Concrete, A Neceary Evil In the L.A. River s Ecosystem

No discussion of the future of the Los Angeles River is ever complete without picturesque renderings of the river resplendent in greenery. Chances are, there will probably be a few birds flying overhead thrown in for optimal ooh factor. But despite the idyllic vision presented by these renderings, it is one that is incomplete.

As it is now, the Los Angeles River is mostly encased in concrete. It's a waterway that is more a built, engineered object than it is an uncharted refuge for the wild. Though it is concrete, however, it doesn't cease to be a home for some of the city's passing residents.

Migratory shorebirds find great feeding opportunities in the wide concrete bottom river channel south of downtown Los Angeles, especially in Long Beach, explained Kimball Garrett, Ornithology Collections Manager at the Natural History Museum (NHM).

Locations such as these are becoming even more crucial, as environments that can support these shorebirds are dwindling. A 2006 report by Daniel Cooper of Cooper Ecological Monitoring notes that there are only a handful of its much-reduced wetlands, split largely between the Oxnard Plain of coastal Ventura County (including Mugu Lagoon) to the north and the coastal marshes of Orange County to the south, are appropriate for shorebirds.

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Everyone is drawn to the natural beauty of the soft-bottomed Elysian Valley area of the Los Angeles River, but it isn't the only stretch of river that supports life. In the last few miles of the river from Willow Street in Long Beach to the 105 freeway in the city of Paramount, where two historical wetlands used to be, there is a wide concrete channel that may seem negligible to commuters zooming past in their automobiles. But migratory shorebirds find this stretch of river indispensable.

According to Cooper's findings, as many as 15,000 shorebirds could be found in this makeshift wetland, including at least 22 different species.

There's just the right amount of water that washes around at the bottom of that channel that create mudflats, which is where they forage for food, explained Garrett. The very shallow water (less than 10 centimeters deep) host a layer of algae, which attracts flies; their eggs and larvae in turn entice shorebirds.

If that part of the river were to carry too much water, shorebirds can't see below the water's surface, can't access their food, can't even stand on the river bottom. If we recycled all our treated water [an efficient goal when it comes to water conservation] then that area would completely dry up, the shorebirds just wouldn't be able to feed there, said Garrett. By accident, we've created the perfect habitat there. People don't think about that because they think that this part of the river is ugly and concrete, but it's a critically important habitat for these shorebirds.

Before the river was encased in concrete, there were natural estuaries, mudflats and marshes created by the river's meandering course. We don't have that anymore, said Garrett. But the humans have incidentally managed to provide a viable, though not the most ideal, alternative.

Animals, as they instinctively do, adapt to it. Garrett notes that river infrastructure meant for city living also does double duty. Cliff swallows and barn swallows nest under many of the bridges that traverse the river. The same goes for red-tailed hawks and power poles.

Decades after the river's confinement, the city is at the cusp of changing its river once again. It has been working towards regaining some of the ecologic functions it had lost when engineers wrapped the waterway in concrete.

As the city makes its decisions about the river's future, it is called upon to be sensitive to all life that has managed to grow around it, despite its not-so-green surroundings. How can Los Angeles respect what is already in the river today while moving toward a greener future for the river?

For good or ill, the concrete on the Los Angeles River has become a fixture on Los Angeles life, as has the urban environment that has grown up around it. The city could no more tear it out than it could tear out the freeways and train tracks that crisscross its banks.

LINK:	https://www.kcet.org/confluence/concrete-a-necessary-evil-in-the-la-ri...
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