If termites cause a tree to fall in a forest where no-one can hear it, was it a causal event?

Maybe not.

The difference is the need for an explanation. That's the trigger. The trigger says why here and now if forest fires are happening all the time then we lose the sense of the trigger and the explanation could involve anything Oxygen or gravity or whatever. We don't have a question to answer so we don't know what factors to mention right the way out to the orbits of Pluto and beyond