In many ways they are like natural trees. Each has an individual shape. They harbour birds and squirrels. They soak up sunlight and exchange gasses with the atmosphere. That is why they look like trees.
Engineering solves the engineering problem the same way biology does.
The canopy of leaves provides and optimal amount of surface area for the volume and weight. Below the surface, though, they are one entity joined by a root system that spans continents and sends great root trunks across the beds of oceans which, themselves, put out hair roots to absorb trace elements from the water. In places roots burrow deep in search of useful mineral deposits, for oil and gas. There are no maps of this network. It changes constantly.