*Rising seas, raising questions
* Low-lying areas of Skagit County could be at risk as sea levels rise
Stand on one of Skagit County’s low spots and imagine what it might be like in 50 or 100 years if the sea rises between 8 and 24 inches.
Highway 20 to Anacortes might be raised onto a causeway. The fertile fields of the Skagit Flats and Fir Island — where tulips, potatoes and other cash crops now grow — could be swallowed by salt marsh and tidal flats.
In the low-lying areas of the county’s shoreline communities — including Anacortes, Bay View, Edison, La Conner, Samish Island and the Swinomish Reservation — waves could slowly eat away dry land, swamp marinas and erode scenic hillside bluffs.
Climate scientists and people concerned about the impact of global warming see that as one possible path the future could take within the next century.
The United Nations’ Intergovernmental Panel on Climate Change has predicted the sea level could rise between 8 and 24 inches over the next 100 years, and between 3 and 13 feet over the next 500 to 1,500 years.
The Nobel Prize-winning panel’s predictions assume that the world’s ice sheets and polar caps don’t melt faster than expected, which they began to do this summer. The difference in the ranges is because of different computer models.
Most computer models looking at Puget Sound are very broad, said Douglas Canning, an expert in sea-level rise and shoreline erosion.
The lower Skagit Valley and Willapa Bay have been identified by the state Department of Ecology as the two areas in Puget Sound that will feel the impact of rising seas first.
The potential impacts on Skagit County — such as the ability of dikes to withstand higher seas or the swamping of low-lying areas — have not yet been determined. At least two local governments — La Conner and the Swinomish Tribe — as well as the tribal group Skagit River System Cooperative have taken steps toward determining the impact of sea level rise.
However, some general assumptions can be made, said Canning, who is retired from the University of Washington Climate Impact Group and Ecology.
“Any of those low-lying areas on the shore, whether they are part of a river delta system or not, are vulnerable,” Canning said. “How vulnerable depends on how low they are.”
National Oceanic and Atmospheric Administration has pinpointed the areas in the United States that are most vulnerable to sea-level rise, and some Washington cities, such as Seattle and Olympia, have hired researchers to look at what the rise will mean for low-lying areas. But in Skagit, there are no clear answers. Likely, farmers in the Skagit and Samish river deltas will feel the effects first.
“We’re asking the questions,” said Mike Rundlett, project coordinator of the Western Washington Agricultural Association. “There are a lot more questions about this than we’ve been able to develop answers for.”
Expanding waters
Like air in a car tire that swells in the heat, the oceans expand when the temperature rises, raising the level of the water.
On a worldwide scale, fractions of a degree can make a difference, and 57 percent of the ocean’s rise is caused by heat expansion, according to a report compiled by the United Nations climate panel.
The partial melting of glaciers and ice sheets, including the North and South poles, accounted for 43 percent of the overall increase from 1993 to 2003, according to the intergovernmental panel’s report.
Sea-level rise may be exacerbated along the West Coast of the United States and Canada, according to Canadian researchers who predict that the rise in the West will be 160 percent of the global average. For instance, if the global average rise was 8 inches by 2100, the Northwest could see the Puget Sound and the Pacific rise by 13 inches.
Like other seas and oceans, Puget Sound’s average annual mean tide also has risen since 1899, the year a tidal gauge was installed in Seattle, and in 1935, when a gauge was installed at Friday Harbor.
Tidal level records indicate that the average annual rate of sea-level rise was about twice as fast from 1993 to 2003 as it was from 1961 to 1993.
This trend, along with the discovery that the North Pole’s ice caps and Greenland’s ice sheets have been melting during the summer at a greater rate than in past years, has caused climate scientists to question their previous predicted rate of sea-level rise.
“Even if we were just to shut the spigot off, bam, right now, you still have centuries of warming built into the system,” said Canning, adding it will take time for the environment to recover. “The opportunity to do something relatively cheap and easy was 20 years ago.”
