Tuesday, March 21, 2017

Elkhorn Slough: An Ecological Treasure in Central California

Elkhorn Slough, near the town of Moss Landing on the edge of California's Monterey Bay, is truly a special place.  The slough, or estuary, winds through 7 miles of freshwater and tidal salt marshes.  The Elkhorn Slough National Estuarine Research Reserve (ESNERR) protects 1,700 acres of habitat, while the California Department of Fish and Wildlife protects even more land in the area.  Together, the Nature Conservancy and Elkhorn Slough Foundation have set aside 3,500 acres of the watershed for preservation. 

However, the greater Elkhorn Slough watershed encompasses 45,000 acres.  This means that any water that falls as rain, is applied to agricultural fields, or runs off city streets within those 45,000 acres finds its way into the Elkhorn Slough.  The implications of this is that water running into the slough from the surrounding watershed is often contaminated with agricultural chemicals, motor oil and other toxins.  What's a slough to do with all those nasties?  Certainly they aren't good for the sea otters!


Elkhorn Slough is California largest remaining tract of tidal salt marsh outside of the San Francisco Bay (and much of the San Francisco Bay's tidal salt marsh has been lost to development).  It supports a great deal of biologic diversity.  135 species of aquatic birds can be found here (not counting others, like songbirds and raptors in surrounding areas) and around 200 additional species of birds stop here during their annual migration.  The slough is home to 550 species of marine invertebrates and 102 fish species. 

Though invertebrate species are typically not the most glamourous creatures out there, they form the critical base at the lowest levels of the food web.  Other animals depend on them for food.  Without the insects and the marine invertebrates, the ecosystem would collapse.  More familiar residents of Elkhorn Slough include California Sea Lions, Harbor Seals, Southern Sea Otters. 


Estuaries in California have been largely lost to development (something like 90% are gone), and as a result a high number of threatened and endangered species are found in these special wetlands.  Elkhorn Slough alone is home to two dozen species that are classified as rare, threatened or endangered. 

Three of the United State's top ten most imperiled habitats are found within the Elkhorn Slough watershed.  These habitats are freshwater marsh, maritime chaparral, and the most biologically diverse grassland in North America, the coastal prairie.


In addition to providing habitat for a vast array of species, the slough provides a number of environmental services.  Estuaries like Elkhorn Slough act as a buffer between land and sea.  The assemblage of native vegetation helps to prevent erosion, and the tidal marshes protect surrounding land from floods by capturing excess water and releasing it slowly. 

And remember those toxins we talked about before?  The chemicals and oils and other nasty things that enter the slough from the surrounding watershed?  Wetlands of all types act as filters to remove toxins and restore water quality.  Plants in the wetlands absorb excess nutrients (nitrogen and phosphorus) from fertilizer runoff, preventing explosions of algae growth which use up all available oxygen in the water and lead to the eutrophication of the ecosystem.  Other wildlife subsequently dies off in such conditions from lack of oxygen.  Aquatic plants trap sediments which often contain pollutants such as heavy metals.  The contaminated sediments are trapped and held in place at the bottom of the wetland.  The study of wetlands and what eventually happens to these sediments is on-going; for now, it seems safe to assume that it's best not to disturb wetland soils.

Wetlands also sequester (capture and store) a large amount of atmospheric carbon, even more than their temperate forest counterparts.  Large amounts of blue carbon, carbon captured by oceans and coastal ecosystems, can be stored in coastal wetlands for two main reasons.  First, most of these plants have a high growth rate, each year producing a substantial amount of new growth that requires plenty of carbon dioxide.  Second, when wetland plants die, they decompose very slowly, buried underwater in the largely anaerobic soils (lacking oxygen) of the wetland.  Since decomposition releases carbon back into the atmosphere, carbon is stored for a much longer period of time (hundreds, perhaps thousands of years) in wetlands than in terrestrial ecosystems where decomposition happens at a much faster rate.


If that's still not enough to convince you of the value of these beautiful places, visit Elkhorn Slough, or any other wetland habitat, and see for yourself.  The intrinsic value of wetlands must be seen and felt.  Elkhorn Slough offers visitors a chance for outdoor recreation and relaxation.  Paddle a kayak, hike the trails, watch the terns diving into the water, or sit quietly and contemplate the beauty before you.

Visit Elkhorn Slough's website to learn more:  http://www.elkhornslough.org/

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