The huge stormsMany Australians have seen trees that had withstanded the weather’s extremes for more than a century fall or were damaged by recent storms.
This is what we can anticipate as climate change makes storms more frequent, winds stronger, and rainfall heavier. All of these factors contribute to the loss or reduction of large trees.
But there’s something you might not think of as linked to climate change. As storms intensify in our new climate, we’re likely to see more lightning strikes. This means that our tallest trees will be struck more often.
Are trees always harmed by lightning?
Most of us are familiar with the rules regarding lightning and trees that were taught to us as children. Don’t shelter under a tree during a thunder storm. Lightning rarely strikes twice in the same spot.
These rules are applicable from the viewpoint of a tree. Old trees are often the largest. They are more likely to be struck by lightning. You’d think a lightning strike would be game over for most trees. The effects can be quite severe. They can vary greatly.
The extent of the damage caused depends on the tree species, whether the lightning was sheet or forked, how wet it is, and where it hits the earth before dissipating.
Strikes can be up to a million volts, generating temperatures up to 20,000℃. For a tree unlucky enough to be hit by one of these events, it’s all over. The tree’s sap instantly turns into steam, which can lead to it to. Literally, explodeLose or deteriorate large areas of bark and wood. It would be a good idea to avoid being under a tree when this happens.
Trees are not good conductors. The lightning will travel through the tree’s trunk if it is very wet from rainfall. little damageto the tree itself. After a strike like that, you may see the sooty residue on certain parts of the tree. You might notice that the tree appears undamaged and continues to grow well.
Lightning sometimes strikes. Strike one sideTree. Such a strike often kills the tree’s living tissues in a strip running along a large branch, vertically down the trunk to the ground, or even ending a metre or two above the ground. You’ll notice the lightning scar on trees like these, as it’s very visible. The scar wood often becomes hollow over time as it decays. Trees can often recover from such strikes if the scarring and decay are not too severe.
There is a splendid variegated elm growing at Melbourne University’s Burnley Campus which was struck by lightning almost 30 years ago. Many thought it would perish, but it survived. I saw the long, narrow lightning scar growing over the years, as the wood began to decay. Its trunk grew larger over time and eventually the scar was gone. You will not see any scarring or wounds if you look past today. But you and I know a secret – its trunk is hollow but strong.
Lightning can cause unexpected tree death long after the strike.
Some trees that have suffered a lightening strike may be fine, but then they die suddenly between two to twelve months later. This may be due to the strike causing a serious disruption to the tree’s metabolism or because it’s been unable to fend off fungal disease or insect pests after being weakened by the strike.
If lightning strikes the earth through roots, there may not be any symptoms above ground. Underground, it could be a very different story. This can lead to severe damage to the root systems. The tree may die quickly if the entire root system is damaged or the roots will eventually fall apart. The tree may slow down if only some roots are damaged.
Some trees are more susceptible to lightning than other. I’ve seen a number of pines and other conifers die after a strike, for instance, while many eucalypts and oaks recover and remain healthy. It is possible to install a lightning protection system on a tree, but they’re costly and rarely installed in Australia.
It is a good idea to watch out for lightning strikes to trees. The serious damage can often not be immediately obvious. Only the truth can be revealedIn the weeks and years ahead. For some trees, the full effect of the fall on their growth is only apparent in the spring. A qualified arborist would inspect the tree and make a good investment.
An arborist might be required to help with a related climate change-driven threat to trees. That’s wind. For example, in Victoria, trees can withstand the windy winds from the west or the north by developing stronger root- and branching systems. But now we’re seeing strong winds and severe storms coming from different directions.
Unusual winds can cause trees to fall or damage, regardless of their age and past experience. The storm which pillaged Victoria’s Dandenong Ranges last year toppled many old, strong trees and led to long-lasting power outages because the winds came from a different direction. An arborist can assess if your trees have been affected by these new threats.
Lightning can strike twice
If you think about the rules that were taught to us as children about lightning, you will see why this is the main one. A thunderstorm can cause you to be too close to a tree.
Some rules aren’t quite accurate. The lightning strike would have likely occurred to the oldest and tallest tree in an area. Lightning can strike twice in one place, so it is possible for lightning to strike twice.
In fact, lightning is likely to strike in exactly the same place – the top of the tallest tree – every few years until the tree is no longer the tallest around, as other trees grow up and around it. Safety is found in numbers, even for older trees.