Ohia trees are dying rapidly, Why?

[Justin]

I don't know - and I'm sure anyone knows - where the problem starts, but the effect is that the roots and the water transmission ability in the trunk are compromised, and accordingly the top of the tree is the first to die off because it's the farthest from the roots.

As an aside, one of the main reasons that Redwood trees can grow so tall in California is that they're constantly in the mist, and the upper branches can get water without having to have it all pumped up from the roots. Most trees reach their maximum height based on how far they can pump water against gravity.