Will North American Carbon Sinks ‘Sink’ Kyoto Treaty?

Published January 1, 1999

Although the United States and Canada produce a substantial amount of industrial carbon dioxide emissions, a new study contends that the North American continent is a net carbon sink whose vegetation may be absorbing the entire annual emissions of the two countries.

The study, published in Science magazine, is said to offer the first global model for carbon dioxide (CO2) uptake. It was released as the Clinton administration prepared for November’s conference of the Kyoto Protocol signatories in Buenos Aires, where administration representatives announced their latest efforts to reduce this country’s CO2 emissions.

Titled “A Large Terrestrial Carbon Sink in North America Implied by Atmospheric and Oceanic Carbon Dioxide Data and Models,” the report was written by S. Fan and colleagues. The paper’s three-part model also includes Eurasia and North Africa, and the Tropics and Southern Hemisphere.

Fan argues that North America, which comprises about 20 percent of the Earth’s vegetated land, has the largest carbon “sink” capable of collecting the gas. “A molecule that gets stuck in (such a) ‘sink’ cannot contribute to the dreaded global warming,” commented the authors of World Climate Report, a publication of New Hope Environmental Services Inc. in Arlington, Virginia.

“If the other 80 percent (of the vegetated areas) behaved in a similar fashion there’s little doubt–given these numbers–that atmospheric carbon dioxide concentrations projected in the future will be drastically reduced,” WCR said of the report.

Fan attributes the North American sink to four factors:

  • U.S. forests are being replenished, in part by new methods of feeding livestock brought on by a growing demand for meat. For example, during the last century hogs and cattle were permitted to wander the mountainous areas of the eastern United States. Today, however, such animals are restricted to concentrated areas like feed lots.
  • Air in the Northern Hemisphere is rich in nitrogen (a plant food), thanks to the area’s industry and agriculture. Science reported in 1992 that nitrogen fertilization was stimulating European forests in the same manner and surmised that China and tropical rain forests were sure to follow this trend.
  • Increased amounts of CO2 increase photosynthesis and water-use efficiency.
  • Satellite data indicate a lengthening of the growing season in the highest latitudes.

The Fan report is not without its critics, including those who note that large amounts of CO2 have been found in South America’s rain forests–a finding difficult to reconcile with Fan’s results.

“But the bottom line,” WCR notes, “is that somewhere, somehow, the world’s vegetation is taking out an ever larger and unanticipated amount of carbon dioxide from the atmosphere.”

Most frightening to critics of the report is the thought that those who oppose the Kyoto treaty will use Fan’s findings to argue that the United States need not reduce its emissions to comply with the accord, wrote WCR.

“We’ll even go so far as to say that some people may now realize that the Kyoto Protocol, and indeed, the Framework Convention on Climate Change, are not based upon anything resembling defensible science. Instead, it looks more and more like the responsible stewardship that North Americans hold for their land may have ‘sunk” Kyoto,” WCR noted.