Wildlife Biologist, Specializing in endangered wildcat research.
Tables Of Contents:
Introduction: Finding A Flowering TreeAs we approached the rare, flowering American chestnut (Castanea dentata), our work crew was greeted by the tangy smell of pollen. I looked up at the white catkins glowing in the July sun and wondered how black bear and deer might have reacted to this sight so many years ago. Did they associate the smell of chestnut pollen with the spiny burs that would cover the ground in October? Did their mouths water in anticipation of the sweet, thin-shelled nuts contained within those painful capsules?
For over fifty years, most wild and human inhabitants of the eastern United States have been deprived of the joys and sensations of living with American chestnut trees. In Colonial times, the range of the American chestnut stretched from southern Maine to Georgia, Alabama, and Mississippi and as far west as Ohio. It is estimated that chestnut trees comprised 25% of eastern forest canopies. However, by the mid-1900's two imported diseases had decimated the species.
Last summer, our volunteer group, members of the Massachusetts Chapter of the American Chestnut Foundation, with personnel and equipment donated by Massachusetts Electric, did our first field work in the decades-long battle to return the "Sequoia of the East" to its former glory.
Some chestnuts still persist in the form of stump sprouts -- ghosts of their former selves. But they seldom live long enough to flower. Also, chestnuts are self-infertile; a tree can not fertilize its own female flowers and produce viable seed. If a sprout does grow large enough to bear flowers, it is very unlikely that another will flower close enough to it for fertilization to take place. Lack of sexual reproduction dramatically reduces the chances that our native chestnut trees would ever naturally evolve resistance to the foreign disease that destroys them.
The aim of our crew, headed by Dr. Anne Myers, was to pollinate the tree located in Randolph, Massachusetts. Reaching the canopy with the help of a bucket truck, retired forester Rufin Van Bossuyt, assisted by David Bellavance of the Asplundh Tree Company, first stripped the pencil-sized male catkins from the terminal end of flowering branches. Then he brushed male catkins from blight resistant Chinese-American hybrids across the tops of the remaining female burs. Finally, he attached a long bag to the end of each twig to insure that nuts would not be lost before they could be harvested. After 100+ bags were in place, we began the long wait. Like anxious parents, we worried all summer whether any chestnut embryos had been produced.
Chestnut species have a worldwide distribution in the northern temperate-zone. European (Castanea sativa), Chinese (Castanea mollissima) and Japanese (Castanea crenata) chestnuts have been cultivated in the Old World for thousands of years. Although tall, forest chestnuts exist in Eurasia, most trees imported into the United States were short, orchard varieties.
One can recognize American chestnut (C. castanea) by its 6-10 inch-long, lance-shaped leaves that are bordered with curved, shark-like teeth. Volunteer workers who survey areas for surviving sprouts say that these leaves grab your attention because they almost snarl at you. American chestnuts can be distinguished from Old World species by examining the leaves. American chestnut leaves are thin, dull, light green, and have tapered bases. Often, American chestnut leaves droop down from branch twigs. Chinese chestnut leaves are thick, stiff and shiny. Also, American chestnut leaves are relatively hairless. The leaves of European trees are so hairy that they often feel fuzzy. Seeds of native chestnuts are usually about 1/2 inch in width, much smaller than cultivated Eurasian nuts sold in grocery stores.
In Massachusetts the tree most often mistaken for the American chestnut is a much-planted ornamental called the horse chestnut (Aesculus hippocastanum). This species displays distinctive, conical clusters of flowers ten inches long and three to four inches in diameter. The horse chestnut also bears large nuts that have a very bitter taste and are considered to be poisonous (Little 1980).
