“We now live in a world that is as clearly our garden as was the Garden of Eden. We are fully responsible for the maintenance of the sustainability and beauty of Earth, our garden … and for its future as well.”
— Dr. Peter H. Raven, president, Missouri Botanical Garden
These were Peter Raven’s last words in his foreword to the Missouri Botanical Garden’s recent book, “Flora Mirabilis,” a beautifully illustrated timeline of how plants have shaped our world. His words echo those of Michael Pollan in his “The Idea of a Garden,” an essay that describes a “garden ethic” to guide Earth’s caretakers.
It is clear that we are not all behaving as caretakers of our garden, planet Earth. In last week’s column, I described how a non-native invasive insect, the Asian longhorned beetle, has destroyed more than 25,000 trees within the Worcester, Mass., urban forest. Why was this allowed to happen? Clearly our leaders are not elected on the basis of their desire and ability to maintain the sustainability and beauty of Earth.
In the well-managed garden, populations of native herbivores are balanced by native predators. The gardener, aware of this connection, works to build predator populations by ensuring that the nectar plants necessary to their survival are nearby.
Non-native pests create havoc because they have no natural predators in the invaded garden and thus the gardener has no control but to destroy the garden. This is what happened in Worcester.
Even after Dutch elm disease, chestnut blight, emerald ash borer and so many other invasive species disasters, something still prevents us from doing what is necessary to assure that there are no new invasions. It was predictable that wood-boring insect larvae would accompany shipments of pallets made from the insect’s primary native host tree. But we let it happen. We imported the beetle.
The Asian longhorned beetle, now precariously close to Maine’s border, was introduced to this country when the desire to capitalize on a booming global economy — in other words, greed — obscured all other thinking, and there were not enough gardeners among Earth’s caretakers to avoid the ensuing disaster. No one thought about inspecting or treating pallets before they left the home port — not until the damage was done.
What are the possible consequences of losing an entire urban forest? After all, Worcester’s lost trees can be replanted, avoiding the maples, birches and other species favored by the invasive beetle. The urban landscape will change in appearance, but in a few decades there again will be tree-lined streets.
But there are other facts to consider when we put a price on our urban trees. A mature tree, during a single season of photosynthesis, can absorb 48 pounds of carbon dioxide. This translates into 800 million metric tons of carbon sequestered in all of our nation’s urban trees, resulting in a saving of $22 billion if we wanted to control the release of all that global-warming carbon dioxide into the atmosphere. According to the U.S. Forest Service, the total carbon sequestration by all U.S. forests, natural and urban, offsets approximately 25 percent of U.S. human-caused emissions of carbon.
In other words, without trees taking carbon dioxide out of the atmosphere and sequestering the carbon within their tissues, the effects of global warming would be much greater and occur much sooner. Worcester’s loss is a global loss, yet experts tell us that future invasions of non-native pests are a certainty.
Where are Earth’s gardeners? Who is acting responsibly to maintain the sustainability and beauty of our world for our children and grandchildren?
I know of one gardener in Eastport, Lisa Garvin, who spends her time handing out leaflets at local campgrounds, asking out-of-state campers to help prevent the introduction of invasive insects, to not bring firewood from home into Maine forests. Lisa also speaks to community groups about the threat of emerald ash borer and Asian longhorned beetle to Maine forests.
Lisa and the other true gardeners of the world need help.
Send queries to Gardening Questions, P.O. Box 418, Ellsworth 04605, or to firstname.lastname@example.org. Include name, address and telephone number.