CORVALLIS, Ore. - A new study has found that the Pacific Northwest, a region famous for its vast forests, should actually have a much greater number and diversity of tree species than it does - many apparently disappeared about 2 million years ago.
In an analysis of ecological data obtained from a sophisticated NASA satellite, researchers from the College of Forestry at Oregon State University also found that the overall productivity of forested regions in the United States can be closely correlated to the diversity of species there - insights that may be critically important in determining how forests will respond to climate change.
Information such as this, researchers say, reveals the increasingly detailed data that can be obtained from remote sensing devices, and used to better understand how climatic and environmental changes may affect broad regions of the Earth, now and in the future.
"In anticipation of major shifts in climate, we need better ways to estimate forest productivity, vegetation patterns, species richness and photosynthesis around the world," said Richard Waring, professor emeritus of forest science at OSU. "It would also be desirable to predict how forests may change before it actually happens, so we can better manage the changes. These new tools are helping us do that."
Prehistoric botanical records, the researchers said in their study, show that climate change tends to obliterate established vegetation patterns and cause new ones to be formed.
In the study, just published in the journal Remote Sensing of Environment, researchers from OSU, the University of British Columbia and the Richard Stockton College of New Jersey used data from the Moderate Resolution Imaging Spectrometer, or MODIS system on NASA's TERRA and AQUA satellites, to determine the gross productivity of forests in about 65 localized "eco-regions" in the U.S.
They found that satellite measurements of productivity in most places were an accurate barometer of what was actually observed on the ground, and also that this productivity could be correlated to diversity of species.
In one of the more unusual exceptions, however, it appeared that the Pacific Northwest should actually be supporting a much greater number of tree species than it does - the area is dominated by surprisingly few species of conifers and deciduous trees, compared to some parts of Korea and China that have similar climates but many more species.
"There's evidence that the Pacific Northwest used to support a much richer genera of trees in the late Pliocene, several million years ago," Waring said. "But in a colder, drier climate, there was a major die off and localized extinction of many species from which the region still has not recovered. The Pacific Northwest now supports about 60 tree species, but given the current climate we think it should have nearly twice that number."
There's a need to be able to estimate forest productivity with remote sensing, Waring said, because ground measurements are costly and not always comprehensive or accurate. And such measurements, he said, may be especially useful in sorting out which changes are being caused by overall climate change instead of land conversion or pollution. This technology would also provide a separate system that could be used to validate the accuracy of global climate models.
In general, the researchers said, the diversity of trees is expected to increase as forest productivity increases. It's less clear, though, whether the changing makeup of forests will be able to keep pace with the demands and pressures of climate change. So far, the forests seem to be keeping up, Waring said.
"With climate change, the patterns of productivity in the future will be different, and clearly there will be winners and losers," Waring said. "These are important changes that we want to anticipate as much as possible so we can deal with them as effectively as possible."
If the Pacific Northwest becomes warmer and wetter, Waring said, its forests overall should be more productive and open the door for even greater species diversity - a characteristic that generally provides more natural defense against insect and disease attacks. However, the new species could also be considered invasive, with all of the ecological uncertainties associated with that.
This research was supported by NASA as part of its Biodiversity and Ecological Forecasting program.
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