What made trees possible? New research points to drought

Key Points:

• A new study by researchers from Cal Poly Humboldt, Yale, University of Hohenheim, and the Czech Academy of Sciences suggests that the evolution of trees was driven by the need to survive drought and hydraulic failure, reframing the traditional view of what defines a tree.
• The study argues that a key feature of trees is their ability to add and replace water transport tissues (xylem) throughout their lives, enabling them to move water efficiently through their large bodies despite the risk of embolisms blocking water flow.
• Trees evolved a compartmentalized water transport system, similar to circuit breakers in a power grid, which limits the spread of damage from embolisms and helps prevent total hydraulic failure.
• This compartmentalization strategy has appeared repeatedly across different tree species throughout evolutionary history, allowing trees to adapt to environmental stresses and survive for long periods, from decades to millennia.
• The findings highlight water transport and drought resistance as central challenges that shaped tree evolution, emphasizing the importance of hydraulic resilience in enabling trees to grow tall and become some of the largest living organisms on Earth.