Among threats to the vital services provided by forest ecosystems, they say, are residential development, climate change and illegal logging operations in the tropics.
"In the 1950s, we assumed that the forests were not going to change," said Richard Waring, retired professor of forestry at Oregon State University and co-author of the book. "We assumed that if you disturbed them in a certain way, they would come back. Right now it looks like some of the drier forestlands will be in continuous transition to ecosystems that may not include trees at all."
Since it is buffered by the Pacific Ocean, the West Coast is relatively unusual. Climate change models show that the conditions there for tree growth are likely to stay the same or even improve.
In the 1980s, Waring said, scientists began to realize that their assumptions of forest stability were wrong. They began incorporating rising atmospheric carbon-dioxide levels into their computer models of forest ecosystems. In a few places, unprecedented insect outbreaks and fires began to occur.
Waring and Joseph Landsberg, a forest biologist in Australia, detail their thoughts in a new book, "Forests in Our Changing World," published by Island Press.
Managing forests for sustainability, they said, will mean controlling destructive, often unregulated logging operations in the tropics; turning forest slash into the soil rather than burning it; increasing resilience by planting multiple species of trees rather than single species; reducing erosion from forest soils; and monitoring broad forest trends through satellite imagery.
In the United States, Waring said, about 1.5 percent of the nation's forestlands are disturbed annually through logging, housing development, fires and clearing. While that may not sound like a lot, he added, it means that most of the country's forests would be replaced with new forests in less than 70 years.
"It's a wake-up call," Waring said. "We think it's real and people should be concerned about it. There's more carbon stored in the forest than anywhere else above ground."
Between 2000 and 2005, about 6 percent of the United States' forestlands were disturbed through fires, insect attacks, disease and logging – the largest percentage of any country with large forested areas. Canada saw the largest area of disturbance, about 40 million acres, in absolute terms. Most human disturbances of forests, Waring and Landsberg wrote, are driven by economic gain that ignores the long-term loss of ecosystem services such as carbon storage, biodiversity and water quality.
Wood products, which can store sequestered carbon, will increasingly come from tree plantations rather than natural forests, they added. At present, plantations account for only 3 percent of the world's forestlands but produce about 25 percent of all forest products.
Future plantation managers would do well to avoid the "debacle" with blue gum (Eucalyptus globulus) in western Australia. Federal tax incentives and exaggerated claims of tree growth led to overplanting and as drought struck the region, water supplies were depleted, and trees stopped growing or died.
Provided by Oregon State University
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