Why is sequoia trees and redwood trees have thick bark?

Sequoia and redwood trees have thick bark primarily as a protective adaptation against environmental threats, such as fire and insect infestations. The thick, fibrous bark insulates the trees from heat, allowing them to survive and regenerate after wildfires, which are common in their native habitats. Additionally, the bark contains tannins, which help deter pests and fungal infections, contributing to the longevity and resilience of these iconic trees.