The
endangered salt marsh harvest mouse (informally “Salty”) is a poster child for
tidal marsh restoration in San Francisco Bay. But recent research, presented by
University of California at Davis postdoc Katie Smith in a State of the Estuary
conference session on tidal wetlands, suggests we’ve misinterpreted what the
mouse needs. “It’s been managed as a habitat specialist,” she said, based on
assumptions that it requires tidal wetlands and a diet of pickleweed.
However,
hours of mouse-tracking around the Bay show that it also thrives in managed
wetlands and eats a variety of plants, including non-native species. Although
restoration projects have created high-tide refuges for the mice, Smith’s
preliminary data suggest other rodent species exclude them from those sites.
That was in a wet year, though; a dry year could shift the dynamic, favoring
salties. “We’ve thought about the species in isolation, ignoring the community
context,” said Smith. “We need to look at it more holistically.”
This, as
she observes, is no ordinary mouse. For starters, it’s the world’s only mammal
restricted to coastal marshes. Genetic studies show that the species originated
four million years ago, long before the Bay came into existence. Salt marsh
harvest mice can drink salt water and swim for hours. Females build crude nests
in tall marsh vegetation, sometimes appropriating marsh wren nests. The mice
are highly vocal, especially on warm summer nights; if Smith can distinguish
their squeaks from those of co-occurring western harvest mice, monitoring calls
may provide a non-invasive way of recording populations.
Smith
credits her research interests to her family’s pet rats and the wildlife at a
pond near her childhood home. After fish-tagging work, she joined ongoing salt
marsh harvest mouse field studies and made the rodent her thesis and
dissertation subject (only the third PhD on the species).
Previous work had detected the mice in managed wetlands, including waterfowl areas in Suisun Marsh where water levels are managed to favor the birds. For her post-graduate research, Smith trapped and radio-tagged mice, spending nights in the marsh tracking their movements. “I was surprised at how diverse their habitat use was,” she recalled. “We had mice running all over the place. There were variations in individual behavior: some crossed levees, some never approached them.” They used high ground for foraging, not for nesting. Reproductive and survival rates and home range sizes of mice in managed wetlands proved comparable to those in tidal marshes.
Smith offered captive mice a buffet of native and non-native plants and watched them chow down on non-natives like rabbitsfoot grass, in addition to native pickleweed. The salt marsh harvest mouse’s food preferences overlap those of waterfowl; the duck-hunting clubs in Suisun Marsh have been inadvertently farming mice.
Mouse buffet. Photo: Katie Smith
Her
current study looks at interactions with other rodent species and how this
affects the mouse’s habitat use, especially during king tides. Even with high
water, winds, and waves, the mice didn’t seek high ground this year; they
stayed out in the marsh, chugging along like little Diana Nyads or clinging to
tall vegetation. Voles in particular may exclude the mice from potential
high-tide refugia, at least in wet years: “It’s like kids that play in the mud
instead of using the nice new playground we built for them because that’s where
the bullies hang out.” The mice might benefit from more vertical structure in
the low marsh; even woody debris can be a life raft.
Food choices salt marsh harvest mouse. Source: Smith & Kelt, 2019
In the
same session, Nadav Nur (Point Blue) and Levi Lewis (UC Davis) discussed other
tidal marsh creatures. Lewis found unexpected fish abundance and diversity in
tidal marshes previously unmonitored, including spawning aggregations of the
threatened longfin smelt. Nur dealt with special-status tidal marsh birds like
rails and song sparrows and their response to features of the transition zones
they use as high-tide refuges, with implications for design parameters in
future restoration projects.
Tidal
wetlands are caught between the rising deep blue sea and the devil of shoreline
development. “We’re losing habitat on both ends,” Smith said. “The marshes have
no chance to migrate.” Industrial and residential construction is pushing right
up to the edge of the marsh all around the Bay.
Mouse on pickleweed. Photo: Katie Smith
Why
invest scarce resources in these obscure creatures? Smith’s take on the salt
marsh harvest mouse would apply to smelt and rails as well: “It should be a
point of pride for the Bay Area to have this cool and unique species — a very
specially adapted and unique mouse. Beyond that, a natural ecosystem is like a
Jenga tower. If you pull out some number of species, eventually it will collapse.”
