Friday, May 12, 2006
Bunker and Naeem have written a letter highlighting the importance of the recent study by Wills reported earlier by this blog. The Wills study noted that nonrandom processes play a key role in maintaining diversity in tropical forests -- forest tree diversity increases as individuals age because of preferential survival by individuals of locally rare species.
Bunker and Naeem argue that all three mechanisms supported by those results imply that species diversity increases ecosystem functioning:
First, the Janzen-Connell model (1, 2) predicts that species escape their specialist herbivores, predators, and pathogens when they are locally rare, whereas common species are more readily attacked. Losses of carbon and nutrients to natural enemies result in lower growth rates and thus lower primary productivity (3). Second, niche complementarity occurs when species exploit resources in different ways and results in more complete resource utilization and thus higher productivity (4) and has been shown to contribute to increased functioning with diversity (5, 6). In tropical forests, tree species may differ in their ability to acquire soil resources, resulting in more complete resource capture and thus higher productivity. Third, facilitation occurs when one species directly benefits another but experiences no harm (7) and has been shown to contribute to increases in ecosystem functioning with diversity (8, 9). In tropical forests, a tree species might fix nitrogen that becomes available to its neighbors. In this case, the tree's neighbors will experience increased growth rates if nitrogen is limiting.
When any of these three nonrandom mechanisms are operating, species extinctions will result in a decrease in productivity due to increased losses to natural enemies, failure to fully utilize essential resources, or the loss of direct benefits of facilitation. In contrast, neutral models of species coexistence (10-12) assume species are functionally equivalent, and therefore ecosystem functioning will not be dependent on species diversity. Wills and colleagues provide strong circumstantial evidence that even in highly diverse tropical forests, biodiversity enhances ecosystem functioning.
Thursday, May 11, 2006
According to a recent study published by Guthrie in Nature, climate change drove mammoths and horses to
extinction in Alaska and the Yukon Territory almost 12,000 years ago, not human hunting. Science report Guthrie's study contradicts previously published studies, noted in this blog, that suggested human hunters were the culprits.
Tuesday, May 9, 2006
My university's Sustainability Council is about to begin its second year. So far, it has raised consciousness, greened our new buildings, supported greener operation of our existing physical plant and operations, funded a number of small staff, faculty, and student sustainability projects, and brought several sustainability scholars to campus. Willamette Sustainability Site It is a grassroots effort that receives significant support from the President, the Board of Trustees, as well as administration, faculty, staff, and students. Although there are many small next steps to be taken, I am wondering what the next giant leap should be. My current nomination is a carbon neutral campus. Can this be accomplished and how??? Please submit links to your campus sustainability efforts and let me know what you think about a carbon neutral campus.
May 9, 2006 in Air Quality, Biodiversity, Climate Change, Economics, Energy, Environmental Assessment, Governance/Management, International, Land Use, North America, Physical Science, Social Science, Sustainability, US, Water Quality | Permalink | Comments (0) | TrackBack (0)