Chestnuts, and other trees that produce large seeds, are collectively called mast-producers. Mast is extremely important to wildlife, because most vegetable foods they consume (grass and leaves) are very low in digestible nutrients. Nuts and seeds, however, contain high concentrations of fat, protein and carbohydrates. Anyone who has owned a horse or raised cattle or poultry knows how critical grain is to the growth and maintenance of body condition in these animals. Similarly, the availability of mast has been linked to great variations in the condition and reproductive performance of deer (Torgerson and Porath 1984) and black bear (Eiler et al. 1989, Elowe and Dodge 1989). Turkey, ruffed grouse, wood ducks and squirrels are also known to consume large quantities of nuts.
The elimination of chestnuts from eastern forests may have negatively affected wildlife populations. Red and white oaks replaced chestnut trees. But red oaks only produce significant numbers of acorns every two to five years and white oaks give a good crop at four to six year intervals (Elias 1980). Chestnuts, perhaps because they flower in July after spring rains and frosts, produce a good crop of nuts almost every year. The consistent mast production of chestnuts probably buffered variable acorn years and supported healthier, more stable populations of mast consumers.
Early records indicate that Native Americans gathered chestnuts for food (Cronon 1983). It can be assumed that they favored them over other American nuts, as did the European colonialists. Chestnuts are better tasting than bitter, tannin-filled acorns and easier to shell than hickory nuts. In southern New England, where birch trees were not available, Indian people hollowed out chestnut trees to make canoes.
No tree in eastern forests was as useful to humans as the American chestnut. The nuts were an important source of cash money and food in poor, rural areas. Trainloads were shipped to big cities each fall, and attics of homes in Appalachia were often stacked to the rafters with bags of chestnuts (Youngs 2000).
Chestnut trees were also an important source of lumber. Unlike most hardwood species, chestnuts often grew with a long straight trunk, to a large diameter, and reached heights of 100 feet. Trees on the best sites were often several feet at breast height; planks wide enough to form the entire back of a church pew could be sawed from them. Although strong, chestnut was lighter and easier to work than many hardwoods, an important attribute in the days before carbide-tipped saws and electric drills.
Chestnut has another very valuable property. It is highly rot resistant. This is due to high concentrations of tannin in the wood. Formerly it was used for sills, floor rafters, fence posts, railroad ties and utility poles. Brian Sullivan, Senior Arborist for Massachusetts Electric, reports that a few years ago, chestnut utility poles were still in service in southern Massachusetts. Today, only relatively scarce redwood or woods treated with toxic chemicals are available for use where wood will be exposed to moisture.
Diseases That Ravaged American Chestnut TreesAlthough the dramatic chestnut die-off of the early 1900's was caused by the chestnut blight (Cryphonectria parasitica), the assault on the American chestnut actually began a hundred years earlier. In 1825, another imported disease, Photophthora root rot (Phytophthora cinnamoni), began killing American chestnuts and a related tree, the chinquapin (Castanea pumila), in Georgia.
Dr. Sandra Anagnostakis, Plant Pathologist at the Connecticut Agricultural Experimental Station, emphasizes that, due to a lack of controls on the importation of plants prior to the twentieth century, both diseases were probably introduced into this country many times. Some pathologists believe that Photophthora root rot may have been introduced via exotic plants brought to southern estates from Asia. This disease is also known to be a serious pathogen affecting cork oak trees in southern Europe. Cork oak trees were extensively introduced into the southern states before the outbreak.
P. cinnamoni is a member of a group of organisms known as water molds. It infects trees hardest in heavy southern soils that do not drain rapidly. The fungus causes the formation of lesions on roots that bleed an inky-blue liquid. Thus it's common name: "ink disease." When the lesions girdle roots and the root collar of a tree, it dies. Some trees on well-drained slopes initially survived this disease.
It is usually reported that chestnut blight was first observed in 1904 on an American chestnut tree in the Bronx Zoological Park in New York City (Cochran 1990). The disease, however, was already widespread in the Northeast by 1904 (Anagnostakis 2000). Unfortunately, the hunger of Americans for chestnuts caused them to start importing potentially infected trees early in this country's history. Thomas Jefferson brought cuttings of European chestnuts to Virginia in 1773. Japanese trees were first imported in 1876. After 1876, a large number of trees were imported from Japan and Europe and distributed throughout the east by mail order nurseries.
