Halfway between California and Asia lies a tiny island formed by ancient volcanoes. Dubbed Midway Island, or occasionally, the Midway Atoll, its purpose has been at the mercy of humans since we discovered it; most infamously, it served as a key base for a World War II naval battle. In the last century, human effects have been much greater as the waste from two continents washes ashore, a rising sea level brings up the tide, and coral reefs break down thanks to ocean acidification. It’s a canary in a coal mine for environmentalists, especially Barbara Heitkamp, an environmental consultant focusing on the island. She’ll be at the Aster tonight to share what she’s seen and perhaps offer some solutions for what each one of us can do to slow the seemingly inevitable disappearance of this island and others. 5:30 p.m. Free. —EK

Aster Cafe, 125 SE Main St., Mpls., 612-379-3138, astercafe.com