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Wildfire Ignition Probability

Technical Details & Access
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What is Wildfire Ignition Probability Data?

Wildfire ignition probability data provides spatially explicit estimates of the likelihood that a wildfire will start in a given location. The resulting datasets, specific to the Western and Southeastern U.S. regions, offer geospatial estimates of wildfire ignition probabilities, distinguishing between human-caused and natural (lightning) ignitions, as well as providing combined probabilities for both. The authors employ Random Forest machine learning, customized for probabilistic predictions, to model ignition likelihood based on spatial trends in observed fire occurrences, topographic features, climatic factors, vegetation characteristics, and human development patterns. The resulting datasets are scaled to recent observed ignition rates (e.g. 2006-2020 fire occurrence database) and have a spatial resolution of 120 meters. These datasets are a valuable resource for wildfire risk assessments (QWRA), risk mitigation planning, and decision support in land management, policy development, and other fire-related contexts.

How can it be implemented?

Wildfire ignition probability data helps us better understand the complex dynamics of the likelihood that a wildfire will start in a specific location by cause, and provides a tool for managers to make informed decisions about how to manage these ecosystems to meet their goals. For example: 

Quantitative Wildfire Risk Assessment (QWRA):

Ignition probability data is a fundamental input for QWRAs, which inform land management decisions, resource allocation, and risk mitigation strategies.

Prevention and Mitigation Planning:

Identifying high-probability ignition areas enables targeted prevention efforts (e.g., public outreach in human-caused hotspots) and the strategic allocation of mitigation resources.

Policy and Land Use:

These datasets can guide policy development, zoning regulations, and building code requirements to enhance community resilience to wildfire.

What sets it apart? 

This study offers several improvements over traditional wildfire ignition data:

  • Cause-Specific Probabilities: Distinguishing between human and natural ignitions allows for tailored risk management strategies.
  • Focus on Growth Potential: Fire-size thresholds ensure the data is most relevant for fires that pose significant management challenges.
  • Probabilistic Outputs: The datasets surpass simple 'presence/absence' fire data, enabling nuanced assessments of wildfire risk

Geographic Coverage

The study covers two major fire-prone regions of the United States: the Western U.S. and the Southeastern U.S..

This map depicts the geographic coverage of the two wildfire ignition probability datasets. The Western United States dataset is highlighted in green, while the Southeastern United States dataset is shown in brown.

Methodology

This study employed a multi-step methodology to develop wildfire ignition probability datasets. First, ignition data from the Fire Occurrence Database (FOD) was filtered, applying region-specific size thresholds to focus the analysis on fires with significant growth potential. In the Western U.S., this threshold was 100 hectares, while in the Southeastern U.S., it was 8 hectares.

A variety of spatial datasets representing topographic, climatic, vegetative, and human development factors were obtained and resampled to a consistent 120-meter resolution for modeling ignition likelihood. A spatial kernel density filter was applied to the FOD data to derive a spatial trend feature, aiming to capture subtle influences on ignition patterns not explicitly represented by other input variables.  The Synthetic Minority Oversampling Technique (SMOTE) was used to address the inherent imbalance between positive (ignition) and negative samples in the dataset, improving model robustness and generalizability.

Separate random forest machine learning models were trained for human-caused and natural ignitions within each study region. Region-specific differences in variable importance were accounted for (Table 2). For example, topography played a more significant role in the Western U.S. models.  The random forest algorithm was customized to produce probabilistic outputs, enabling more nuanced risk assessments.

Finally, model predictions were scaled to match the observed ignition rates from the FOD (2006-2020). This scaling step transformed the predictions into real-world units of mean annual ignitions per square kilometer, ensuring relevance for practical applications. Non-burnable areas were excluded during the scaling process to enhance accuracy.

Whether the particular situation calls for wildfire to be promoted, prevented, or mitigated, understanding and quantifying wildfire risk provides useful information for its management.

Scope & Limitations

  • Spatial Scope: The datasets provide comprehensive coverage of the Western and Southeastern United States. However, they are not applicable outside these regions, and wildfire ignition patterns in other parts of the world may differ significantly.
  • Temporal Scope: The annual ignition probabilities reflect the conditions recorded in 2022, as observed in the Fire Occurrence Database (FOD), which was used for model training. Climate change, vegetation shifts, and evolving social factors could alter ignition patterns over time. Model performance may decline if not periodically updated to reflect these changes. In addition, the data products do not characterize the dynamic intra-annual variability observed in ignition probability and the input features.
  • Fire Size Threshold: The emphasis is placed on fires with significant growth potential, determined by different area thresholds in the Western and Southeastern U.S..  The datasets may be less informative regarding smaller ignition events or those that do not spread extensively.
  • Input Data: The accuracy of the ignition probability models is inherently tied to the resolution and uncertainties within the input datasets (topography, climate, etc.). For a full list of input datasets used in this analysis, please review the original article of the authors, linked below.
  • Human Influence: While the models explicitly account for human infrastructure and development, they may not fully represent the indirect ways in which humans influence ignition patterns. Factors such as fire suppression policies, varying public awareness levels, and cultural practices related to burning could introduce localized differences not captured by the available input data.