The chestnut blight fungus also infects European, Chinese and Japanese chestnut species (Griffin 2000). Presumably, because the ancestors of these trees evolved with the disease, they show differing degrees of resistance to it. They can, therefore, act as dangerous vectors or carriers of the disease.
Efforts were made to limit the spread of the chestnut blight by cutting diseased trees and buffer areas of healthy trees (Newhouse 1990), but nothing worked. By the 1950's, the plague of blight had reduced billions of stately trees to the scattered broomstick-sized sprouts that we see today.
A great deal of salvage logging took place in the early 1900's so that the wood of dying trees would not be wasted. In retrospect, because so many living trees were also cut, it is possible that genes of trees that might have been resistant to the disease were lost forever (Anagnostakis 2000). The practice of cutting live trees in the path of an insect pest or potentially lethal disease is common today and should be reevaluated.
Chestnut blight disease spreads when sexual spores of the fungus are released into the air in the fall. Spores also move through the forest on the feet and bodies of forest animals and insects. The spores infect trees through small wounds in the bark. In American chestnut trees, the organism kills the living tissues under the bark down to the wood. The result is a gaping wound or canker, which increases in size until the affected branch or trunk is girdled. The portion of the tree above the girdled area dies. In untreated American chestnuts, most above-ground stems of trees are killed within a few years of initial canker appearance.
Then something life affirming happens at ground level. Other fungus species in the leaf litter halt or kill the blight organism. The roots survive and often send up sprouts from embryos present in the root collar. While not a practical large-scale solution, infections can be killed or retarded on selected trees by "mud packing" leaf mold on open cankers.
Another type of biological conflict causes the blight to be non-lethal to many infected European chestnuts. Strains of the blight in Europe are infected with a fungal virus (Cryphonectria hypovirus 1). These "hypovirulent" strains of the blight infect only the outermost bark tissues and usually do not kill a tree. It is believed that these blight strains do not kill European trees because 1) the virus weakens the blight fungus, and 2) because European trees have some natural resistance to the disease. Efforts have been made to use hypovirulent strains of the blight as a biological weapon to defend chestnuts in American forests. Control of the blight on individual trees and in localized areas has been achieved by applying virus-infected blight to cankers and trees targeted for protection.
This strategy, however, does not appear to be the solution necessary for widespread control of the blight on this continent. The infected strain of blight does not always survive in the field and it is not efficient at passing the virus to blight fungus in adjacent areas. This means a large reservoir of the deadly wild type blight remains in the local ecosystem waiting to kill vulnerable trees. Finally, although American chestnut trees protected with hypovirulent blight survive, their growth often appears to be retarded and numerous healed cankers reduce the quality of the trees for lumber.
The approach that promises the fastest results involves using individuals of the Chinese and Japanese chestnut species that exhibit a high level of natural resistance to the disease. Theoretically, it should be a straightforward process to breed blight resistant characteristics into American chestnuts by crossing them with Asian varieties.
Unfortunately, long generation time and conflicting characteristics of American and Asian species have combined to prolong breeding efforts over many decades. Chestnuts take six to seven years to bear seed, so it requires many years to accomplish even a few cross attempts. In addition to blight resistance, a tall, upright forest chestnut is needed that will compete well with other American trees Many progeny of breeding trials retain the short, orchard growth form and are unacceptable.
Arthur Graves started making chestnut crosses at the Connecticut Experimental Station in 1930. The better hybrids from the Connecticut effort are now being bred with surviving Virginia American chestnuts at the Meadowview research farm in Virginia. Dr. Fred Hebard is directing this breeding program for The American Chestnut Foundation [TACF] (Hebard 2000). It is expected that their sixth generation Intercross (BC3F3) will be blight resistant and have 93.75% American characteristics. The TACF hopes to have seed of this blight resistant American chestnut by the year 2006.
