When will this tree fall down?

I drive, walk, or run by this tree just about every day.

It has no bark most of the way around the base, and the wood beneath is significantly decayed. It looks like it could fall down any minute – right?

I took the picture of the tree from the roadway. It is a divided state highway with a two lanes in each direction, a large median in the center, and a hiker-biker lane on each side. It is a major road. Thousands of people pass the tree every day. If it fell, it could land on walkers, joggers, or drivers. There is also a nearby parking lot.

I sent a warning note to the parent of the organization that the tree and site belong to (though the site is frequently used, the local facility does not have a web presence or published phone number). The tree had open and obvious defects for some time when I sent that note in December of 2012. We have since had many major storms – wind, rain, snow, and ice. Yet the tree stands.

Tree risk assessment standards say risk = probability (how likely is it to happen?) x consequences (if it does happen, what will the impact be?). The purpose of tree risk assessment is not to make us fortune tellers (i.e., this tree will fall down in 3-6 months); it is to reasonably reduce risk and prevent harm. This is an art as well as a science in many cases. This case is an easy one as the tree cannot be fixed – it will continue to decay.

I don’t know when this tree will fall down; frankly, I thought it would have happened long before now. I do know the probability of failure and impact is likely, that the consequences would be significant, and the risk therefore is high. The defects are open and obvious even to those that don’t know much about trees, and the risk is foreseeable and preventable. Whenever the tree fails, in the unfortunate event of bodily injury or property damage, one question will need to be answered: why didn’t anyone act to prevent this from happening?