School and Group Programs
Natural Communities of the Marin Headlands
The Marin Headlands includes a wide variety of natural communities for your class to explore. You may choose to use this list as a comparison between the fauna and flora of your area and the Marin Headlands in conjunction with your visit.
Pelagic/Open Ocean
This community is composed of the life forms living, swimming, and floating in the ocean's water column. In the Marin Headlands, we sometimes see animals that live in the open ocean as they take a break on the rocks, like the harbor seals, or we spy migrating animals like the gray whale from the cliffs above the ocean.
Kelp Forest
Kelp forests are ocean areas shallow enough for the sun to penetrate to the bottom. Sunlight allows kelp to photosynthesize and proliferate. They resemble terrestrial forests in that they have a layered structure and provide food and shelter for various ocean animals. On Rodeo Beach, after large storms, we sometimes find long and bulbous "bull kelp" strands from the kelp forest.
Intertidal/ Rocky Coastline
The intertidal community is defined as the area where the rocky coast meets the ocean. At high tide the rock is underwater, but at low tide it becomes exposed coastline. Being on the edge of these drastically different land and water worlds, the intertidal community supports an immense diversity of critters adapted to life on land and water. This is the habitat in which you will see seastars, giant green anemones, California mussels, and gooseneck barnacles.
Sandy Beach/Sand Dune
The sandy beach is a harsh environment where the floor is far from stable. The sand is constantly moving by wind and water action; it is transported across land or thrust back into the ocean. Wave action also brings ocean life such as dead animals, kelp, and drift wood to the beaches and expands the habitat. Many of the animals, like Beach Hoppers, are adapted to burrowing into the sand or eating those that burrow. At the crest of the beach, above the turbulent surf, resilient dune plants grow. These plants have thick, extensive root systems that enable them to hold sand particles together, and which allow the plants to hold water during long, dry periods. At the Marin Headlands, our ancient sand dunes are covered with sea rocket, sand verbena, and beach burr.
Lagoon/Estuary/Saltmarsh
These are partially enclosed bodies of water with a connection to the ocean. Therefore fresh water draining from the hills mixes with ocean salt water to create a brackish water environment. Our best example of this in the Marin Headlands is Rodeo Lagoon. Year round, fresh water from Rodeo Creek and Rodeo Pond flow into Rodeo Lagoon. In the winter, salt water enters when ocean waves break over the sandbar into the lagoon. Unique plant communities have learned to adapt to these seasonal fluctuations. Long waving cattails are a characteristic plant lining the banks of Rodeo Lagoon.
San Francisco Bay
The San Francisco Bay is a uniquely large brackish estuary that receives most of its water from the rain run-off of the Sierra Nevada Mountains. In fact, 40% of the California's water flows through the bay and empties into the ocean. San Francisco Bay's contains the largest continuous marshes on the west coast of North America. Marin Headlands borders the water entrance to the bay.
Pond
A pond is a shallow body of fresh water with a muddy or silty bottom. It supports plant life along the shores and within the water body, as well as invertebrates, amphibians, ducks, and mammals. Our pond, Rodeo Pond, is a depression in the land where the water and sediment draining from Rodeo Creek collects.
Coastal Scrub
Coastal scrub is an environment that is characterized by low growing shrubs intermixed with grassy meadows. Scrub communities thrive in dry, rocky soils and can tolerate high winds and some salt spray. The dominant shrub in the Marin Headlands is coyote brush. It maintains its green color throughout the year and produces off-white fuzzy flowers in the winter that can be seen on separate male and female flowers.
Grassland
The grassland habitat at the Marin Headlands is a special kind of grassland called coastal prairie. Geologic forces have exposed ancient seafloor beds and provided nutrient rich, well-drained soil for the plant communities. Most of the types of grasses found at the Marin Headlands are invasive species from Europe.
Woodland/Forest
The woodland community occurs in small areas throughout the Marin Headlands. Most of the trees are non-native, such as, Eucalyptus and Monterey Cypress. These small clusters of woodland areas provide habitat for raptors and nocturnal creatures. The Marin Headlands also has small pockets of Redwood trees, Douglas Fir, and Coast Live Oak. These communities can be found on the leeward side of the hills where there is shelter from the wind and thus more moisture.
Redwood Forest
The Coastal Redwood communities are often a mile inland from California ocean cliffs, where salt spray is diminished. Fog is an important component in a redwood forest. The fog collects and condenses on needles and branches and drip to the ground to feed the roots of the tree. With such an abundant amount of moisture in the forest the trees can grow up to an average of 300 feet tall and live to be 2,000 years old.
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Photographs by Willie Williams.
