Peter Cowan - POST
By ,
Director of Conservation Science

It was a worrying harbinger of the future.

Standing on a sidewalk just east of downtown Redwood City, I watched as sea water seeped through the cracks of a retaining wall, pooled in the gutter and flowed down the street. The sidewalk I was standing on, normally well above sea level, was wet with cold winter seawater.

It was Monday, January 21 during a King Tide event, one the largest tides of the year, that I visited POST-protected Bair Island. The large tidal event that day was an opportunity to see what our coastline may look like every day in the future, when the mean sea level has risen to this high mark. I had expected some flooding and was curious to see what it looked like and get a sense for what the future might hold. I was surprised at what I found:

 

I visited Bair Island that day in January full of questions about the future and, not surprisingly, I left with even more. What will the San Francisco Bay look like in the future? What will happen to places like Bair Island, one of the largest islands in the bay, as the sea rises? And what are we doing to prepare for this new reality?

These are complicated questions that we may not be able to answer in the foreseeable future. But we’ve learned a lot about sea level rise and how it will affect the future of the San Francisco Peninsula and its natural lands.

Sea level is rising faster than we expected.

You may be aware of the fact that since the turn of the 20th century, the oceans have risen about eight inches. What you might not know is that scientists expect this trend to accelerate in the coming decades and that, by the end of this century, our oceans might rise another one to four feet.

bair island - POST
The ocean has risen eight inches since record keeping began in the 20th century. With this trend expected to accelerate in the coming decades, it’s helpful to have tools like this Risk Zone Map from Climate Central to see what the potential impacts could be.

We need the Bay’s baylands more than ever.

The baylands of the San Francisco Bay, the marshy habitat found at the water’s edge, play an important role in buffering our communities from storm surge and provide habitat for many critically endangered species of wildlife. As sea level rise accelerates, we will rely on this landscape more and more to protect our communities from coastal flooding and provide refuge for wildlife.

Sea level rise is threatening the bayland ecosystem.

The plants and animals of the baylands have adapted to intermittent flooding like the King Tides I witnessed, but to survive and be healthy, their habitats need time to dry out—something that might become impossible as the sea level continues to rise. Wetlands drowned by the rising sea would eventually be transformed into large mudflats. Devoid of vegetation, they would no longer support the wildlife they do today or be as effective at buffering our communities against storms.

But the baylands themselves are rising too (and that’s good news)!

With each passing tide, large quantities of sediment from our local creeks and rivers are moved throughout the bay. As currents slow, these sediments settle and accumulate within our bayland marshes, causing the bayland soils to creep higher over time.

You can see this best at Bair Island. Many decades ago, the island had been leveed (an embankment built to prevent the flow of tidal waters) and used for ranching cattle, farming and salt production for much of the last century. In 1997, POST protected 1,623 acres of Bair Island and it is now protected as part of Don Edwards San Francisco Bay National Wildlife Refuge managed by U.S. Fish and Wildlife Service.

With the help of our partners, we worked to restore the land back to its natural state by removing the levees. The final levee was breached in December of 2015, allowing the rich waters of the bay to return and nourish the island landscape ever since. Sediment from the bay is now being deposited here and the island is once again on the rise. See it for yourself:

Bair Island - POST
With the final levee breached in 2015, the life-rich waters of the bay have returned to Bair Island. Sediment and nutrients are now being deposited here, vegetation has established and the island is, once again, on the rise. These images were taken by local citizens as part of a shared monitoring effort organized on Instagram.

What’s the bottom line?

The truth is that there’s still a lot of debate about exactly how extensive the impacts of climate change will be here in our corner of California. And to know exactly what the future will hold for places like Bair Island, we first need to have a better understanding of the changes that are coming to the region as a whole.

One thing that is certain is that the San Francisco Bay needs more sediment to buffer against sea level rise. Just how much sediment and where it might come from are questions that our partners at the San Francisco Bay Estuary Institute (SFEI) are working to answer within the year.

Seeing the King Tide events opened my eyes to the complexity of this place and the challenges we face as stewards of this landscape. The questions I started with have only led me to more questions. So, stay tuned for more stories from my explorations of Bair Island and, in the meantime, get out there and see it for yourself  (on February 19 at midday, the tides will be nearly as high as they were in January).

About Post

Peninsula Open Space Trust (POST) protects open space on the Peninsula and in the South Bay for the benefit of all. Since its founding in 1977, POST has been responsible for saving more than 78,000 acres as permanently protected land in San Mateo, Santa Clara and Santa Cruz counties. Learn more

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