Data & Methods

The sections below describe in detail the data sources and methods used to generate the maps and other summary statistics presented throughout each section of the Track & Trace website.

Forest Trend Map Data Sources & Methods

Map Data Source: FIA

The data displayed on the Forest Trend Map page are from the USDA Forest Service’s Forest Inventory and Analysis (FIA) program for the inventory time periods covering 2000 through 2016. The summary charts below the map show estimates of total forest area (in acres) and forest growing stock inventory, or the volume of live trees above 5 inches in diameter at breast height growing in the forest (in cubic feet). The forest area data were also used to fill each county on the map with varying shades of green according to the total percentage of the county area covered in forest.

FIA Program

The FIA program collects data on U.S. forest extent and conditions using field measurements gathered from a fixed set of field plots throughout the country. The program maintains one field plot site for every 6,000 acres, and 15-20 percent of the plots are revisited every year. This means that the “2016” annual inventory data, for example, might represent plot measurements collected during the 2011–2016 survey cycle. However, because inventory changes slowly, small differences in measurement years are usually insignificant.

Filling in FIA Data Gaps

Because the FIA annual inventory system was not fully implemented until recently, there are occasional years for individual states where data are missing or incomplete. For years within the time frame of this analysis (2000-2016) for which there are no FIA data available, data from the most recent adjacent year in that state are substituted. The table below shows where substitutions were made, with a “×” noting years for which concurrent inventory data are available. For years where concurrent inventory data are not available, the substitute data year that was used as proxy is listed.

2000  × 2005 2004  × 2004 2008 2006 2002 2001  × 2001  ×
2001  × 2005 2004  × 2004 2008 2006 2002  ×  ×  × 2000
2002  × 2005 2004  × 2004 2008 2006  ×  ×  ×  × 2000
2003  × 2005 2004  × 2004 2008 2006  ×  ×  ×  × 2000
2004  × 2005  ×  ×  × 2008 2006  ×  ×  × 2003  ×
2005  ×  × 2004  ×  × 2008 2006  ×  ×  ×  ×  ×
2006  ×  × 2004  ×  × 2008  ×  ×  ×  ×  ×  ×
2007  ×  ×  ×  ×  × 2008 2006  ×  ×  ×  ×  ×
2008  ×  × 2007  ×  ×  × 2006 2007  ×  × ×   ×
2009  ×  ×  ×  ×  ×  ×  ×  ×  ×  ×  ×  ×
2010  ×  × ×   ×  ×  ×  ×  ×  ×  ×  ×  ×
2011  ×  ×  ×  ×  ×  ×  ×  ×  ×  ×  ×  ×
2012  ×  ×  ×  ×  ×  ×  ×  ×  ×  ×  ×  ×
2013  ×  ×  ×  ×  × ×   ×  ×  ×  ×  ×  ×
2014  ×  ×  ×  × ×  ×  ×  ×  × ×  ×  ×
2015  × ×  × × × ×  ×  ×  × × ×  ×
2016  × ×  ×  × 2015 ×   ×  ×  × 2015 ×  ×

Track & Trace Data Sources & Methods

T&T® Data Collection

When Enviva is contacted by a supplier who is interested in setting up a contract to sell wood from a new harvest tract, we first determine whether the tract meets the Responsible Sourcing requirements. If we decide to move forward with the purchase, suppliers submit a questionnaire with data on forest and harvest characteristics and the tract is entered in the Track & Trace (T&T) database.

In 2018, Enviva embarked on the first major review and revision of its T&T program, which was implemented on January 1st, 2019. Throughout the process, we consulted our suppliers, field staff, and external experts in the revision of our T&T harvest questionnaire and data collection procedures. Specific improvements to the questionnaire include refined definitions and guidance, an option to add details for multiple forest stands, and new questions on stand establishment, regeneration, timber stocking level, and management history. We also added procedures for monitoring our tract information and checking for accuracy. We check that all questions on our questionnaire have been answered, and that we receive a map for each tract set up in our database. We also use remote sensing data to check that the location, size, and forest cover type information is correct.


Explanation of fields on our questionnaire

The details we collect from the supplier include:

Definitions of fields on our questionnaire

Tract and Stand:

Establishment and Regeneration:
Forest Cover Type:
Harvest Type:

All of these details are entered into the database, and a unique ID number is generated for the tract.

