The Next Page: Six Degrees of Vegetation -- keeping our trees and plants hardy and hale
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Each generation takes the earth as trustees. We ought to bequeath to posterity as many forests and orchards as we have exhausted and consumed. -- J. Sterling Morton
Soon after newlyweds Julius Sterling and Caroline Morton staked their Nebraska City land claim in 1854, they realized how much they missed the lush treescape of their former home in New York. Even more homesickness-inducing was that, in the bustling nexus of adventurers, homesteaders and profiteers that was the Midwest of the time, the sense of community was as featureless as the windswept landscape.
But J. Sterling -- journalist, statesman and outspoken nature lover -- passionately believed in the power of planting. If he could just get local folk to gather around the park -- after building one, that is -- he was sure that the benefits of nature-based community involvement would flower.
As editor of the Nebraska City News, and later as secretary of agriculture under President Grover Cleveland, Morton promoted the many ways in which trees, and nature in general, could improve lives. On the economic end of things, tree cultivation would lock down the soil for agriculture and housing -- and responsible harvesting of the mature trees years hence would be a commercial boon to future generations.
More important to Morton, though, was the bonding that might occur over hoes, shovels and mulch. Morton's vision was of a society whose civic pride centered on the preservation of nature, with generation upon generation of citizens drawing inspiration under the shade of trees planted by their elders. You may even know the quasi-holiday that Morton founded to bring up younger generations in the ways of trees: Arbor Day.
I speak for the trees, for the trees have no tongues. -- The Lorax, via Dr. Seuss
Jump to 2010 and another tree-loving Morton, my colleague Cynthia Morton, associate curator of botany at the Carnegie Museum of Natural History. With a scientific mission that parallels J. Sterling's societal one, this Morton (no relation to J. Sterling) has been investigating the impact of genetic cloning upon the biological and genetic diversity of nursery-stock trees.
Cloning is a widespread horticultural technique for reproducing desirable plants on a large scale. Certain plants -- chosen for hardiness, size or even pretty pink stripes -- are reproduced through seeds, cuttings, grafts and the like. The new plants are genetically identical to their parents, and off they go to market.
Slightly amazed that no one had ever researched the long-term impact of the practice, Dr. Morton and colleague Phil Gruszka, director of park management and maintenance for Pittsburgh Parks Conservancy, began to investigate. They started with the London plane trees (sycamores) planted during the Schenley Park renovation of 2006-07.
Dr. Morton and Mr. Gruszka's preliminary research suggested something stunning: the genetic diversity among widely planted urban trees was much less than that of even the population-challenged American chestnut tree.
For the benefit of those who weren't around for the chestnut blight: In the first half of the 20th century, a fungus wiped out about 4 billion American chestnut trees, amounting to a quarter of the U.S. hardwood tree population. This devastated not only the lumber industry, but also mom-and-pop economies based around the consumption of nuts by both humans and livestock. The U.S. chestnut population has not recovered.
Such blights often go hand in hand with a chain of repercussions that eventually affect humans -- a kind of "six degrees of vegetation." Infamy has laid claim to the Irish Potato Famine of the 1840s, caused by a fungus affecting the most widely planted species of potato in Ireland.
The last decade has witnessed the mischief of the emerald ash borer. As its name implies, this little beetle's larva munches right into its tree victim, creating so much damage that the ash dies within three or four years. (The pretty green bug has even earned its own holiday of sorts: Emerald Ash Borer Awareness Week, which begins today. Fire up the grill and chill some brewskies.)
Past eco-disasters involving widespread tree loss have secondary effects: reduced pollution control (trees "scrub" the air of grime), more soil runoff (a particular problem in Pittsburgh's rapidly developing suburbs), higher air-conditioning bills in the summertime (trees provide cooling shade). The Pennsylvania Landscape & Nursery Association will only estimate the pending economic impact as "in the millions." Its leaders have crossed their fingers that damage caused by the beetle doesn't reach the billions.
What does all this have to do with the identical DNA of the Schenley Park trees?
Well, the aforementioned devastation to lives and livelihoods has been caused by fungi or critters that homed in on one certain plant group. When a particular region -- whether a city park or a whole state -- is chock full of one or a few closely related species of plant, it sets up a smorgasbord for any opportunistic attackers that might have a taste for those species.
Preliminary studies indicate that 60 percent of urban forests are made up of only 10 different tree species, which is what caught Cynthia's attention in Schenley Park: The new trees might be genetic sitting ducks.