Skagit’s situation
Losing thousands of acres of dry land — either developed or agricultural — is one of two scenarios laid out in a yearlong study by the National Wildlife Federation that looks at what Puget Sound’s shorelines might be like in 50 and 100 years.
The study, called “Sea-level Rise and Coastal Habitats in the Pacific Northwest,” explored the impact of rising water on Padilla and Skagit bays, as well as 10 other ecosystems.
The federation considered several scenarios of sea-level rise in the Sound, a range of between 5 and 27 inches by 2100. For Skagit, the study assumed an increase of 11 inches by 2050 and 27 inches by 2100 — numbers that fall between the predictions of the international panel and a group of Canadian scientists.
In the first scenario, researchers assumed all the dikes protecting the Skagit shoreline would remain in place, said Patty Glick, the federation’s senior global warming specialist and the study’s lead author.
The result would be a loss of 4 percent of dry agricultural land. But acres of marshes and swamps on the seaward side of the dikes would transform into tidal flats, including a large portion of the state Department Fish and Wildlife Fir Island reserve. Those marshes and swamps are important wildlife and fish habitat.
The study’s second scenario projects what might happen in the ecosystems of Padilla and Skagit bays if the dikes were removed: a 40 percent loss of dry farmland land that would become marshes or tidal flats.
Although it’s possible that the marshy land could become fish and wildlife habitat, there are questions as to whether it would be productive. It’s unknown whether natural vegetation would return or what impact farming fertilizers or pesticides would have on wildlife there, scientists say.
But the federation’s study doesn’t provide enough detail for communities to use it in planning a response to rising oceans. The study started with information from the National Wetlands Inventory, and researchers had to add information on dikes and drainage ditches.
“We made a simple assumption that urban areas are going to be protected,” Glick said. “That is over-simplifying things.”
A more likely scenario would be keeping some dikes and moving others — all decisions that would have to be made in anticipation of the sea-level rise.
Rising seas could exacerbate the long conflict between saving the salmon and saving Skagit farmland.
“There’s definitely the trade-off between losing habitat on the one hand and seeing an inundation of what is largely agricultural,” Glick said. “That’s a trade-off the public needs to make a decision on.”
Rundlett, with the Western Washington Agricultural Association, said that no one can think about rising sea levels without considering its impact on salmon habitat restoration projects under the Endangered Species Act, and what that might mean for farming land.
“Everything is so interconnected, when you look at sea-level rise, it automatically divides into 10 other questions we’re looking at,” Rundlett said.
Other issues
Higher sea levels bring other issues, as well.
Wave action can undercut bluffs, possibly threatening structures on top with erosion.
Sea-level rise can affect sewage treatment plants that discharge into the Sound because higher tides may mean that cities pay a higher power bill to pump the discharge. Also, the water that flows out the gravity-flow tidal gates may need to be pumped.
“This becomes a dilemma for local government and elected officials,” Canning said. “Many of them are starting to think about this.”
The most intensive Skagit study planned to date won’t be completed for at least 2 1⁄2 years. That computer model will look at salmon habitat in the Skagit River delta and Skagit and Padilla bays, not at problems that could be faced by shoreline developments.
The Environmental Protection Agency gave a $879,247 grant to the scientists at the Skagit River System Cooperative, Western Washington University and Pacific Northwest National Laboratory in Seattle to study the impact of sea-level rise on salmon habitat.
The computer model they will create will allow them to plan restoration work by taking the sea-level rise into consideration, said Greg Hood, a senior restoration ecologist at the Skagit River System Cooperative. The computer model also will be able to look at different water levels, restoration areas and predict what might happen if a dike was moved.
Rundlett said that since the state, federal and tribal governments are spending millions on projects in the delta to help restore the threatened chinook salmon, it’s important to take into account rising seas and other impacts of climate change. That’s because farmers fear that they could lose agricultural land to fish habitat if the restoration efforts don’t succeed.
“The only way we’re ever going to get through this is facing these things together,” Rundlett said.
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* Marta Murvosh can be reached at 360-416-2149 or .
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