Overview
The American forest is not what it used to be. This comment has nothing to do with the amount of wilderness and wild lands located around the USA, but instead, refers to the diversity of plant life in forests that are left to natural selection. This demise is a process that has been occurring for over a hundred years. It began when the chestnut tree succumbed to the Chestnut blight and still continues today. Unfortunately recent evidence suggests that various species of trees are loosing their ability to survive at an increasingly alarming rate.
The Demise of the Dogwood
One of the most recent examples of a common type of tree that is close to being eliminated from the woods is that of the Flowering Dogwood, Cornus florida. Up until recently this understory shrub would light up the Appalachian understory and other parts of the Eastern Woodlands with its beautiful and showy white blossoms. Not only was this dogwood common in the forest, but it was prized by homeowners for its ornamental value as a medium-sized, flowering shrub that always put on a brilliant spring display.
The culprit in this trees demise is a blight caused by a destructive fungus, known as the dogwood anthracnose (Discula destructiva). The Texas Department of Parks and Wildlife describes the problem in this way; “Some scientists feel that the blight is so widespread that they hold little hope of saving flowering dogwood in the wild.“ Even horticulturists are turning to cultivars and other species of dogwoods to avoid the fungus infection.
The Chestnut Was the First To Go
The biggest change in American forests came in the early 1900s, when a fungal infection, called the Chestnut blight (Cryphonectria parasitica), virtually eliminated the mature American Chestnut from the forest. By 1940, mature chestnut trees were eliminated. Only trees aged seven years or less can survive, but the blight, kills these individuals before they can flower and bear fruit. The change in the forest, when this tree died was huge, for the chestnut was very important to wildlife and humans as a major source of food.
The Dutch Elm Disease
During the 60s and 70s, Dutch Elm Disease ravaged a huge number of ornamental trees, which had been planted throughout the Midwest and Eastern US. At the same time the tree was practically eliminated from the forest. These stately trees have survived on farms, front yards and street corners, but coming across a healthy tree in the forest is a rare event. Again the disease element is a fungus (Ophiostoma ulmi), but bark beetles play an important role in distributing the devastating micro-organism.
An Ominous Sign, The Potential Demise of the Beech Tree
The latest victim to plant disease is the American Beech. The threat is the beech bark disease, a fungus that is transported by an insect. Presently, the beech of the northeastern forests is in decline, but past history shows us that this decline could accelerate, thus destroying a very important source of food for deer, bear and other wild animals.
Global Warming and Plant Diseases
So far, the biggest factor in the spread of plant diseases has been the expanded mobility and commerce of modern man. Most of the problems discussed in this article are the result of fungal pathogens accidentally imported from foreign places, especially Asia. However, scientists are well aware that changes in the earth’s climate could affect the viability of various plant infections. Though research in this area is inconclusive, it is a definitely a place for real concern about the future quality of life.
