For two ÌìÃÀÓ°ÊÓ´«Ã½ researchers, the real test came as they walked across a barren-looking field.

They were on the Columbia Plateau with two state wetland ecologists, searching for a 1-acre body of water identified and mapped for the first time using a new method they developed. But when the group arrived at the expected coordinates, map in hand, the soil was dry and cracked and there wasn’t a wetland in sight.

Then, one of the ecologists sunk a shovel into the ground, looked at the characteristics of the soil, and put everyone’s worries to rest: The wetland was there, all right — it just happened to be in a dry phase.

“I remember getting goosebumps when I realized our method worked,” said , an associate professor in the UW’s .

This fine-tuned knowledge is the result of a new approach to better understand the hydrology of Eastern Washington’s wetlands. Now, researchers have an abundance of data about how these wetlands behave seasonally, which will also help monitor how they change as the climate warms.

“One of the things that makes wetlands so hard to study is their dynamic nature, the patterns of flooding and drying,” said , a UW doctoral student in environmental and forest sciences and lead author of a appearing in the May edition of .

“That element is also the thing that makes wetlands so fascinating and so unique. They have really high levels of biodiversity and unique species you won’t find anywhere else.”

In Washington and elsewhere, wetlands hold water on the landscape and help prevent flooding. They also filter and remove sediment and excess nutrients from entering rivers and larger bodies of water like Puget Sound, and they provide an important water source for grazing animals and migrating species.

Across the U.S. and particularly in Washington state, very little is known about the acreage, yearly flooding cycles and even the actual locations of wetlands. Even hazier is what could happen to these vital ecosystems under climate change.

To get at these questions, Halabisky and collaborators used open-access satellite images (through , a joint effort by the U.S. Geological Survey and NASA) taken every 16 days from 1984 to 2011 in Washington’s Douglas County. Though these images are shot with impressive regularity and can show changes over time, the resolution is coarse. One Landsat photo pixel is roughly 30 meters square (100 feet square), making it impossible to see wetlands smaller than that size.

They used high-resolution images from the same region to train a computer algorithm to “see” structural elements of wetlands and delineate them from other parts of the landscape. For example, water absorbs light differently than sagebrush or other plants, giving the water in a wetland a unique, identifiable signature.

“Each material has a unique pattern of absorbing and reflecting light. And based on those unique patterns, we can deconstruct each Landsat pixel and find out how much water, sage steppe and other vegetation is composed within that pixel,” Halabisky said.

The researchers applied this method to satellite images taken on about 200 dates over the same areas on the landscape, producing flooding and drying patterns (called hydrographs) for 750 wetlands in Eastern Washington.

“This method is unique because it’s essentially taking the pulse of the landscape — the time-series data (graphs) look like a heartbeat as the water in wetlands fills up, then goes down. We can track this for decades now,” said Moskal, senior author on the paper and director of the UW’s .

They also are able to identify wetlands, particularly small ones, that weren’t previously on the radar of land managers and other stakeholders who use the semi-arid landscape in Douglas County. The wetlands in this region are an important resource for cattle ranchers, tribes and organizations like Ducks Unlimited.

Researchers with the UW’s will use these data in their models to make projections on how individual wetlands in Eastern Washington could behave under climate change. Halabisky, who has worked in the region for years and revisited a number of the same sites, is sometimes surprised by what she sees.

“I think there’s an assumption that wetlands in arid regions are just going to dry out. In two of my study areas that wasn’t the case at all,” she said. “That may change under climate change when we do that modeling.”

Halabisky is leading an effort in Douglas County to convene land managers and stakeholders in planning for the future of wetlands as the climate warms. Their first workshop in early March drew upon the new seasonal data available for each wetland in the region.

Little is known about wetlands in Western Washington as well, and the researchers hope to use other remote-sensing techniques such as to characterize their locations and seasonal patterns. Shadows from tree cover west of the Cascades make it hard to use the method described in this paper.

Other co-authors are of the UW’s Earth and space sciences department and Michael Hannam of the Smithsonian Environmental Research Center in Maryland. Hannam is a recent graduate of UW who worked with Moskal and , a professor of environmental and forest sciences.