At Amory, approximately 85% of the wood is purchased from sawmills and other wood processing facilities. The 15% of the wood that is delivered from the forest comes from one supplier, and so the T&T program is not deployed in the same way in this supply area. Instead of entering individual harvest tracts in the T&T database, Amory’s forestry team receives regular updates from the supplier on the forest type, harvest type, and age class of the forests from which the wood was sourced.

T&T Data Monitoring & Validation

Tract information that was entered into the T&T database is checked for accuracy during our desktop monitoring. We use remote sensing data to monitor harvest location, acreage, and forest cover type, and we also check for data inconsistencies. This monitoring is our first assessment of the data’s accuracy. Enviva foresters audit a subset of the tracts in the database while the harvest is active to verify the information entered into the T&T database and ensure the logging crew has the training credentials required in our contracts. A further subset of tracts are visited upon completion of the harvest to collect additional T&T information, including an assessment of the logging crew’s adherence to soil and water quality Best Management Practices (BMPs).

The T&T procedures are subject to auditing throughout the year, as data from the T&T program provide evidence for Enviva’s third-party forestry and sustainability certifications. In addition, we are working with a third party to develop a Track & Trace standard and build procedures for auditing our data for accuracy. Refer to our Responsible Sourcing Policy page for mid and end-of-year progress updates on this work.

T&T Data Display

A small subset of tracts that make up less than 5% of total wood supply are not included in the mapped database because of agreements with suppliers prohibiting the mapped display of harvest data. Enviva collects summary T&T data from these forests and includes them in feedstock origin summaries.

The Wood Supply Map displays the tracts entered into the T&T database during the reporting period as point data.  

When the user hovers over a point on the map, detailed information on that harvest from the T&T database is displayed, including the county of origin, forest type, harvest type, landowner type, dominant forest age class, tract size, the estimated percentage of the total harvest volume that is sold to Enviva, and the tract’s certification status.

Preserving Supplier Confidentiality

To maintain the privacy Enviva’s suppliers and landowners, tract points are located in the vicinity, but not the precise location, of the harvest. The tract GPS coordinates are fuzzed for security, and then altered again randomly to within 10 miles of their original location each time they are rendered in the map tool.

Infographic Data Sources & Methods

FIA Data for Southeast Forest Characterization

The information presented in the infographic on the T&T introductory page regarding the southeastern United States is derived from the FIA data described above. Here, we report the estimated increase in forested area and timber inventory since Enviva opened its first mill in 2011.

T&T Data for Summary Statistics

The T&T database also provides the summary statistics displayed on the T&T introductory page and below the Wood Supply Map, including the number of tracts Enviva sourced from, states and counties where those tracts were located, average tract age, and average percentage of the total volume of wood from final harvests sent to Enviva.

The unique tract ID number that is generated when a harvest is entered into the T&T database is also recorded whenever a load of wood is delivered to a mill from that specific harvest. This enables us to keep track of how much wood each of Enviva’s mills receives from each harvest and analyze Enviva’s feedstock sources by volume. The volume-based analysis provides summary statistics displayed on the T&T introductory page and below the Wood Supply Map, including the percentage of hardwood and pine feedstocks received and the percentage of wood delivered from each origin, i.e. forest type, sawmills, and/or wood processing facilities.

In addition, our sourcing has changed such that we sometimes receive material from chip mills or other mills that are considered to be non-typical primary suppliers. In these cases, we set tracts up in the database, and work with the supplier to receive volume information from those tracts to their mill, so that we may attribute our volume received to those tracts for the derivation of our feedstock sourcing figures.

With the update of the forest cover types on our questionnaire in 2019, we’re now presenting additional forest types in the sourcing infographic on the T&T landing page. Since we are still receiving volumes from tracts entered into our database prior to the revision (before to January 1st, 2019), and are also receiving volumes from tracts entered since that date, we’ve re-categorized old types to fit into the new forest type categories. For example, in 2018 we would have called a forest “southern yellow pine”, but after this revision, we now call that “Pine Forests”. In the future, volumes received from prior to January 1st, 2019 tracts will phase out, and we will not need to re-categorize any of our forest cover types. Learn more about our 2019 Track & Trace system improvements at our Voices of Enviva Blog.

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