A fire ends. Its effects keep unfolding.
An outline on a map shows the extent of a fire event, including ground that may not have burned. Satellite assessments can map the area that did burn and how vegetation changed within it. Those are different measurements, with different coverage and dates.
Read four views together: the event boundary, observed burned area, severity, and later conditions.
July 19, 2020 / before
September 27, 2020 / afterHow far did the event extend?
The outline may include ground that did not burn.
Which ground burned?
Satellite assessments map this for fires they cover.
How did it change?
Effects vary within the burned area and across ecosystems.
What happened later?
Repeated observations can check the outcomes that matter here.
The USGS Wildland Fire Trends Tool uses separate perimeter and observed burned-area views. Each has its own years and coverage.
A perimeter is a boundary
An incident perimeter outlines an event; it is not a measurement that every acre inside burned. A treatment-unit boundary describes planned or recorded work, which is another kind of geography.
For border-crossing fires, the whole incident’s reported acreage differs from its mapped area within Oregon. Label these separately. Repeated or overlapping events also require care before adding area totals.
Burned area is a different measurement
USGS's Wildland Fire Trends Tool separates its historical perimeter view from a satellite-classified burned-area view. The latter excludes unburned ground within a mapped fire boundary. It covers a different time period and a subset of larger wildfires, so the two totals are not interchangeable.
A trend chart must say which area it counts, which years and fire sizes are included, and where older records are incomplete. Neither total, by itself, tells us whether the fire helped or harmed a place.
Severity describes particular effects
MTBS uses defined satellite assessment methods and maps a subset of larger fires. Coverage thresholds mean many small fires and treatments are absent. Unassessed and unavailable pixels are different from unburned or low-severity pixels.
A severity color alone cannot decide whether an outcome was ecologically desirable. Read its definition, timing and landscape context alongside project objectives and field observations.
Use a common place and dated observations
The main page compares the same western Oregon extent in Terra MODIS imagery before and after the September 2020 fires. False color helps reveal landscape changes; clouds, season and other dark surfaces affect interpretation.
For quantitative summaries, use reviewed source products and appropriate masks and methods. The displayed images are observations, not a calculation of burned acreage or habitat recovery.
Follow more than greenness
Egley’s one- and nine-year field visits examined vegetation and fuels as well as satellite signals. Useful outcome measures can include surviving trees, regeneration, invasive plants and habitat condition, chosen for the site’s objective.
Community outcomes require their own evidence: smoke observations, water-system impacts, damage records or other documented effects. They do not follow automatically from a forest severity map.
Could two sites look equally green from space while having very different numbers of surviving large trees?
Read the evidence
- USGS · Wildland Fire Trends Tool methods ↗Perimeter dashboard versus Landsat-classified burned-area dashboard; periods, size thresholds and older-record limitations
- MTBS · Assessment methods and coverage ↗Severity, mapping thresholds and limitations
- NASA · Oregon’s 2020 fire scars ↗Terra MODIS false-color observation and original explanation
- Dodge and colleagues · Egley Fire Complex study ↗2019; abstract, methods and one-/nine-year field observations. Reported percentage/hectare denominators require clarification