Chatham Strait is a well-traveled route from the Gulf of Alaska into Southeast Alaska's Inside Waters. Glacially carved peaks rise above old-growth temperate rain forests of Sitka spruce and western hemlock, watered by some of the highest rainfall in Southeast Alaska. A weather station on the southeast coast of Baranof Island has recorded annual precipitation of more than 200 inches, mostly as rain. Storm winds here may exceed 100 miles per hour in fall and early winter.
Sea lions and seabirds are numerous as you approach Chatham from the Gulf of Alaska - Coronation Island and Warren Island to the east are important roosting and nesting areas for seabirds. Common murres, marbled murrelets, pelagic cormorants, pigeon guillemots, and several species of gulls can be found in these waters. Windswept and largely inaccessible Coronation Island and Cape Ommaney, the southern tip of Baranof Island, are important Steller sea lion haulouts. Sea lions congregate to breed and have pups at nearby Hazy Island, one of the five major sea lion rookeries in Southeast Alaska and part of the Alaska Maritime National Wildlife Refuge.
The South Baranof Wilderness, the Tebenkof Bay Wilderness and the Kuiu Wilderness border the strait. Sea otters, humpback whales, porpoises and dolphins inhabit the area.
South Chatham Strait, separating Baranof Island from Kuiu Island, is also a boundary between types of island fauna. Baranof Island is home to brown bears. Kuiu Island has no brown bears but does have one of the highest density black bear populations ever documented (about four bears per square mile) and a thriving population of Alexander Archipelago wolves. The existence of two large predators on Kuiu Island may be one reason why it has a lower density of Sitka black-tailed deer than Baranof and other Southeast Alaska islands, where brown bears are the only large predator.
The steep, rugged mountains of South Baranof Island rise about 4,000 feet above the sea within just two or three miles of the beach. The higher elevations are covered with permanent snowfields and numerous active glaciers. Mount Ada, the highest point in the area, is a commanding landmark at 4,528 feet. On the higher, steeper slopes of central Baranof Island, one may spy mountain goats - part of an estimated population of over 1,000 animals descended from an original 1923 transplant of 18 goats.