When marsh habitat changes, fish and birds can move elsewhere, but the mice,
with their fragmented populations, lack that option: “If we’ve lost our mice,
we know something bad is happening.”
All
photos and video accompanying this are the property of Katie Smith and Chris
Rudolph and may not be replicated without permission.
Top Photo: Katie Smith and marsh mouse. Photo: Chris Rudolph
Joe Eaton writes about endangered and invasive species, climate and ecosystem science, environmental history, and water issues for ESTUARY. He is also "a semi-obsessive birder" whose pursuit of rarities has taken him to many of California's shores, wetlands, and sewage plants.
Our magazine’s media motto for many years has been “Where there’s an estuary, there’s a crowd.” The San Francisco Estuary is a place where people, wildlife, and commerce congregate, and where watersheds, rivers and the ocean meet and mix, creating a place of unusual diversity. In choosing to tell the...
Ever since the state and federal water projects were built in the 1930s and 1940s, California has captured snowmelt in foothill reservoirs, and moved the fresh water from dam releases and river outflows to parched parts of the state via aqueducts hundreds of miles long. A convoluted system of ancient...
Though the Clean Water Act did an amazing job of reducing wastewater and stormwater pollution of the San Francisco Estuary, some contaminants remain thorny problems. Legacy pollutants like mercury washed into the watershed from upstream gold mining, PCBs from old industrial sites, and selenium from agricultural drainage in the San...
Hothouse Earth
By Ariel Rubissow Okamoto
Photo by Megan Nguyen
Nothing could be stranger than sitting in the dark with thousands of suits and heels, watching a parade of promises to decarbonize from companies and countries large and small, reeling from the beauties of big screen rainforests and indigenous necklaces, and getting all choked up.
It was day two of the September 2018 Global Climate Action Summit in San Francisco when I felt it.
At first I wondered if I was simply starstruck. Most of us labor away trying to fix one small corner of the planet or another without seeing the likes of Harrison Ford, Al Gore, Michael Bloomberg, Van Jones, Jerry Brown – or the ministers or mayors of dozens of cities and countries – in person, on stage and at times angry enough to spit. And between these luminaries a steady stream of CEOs, corporate sustainability officers, and pension fund managers promising percentages of renewables and profits in their portfolios dedicated to the climate cause by 2020-2050.
I tried to give every speaker my full attention: the young man of Vuntut Gwichin heritage from the edge of the Yukon’s Arctic National Wildlife Refuge who pleaded with us not to enter his sacred lands with our drills and dependencies; all the women – swathed in bright patterns and head-scarfs – who kept punching their hearts. “My uncle in Uganda would take 129 years to emit the same amount of carbon as an American would in one year,” said Oxfam’s Winnie Byanyima.
“Our janitors are shutting off the lights you leave on,” said Aida Cardenas, speaking about the frontline workers she trains, mostly immigrants, who are excited to be part of climate change solutions in their new country.
The men on the stage, strutting about in feathers and pinstripes, spoke of hopes and dreams, money and power. “The notion that you can either do good or do well is a myth we have to collectively bust,” said New Jersey Governor Phil Murphy whose state is investing heavily in offshore wind farms.
“Climate change isn’t just about risks, it’s about opportunities,” said Blackrock sustainable investment manager Brian Deese.
But it wasn’t all these fine speeches that started the butterflies. Halfway through the second day of testimonials, it was a slight white-haired woman wrapped in an azure pashmina that pricked my tears. One minute she was on the silver screen with Alec Baldwin and the next she taking a seat on stage. She talked about trees. How trees can solve 30% of our carbon reduction problem. How we have to stop whacking them back in the Amazon and start planting them everywhere else. I couldn’t help thinking of Dr. Seuss and his truffala trees. Jane Goodall, over 80, is as fierce as my Lorax. Or my daughter’s Avatar.
Analyzing my take home feeling from the event I realized it wasn’t the usual fear – killer storms, tidal waves, no food for my kids to eat on a half-baked planet – nor a newfound sense of hope – I’ve always thought nature will get along just fine without us. What I felt was relief. People were actually doing something. Doing a lot. And there was so much more we could do.
