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New study finds U.S. and Canada have lost more than 1 in 4 birds in past 50 years（图）
U.S. Canada lost birds past 50 years
2019/10/18
Since 1970, bird populations in the U.S. and Canada have declined by 29%, or almost 3 billion birds, signaling a widespread ecological crisis, a study published in the journal Science reveals. The res...
Abstract: Based on the mean yearly precipitation and the total yearly evaporation data of 295 meteorological stations in China in 1951-1999, the aridity index is calculated in this paper. ...
Process and mechanism of arable land change in Hebei Province during the past 50 years
XU Yue-qing
(Institute of Geographical Sciences and Natural Resources Research, CAS, Beijing 10010...