The Resilient World

A great post on an ecological holocaust that happened in my own back yard. The loss of this vast economically important forest resource was a blow to Appalachian communities and may have driven many into poverty. Its cause was horticulture - it is believed that the blight was introduced in nursery stock from Asia for plantings in the New York Botanical Garden.

Modern introductions can be prevented through high standards for handling of nursery stock, and early detection and rapid response. But how effective are our quarantine measures? Seen any stinkbugs lately? The presence of these introduced pests strongly suggests that our systems are not working. It is only a matter of time before another economically devastating epidemic occurs without vigilance. And are we prepared to pay for that vigilance? In light of the current economic distress, there is every reason to expect that budgets for control of invasive species will be cut to the bone. This is not a strategy that promotes resilience.

Amplify’d from schaechter.asmblog.org

When you read the title—The Great Epidemic—what came to mind? The Black Death (Yersinia pestis) that in two years killed 20 million people in Europe—approximately 30-60% of the population? The 1918 flu pandemic with its tally of 50 million dead in three years? AIDS, with a death toll projected to reach 200 million by 2025? Or perhaps that 20th century epidemic that struck down over three and a half billion in North America in the space of a few decades—the American chestnut blight? These chestnut trees, Castanea dentata to be precise, were stately giants often 100 feet or more in height with crowns that spanned 100 feet. Their straight trunks provided billions of dollars worth of beautiful, rot-resistant wood, and the bountiful nuts provided far more than the traditional stuffing for Thanksgiving turkeys. Combined they had made up a quarter of the forest canopy from Maine to Mississippi.

What does the future hold for the American chestnut? Several strategies are being pursued in hopes of countering the blight. One is to employ the hypovirulence plasmid as a biological control agent. Hypovirulent strains had spread naturally throughout many parts of Europe in the wake of the blight itself, reducing mortality but not eliminating the virulent strains. Since the 1970s this process has been helped along in European chestnut orchards by inoculating virulent cankers with a hypovirulent strain. This proved to be quite successful in spreading the hypovirulent strains and reducing the severity of the blight in Europe, but similar efforts in America failed. Why? The answer is not known, but one can make various conjectures here. It could be that the European hypovirulence plasmid can't compete with other genomic elements already present in the American chestnut or its spread by anastomosis is hampered by vegetative incompatibilities between fungal strains that prevent hyphal fusion. Also, since the hypovirulent fungal strains produce fewer spores, they may lose out in the competition for new hosts. Read more at schaechter.asmblog.org