Forest industry professionals have a renewed interest in understanding the extent to which forestland area has changed in regions where they procure wood. A few examples include:

• On June 30, 2023, the European Union implemented the European Union Deforestation-Free Supply Chain Regulation (EUDR), a process that bans imports into the EU marketplace if they originate from areas that have seen deforestation or forest degradation. All operators (including wood suppliers) will need to collect and maintain information on these products, including providing “adequately conclusive and verifiable information” that products are deforestation-free.
• The 2022 Sustainable Forestry Initiative’s (SFI) Fiber Sourcing Standard contains a performance measure to “develop and implement a due diligence system to manage the risk of sourcing fiber from controversial sources.” Controversial sources are defined in a number of ways and include “conversion sources originating from regions experiencing forest area decline.”

These issues alone make quantifying the extent of forestland area change necessary for forest products companies that export wood and seek to maintain compliance with certification standards. Fortunately, using over 130,000 forest inventory plots across the US, there are tools available to estimate forestland area change across states and regions.

This post describes how EVALIDator, a web-based application programming interface (API) created and maintained by the USDA Forest Service, can be used to estimate forestland area change. The program uses Forest Inventory and Analysis (FIA) data to determine estimates for several forest conditions of interest.

Now we can use data compiled from a previous inventory in Minnesota to estimate forestland area change. This time, open the EVALIDator homepage in a new window and run a similar analysis. This time, on the second page, select Show all available inventories. Now you’ll see many rows for an individual state available with many years to choose from.

The FIA data are measured in a panel design where all plots in an inventory take several years to complete. In the eastern US, forests are inventoried on a five to seven year cycle, while western US forests are measured on a 10-year cycle. If we want to compare current forestland area estimates (2017-2021) with those from ten years prior (2007-2011), we can select 272011N MINNESOTA 2007;2008;2009;2010;2011 as the evaluation. On the next page, select Forest type group again as the row variable and choose Ownership group - major as the column variable.

The output based on the 2007-2011 data show a total of 17.37 million acres of forestland existing in Minnesota. Hence, the state has seen an increase in forestland area by 295,418 acres over the last 10 years. A closer inspection of forest types shows that some have decreased in area (e.g., aspen/birch) while others have increased (e.g., maple/beech/birch and oak/hickory; Fig. 1).

While this analysis used data collected across the entire state of Minnesota, users can also select more specific geographic regions tailored to their organization. For example, selecting a “circle retrieval” in step one on the EVALIDator web page will allow a user to input latitude and longitude coordinates to access data within a specified radius (e.g., 50 miles). This is helpful for understanding how forests have changed within wood procurement zones around a mill.

Similarly, if an organization has a list of counties where they have procured wood from in the past, the county within each state can be selected as a row or page variable in step 4 on the EVALIDator web page to obtain forestland area changes estimates within those counties. If this latter approach is done, be sure to look at the number of FIA plots that are being evaluated within each county in the EVALIDator output to make sure there is a suitable number of them being used (say, greater than 25 plots) to generate the estimate.