Invasive species, also known as exotics, are plants, animals,
insects, and aquatic species introduced into non-native habitats.
Without natural predators or threats, these introduced species
then multiply.
Often,invasive species travel to non-native areas by ship,
either in ballast water released into harbors or attached to the
sides of boats. From there, introduced species can then spread
and significantly alter ecosystems and the natural food chain as
they go. Another example of non-native species introduction
is the dumping of aquarium fish into waterways.
Invasive species also put water conveyance systems at risk. Water
pumps and other infrastructure can potentially shut down due to
large numbers of invasive species.
Strolling atop levees at Grizzly Ranch in the Suisun Marsh,
south of Fairfield, wildlife biologist Robert Eddings stops in
front of a brackish pond. Unlike most of the surrounding
wetland, this pond stays flooded all year. Its lush green
cattails make it a haven for waterfowl and an irresistible
feast for invasive nutria — housecat-sized, semi-aquatic
rodents with bright orange teeth. … Indeed, this pond is
where the first nutria at Grizzly Ranch were found in 2023.
Native to South America, nutria are elusive, burrowing inside
of levees during the day and emerging at night to devour marsh
plants. … The animals’ destructive eating habits, combined
with the fact that their burrows can weaken levees, means that
nutria pose a serious threat to this precious remnant of
California’s once-extensive wetlands. That’s why wildlife
biologists and landowners across the state are on the lookout
for nutria, reporting all sightings to the California
Department of Fish and Wildlife, which has a unit dedicated to
their eradication.
A California ecosystem has gotten a big boost from an adorable,
fluffy and hungry friend. At Elkhorn Slough National Estuarine
Research Reserve, a newly-reinvigorated population of native
southern sea otters has eaten so many invasive European green
crabs that researchers say the otters have locally solved a
problem that has plagued the West Coast for years. States are
spending millions to protect their inland waterways from the
tiny crabs. Though small – they reach only four inches in width
– the invaders harm native wildlife and shoreline ecosystems.
At stake are multi-million dollar shellfish industries for
Dungeness, king crab and other species. But at the reserve,
otters have almost wiped the crabs out, helping the estuary’s
ecosystem come back into balance.
The California Fish and Game Commission (Commission) acted on a
variety of issues affecting California’s natural resources
at its Dec.11-12 meeting in Sacramento, including
emergency action to list the invasive golden mussel as a
restricted species. The Commission also acted to extend
emergency regulations 90 days for the recreational
catch-and-release white sturgeon season and added language for
permitted catch handling. The public was able to participate in
the meeting in person, via webinar and by phone. To protect
California against the spread of invasive golden mussel
(Limnoperna fortunei) discovered Oct. 17 at the Port of
Stockton, and in the days following as far south as San Luis
Reservoir’s O’Neill Forebay, the Commission added golden
mussel to the list of species restricted from live
importation, transportation and possession. This discovery is
North America’s first; golden mussel is native to China and
Southeast Asia and was likely transported across the ocean on
large ships.
Although sea otters are an unofficial mascot of the Monterey
Bay area and popular among tourists and locals alike, they are
also described by scientists as voracious predators that help
keep problematic invaders out of coastal waters. A recent study
was published in the scientific journal Biological Invasions,
detailing that otters at the Elkhorn Slough are keeping
populations of globally invasive green crab at bay. … Green
crabs were first found at the slough in 1994 and the population
peaked in the early 2000s. Since then, the population has
declined and hasn’t reached the peak numbers again. Meanwhile,
the population of sea otters has risen. Sea otters were
recovering from near extinction in California in the early
2000s. The new study is first-time evidence that the recovery
of the otters is benefitting the overpopulation of invasive
species.
An invasive species in the San Joaquin County Delta is putting
water officials on high alert. Despite its name, the golden
mussel isn’t native to the Golden State, but instead to
Southeast Asia. Now, some lake boat ramps and launches are
closed, to try and keep the invasive species at bay. The
mussels were first detected upstream on the San Joaquin Delta
back in October. Officials say it likely got here from an
international shipment into the port, and it’s the first time
this species has been found in North America. Underneath the
ripples and waves of the San Joaquin Delta, the invasive
species is threatening the surrounding wildlife.
