I have a theory that the wiliwili trees skin/bark adopt to the sun’s UV by turning orange like human skin. Younger plants have greenish bark. When they get older, the bark gradually turn orange. I have noted that parts of plants: trunk and branches that are not protected by shade from its one canopy and others around will turn orange as though sun tanned. On the same trunk, the side facing downward and away from the sun remains greenish. There are hosts of things that are still not know about the wiliwili trees for us to understand why some older trees that have survived for hundred of years are dying. Environmental factors such as erosion due to fire, removal of trees and vegetation for cattle grazing which in turn reduce rain fall over time may be the main culprit. 200 years old plus trees may start to die naturally, or their demises could be hasten by dwindling resources that nourished them centuries previous. It is more likely a systematic degradation and less likely individual causes.