What natural element can be an indicator of potential decay when observed?

Cracks in the bark serve as a significant indicator of potential decay in trees. When the bark is damaged or compromised, it can expose inner tissues to pathogens and environmental stresses, creating an opportunity for decay organisms to infiltrate. The presence of cracks often signifies underlying issues with the tree's health, potentially related to structural integrity or stress factors.

While other factors like leaf discolouration, fungal growth, and wildlife activity can also suggest problems within a tree, cracks in the bark provide direct visual evidence of physical damage that can lead to internal decay. This makes it a more definitive indicator of a tree's potential decline or susceptibility to decay compared to the other options, which may be symptomatic of various other conditions.