During the Terraforming process for many worlds, one of the first large forms of plant life introduced are genetically-engineered pine trees. Pine trees are naturally fast growing, are tolerant of a wide range of soil types, temperatures, and rainfall patterns, and are wind-pollinated so they don't require the introduction of symbiotic pollinating insects. Through genetic engineering, these traits have been magnified, producing a very rapidly growing tree that can break up rocky soils with its roots, increase atmospheric oxygen levels, lower carbon dioxide levels, and by being darker than many soil types increase the absorption of sunlight and raise planetary temperatures.
The sheer ubiquity of terraforming pines on many human-settled worlds is one reason pretty much every planet has at least one area that looks exactly like Vancouver, British Colombia.
Behind the ScenesEdit
Inspired by a throwaway line in an episode of Gene Roddenberry's Andromeda, which was indeed used to explain why every planet the crew visited looked like the same Fjord outside Vancouver.