The 22-mile Mountains to Sea Trail provides a continuous path from inland canyons to the Orange County coast, connecting Irvine with four other cities. The trail begins at Weir Canyon, with other access points at Irvine Regional Park or Peters Canyon Regional Park. It links Anaheim, Orange, Tustin, Irvine, and Newport Beach.
Hikers and bikers use the trail, which meanders through a variety of habitats. Wilderness areas and parks along the route include Col. Bill Barber Marine Corps Memorial Park in Irvine, the San Joaquin Wildlife Sanctuary, and Upper Newport Bay. Several sections of the trail run alongside the San Diego Creek Trail.
Along the trail, observers can note the native vegetation such as oaks in the canyons and buckwheat, which changes color seasonally. Wildlife sightings may include red-tailed, red-shouldered, or Cooper’s hawks overhead, as well as white-tailed kites or peregrine falcons. The sound of a Nuttall’s woodpecker can be heard seeking insect larvae. Other birds like the California gnatcatcher and cactus wren are also present. The air carries the scent of coastal sagebrush and white sage.
For navigation, following Peters Canyon Wash south until it transitions into the San Diego Creek Trail, then continuing west on San Diego Creek to Back Bay, is a straightforward route. Users may choose to walk or bike sections of the trail, rather than its entire length.
The trail's final segment enters the Upper Newport Bay Nature Reserve, a three-mile paved path known for bird-watching. This tidal basin serves as a stopping point for migratory birds and a home for local species. Shorebirds such as herons and egrets are common on the mudflats. At low tide, godwits, curlews, and willets can be seen searching for food. Ospreys may also be observed hunting fish.
Vegetation along the bay contrasts with inland areas, featuring green willows, mulefat, cattails, and California bulrush against the bay's blue waters. The Back Bay section is suitable for family bike rides, with opportunities to stop and observe the birdlife or kayakers. The Peter and Mary Muth Interpretive Center is located nearby, offering educational displays. The journey concludes on Balboa Island, where amenities are available. Those planning to use the trail should carry water and snacks.
