The wetlands of eastern Washington’s Columbia Plateau provide critical habitat for a range of fish and wildlife species.  Wetlands here and elsewhere serve important landscape functions such as storing carbon, preventing flooding, and keeping excess sediment and nutrients from flowing into other water bodies. Because of the crucial role of wetlands, understanding the impacts of climate change on wetland dynamics is essential. In order to make projections about what might happen in the future, scientists need to have a record of the historic hydrologic dynamics of wetlands. Yet in the Columbia Plateau, scientists don’t even have enough basic information about their locations.

To address this lack of information, University of Washington associate professor L. Monika Moskal and doctoral student Meghan Halabisky are using open-source Landsat satellite imagery, collected from 1984 to 2011. The resolution of these images is coarse—the pixels that make up the images are each 900 m2 in area, meaning wetland features smaller than that size are not visible. In order to use this imagery, researchers are applying a special image analysis technique that detects the unique ways in which wetlands emit and reflect light (known as their ‘signatures’), allowing them to identify even small wetlands.

According to Halabisky, “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”. Using this method, Moskal and Halabisky are able to identify wetlands that are smaller than a single Landsat pixel.

Thanks to the long history of the Landsat satellite, they’re now also able to examine how the water levels of these wetlands have changed over time. In particular, the researchers are creating a record of flooding and drying patterns over time for 750 wetlands in the Columbia Plateau. “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.

The next step of the project will be to incorporate this data into models to project how individual wetlands in the region may respond to future climate change. The results of this study will help managers determine what actions should be taken to protect this vital resource well into the future.

This project is funded by the Northwest Climate Science Center (NW CSC). Learn more about the project here.