What's the scientific reason for fractals being present in nature at such a large scale? Is it perhaps the solution of an optimization problem? For example, would the fractal based shape of certain plants, be the the solution evolution has given to the problem "what is the shape which could capture the largest amount of light from the sun in a given environment"? If yes, do you have other examples?

Would highly appreciate some book references which are on topic (i.e. not fractals per se but WHY fractals are out there).

Thanks.