Local Ecological Area Foundation.
A LEAF is an area of the Earths Crust. A LEAF is defined by the topography of that area of the crust. The most common form is a River Basin, A river basin's boundaries are defined by the hills or mountains that create the catchment area of rainfall that creates the river. This river flows into the sea, and affects the topography of the seabed, creating valleys and interacting with currents present in the sea. This link has ten pages to view and is an excellent introduction to River basins
LEAFs can be other configurations such as an Island, Group of Islands, Peninsular, etc. The main criteria being the topography, climate and population, which dictates the optimum size for measuring energy transactions of how the local economies of humans and all other lifeforms interact, including the marine life.
More detail to follow.