How the big picture changes from tiny beginnings

It pays to think small when forecasting environmental change.

By Robert C. Cowen

from the May 15, 2008 edition

It pays to think small when forecasting environmental change. That's "small" as in bacteria, atmospheric molecules, or beetles. Individual activity on this small scale can add up to major environmental effects that computer-based forecast modeling doesn't adequately cover.

Take the toxic algae blooms such as the red tide that has appeared off Maine this month. Biologists don't understand how blooms start or stop. But they now have a clue to their demise thanks to research by Xavier Mayali, Peter Franks, and Farooq Azam at Scripps Institution of Oceanography. They found that microbes called RCA cluster bacteria attack red-tide organisms, which are 25 to 30 times their size. Several bacteria at a time attach to a red-tide cell and kill it. Professor Franks says it's "something like three chipmunks attaching themselves to an elephant and taking it down."

The experiments were run using red-tide samples taken off the institution's pier in San Diego. Judging from that small-scale study, Dr. Mayali says it's possible that the bacteria are important in "regulating algal-bloom dynamics in temperate marine waters all over the world." The Scripps announcement adds that Mayali's novel cultivation methods open "a new world of inquiry to understand the ecological roles of these organisms," which are ubiquitous in temperate and polar seas.

Then there's the question of what happens when trees and other plants send volatile organic compounds (VOC) into the air. Air has a potentially cleansing chemical called hydroxyl (OH) consisting of one oxygen and one hydrogen atom per molecule. OH initiates reactions that remove the VOC. Atmospheric chemists had thought this also destroyed the OH molecules. This isn't necessarily so. Last month, Johannes Lelieveld at Germany's Max Planck Institute for Chemistry in Mainz and colleagues published research in Nature showing that under natural conditions OH is conserved. The chemical reactions it initiates not only clean out VOC, they also recycle much of the OH to be used again.

The scientists conclude that their research with data collected over the Amazon jungle by aircraft and their laboratory experiments "demonstrate that the biosphere maintains a remarkable balance with the atmospheric environment." This is important in assessing the effects of man-made pollution. In that case, nitrogen oxides go into the air, producing smog and destroying OH.

Meanwhile, British Columbia is experiencing the largest most severe pine-beetle outbreak ever recorded. Such attacks kill trees, which then send carbon dioxide into the air as they decay. This can turn a forest that was soaking up atmospheric carbon into a carbon emitter. Last month, Werner Kutz with Canada's Pacific Forestry Center in Victoria and colleagues reported in Nature that the current pine-beetle outbreak "has converted the forest from a small carbon sink to a large net carbon source."

The scientists note that climate change has encouraged the infestation. Now that infestation is augmenting global warming. They warn that insect outbreaks "represent an important mechanism by which climate change may undermine the ability of northern forests to take up and store atmospheric carbon, and such impact should be accounted for in large-scale modeling analyses."