In the face of climate change, loss of trees could become ‘last resort’

The Trump administration’s decision to reverse a presidential directive that designated more than 10 million acres in central and southeastern U.S. as protected wilderness has garnered headlines. Even the governors of both Alabama and Texas took the opportunity to pressure the White House to reconsider.

But in terms of lost tree cover — a measure of land affected by trees dying or turning to dirt, land that might not make news today, but could have been an important means of mitigating climate change — there has been little attention paid. And yet, there is no doubt that trees are playing a major role in mitigating climate change.

“The climate models say we are not going to have more rainfall, and we are going to have less,” David Barber, a tree researcher at the University of Alabama, told Time. The loss of trees “lessens the water supply, it alters the chemistry of the air, and decreases the amount of pollutants we can take into the atmosphere.” In other words, climate change is bad for the trees.

While planting new trees, whether new trees or old trees, is not going to reverse the climate change, it is an important part of mitigating climate change. And the issue is not only a matter of lost trees. Several environmental groups have put forth the idea of “desertification,” in which land temperature in certain regions of the U.S. is steadily rising and soil moisture is declining, especially in the arid areas of the southeastern U.S. The rising temperatures and lower levels of moisture have made it increasingly challenging for the trees to survive and to make new leaves that can provide the vital nutrients for the root system. Without new leaves, the tree starts to burn out prematurely. The fact that these fields of drought-stressed trees can take on water, say scientists, means that the loss of trees in these areas will play a critical role in global warming.

“The more areas of arid land where trees die, the less able we will be to cool the climate,” said Barber.

This situation can be seen, too, in the western U.S., where many younger trees are dying as the years progress. Cities in the Northwest have in recent years introduced programs to replant these dead-leaf areas, and to help control soil erosion, which can be increased by drought.

On the other hand, in regions where some older trees are performing well, they are even capturing carbon dioxide. So, while the loss of trees is a significant problem that affects the globe, cities and communities in the U.S. can, if they take action, lessen the blow.

To a certain extent, the lack of focus on this issue in the news is understandable. Climate change is a relatively slow-moving event, and many of the developments that will most affect people over the next 50 years are not immediate. The forest canopy is also very much an urban phenomenon, and a movement toward an “urban forest,” with cities planting trees in abandoned lots and in streets, is already under way in many cities.

If we do see a retreat from these trees, it is possible that they may lose some of their ability to absorb carbon dioxide — a point that has some people warning that any potential loss of trees could prove the “last resort,” to the point where a tree no longer acts as a carbon sink.

“If not looked after, forests like this could be disappearing, and our CO2 needs them — or helping prevent global warming — from continuing,” said John Nichols, a Washington Post columnist.

For the city residents in which this is already happening, it is also important that decisions are made in the near term about planting trees and about planting varieties of trees that can soak up carbon dioxide better. At the same time, these trees must be planted on suitable land, not on riverbanks and other unsuitable and very difficult areas to plant trees. It is necessary, as William Stearns, the chairman of the Tree Atlas Project, notes, to understand the characteristics of different tree species to determine which varieties could do the best job in a given area.

Loss of trees can be a health problem for cities, but its consequences are largely beneficial. Loss of trees and the loss of carbon is a function of the weather and of our behavior, and, in some cases, it is the effects of the new climate that are most important in assessing the full extent of the problem.

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