Unfortunately, Meadowview trees may not be well adapted to living in areas far from Virginia. In an attempt to produce blight resistant trees better adapted to local conditions, state Chapters of the TACF are pollinating neighborhood American chestnut survivors with pollen from Meadowview blight resistant crosses.
Another group, The American Chestnut Cooperator's Foundation [ACCF], lead by Professor Gary Griffin, Virginia Polytechnic Institute, is attempting to breed a blight resistant tree by using only American chestnut parents. This "all-American" program has already identified American chestnut trees with low levels of blight resistance. A good chance exists that crossing, raising, and testing large numbers of these trees will eventually result in the discovery of individuals with a significant level of blight resistance. This is a massive effort. As of March 2000, cooperating growers have planted 64,003 seedlings and approximately 23,570 seed nuts from ACCF's orchards. Information on their efforts is available at: http://ipm.ppws.vt.edu/griffin/accf.html.
Dr. Anagnostakis, at the Connecticut Agricultural Experimental Station, has proposed an elegant recovery procedure that combines elements of the strategies described so far. Her procedure addresses a problem of limited genetic diversity. To date, only 30+ American parents have been used to produce blight resistant hybrids.
Dr. Anagnostakis plans to plant 40 tree plots of blight resistant Asian/American hybrids in forest areas populated with surviving American chestnut sprouts. American sprouts surrounding the plot will be protected with applications of a biological control based on the virus-infected strain of the chestnut blight. Kept alive long enough to flower, the American sprouts will have the opportunity to interbreed with the resistant hybrids. The progeny will incorporate the genetic variety of surrounding American trees; many will have the blight resistance of the Asian/American hybrids. Virulent forms of the blight present in the environment will kill off individuals that are not strongly resistant. In the future, the forest stand will consist of highly diverse, blight resistant American trees.
Our group returned to the Randolph tree in mid-October. Many bags contained small burs suggesting that our pollination attempt had failed. But after ripening for two weeks, the burs opened and yielded 62 nuts. Another work crew headed by Timothy McKechnie recovered approximately 100 nuts from a tree they pollinated in Holland, MA. Not a great harvest, but we have enough seeds to start breeding a blight resistant tree adapted to the colder climate of Massachusetts.
Review of breeding projects suggests that it is technically possible to recover the American chestnut as a dominant species in the eastern United States. However, the history of past efforts to recover extirpated species indicates that success will depend upon whether human society acts to support or obstruct the effort.
There are two major obstacles to the recovery of the American chestnut. First, the continued importation of diseased and insect-infested plants into North America threatens to overwhelm the efforts of biologists and concerned citizens. Second, the unethical and unsustainable economic strategy of using population growth to fuel economic growth is rapidly consuming space that is needed for all species of wildlife in the United States.
In 1912, the Plant Quarantine Act was passed in response to the chestnut blight epidemic. The US Customs Service, the U.S. Department of Agriculture and other governments agencies are working hard to prevent future biological catastrophes, but they need the help and cooperation of all Americans. Those concerned about the environment should consider a self-imposed moratorium on the transport of plant or animal material into American ecosystems. Exotic plants and animals are luxuries that people with the highest standard of living in the world should be able to do without. The most rigorous inspections and quarantines may not detect insect eggs, fungus, and viruses lurking in plant tissues.
In 1974, a new threat to the American chestnut was imported into Georgia. Some Japanese chestnut twigs that did not go through plant quarantine contained an insect called the Oriental Chestnut Gall Wasp (Anagnostakis 2000). It has now spread to Alabama, southern North Carolina and Tennessee. Another research and breeding effort, that will take many years, may be necessary to control this new enemy.