For a comprehensive exploration of the research, including detailed methodology, data descriptions, and model development, please refer to the original article by the authors:
Wildfire ignition probability datasets by cause for the Western and Southeastern United States

GIS Data Overview

The wildfire ignition probability analysis produced three primary spatial datasets for both the western and southeastern US. These datasets are available in the following formats:

  • GeoTIFF (Albers Projection): This format is ideal for detailed GIS analysis within the continental United States as it preserves area measurements accurately.
  • Cloud-Optimized GeoTIFF (Albers Projection): This format is optimized for cloud-based analysis, web performance, and working with large datasets.
  • Cloud-Optimized GeoTIFF (Mercator Projection): This format is specifically designed for web mapping applications.

All datasets have a 120-meter pixel resolution with probability values ranging from 0 (very low likelihood) to a theoretical maximum of 1 (very high likelihood). However, it's important to note that in practice, the likelihood of a wildfire starting in any given pixel is quite low. Even in high-risk areas, the highest observed probability is around 0.0004, meaning a probability of 1, while theoretically possible, is extremely unlikely. All datasets are calibrated to match observed annual wildfire ignition rates from 2006-2020.

As described above, the datasets encompass three types of ignition probabilities:

  • Human Ignition Probability: Indicates the likelihood of human-caused wildfire ignition.
  • Natural Ignition Probability: Indicates the likelihood of lightning-caused wildfire ignition.
  • Composite Ignition Probability: Represents the combined likelihood of wildfire ignition from both human and natural causes.

GIS Data Access

Western U.S.

GeoTIFF (Albers Projection)

Best for analysis in GIS software focused on the continental U.S. where preserving area measurements is important.

933.6
MB
Human Ignition Probability
What’s inside
918.3
MB
Natural Ignition Probability
What’s inside
930.3
MB
Composite Ignition Probability
What’s inside
Cloud-Optimized GeoTIFF (COG)

Ideal for cloud-based analysis, fast web visualization, and large datasets.

1019.1
MB
Human Ignition Probability
What’s inside
962.6
MB
Natural Ignition Probability
What’s inside
1.0
GB
Composite Ignition Probability
What’s inside
GeoTIFF (Mercator Projection)

Optimized for web mapping applications.

989.3
MB
Human Ignition Probability
What’s inside
941.9
MB
Natural Ignition Probability
What’s inside
993.7
MB
Composite Ignition Probability
What’s inside

Southeastern U.S.

GeoTIFF (Albers Projection)

Best for analysis in GIS software focused on the continental U.S. where preserving area measurements is important.

709.3
MB
Human Ignition Probability
What’s inside
662.5
MB
Natural Ignition Probability
What’s inside
709.6
MB
Composite Ignition Probability
What’s inside
Cloud-Optimized GeoTIFF (COG)

Ideal for cloud-based analysis, fast web visualization, and large datasets.

764.4
MB
Human Ignition Probability
What’s inside
654.6
MB
Natural Ignition Probability
What’s inside
768.5
MB
Composite Ignition Probability
What’s inside
GeoTIFF (Mercator Projection)

Optimized for web mapping applications.

763.0
MB
Human Ignition Probability
What’s inside
650.8
MB
Natural Ignition Probability
What’s inside
767.8
MB
Composite Ignition Probability
What’s inside

Explore Datasets Interactively with our STAC Browser

STAC Browser

What is a STAC Catalog? Think of the STAC catalog like a digital library index for our wildfire ignition datasets. It provides organized information (metadata) about each dataset, including location, time periods, and other important details. This makes it easier for you to find and use the data relevant to your research or projects.

Exploring the Data:
STAC Browser:
Below we provide an easy-to-use STAC Browser for basic data exploration. This lets you quickly visualize the datasets and filter them based on your needs.

Metadata

Literature Cited:

Moran, C. J., Scott, J. H., & Vogler, K. (2023). Wildfire ignition probability datasets by cause for the western and southeastern United States.

Acknowledgements:

This wildfire ignition probability data was made possible in part by funding from the Strategic Analytics Branch, Fire and Aviation Management, National Headquarters, United States Forest Service.