If landscaping choices that are low in biodiversity include plants with low genetic diversity, no one really knows what the impact of the next infestation might be -- regionally or globally, ecologically or economically.
Have cities and homeowners been planting their way into a genetic crisis?
What would J. Sterling think of us?!
Well, all is not lost. This is where future-reaching technology steps in to save the day -- or at least to lend a helping hand.
If you think in terms of a year, plant a seed; if in terms of 10 years, plant trees; if in terms of 100 years, teach the people. -- Confucius
The population explosion of trees and plants cloned over the past two decades impacts anyone affected by ecology and economy ... which is everyone.
As we've learned from the chestnut, potato and ash calamities, the genetic makeup of plants may set them up for some serious damage. Actions of humans are not to blame for the widespread devastation wrought by those particular species. However, humankind might definitely be in the hot seat for ignoring the implications of artificially limited genetic diversity. How much worse might these blights have been if engineering by humans had made these plants even less genetically diverse?
Now, don't rip out your propagated posies just yet. This is not to say that the cloned plants gracing your neighborhood are going to shrivel up and die tomorrow. To paraphrase stock market lore, past genetic performance does not predict future results, and there's no guarantee that cloning will or won't be at the (ahem) root of the next major blight.
However, by taking genetic factors into consideration, modern conservation efforts are now applying the chestnut/potato/ash lessons learned. Great strides have been made in cross-breeding at-risk species with related species that show increased disease resistance. These genetically engineered versions are proving more capable of withstanding the onslaught of the creepy crawlies.
And then there are the naturally occurring, non-engineered species that are cloned to promote a specific trait -- and which have excelled in that capacity.
Take the American Liberty elm. It's highly resistant to the single-minded Dutch elm disease, which has wiped out an estimated 50 percent of the nation's elm trees since the responsible fungus' arrival in the United States in 1928. The same goes for the Chinese chestnut, which is naturally resistant to the American chestnut blight. We simply have to start considering what we're cloning, and why we're cloning it.
Cynthia Morton is in the thick of things. Her use of genetic research techniques that have only become available within the past decade or so is an early step toward determining the extent and importance of genetic diversity among common nursery-stock plants. Future goals for this research by Dr. Morton and her colleagues include recommendations to the USDA on the study and regulation of propagation techniques.
Without love of the land, conservation lacks meaning or purpose. For only in a deep and inherent feeling for the land can there be dedication in preserving it. -- Sigurd F. Olson
The modern Morton's research goals dovetail with J. Sterling's vision of more than 130 years ago: Long-term management of the environment is the responsibility -- and pleasure -- of every citizen. We betray this trust at the peril of lasting ecological and economical effects.
Both Mortons would highlight the measure of personal responsibility inherent in horticultural practices, whether you're a grower or a buyer. Not to mention the economics of beautification, on which both Mortons also agree: If federal and local agencies are going to spend trillions on property improvement -- and homeowners are shelling out their own millions -- isn't it worth our time and money to invest in species that both please the eye and stand a better genetic chance of surviving the next blight that might emerge?
You may wonder: How do we follow in the Mortons' footsteps?
First, check out local conservation and beautification efforts. The Western Pennsylvania Conservancy relies on volunteers to cultivate gardens along roadsides and other urban nooks. The Pennsylvania Department of Conservation and Natural Resources throws regular events where nature lovers can come face-to-face with some of the plants and critters being saved. Also be sure to check out the sidebar on how to choose plants for your own landscaping project.
J. Sterling would be proud.
Planning your own landscaping project? Here are some tips on choosing ecologically and genetically responsible foliage:
Ask your nurseries where they get their stock. Avoid mass-cloned choices in favor of varietals propagated from older trees and plants-often carrying the designation "heritage."
Encourage elected officials to develop "recycling" programs that offer healthy plants reclaimed from land development projects. As Cynthia Morton points out, "If we're recycling and reusing everything else from cans to parts of old buildings to shopping bags, why can't we recycle and reuse our plants?"
"Plant native, grow local" goes the eco-proverb. Seek out local nurseries and growers who are knowledgeable about plants native to the area. A great Western Pennsylvania resource is the Audubon Center for Native Plants at Beechwood Farms Nature Reserve (aswp.org).
Learn more about species of concern and how you can help. As a start, a wealth of information is available from the American Chestnut Foundation (acf.org) and from the U.S. Forest Service's emerald ash borer site (emeraldashborer.info).
First Published May 23, 2010 12:00 am