The issue is timely not only because it feels very much like fall/winter around these parts but because reminders of our dependence on trees are always timely.That dependence is an an underpinning of civilized life here on earth that we're prone to forget.
Because plants absorb carbon dioxide from the air and release oxygen, they make the atmosphere a lot more friendly for creatures who need oxygen to breathe like us. We in turn release carbon dioxide in our breathing process, a gas that trees like all green plants take in.
That oxygen-CO2 cycle is one of the reasons people are more likely to live a rich and happy life where trees flourish, Audubon Society writer Teri Dunn Chace points out in her essay "Tree Work: What trees do and how they do it" in the current issue. "Where there are no trees," she writes, quoting traditional wisdom, "life is as barren as the desert."
The value of this inter-dependent relationship between people and trees can be seen in landscapes that have lost their trees -- places that have been logged or stripped of trees by disease and the grazing animals that eat the new shoots before they can grow high. In these landscapes the soil erodes without tree roots to hold it. Poor soil produces less food. Human population declines.
But we're just getting started on what trees do for human beings. Trees also counter some of the effects of burning fossil fuels. These fuels produce greenhouse gases such as carbon dioxide. The gases trap sunlight and raise the air temperatures the way a plant nursery "greenhouse" heats the air inside of it. The process is the principal accelerator of global warming.
Trees reduce the greenhouse effect by removing some of the carbon dioxide from the air. They help make our environment more habitable for human beings and other living things. They can help, as scientists have been telling us for some time, save the world.
The cooling effect of trees works on the micro level as well. We're all aware of the relief from the heat provided by shade trees in summer. Shade trees cool our homes, streets and other impervious surfaces that turn densely developed urban areas into asphalt jungles. When it's hot downtown, my advice is to find a place with trees, grass, other plants. The air around you cools down at once and becomes more livable.
Trees provide habit for birds, squirrels and insects. We're not crazy about insects, but the birds who come to feed on the trees also reduce the noxious pests we really do have to worry about, mainly mosquitoes.
We're a long way from understanding how trees "think," but we do know they release chemicals that fight insect infestations and other pests such as harmful fungi. They also release substances that stimulate the growth of beneficial fungi that destroy insects pests such as gypsy moth caterpillars.
Given these considerations it's interesting, though perhaps not surprising that the the writers of the Audubon's "The Lives of Trees" issue invoke Tolkien's "Ents," the tree-like beings who watch over forests, to give trees their just place in our world view.
"Tolkien's sense that trees are sensitive and worried about their survival or indignant at abuses doesn't seen so fanciful," Chace writes. "Although trees seem permanent and durable, they are vulnerable. We ought to be giving these grand complex beings the space and respect they need and deserve -- for their survival as well as our own."
In another article called "The Oak Tree's World," writer Michael Caduto also references the Ents. "I imagined a wise oak and wondered what it would have to say if I understood the language of Ents," he writes. The tree might say that it has seen it all, he concludes. Native trees can live at least three times as long as humans, giving them a unique standing in nature.
The tree is "the suture that ties mineral to air, water... and fire," Caduto writes.
We also also, it seems to me, can continue that metaphor to say that trees are one of the main "sutures" that tie human beings to the earth.
We see trees come down in storms, attacked by blights and removed for a host of reasons by human society. But we should never take them for granted. One of the foundations of human existence on earth is "living with the trees."