Plant Diversity Threatened by Climate Change, Greenhouse Gas Buildup, Study Finds

admin — Wed, 05 Aug 2009 18:02:41 +0000

Stanford Report, June 18, 2003

BY MARK SHWARTZ

Doubling the amount of carbon dioxide in the air significantly reduces the number of plant species that grow in the wild, according to a newly released study on climate change in California.

The results, published in the Proceedings of the National Academy of Sciences (PNAS), are the latest findings from the Jasper Ridge Global Change Project at Stanford University — a multiyear experiment designed to demonstrate how grassland ecosystems will respond to predicted increases in temperature and precipitation caused by the continual buildup of carbon dioxide and other greenhouse gases in the atmosphere.

Writing in the June 16 edition of PNAS Online, researchers found that exposing open grasslands to large doses of carbon dioxide gas for three years caused a nearly 20 percent reduction in wildflower species and an 8 percent decline in plant diversity overall. The addition of excess nitrogen and other predicted climate changes caused diversity to plunge even further, the study found.

“I was surprised how quickly we lost species over such a short time,” said the study’s lead author, Erika S. Zavaleta, a former Stanford doctoral student who recently joined the faculty at the University of California-Santa Cruz. “It only took three years in our experiment. What does that say about the impact global change will have on plant diversity in the longer term?”

Global changes

Located in the grassy foothills of Stanford’s Jasper Ridge Biological Preserve, the Global Change Project relies on a system of infrared heat lamps, sprinklers and emitters to simulate four conditions that climate experts predict could exist a century from now as a result of continued fossil fuel consumption and deforestation:

A temperature increase of 2 degrees Fahrenheit;

A 50 percent rise in precipitation;

Double the amount of carbon dioxide in the air;

Higher concentrations of nitrogen pollutants in the soil.To study the environmental impact of such future global changes, researchers monitored 36 circular plots of land, each about 6 feet in diameter, between 1998 and 2001. Four circles were left undisturbed as experimental controls. Each of the remaining 32 circles was divided into four quadrants — like a birthday cake cut into equal pieces — for a total of 128 experimental plots.

Different treatments were applied to different plots. Some were given a single application, such as excess carbon dioxide gas, while others received various combinations of elevated carbon dioxide, heat, water and/or nitrogen fertilizer.

Initially, each plot contained between five and 20 varieties of grasses and wildflowers. The goal of the experiment was to see how different combinations of treatments would affect species diversity over a three-year period.

Diversity loss

The results were dramatic. Plots that received all four treatments lost more than one-fourth of their wildflower species, while those given elevated nitrogen or carbon dioxide suffered a 10 to 20 percent decline. However, plots treated with excess water experienced a 10 percent increase in wildflower diversity and a 3 percent gain in the number of annual grass species.

“We found that elevated carbon dioxide caused a loss in species, while added precipitation caused an increase. We were surprised they had such opposite effects,” said study co-author Christopher B. Field, a professor by courtesy of biological sciences at Stanford and director of the Carnegie Institution’s Stanford-based Department of Global Ecology. “One hypothesis is that elevated carbon dioxide added moisture to the soil, which tended to extend the growing season of the dominant plants, leaving less room for other species to grow.”

On the other hand, he noted, increasing precipitation by 50 percent may have encouraged growth in late-season plants that normally stop growing during the dry California summer: “We think the effects of elevated carbon dioxide and increased precipitation were more or less the same, but because they were separated in time by a couple of weeks, they actually produced opposite results. In our ecosystem here, things that happen at different times in the season are really important.”

The study also revealed that heat, in the absence of other treatments, had no significant impact on diversity. However, when experimental plots were exposed to higher temperatures along with excess nitrogen, carbon dioxide and water, the number of wildflower species plummeted.

“One take-home message of our study is that certain kinds of species are much more sensitive to climate and atmospheric changes than others,” Zavaleta observed.

“It turned out that wildflowers were much more sensitive to the treatments than grasses were, no matter what combination of treatments we tried,” she added, noting that a large-scale change in diversity could diminish the ability of grasslands to support birds, deer, butterflies and other wildlife — as well as commercial grazing.

Additive response

The researchers discovered that they could make remarkably accurate predictions of species diversity in plots where multiple treatments had been applied simply by adding up losses and gains observed under single treatments. For example, in quadrants receiving excess nitrogen, heat and carbon dioxide, wildflower diversity decreased by about 27 percent — almost exactly what would be expected if one added up the percentages of loss in quadrants given single treatments of carbon dioxide (18 percent), nitrogen (8 percent) and heat (2 percent).

“One possible reason we see this overall additive response is that the mechanisms that are driving the changes are not interacting,” Field said — a finding that could prove beneficial in forecasting how global environmental changes will affect plant diversity in other ecosystems.

“We hope to move into the domain where we can predict responses rather than just record them and report them,” he added.

