On January 22 and 23, major new outlets reported on a study of tree death in the American West, a sobering analysis of how warmer temperatures affect old-growth trees.

The study was released that day in the journal Science. Trees have been dying faster than new ones can replace them for the last half-century, and the probable cause is a warmer regional climate and accompanying drought, the authors had written. The widespread coverage grew out of a teleconference organized on January 21 by the American Association for the Advancement of Science, which publishes Science.

Analysis of 10 of the articles that came out of the teleconference (see the list below) shows that although all conveyed the most important points in this landmark study, some of the stories failed to address important questions that might have arisen naturally.

It begs a question: Is it a little too easy to report a story from a press conference without going the extra mile?

The important points, laid out clearly in each story, were: that tree deaths have increased in 76 forest plots in the West over many decades and that the very likely reason is a warmer climate. They also reported that these death rate increases aren’t noticeable to the eye and appear very small in number – death rate increases of 1 percent in many cases – but they add up to a very significant trend. Finally, the stories all conveyed that the researchers considered and could discount every possible reason except the rise in average temperatures in that region.

Among the best-written pieces were:

  • Catherine Brahi’s report in the New Scientist, which made clear the ages of the trees studied and reported that the plots hadn’t been “managed” (thinned), showing that the trees died naturally;
  • Brian Handwerk’s short but clear dispatch for Nationalgeographic.com which, despite the dramatic headline about forests “withering with warming,” said high up, “Forests are losing trees faster than new ones can grow,” the key point of the study;
  • Susan Milius’s piece in Science News, which went into more detail than most and had a fetching lead, “Those trees falling in the forest with no one listening – in the changing climate of the West, they’re falling about twice as fast as they were 50 years ago, says a new study”; and
  • Jeff Barnard’s Associated Press dispatch, the only one I read that listed all of the study sites (six states in the west and British Columbia).

The Arizona Republic‘s Shaun McKinnon also deserves note for laying out how this data builds on earlier problems in western forests and the broader implications of this study for the future. That is, that further tree losses will weaken ecosystems.

Some points from the actual Science article that might have led to more reporting by those covering the story:

  • In tropical forests, where scientists have studied tree demographics and climate change, trees have reacted differently from those in North America: both new growth and the death rates have increased there. So in the tropics, it would appear that the forests are keeping up with changes in world climate while in the American West, they aren’t. Why is this?
  • The findings were significant to the scientists not because of total trees that died but because the death rate of trees has increased slightly in most of the plots studied – 87 percent. Most of these articles explained well that the death rates increased only slightly, quoting scientists explaining that a slight increase can mean a great deal. But they did not get into the equally important finding, which was that new growth, or “recruitment rates,” increased in only 52 percent of the plots. So the important thing here is that the researchers found no corresponding increase in the rate of new trees taking over.
  • Mean annual precipitation has remained the same in this study’s area, the American West. Most of the stories correctly made the point that this region has been suffering a major drought for the past several years. One question to ask, then, might be whether regions without drought might reasonably make researchers try to quantify whether tree death rates are increasing.

A few factual errors crept into some of the reporting. Associated Press correspondent Jeff Barnard of the AP got the total number of trees wrong by 1,000: he said 59,736 while the Science article said 58,736. An unfortunate but important glitch in an article that overall was among the best of the lot. He crammed a good amount of information into a short piece, and only his reporting noted that the death rates varied from study plot to study plot, with the highest death rates in the Sierra Mountains of California.

Another factual error: Seattle Times reporter Michelle Ma reported that the average temperature increase over a half-century in the study areas was 2 degrees Fahrenheit. The actual figure was closer to 1 degree F, likely the result of scientists’ reliance on Celsius and an inaccurate conversion. Most of the stories explained that when the average temperature in the American West increased by 0.3 degrees Celsius to 0.5 degrees Celsius from 1955 to the present, the increase amounts to about 1 degree Fahrenheit.

All of the reporters quoted at least three scientists, most of them co-authors of the study. Time quoted just one and used the Global Carbon Project as a source. Time‘s reporter Eben Harrell wrote an entertaining short piece, but his use of “giant lungs” as a metaphor for how trees absorb carbon dioxide, and his comment that the forests have “fallen ill,” seemed out of tune. It’s not really accurate, but some people might find these images helpful in realizing that trees’ important function is to absorb carbon dioxide.

Among those reporters who sought outside comments (from those other than the Science article co-authors), Susan Milius in Science News quoted two scientists from the University of Leeds who helped her article establish the importance of the study. Mireya Navarro in The New York Times quoted a Department of Agriculture study that had linked climate change to forest fires, insect infestations, and die-offs. She also quoted an environmental historian at the University of Texas, Steve Pyne. The AP’s Barnard, an experienced environmental beat reporter, quoted Barbara Bond, a professor of forest physiology at Oregon State, not far from his home base.

Reporters are getting bolder at expressing the overwhelming evidence of climate change and noting when scientists link warmer temperatures to environmental stressors. They might also attempt to better address broader questions still floating around where tree deaths are concerned. For example, the 11 co-authors wrote in their study that they had ruled out air pollution as a cause of these trees’ deaths.

Reporters might better serve the public if they would ask for a more detailed explanation. Not long ago, activists and some scientists were pointing their fingers at air emissions as a cause of tree death elsewhere in the country. For this study to say air pollution was not a cause suggests that air pollution is no longer considered a serious cause of tree decline. Acid rain, too, ought to be on the lips of reporters asking scientists about tree death. If scientists have ruled it out in a study this broad, the public deserves to know why.

Finally, consider that reporters rarely spell out in a story that their sources were gathered for them by way of a press event. Only three of these 10 reporters – in Science News, The New York Times, and Reuters – even mentioned the AAAS teleconference. Not to do so can suggest that the reporter was more enterprising or did more choosing and tracking down sources than was actually true.

Listed below are links to the stories analyzed in this piece. See also ksjtracker.mit.edu, the Knight Science Journalism Tracker, which lists these and a few others.

Associated Press, Jeff Barnard: See article.

Reuters, Maggie Fox: See article.

Science News, Susan Milius: See article.

National Geographic online, Brian Handwerk: See article.

New Scientist, Catherine Brahic: See article.

New York Times, Mireya Navarro: See article.

Seattle Times, Michelle Ma: See article.

Arizona Republic, Shaun McKinnon: See article.

Washington Post, Juliet Eilperin: See article.

Time, Eben Harrell: See article.

Christine Woodside

Christine Woodside is a writer and editor based in Deep River, Connecticut. She started her career in 1981 in Philadelphia, first as a news clerk at the Philadelphia Inquirer and then as associate editor...