a foolproof alert system to give sufficient warning of approaching lightning to get infield personnel out of the danger zone. “It can be customised in terms of how clients receive notifications and alerts - usually directly to their cellphone - with access to a lightning map as an option.” Dtect can cross-reference between multiple sensors and is linked to the world’s largest lightning sensor network with over 1 200 sensors, ensuring the most accurate strike information available globally.
We know the mantra: when lightning roars, go indoors. Yet around 200 South Africans die from lightning annually, mainly in rural areas when victims seek shelter under trees. Alarmingly, lightning can strike far from where rain is falling (even 16km or so away). The safest option is to retreat to a brick structure or hard-topped vehicle until you cannot see or hear lightning - an app like WeatherBug is useful for identifying how close lightning strikes really are. A roof over your head isn’t enough: sheds, pavilions, tents and covered stoeps offer no protection from lightning.
Debunking the myths
• Lightning can strike twice: the Empire State Building is hit about 25 times per year, on top and on the sides of the structure.
• You cannot be electrocuted if you touch a victim - the human body does not store electricity.
• Being inside behind closed doors is no guarantee of safety - stay away from conducting paths leading outside such as wires, plumbing, cables, metal doors and window frames.
• Lightning doesn’t always strike the highest point. It may strike the ground right next to a telephone pole or tree.
• Crouching or lying down will not make you any safer.
Remember, we live in the third most risky country in the world in terms of being killed by a lightning strike. Get inside as soon as you can.
Related article: How to calculate plantation fire damage