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"A warmer climate poses several threats to sugar maples. First, sugar maples require cold winters to convert the starch it has stored in the summer to sucrose that will promote new buds in the spring. Sugar maples are also vulnerable to climate-induced drought. And, warmer winters have left the trees more vulnerable to infestations."

Source:http://www.edf.org/page.cfm?tagID=42708"Global Warming" has a significant impact, so an analyst should put more weight into it.