Every year, the weather gets colder and the trees and bushes begin their preparations for the coming winter. They conserve energy through the less hospitable season by stopping energy transfer to their extremities. This leads the leaves and buds and flowers to wither and die. The loss of chlorophyll and loss of nutrients leads the leaves to decompose, changing colours as they do through pale green, yellow, orange and umber, before they finally fall and become part of the decomposing mass on the forest floor. This mass feeds the plants, and its warmth keeps the plants’ roots healthy. This process makes the plants cannibalistic, in a way.
The process takes place every year across the majority of the planet. And yet the internet is still bombarded with photos of yellowed and orange scenes; not because of the amazing science behind the process, but because of the attractive colours which the decomposition produces.