Rising more than 70 metres above the rainforest canopy, a giant skyscraper of a tropical tree can seem almost invincible. Some have survived centuries of storms, droughts and competition.

Large trees face a formidable engineering challenge, lifting water tens of metres from the soil to leaves high above the forest floor. A challenge which intensifies during drought.

But are giant trees uniquely vulnerable to drought or could they help forests remain resilient as temperatures rise?

Research in this area over the last decade shows there is no single way tropical forests respond to drought. In some forests large trees die disproportionately; in others they appear surprisingly resilient.

In 2015, my colleagues and I analysed how drought affected forests around the world. We found that, during drought, larger trees were more likely to die or have stunted growth than smaller trees.

It seemed logical to us. Larger trees must transport water over greater vertical distances. They are more exposed to sunlight and atmospheric demands. Their crowns sit above the canopy where temperatures are higher and conditions are harsher.

Hydraulic theory pointed in the same direction. Trees move water from roots to leaves through a continuous column under tension, like drinking through a straw. During severe drought that column can break, causing hydraulic failure and potentially tree death. In 2012, researchers showed that many tree species operate very close to the limits of their water transport systems........

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