Landsat-based monitoring of annual wetland change in the Willamette Valley of Oregon, USA from 1972 to 2012

  • Published source details Fickas K.C., Cohen W.B. & Yang Z. (2016) Landsat-based monitoring of annual wetland change in the Willamette Valley of Oregon, USA from 1972 to 2012. Wetlands Ecology and Management, 24, 73-92.


This study is summarised as evidence for the following.

Action Category

Require mitigation of impacts to marshes or swamps

Action Link
Marsh and Swamp Conservation
  1. Require mitigation of impacts to marshes or swamps

    A before-and-after study in 1972–2012 in Oregon, USA (Fickas et al. 2016) found that after legislation to offset impacts to wetlands came into force, the overall area of vegetated wetlands still decreased, but at a significantly slower rate than before the legislation came into force. Over 22 years with offsetting legislation, the area of vegetated wetlands in the study region decreased by 2.1 ha/year (vs 13.3 ha/year over the 17 years before legislation). More specifically, the area of shrubby and forested wetlands decreased by only 3.6 ha/year after legislation (vs 9.3 ha/year before legislation). Furthermore, the area of emergent herbaceous wetlands (marshes, wet meadows, bogs and fens) increased by 1.4 ha/year after legislation (vs 3.5 ha/year decrease before legislation). The study notes that wetland gains/losses in the study area might compensate for losses/be compensated by gains outside the study area. Methods: Section 404 of the Clean Water Act came into force in 1990 and required compensatory mitigation for some unavoidable impacts to wetlands. The area of vegetated wetlands along the Willamette River floodplain was estimated from satellite images, taken every summer between 1972 and 2012. Wetland classifications were checked using aerial photographs and field surveys.

    (Summarised by: Nigel Taylor)

Output references
What Works 2021 cover

What Works in Conservation

What Works in Conservation provides expert assessments of the effectiveness of actions, based on summarised evidence, in synopses. Subjects covered so far include amphibians, birds, mammals, forests, peatland and control of freshwater invasive species. More are in progress.

More about What Works in Conservation

Download free PDF or purchase
The Conservation Evidence Journal

The Conservation Evidence Journal

An online, free to publish in, open-access journal publishing results from research and projects that test the effectiveness of conservation actions.

Read the latest volume: Volume 21

Go to the CE Journal

Discover more on our blog

Our blog contains the latest news and updates from the Conservation Evidence team, the Conservation Evidence Journal, and our global partners in evidence-based conservation.

Who uses Conservation Evidence?

Meet some of the evidence champions

Endangered Landscape ProgrammeRed List Champion - Arc Kent Wildlife Trust The Rufford Foundation Save the Frogs - Ghana Mauritian Wildlife Supporting Conservation Leaders
Sustainability Dashboard National Biodiversity Network Frog Life The international journey of Conservation - Oryx Cool Farm Alliance UNEP AWFA Bat Conservation InternationalPeople trust for endangered species Vincet Wildlife Trust