In an article that will appear in Science magazine tomorrow, January 9, a team led by D.S. Battisti (University of Washington, Seattle) warns that the worldâ''s future food supplies will be seriously threatened by unprecedented summer heat in temperate zones. By the end of this century, they predict, growing season temperatures will exceed the most extreme seasonal temperatures recorded from 1990 to 2006; the hottest seasons on record will, many places, represent the new norm. Crops and livestock will be stressed worldwide, and so heat- and drought-resistant crop varieties and more diversified irrigation systems will be widely needed.
Those conclusions, though broadly consistent with patterns known to climate modelers for a couple of decades, are sharper. The same can be said of some recent findings related to ocean acidification, an effect of human carbon emissions that been rapidly ascending in rankings of most serious impacts, as we reported years ago. Last weekâ''s Science contained an article about the recent history of Australiaâ''s Great Barrier Reef, by a team led by a person with the ominous-sounding name Glenn Deâ''ath. Regrettably, it seems to be a slow-motion death that the Deâ''ath team has been monitoring. They found that the deposit of calcium carbonate by Porites corals has declined more than 13 percent since 1990. Though the ultimate causes are not fully understood, increasing temperature stress and a declining saturation state of seawater aragonite would seem to be at the root of the problem.
Similar results come from a University of Chicago team thatâ''s been looking closely at ocean acidity over an eight-year period around Tatoosh Island, off the coast of Washington state. They found that calcareous species generally performed poorly in years when acid levels were relatively high, and predict substantial changes in dominant species, both because of direct calcification effects and ramifying species interactions. â''Our results indicate that pH decline [i.e. acidification, for those of you who donâ''t remember your high school chemistry] is proceeding at a more rapid rate than previously predicted in some areas, and that this decline has ecological consequences for near-shore benthic [sea-bottom and deep-water] ecosystems.â''