How Trees Sweat

How Trees Sweat

If Trees Had Sweating Glands to Cool Off From The Heat

During extreme heat waves it’s common for people to seek relief under the shade of a tree yet few of us wonder how trees themselves survive these extreme conditions. Researchers from the University of Western Sydney’s Hawkesbury Institute for the Environment grew trees under controlled climate conditions to see how trees survive these harsh conditions. They discovered that leaves have their own way to survive abnormal heat by releasing water to cool themselves off. This act is very similar to the way humans sweat in order to cool our body temperature.

Over the course of one year researchers learned that trees continuously expel water through leaves when under duress caused by extreme heat. Essentially, this is how trees survive heat waves. Before this was discovered, scientists thought that photosynthesis and water expulsion were merged processes, which means for one to happen, another also needed to happen. They learned this is not the case.

Although these trees were grown in artificial conditions, they provide accurate projections of how trees will respond during extremely hot weather conditions.  When trees under artificial conditions were exposed to the equivalent of a four day heat wave, during peak temperatures, trees stop sequestering carbon. On a larger scale, this means that forests, whether urban or rural, if exposed to extreme heat will stop sequestering carbon. Over time, if global temperatures continue to rise, this could have greater consequences on a forest’s ability to act as a carbon sink.

How Trees Cool Themselves

Under normal conditions, trees cool themselves by a process calls evapotranspiration. Evapotranspiration is the process of water evaporating from leaves when the sun’s rays hit the trees canopy. In some cases tree canopies can divert up to 60% of incoming radiation through this process. However, it can only happen when trees are healthy. If a tree is stressed due to drought or a beetle infestation then the process of evapotranspiration could be slowed or absent entirely.

In North America, more trees are planted than are harvested due to its high standards of sustainable forest management practices. When forests are healthy and sustainably managed they sequester carbon from the atmosphere to help lower global temperatures. Nature’s Packaging supports the use of sustainably sourced lumber used in wood packaging across North America.


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