So, why are the plant zones changing?

The interesting front-page story about the shifts in the Agriculture Department’s plant hardiness zone maps since 1990 [“New plant map shifts area to warmer zone,” Jan. 26] included this headline on the continuing page: “Plant map doesn’t measure climate change.” However, nothing in the article discusses the relationship of the zone changes to climate change, whether global, national or regional. The nearly uniformly northward shifting zones reflect increases in “average winter low temperatures between 1976 and 2005 at 8,000 weather stations.” While this doesn’t fully measure all the changes in climate, if this nationwide pattern is not attributable to global climate change — specifically to the global warming that scientists have concluded is unequivocal — what, pray tell, is responsible? The failure of The Post, not only to make the connection with global climate change but also to seemingly disavow it, is most puzzling.

Donald F. Boesch, Annapolis

The writer is president of the University of Maryland Center for Environmental Science.

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The new USDA map shows a clear change from 1990 to the present. You then allow the USDA to get away with the claim that it “doesn’t measure climate change.” How silly. Maps showing climate change are evidence of climate change.

One can only wonder whether the political appointees that run the Agriculture Department are so fearful that they are trying to present evidence of climate change without offending the anti-science wing of the Republican Party. If so, it’s a sad day for science. Don’t we have enough people in our society who habitually shape their words to fit their ideology? Can’t we leave a sliver of room for facts as facts?

Robert A. Metcalf, Rockville