This research was funded by the U.S. Geological Survey, the U.S. Department of the Interior’s Northwest Climate Science Center and the UW’s Precision Forestry Cooperative.

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For more information, contact Halabisky at halabisk@uw.edu and Moskal at lmmoskal@uw.edu or 206-221-1510.

Grant number: GS276A-AUSGS

If abundant P-Patches and backyard gardens teeming with kale come to mind, you’re like many residents who assume urban agriculture in Seattle could support 50, 80 or even 100 percent of the people who live in the city.

It turns out that the actual number is drastically lower. A new ÌìÃÀÓ°ÊÓ´«Ã½ study finds that urban crops in Seattle could only feed between 1 and 4 percent of the city’s population, even if all viable backyard and public green spaces were converted to growing produce. The , published this month in the journal of , draws on Seattle’s current land use, light availability and national nutritional guidelines to determine the city’s carrying capacity for feeding its population.

The results show that it would require a 58-mile expansion around the city to meet 100 percent of Seattle’s food needs.

“We really need a regional solution to food sustainability in the Seattle area,” said lead author , a postdoctoral researcher in the UW’s . “It’s not going to come from Seattle and it’s not even going to come from King County. We’re going to need the entire region and all these food-producing areas to help achieve food security.”

As more people cluster in urban areas and cities seek long-term food security, it’s important to consider what is required to achieve that, and who benefits, the authors said.

“This is the first systemized way of looking at all the different crops a city could grow, as well as looking at the nutrition and actual amount of food people need to survive,” said senior author , a UW associate professor of environmental and forest sciences.

The researchers combined imagery and available data for Seattle, which are captured by flying aircraft and scanning the landscape with lasers. The resulting 3-D data are useful for geologists and geomorphologists looking at topography and landslides, but also for measuring tree cover in a city, including the height and leaf density of individual trees.

That’s one of the applications that Moskal’s (RSGAL) explores. Her team is working with a number of Puget Sound urban areas, including Olympia, , Seattle and Bainbridge Island, to map tree cover and explore socioeconomic issues related to having greater or fewer trees in a neighborhood.

Because Lidar lets researchers see a 3-D version of a city, down to an individual tree or building, it can also figure out how much sunlight hits an area — and how likely a food crop could flourish in that spot.

The researchers combined this data with nutritional information from the that assesses the calories, macronutrients and micronutrients in each food group. They analyzed nutrients needed for a vegetarian diet, because growing vegetables, grains and nuts usually requires less land than raising livestock for meat.

In order to meet the nutritional needs of an adult eating a vegetarian diet, only about 6,000 people (1 percent of Seattle’s population) could be fed if all single-family backyard space were converted to farming. That number rises to about 24,000 people (4 percent of the population) if all additional public green spaces were converted.

It’s an eye-opening figure, Moskal said, and it forces people to really think about what must be eaten to survive. A city can grow tons of tomatoes, kale and lettuce, but it gets more complicated once you factor in other necessary proteins, fats and carbohydrates that often travel from across the county and world.

“I think many people see food growing in their backyard and a salad at dinner throughout the summer season and assume they are feeding themselves,” Moskal said. “They don’t realize that calorie-wise, that’s not really the whole picture.”

Requiring all of those calories to be grown in Seattle takes up a lot of space in an urban area that is densely populated, amply tree-covered, and surrounded by water and mountains.

Richardson, who also farms 10 acres in Washington’s Skagit Valley, sees firsthand the difficulty of growing food locally. He raises pigs and turkeys, along with vegetable crops, but the livestock corn feed probably comes from Iowa, he said.

The researchers say their model can be used by other cities that have good geospatial data on sunlight and tree cover if planners input the relevant crops that grow well in a particular area. A sunny, sprawling city like Los Angeles, for instance, might be able to grow more crops than Seattle.

“If food sustainability is something that a city is really interested in, then this is a way you can test it,” Richardson said. “In refining this study, we really factored in all the different nutritional aspects of the diet to make sure there was a baseline way you could assess this for any city based on a diet that works and keeps people alive.”

This study was funded by the American Recovery and Reinvestment Act, the U.S. Forest Service and the at the UW.

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For more information, contact Moskal at lmmoskal@uw.edu or 206-221-1510 and Richardson at jeffjr@uw.edu or 206-778-4290.