As we all pumped fists in the dark, as the presentations went on and on and on because so many people and businesses and countries wanted to STEP UP, I realized how swayed I had let myself be by the doomsday news mill.
“We must be like the river, “ said a boy from Bangladesh named Risalat Khan, who had noticed our Sierra watersheds from the plane. “We must cut through the mountain of obstacles. Let’s be the river!”
Or as Harrison Ford less poetically put it: “Let’s turn off our phones and roll up our sleeves and kick this monster’s ass.”
4th California Climate Change Assessment Blues
by Isaac Pearlman
Since California’s last state-led climate change assessment in 2012, the Golden State has experienced a litany of natural disasters. This includes four years of severe drought from 2012 to 2016, an almost non-existent Sierra Nevada snowpack in 2014-2015 costing $2.1 billion in economic losses, widespread Bay Area flooding from winter 2017 storms, and extremely large and damaging wildfires culminating with this year’s Mendocino Complex fire achieving the dubious distinction of the largest in state history. California’s most recent climate assessment, released August 27th, predicts that for the state and the Bay Area, we can expect even more in the future.
The California state government first began assessing climate impacts formally in 2006, due to an executive order by Governor Schwarzenegger. California’s latest iteration and its fourth overall, includes a dizzying array of 44 technical reports; three topical studies on climate justice, tribal and indigenous communities, and the coast and ocean; as well as nine region-specific analyses.
The results are alarming for our state’s future: an estimated four to five feet of sea level rise and loss of one to two-thirds of Southern California beaches by 2100, a 50 percent increase in wildfires over 25,000 acres, stronger and longer heat waves, and infrastructure like airports, wastewater treatment plants, rail and roadways increasingly likely to suffer flooding.
For the first time, California’s latest assessment dives into climate consequences on a regional level. Academics representing nine California regions spearheaded research and summarized the best available science on the variable heat, rain, flooding and extreme event consequences for their areas. For example, the highest local rate of sea level rise in the state is at the rapidly subsiding Humboldt Bay. In San Diego county, the most biodiverse in all of California, preserving its many fragile and endangered species is an urgent priority. Francesca Hopkins from UC Riverside found that the highest rate of childhood asthma in the state isn’t an urban smog-filled city but in the Imperial Valley, where toxic dust from Salton Sea disaster chokes communities – and will only become worse as higher temperatures and less water due to climate change dry and brittle the area.
According to the Bay Area Regional Report, since 1950 the Bay Area has already increased in temperature by 1.7 degrees Fahrenheit and local sea level is eight inches higher than it was one hundred years ago. Future climate will render the Bay Area less suitable for our evergreen redwood and fir forests, and more favorable for tolerant chaparral shrub land. The region’s seven million people and $750 billion economy (almost one-third of California’s total) is predicted to be increasingly beset by more “boom and bust” irregular wet and very dry years, punctuated by increasingly intense and damaging storms.
Unsurprisingly, according to the report the Bay Area’s intensifying housing and equity problems have a multiplier affect with climate change. As Bay Area housing spreads further north, south, and inland the result is higher transportation and energy needs for those with the fewest resources available to afford them; and acute disparity in climate vulnerability across Bay Area communities and populations.
“All Californians will likely endure more illness and be at greater risk of early death because of climate change,” bluntly states the statewide summary brochure for California’s climate assessment. “[However] vulnerable populations that already experience the greatest adverse health impacts will be disproportionately affected.”
“We’re much better at being reactive to a disaster than planning ahead,” said UC Berkeley professor and contributing author David Ackerly at a California Adaptation Forum panel in Sacramento on August 27th. “And it is vulnerable communities that suffer from those disasters. How much human suffering has to happen before it triggers the next round of activity?”
The assessment’s data is publicly available online at “Cal-adapt,” where Californians can explore projected impacts for their neighborhoods, towns, and regions.
The results are alarming for our state’s future: an estimated four to five feet of sea level rise and loss of one to two-thirds of Southern California beaches by 2100, a 50 percent increase in wildfires over 25,000 acres, stronger and longer heat waves, and infrastructure like airports, wastewater treatment plants, rail and roadways increasingly likely to suffer flooding.