Sentence:  Since the hazards of poor communication are so great , p can be justified as a habitable site only on the basis of unusual productivity such as is made available by a waterfall for milling purposes , a mine , or a <WSD>sugar</WSD> maple camp . 
Meaning of the word marked with <WSD> tags:  maple of eastern and central North America having three-lobed to five-lobed leaves and hard close-grained wood much used for cabinet work especially the curly-grained form; sap is chief source of maple syrup and maple sugar; many subspecies