The Planet's Forests Are Becoming Younger And Shorter As Climate Change Bites

Large Samanea saman tree in Kanchanaburi, Thailand. karunpon/Shutterstock

The world’s forests are dramatically changing. A destructive cocktail of deforestation and climate change are leading to younger and shorter forests across the globe, ridding the world of the older and bigger trees that once watched over the forests. By no surprise, this radical change is only set to deepen over the coming decades and could make the planet’s environmental challenges all the more difficult to solve.

Reported in the journal Science, researchers from the US Department of Energy’s Pacific Northwest National Laboratory (PNNL) and a number of other research organizations investigated how deforestation and climate change have meddled with the planet’s forests over the last century. By reviewing over 160 previous research papers and combining their findings with satellite imagery, the team showed that human-driven environmental changes are reducing the quantity of older and bigger trees, replacing them with forests that are shorter and younger.

It’s as if the wise old elders are disappearing, handing over the reins to the inexperienced newbies. 

“This study reviews mounting evidence that climate change is accelerating tree mortality, increasingly pushing the world’s forests towards being both younger and shorter,” Dr Tom Pugh, study author and scientist at the Birmingham Institute of Forest Research in the UK, said in a statement“This implies a reduction in their ability to store carbon and potentially large shifts in the mix of species that compose and inhabit these forests.

While you might expect the atmosphere’s rising carbon dioxide levels to favor tree growth, the study argues that the bigger picture reveals that the negatives of climate change outweigh the positive when it comes to tree growth. With rising temperatures comes increases in wildfires, droughts, insect outbreaks, and other stresses that favor younger trees. Furthermore, the rate of global deforestation is sharply rising, which quite obviously is bad news for larger trees.

Forests play a major role in the carbon cycles of the global ecosystem, “sucking up” and storing vast quantities of carbon dioxide. On top of this, they are also home to an incredible amount of biodiversity, can help to regulate rainfall, and can prevent flooding. The researchers warn that younger forests just aren't as capable of fulfilling these roles, which in turn could spark a vicious cycle that drives further environmental changes.

“A future planet with fewer large, old forests will be very different than what we have grown accustomed to. Older forests often host much higher biodiversity than young forests and they store more carbon than young forests,” warned Dr Nate McDowell, lead study author and Earth scientist at the PNNL.

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