In addition, a number of other introduced diseases and insects are currently rampaging through the forests of North America. These include the woolly adelgid (Adelges tsugae Annand), an insect that kills Eastern hemlocks (Ellis 1994, Allen 1999), and beech bark disease, a scale insect/fungus combination that strips bark off American beech trees (Cammermeyer 1993, Houston and James 1999). In the western states another imported fungus, Blister rust, is destroying the whitebark pine (Baskin 1999).
Both the American beech and the whitebark pine are important mast producers. Lose of whitebark pine mast has already negatively affected struggling grizzly bear populations in the Rocky Mountain states (Mattson et al. 1992, Tomback 2000).
If transport of biological material is necessary, citizens should obey rules and regulations regarding the importation of plant and animal material into the United States. Elected officials should be encouraged to support government quarantine efforts and to increase publicity advocating compliance with the 1912 Plant Quarantine Act. Penalties for violating this act should be increased to a level commensurate with the damage done by past introductions of pathogens like the chestnut blight.
The planting of exotics already present in the United States should also be avoided. The movement of non-native plants around the country can facilitate the spread of undetected diseases and insects. In addition, exotic plants can escape cultivation and crowd out American species. Also, many aggressive foreign plants have little nutritional value to North American birds and mammals.
North America has a great diversity of native species that can be used in gardens and for landscaping. Gardeners should question retailers about the origin of their plants and trees and request that they stock species native to the local region. A great business opportunity exists for enterprising nurserymen to cultivate interesting native plants and to encourage people to "Plant American." People should also insist that local and state agencies stop planting exotic trees and plants. They should find or develop resistant strains of American species if salt or pollution tolerant varieties are needed for roadside plantings.
Cutting or replacing dead or live exotic trees with native species should be considered. An eradication effort is now under way in southern California because of the self-proliferation of imported eucalyptus trees. In the east, space is needed to recover the American elm that was devastated by Dutch elm disease a few decades ago. Cutting of Norway maples that are beginning to get out of control and replacing them with disease resistant American elms would accomplish two environmental tasks. A resistant tree called the American Liberty Elm was developed (Laycock 1990) and is distributed by The Elm Research Institute in Westmoreland, NH.
The expansion of the human population in Massachusetts threatens to defeat the recovery of the American chestnut in this state before the first blight resistant tree is planted. From 1992 to 1997, an average of 56,300 acres per year were developed here (Kosova 2000). States like Texas have had more growth recently (243,930 acres/year). But the small size of Massachusetts and its already high population density of 780 persons per square mile (Texas has 74 persons/square mile) (Rand McNally 1999) mean that further development will have an extremely negative effect on our local ecosystems. Well-drained woodland, which is the only good habitat left for chestnut trees, is under development pressure by builders in many Bay State communities.
Local officials have recently expressed a lot of well-intended interest in suburban planting of blight resistant American chestnuts as a way to participate in the preservation of this species. There is, however, a real danger that the conspicuous presence of a few trees will delude the public into thinking that the species has been truly recovered. If remaining woodland is bulldozed to house and service an increasing human population, the relatively few trees that can be planted around public buildings and in people's backyards will not constitute a large enough population to survive future biological attacks.
Success will only be achieved when whole hillsides, in every community, turn white with July blossoms and when great expanses of forest floor are covered with jewel like chestnuts every October.
More information about efforts to recover the American chestnut -- and how you can help -- can be found at the Massachusetts and National Chapters of the American Chestnut Foundation, www.machapter@acf.org and www.chestnut@acf.org.
Most ecologists believe that the human population of the United States must be stabilized to insure environmental health, a decent standard of living and basic human rights. Some wildlife biologists (Czech 2000, Hoecker 1997) and a number of advocacy groups are beginning to expose the fallacy that human population and economic growth can continue in a sustainable way. Brian Czech in his article "Economic growth as the limiting factor for wildlife conservation" and in his book, Shoveling Fuel to a Runaway Train, recommends transition to a steady-state economy. Of the groups advocating population stabilization, The Carrying Capacity Network most accurately communicates the link between population growth and environmental degradation through articles in its quarterly publication Focus (Abernethy 1994, DinAlt 1994, Giampietro and Pimentel 1994, Hartley 1994). The website is www.carryingcapacity.org.
