The Eastern Hemlock, often called the Redwood of the East, is a large tree that can grow 175 feet tall, 6 feet in diameter, and live for hundreds of years; the oldest recorded specimen, found in Tionesta, Pennsylvania, is at least 554 years old. Extremely shade tolerant, it prefers moist, acidic soil and is most often found along streams and on north- and east-facing slopes. Its dense canopy creates a dark, cool environment that retains moisture, reduces evaporation, and supports many plants and animals. Along streams, hemlocks moderate water temperature, keeping it cooler in summer and warmer in winter. Hemlock-dominated watersheds have greater diversity of macroinvertebrate and aquatic insects, and hemlock streams hold twice as many brook trout. Hemlocks provide nesting, roosting, and forage for more than 90 species of birds, especially warblers and flycatchers, and they also provide essential shelter, bedding, and cover for ruffed grouse, white-tailed deer, rabbits, turkeys, and many other animals. Since the 1980s, both the Eastern and Carolina hemlocks have been increasingly threatened by the non-native hemlock woolly adelgid, a tiny aphid-like insect spread by wind, birds and other animals, and human actions. The insect feeds on hemlock sap, depletes the tree's nutrients, and can kill it in as little as 3-5 years. Loss of hemlock forests opens the canopy, increases light on the forest floor, reduces soil moisture, raises stream temperatures, and causes streams to dry up more quickly, while hardwoods and invasive species that do not provide the same ecological functions fill the space left behind.