In the vast labyrinth of the West
Coast’s largest freshwater tidal estuary, one native fish species
has never been so rare. Once uncountably numerous, the Delta
smelt was placed on state and federal endangered species lists in
1993, stopped appearing in most annual sampling surveys in 2016,
and is now, for all practical purposes, extinct in the wild. At
least, it was.
This tour guided participants on a virtual journey deep into California’s most crucial water and ecological resource – the Sacramento-San Joaquin Delta. The 720,000-acre network of islands and canals support the state’s two major water systems – the State Water Project and the Central Valley Project. The Delta and the connecting San Francisco Bay form the largest freshwater tidal estuary of its kind on the West coast.
Nutria are large, beaver-like
rodents native to South America that have caused alarm in
California since their rediscovery along Central Valley rivers
and other waterways in 2017.
The growing leadership of women in water. The Colorado River’s persistent drought and efforts to sign off on a plan to avert worse shortfalls of water from the river. And in California’s Central Valley, promising solutions to vexing water resource challenges.
These were among the topics that Western Water news explored in 2018.
We’re already planning a full slate of stories for 2019. You can sign up here to be alerted when new stories are published. In the meantime, take a look at what we dove into in 2018:
Sixty percent of California’s developed water supply
originates high in the Sierra Nevada mountains. Our water
supply is largely dependent on the health of our Sierra forests,
which are suffering from ecosystem degradation, drought,
wildfires and widespread tree mortality.
We headed into the foothills and the mountains to examine
water issues that happen upstream but have dramatic impacts
downstream and throughout the state.
GEI (Tour Starting Point)
2868 Prospect Park Dr.
Rancho Cordova, CA 95670.
For more than 100 years, invasive
species have made the Sacramento-San Joaquin Delta their home,
disrupting the ecosystem and costing millions of dollars annually
in remediation.
The latest invader is the nutria, a large rodent native to South
America that causes concern because of its propensity to devour
every bit of vegetation in sight and destabilize levees by
burrowing into them. Wildlife officials are trapping the animal
and trying to learn the extent of its infestation.
Estuaries are places where fresh and
salt water mix, usually at the point where a river enters the
ocean. They are the meeting point between riverine environments
and the sea, with a combination of tides, waves, salinity, fresh
water flow and sediment. The constant churning means there are
elevated levels of nutrients, making estuaries highly productive
natural habitats.
A troublesome invasive species is
the quagga mussel, a tiny freshwater mollusk that attaches itself
to water utility infrastructure and reproduces at a rapid rate,
causing damage to pipes and pumps.
First found in the Great Lakes in 1988 (dumped with ballast water
from overseas ships), the quagga mussel along with the zebra
mussel are native to the rivers and lakes of eastern Europe and
western Asia, including the Black, Caspian and Azov Seas and the
Dneiper River drainage of Ukraine and Ponto-Caspian
Sea.
This 24×36 inch poster, suitable for framing, explains how
non-native invasive animals can alter the natural ecosystem,
leading to the demise of native animals. “Unwelcome Visitors”
features photos and information on four such species – including
the zerbra mussel – and explains the environmental and economic
threats posed by these species.
This 24×36 inch poster, suitable for framing, explains how
non-native invasive plants can alter the natural ecosystem,
leading to the demise of native plants and animals. “Space
Invaders” features photos and information on six non-native
plants that have caused widespread problems in the Bay-Delta
Estuary and elsewhere.
The 24-page Layperson’s Guide to the Delta explores the competing
uses and demands on California’s Sacramento-San Joaquin Delta.
Included in the guide are sections on the history of the Delta,
its role in the state’s water system, and its many complex issues
with sections on water quality, levees, salinity and agricultural
drainage, fish and wildlife, and water distribution.
