Trees Are Dying at Alarming Rate
A new study revealed the worrying plight of trees in the moist tropics where mortality rate of trees is increasing at an alarming pace.
According to the study led by Nate McDowell of the Department of Energy’s Pacific Northwest National Laboratory, lead author of the research, trees in some areas in the tropics are dying at about twice the rate they were 35 years ago.
McDowell projected worse to come.
“No matter how you look at it, trees in the moist tropics will likely die at elevated rates through the end of this century relative to their mortality rates in the past,” said Nate McDowell.
The study was based from the results of assessment of tree health in the tropical zone that spans South America to Africa to Southeast Asia.
Two Phenomena That Kill Trees
The scientists have named several factors contributing to the rising mortality rate of trees including including rising temperatures and carbon dioxide levels, drought, fires, more potent storms, insect infestation, and the abundance of woody vines known as lianas. However, two phenomena were found to be the dominant factors that led to the demise of world’s trees: “Carbon starvation” due to lack of food and “hydraulic failure” due to a lack of water.
Carbon starvation refers to negative impact of the higher temperatures that choke off trees’ ability to absorb CO2, in addition to intensifying their loss of water.
The researchers found that stomata, the tiny pores in the leaves of plants, close during hot and dry conditions. This will result in the failure of trees to absorb CO2. And if stomata remain closed for a long enough time, it can result in carbon starvation.
In addition, the lack of water also threatens the survival of trees particularly in hot temperature. The lack of water can happen in many ways. Rising temperatures pull more moisture out of trees due to higher evaporation rates.
The Importance of Protecting trees in the Tropics
Trees in the moist tropics play an especially important role in Earth’s ability to regulate carbon dioxide, absorbing much more carbon proportionally than all the other forests combined. Their deaths reduce the planet’s ability to cope with the high levels of CO2 that caused them to die to begin with, said McDowell, whose study was funded by DOE’s Office of Science.
“Trees have a great ability to survive, but there is only so much they can withstand – the question we now face is identifying those thresholds so we can predict risk to tropical forests,” added McDowell.