Agricultural biodiversity is a fascinating subject. Apples are a prime example: There are hundreds of varieties, all of which are different from one another. In our orchard, we have an early Macintosh that ripens in late July, and is sweet and yummy. Then there are Empires and Delicious and Paula Reds that are tart and not fully ripe until after the first frost, generally in October. Then we have to race the bears and the wild turkeys and the deer, who love the apples and are trying to fatten up for the winter, to harvest them for ourselves.
In the tropics, multistrata agroforestry makes a lot of sense. Shade-grown coffee, for example, uses less fertilizer, less toxic chemicals, and is more friendly to birdlife. Sun-grown coffee, on the other hand, is generally grown as a monoculture, which is like an ecological desert to wildlife, and requires many more chemicals to survive.