“Altogether, the collection was challenging to curate, which may go some way in reflecting an otherwise challenging year,”
岁近年末，所以国家地理杂志选出了30张过去一年当中最震撼人心的照片；上面那句是照片简介的小结。我不懂的是”an otherwise challenging year”是什么意思？按照我对otherwise的用法， “an otherwise challenging year”意思就是这一年“实际上并不challenging”。但这样的话又跟上下文不符了（文章后面有继续说 “It's been a difficult year for many people," says National Geographic photo editor Jehan Jillani. "But while selecting these photos, I was reminded of how beautiful and complex our world is.”）
谢谢指点！

http://www.dictionary.com/browse/otherwise?s=t-> 3 ... 或是这个较白话的:https://www.ldoceonline.com/dictionary/otherwise-> 4 ...原内容算是偏幽默性的表达。过去一年很challenging的事情不是只有收集这些照片(若"是"的话，那么除去这事，过去一年就没有其它challenging的事)。所以"in other respects"("other"是相对于前头说的事情)或是除去前头提的事情，过去一年也是有很多/发生过...."幽默"是因为若是以过去一年发生的(比如*1)枪击案，天灾等等来看的话，收集那些照片根本不算什么(*1)你没给出处link，所以我只能猜

遇到otherwise ?等同于中文的"否则~" 解, 用"另一方面则~" 解释适用性较广些.