Abernethy, Virginia. The demographic transition revisited: Lessons for foreign aid and U.S. immigration policy. Focus. Carrying Capacity Network. Vol. 4, No. 2. 1994.
Allen, Scott. Trees lives cut short. Boston Globe. August 9, 1999.
Anagnostakis, Sandra. Plant Pathologist. Connecticut Agricultural Experimental Station. Two interviews and seminar presentation titled: "Chestnut research in Connecticut; Chestnut history in New England" First Annual Meeting of Massachusetts Chapter of The American Chestnut Foundation. Framingham State College. Framingham, MA. November 18, 2000.
Baskin, Y. Trouble at timerline. Natural History. November 1999.
Cammermeyer, Jay. Life's a beech - & then you die. (Insect and fungus infestation of US forests). American Forests. v99 n7-8. July-August 1993
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Cronon, William. Changes in the Land: Indians, Colonialists, and the Ecology of New England. Hill and Wang, New York. 1983.
Czech, Brian. Economic growth as the limiting factor for wildlife conservation. Wildlife Society Bulletin. Spring 2000.
Czech, Brian. Shoveling Fuel for a Runaway Train. University of California Press. Fall 2000.
DinAlt, Jason. The environmental impact of immigration into the United States. Focus. Carrying Capacity Network. Vol. 4, No. 2. 1994.
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Ellis, David. The war on woolly adelgids. American Horticulturist. V73 n9. September 1994.
Elowe, K. D. and W. E. Dodge. Factors affecting black bear reproductive success and cub survival. Journal of Wildlife Management. 53:962-968. 1989.
Giampietro, David and Pimentel, David. The tightening conflict: Population, energy use, and the ecology of agriculture. Focus. Carrying Capacity Network. Vol. 4, No. 2. 1994.
Griffin, Gary J. Blight control and restoration of the American chestnut. Journal of forestry. February 2000.
Hartley, Peter. Sustainable engineering: Resource load carrying capacity and K-phase technology. Carrying Capacity Network. Vol. 4, No. 2. 1994.
Hebard, Fred V. Meadowview notes 1999-2000. Journal of the American Chestnut Foundation. Summer 2000.
Hoecker, Steve. Human population growth: Striking at the root. Bugle. Fall 1997.
Houston, D. R. and James T. Beech bark disease. Forest insect and disease leaflet 75. Dept. of Agriculture. Forest Service. 1999.
Kosova, Weston. The race to save open space. Audubon. April 2000.
Laycock, G. There will always be elm. Audubon. May 1990.
Little, Elbert L. National Audubon Society Field Guide to North American Trees, Eastern Region. Chanticleer Press, Inc. New York. 1980
Mattson, David J., Bonnie M. Blanchard, and Richard R. Knight. Yellowstone grizzly bear mortality, human habituation and whitebark pine crops. Journal of Wildlife Management. V56 n3. July 1992.
Newhouse, Joseph R. Chestnut blight. Scientific American. July 1990.
Rand McNalley. Data for density calculation taken from: Rand McNalley Road Atlas, United States, Canada, Mexico. 1999.
Tomback, Dianna. Whitebark Pine Communities. Island Press. Covelo, Cal. 2000.
Torgerson, Oliver and Wayne R. Porath. Midwest oak/hickory forest. In White-tailed Deer Ecology and Management. Editor Lowell K. Halls. Stackpole Books. Harrisburg, PA. 1984.
Youngs, Robert L. A right smart little jolt: Loss of the chestnut and a way of life. Journal of Foresty. February 2000.
Serial Rights © 2000 Winthrop Staples 14 Abbey Street, Randolph, MA 02368 || Telephone 781-963-4762 || All photographs by W. Staples. Photographs cannot be reproduced without permission of photographer