Remote Sensing as a Tool for Monitoring Wetland Habitat Change

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Remote Sensing as a Tool for Monitoring Wetland
Habitat Change

• Thomas Dahl
• U.S. Fish and Wildlife Service
• Branch of Habitat Assessment

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Wetlands Status and Trends

• Goal
• Determine the status and trends of wetlands in
  the United States and produce comprehensive,
  statistically valid acreage estimates of the
  Nations wetland resources.

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Study Elements

• Scientific approach - biological definition,
  monitor all wetlands
• Statistical (stratified, random) sample of lower
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• Use remotely sensed imagery in combination with
  field work (T1 vs. T2)
• Produce reports on wetland status and trends

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National Sample Plots (4,375 plots 4 sq. mi)
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Study Elements

• Lumpers and splitters
• Status and trends takes generalist approach
• Use broad categories i.e. Agriculture
• Trade specificity for statistical rigor
• Practical constraints
• Budget constraints

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Why Monitor Wetland Area?

• The Emergency Wetlands Resource Act of 1986
• Requires the Fish and Wildlife Service to report
  to Congress on the status of wetlands every 10
  years.

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Why Monitor Wetland Area?

• Our Nations wetlands goals have traditionally
  been based on wetland acreage. This standard has
  and will continue to serve us well as we strive
  to achieve sustained net gains of wetland
  acreage. (Council on Environmental Quality)
• 11 Federal agencies working to achieve a net
  increase in acres by 2005
• Status and Trends provides performance measure
  for these agencies

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Why Monitor Wetland Area?

• Earth Day (April 2004) the President announced
  that the Fish and Wildlife Service would complete
  an updated wetlands status and trends study five
  years ahead of schedule.

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Technical Challenges

• Monitoring more frequency means measuring less
  change.
• Approaching No-net-loss means change rate is
  harder to measure with the same degree of
  reliability

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Technical Challenges - Imagery
Photography
Satellite
Satellite
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1999
1989
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Detecting Change
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Detecting Changes
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Remote Sensing Wetlands

• Imagery reflects on-the-ground condition
• Imagery captures a single point in time
• Lands in transition or undergoing change require
  special attention

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Determining What is Wetland

• Land with too much water
• Lands that have been disturbed
• Require supplemental information
• Collateral data
• Field verification

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Future Actions

• Continue to ensure statistical rigor
• Expand use of high resolution satellite imagery
• Adapt to assessment/qualitative monitoring

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Summary

• Determining wetland habitat change nationally
• Relies on remote sensed observables
• Uses statistical estimates
• Provides a measurable element to gauge
  policy success
• Must adapt to future monitoring needs

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