被称为全球三大生态系统的是（ ）。

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SQL Error: select id,body,options from ***_enewstiku where sourceid='31911' and id < 2551402 and id<>'2551402' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku where sourceid='31911' and id > 2551402 and id<>'2551402' order by id asc limit 5