Other coauthors of the PNAS study are Harold A. Mooney, the Paul S. Achilles Professor of Environmental Biology at Stanford; Nona R. Chiariello, research coordinator of the Jasper Ridge Biological Preserve; and M. Rebecca Shaw of the Nature Conservancy.

The study was supported by the National Science Foundation, the David and Lucile Packard Foundation, the Morgan Family Foundation, Jasper Ridge Biological Preserve, the Carnegie Institution of Washington, the U.S. Department of Energy, the U.S. Environmental Protection Agency, the Switzer Foundation, the A.W. Mellon Foundation and the Nature Conservancy.

Doubling the amount of carbon dioxide in the air significantly reduces the number of plant species that grow in the wild, according to a newly released study on climate change in California. Photo: L.A. Cicero

Columbia Scientists Find Undersea Volcanic Rocks May Offer Vast Repository for Greenhouse Gas

admin — Tue, 04 Aug 2009 18:28:24 +0000

Jul. 15, 2008

A group of scientists at Columbia has used deep ocean-floor drilling and experiments to show that volcanic rocks off the West Coast and elsewhere might be used to securely sequester huge amounts of carbon dioxide, a greenhouse gas, captured from power plants or other sources. In particular, they say that natural chemical reactions under 78,000 square kilometers (30,000 square miles) of ocean floor off California, Oregon, Washington and British Columbia could lock in as much as 150 years of U.S. carbon dioxide production. The findings are published today in the Proceedings of the National Academy of Sciences.

Deep-sea basalt on the seafloor

Photo credit: David S. Goldberg

Interest in so-called carbon sequestration is growing worldwide. However, no large-scale projects are yet off the ground, and other geological settings could be problematic. For instance, the petroleum industry has been pumping carbon dioxide into voids left by old oil wells on a small scale, but some fear that these might eventually leak, putting gas back into the air and possibly endangering people nearby.

Lead author David Goldberg, a geophysicist at Columbia University’s Lamont-Doherty Earth Observatory, called the study “the first good evidence that this kind of carbon burial is feasible.”

“We are convinced that the sub-ocean floor is a significant part of the solution to the global climate problem,” said Goldberg. “Basalt reservoirs are understudied. They are immense, accessible and well sealedâ€”a huge prize in the search for viable options.” One of the main advantages, he said, is a chemical process that takes place between basalt and pumped-in liquid carbon dioxide that would form a solid, nontoxic mineral. Basalt is rock formed by solidified lava.

In their paper, Goldberg and his colleagues Taro Takahashi and Angela Slagle, both at Lamont-Doherty, used previous deep-ocean drilling studies of the Juan de Fuca plate, some 100 miles off the Pacific coast, to chart a vast basalt formation that they say could be suitable for such pumping. Basalt, the basic stuff of the ocean floors, is hardened lava erupted from undersea fissures and volcanoes. In this region, much of it lies under some 2,700 meters (8,850 feet) of water, and 200 meters (650 feet) or more of overlying fine-grained sediment. Drilling by the Integrated Ocean Drilling Program has shown the rock is honeycombed with watery channels and pores that would provide room for liquid carbon dioxide pumped down under high pressure. The scientists have mapped out specific areas that they say are isolated from earthquakes, hydrothermal vents or other factors that might upset the system.

Deep-sea basalt region for carbon dioxide sequestration

Photo credit: David S. Goldberg

Ongoing experiments by Lamont scientists on land have shown that when carbon dioxide is combined with basalt, the two naturally react to create a solid carbonateâ€”basically, chalk. Later this year, a separate team headed by Lamont geochemist Juerg Matter will begin pumping carbon dioxide into a landbound basalt formation at a power plant near Reykjavik, Icelandâ€”the first such large-scale demonstration. Basalts lie at or near the surfaces of other land areas including the northeast United States, the Caribbean, north and south Africa and southeast Asia.

Goldberg says that undersea basalts, which are widespread, may be bigger and better than ones on land. At the depths studied, any carbon dioxide that does not react with the rock will be heavier than seawater, and thus unable to rise. In places like the Juan de Fuca, even if some did escape the rock, it would hit the overlying impermeable cap of clayey sediment.

Skeptics point out that getting the carbon dioxide to such sites could be expensive and tricky. But Goldberg says the West Coast formations should be close enough to the land for delivery by pipelines or tankers. He called on government to study the details of how the idea might work, and whether it would be economically feasible. The United States currently spends about $40 million a year studying carbon sequestration, but nearly all of that goes to land-based research. “We need policy change now, to energize research beyond our coastlines,” said Goldberg.

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Plant Diversity Threatened by Climate Change, Greenhouse Gas Buildup, Study Finds

Columbia Scientists Find Undersea Volcanic Rocks May Offer Vast Repository for Greenhouse Gas