The Bay Foundation (TBF) has found that over half, approximately 60%, of the areas covered by plants (vegetated habitats) on the Ballona Wetlands Ecological Reserve (BWER) are dominated by plants that are either not native to the region or invasive.
Much of the BWER has had fill dumped on site, raising the elevation of the ground above wetland elevations. These areas covered by fill soils are no longer connected to the ocean by tidal waters or Ballona Creek, and are among those most impacted by non-native vegetation.
These findings are part of a comprehensive, site-wide GIS mapping study conducted by TBF throughout 2013, and represent one of many significant scientific, data-driven studies that TBF has contributed to the upcoming Draft Environmental Impact Report (DEIR) for the Reserve, which will be released in 2015 for public comment.
For the study, “Ballona Wetlands Ecological Reserve Vegetation Alliance and Habitat Crosswalk” (found at BallonaRestoration.org), over 800 distinct areas were classified, making the survey the highest resolution vegetation study performed on the approximately 600-acre site to-date.
Over the last six years Foundation staff have been tasked with conducting a comprehensive monitoring and assessment program to provide an in-depth evaluation of the existing conditions of the BWER, also referred to as the Reserve, all of which are contributing to the DEIR.
The program has intensively researched a broad suite of biological, chemical, and physical components at the BWER, which, in addition to vegetation, included fish, birds, algae, water quality, mammals, invertebrates, amphibians, reptiles, soil, marine sediments, vertebrate mortality, and physical characteristics. Full reports are available at http://www.ballonarestoration.org.
While there have been other vegetation studies conducted over the last 30 years, this is the first to incorporate additional non-native habitat categories which most accurately reflect the current conditions across the Reserve’s approximately 600 acres.
The impacts to the BWER over time have made the habitats highly susceptible to non-native plant invasions. For instance, since the late 1800’s, 3.1 million cubic yards of fill have been placed on top the former wetland, burying the former wetland under as much as 25 feet of dirt, and significantly changing the type of plants, or species, that could live there.
TBF Watershed Programs Manager Ivan Medel led the vegetation mapping surveys from May-October 2013. He and his team used GIS (geographic information systems) technology to divide the Reserve into “georeferenced polygons” based on the dominant plant communities found on the Reserve. Each area (or polygon) is classified as a habitat type based on both the plant community and physical characteristics such as soil and hydrology.
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