A COMPLEX MOSAIC
Ballona contains a complex mosaic of habitats defined mainly by hydrology, including wetland habitats, such as brackish and freshwater marshes, seasonally flooded freshwater wetlands, salt pans, riparian and upland habitats, like coastal sage scrub and sand dunes. Many wildlife species, especially birds, utilize more than one habitat type – thus the juxtaposition of these habitats next to one another, also known as heterogeneity, which is important for biodiversity.
Estuarine and Brackish Marshes
At the heart of the Ballona Wetlands is the coastal salt marsh or estuary, the crown jewel of current restoration planning. Estuarine marshes, the historically dominant habitat type of the Ballona Wetlands Ecological Reserve (BWER), require oceanic tidal influence.
Under natural conditions, tidal movements, along with variations in freshwater flow coming from inland, create complex and ever changing environmental gradients of topography, moisture, temperature, and salinity that enable many kinds of organisms to find their own particular place. As a result, coastal salt marshes are one of the most biologically diverse and productive habitats in the world.
When Ballona Creek was channelized, the BWER was cut off from this necessary disturbance regime.
After tide gate installation in 2004, the western and southern portions of Area B (see map below) began to reflect estuarine conditions, at least hydrologically. However, species diversity has yet to recover. About 26% of historic species have not been seen since the 1930s, including coastal dunes milk vetch and Pacific silverweed, and many others are only present in superficial amounts.
The majority of the BWER is dominated by non-native and invasive weeds. Low native diversity is due to restricted tidal influence, unnatural elevation, farming, oil drilling, and other disturbances. These conditions will change when restoration plans are implemented. Narrow tidal channels, which are artifacts of past disturbance and attempts to drain the marshes, affect the distribution of estuarine habitat. Pickleweed, a high marsh species, is the dominant and most recognizable salt marsh plant. You can read about the other plants at Ballona here.
Area B also contains salt pans, relatively flat depressions which can be flooded with salt water during high tides, or become ponds during the rainy season. Salts in the clay soil leach out to the surface, and over time these salts accumulate, leading to exceptional saline conditions when water is present and a white hue on the dried soil. Hundreds of birds can be seen flocking to these salt pans when ponds have formed after rains or high tides. This habitat is naturally lacking in vegetation cover.
Freshwater Marsh and Riparian Habitats
The Freshwater Marsh is located southwest of the intersection of Lincoln and Jefferson Boulevards, adjacent to the Ecological Reserve. Apart from riparian, this constructed wetland is currently the only major freshwater habitat at Ballona, representing a small fraction of a much more extensive freshwater wetland that once existed before Ballona and Centinela Creeks were channelized, primarily east of Lincoln Blvd. Historically, the creeks would have released water into Ballona’s freshwater wetlands, which then would have connected to brackish marshes leading to the mouth of the estuary and the Pacific Ocean.
Since construction was completed in 2003, the habitat has attracted more than 250 species of birds, some of which are now returning every year to nest after more than a 70-year absence. The marsh receives water from the riparian corridor and runoff from surrounding streets and landscape. The freshwater marsh releases water into Ballona Creek and some spills over into the southern part of Area B of the BWER during heavy rains. After restoration, more water will be released into the BWER.
Riparian habitat is defined by a freshwater stream or presence of fresh groundwater within reach of plant roots. Riparian habitat at Ballona consists of a corridor along the base of the Westchester Bluffs and the south edge of the BWER. This habitat represents a small fraction of what must have been present before Centinela and Ballona Creeks were channelized. Historical records show the riparian habitat dominated by alder trees. Currently, most of the riparian habitat consists of willows. Freshwater marsh and riparian habitats are characterized by water-loving plants, such as mulefat, cottonwood, sycamores, cattails, bulrush, and many more.
Seasonal wetlands are valuable habitats that provide additional foraging space and wintering grounds for wildlife. Currently, the seasonal wetlands at Ballona were created by past human disturbance. These wetlands are in areas that are isolated from stream or tide influence because they are too high in elevation or have been cut off from natural surface water sources. These wetlands have formed in small depressions and depend entirely on rainfall as a source of water. Due to soil salinity, pickleweed (normally a salt marsh plant) tends to dominate these wetlands. During restoration, many of these areas will be reconnected to a more consistent water source.
Two important upland habitats exist in and around Ballona, coastal sage scrub, along the face of the Westchester Bluffs, and coastal sand dunes, located on the west side of Area B. The dunes have been a major focus of restoration by Friends of Ballona Wetlands. Preservation of habitat is now entirely dependent on rainfall and weeding maintenance. Natural forces of wind and water, which shaped the dunes historically, have been lost. This situation is unlikely to change in future due to constraints of adjacent development and roads. Most other upland areas in the BWER have been invaded by non-native species and do not fit any standard habitat classification. Management and control of these non-native species, and their replacement with native habitat, will be one of the goals of restoration.
Habitat Heterogeneity - Important for Wildlife
With the variety of habitats in and around Ballona Wetlands, many species of wildlife live and visit each year. More than 300 bird species have been observed at Ballona, about 250 of which are at the Freshwater Marsh and Riparian Corridor. Most of these bird species depend on more than one habitat type and exemplify the interlinked nature of the Ballona ecosystem. New birds observed at the Freshwater Marsh system each season, including species like the least bittern (a State Species of Special Concern) seen breeding at the Freshwater Marsh, are tantalizing indications of what is possible when the larger Ballona ecosystem is restored.
To discover more about the wildlife of Ballona Wetlands, check out the Field Guide to the Wetlands.