Pennsylvania remains one of the most heavily forested regions in the Eastern United States, a designation that prompts curiosity about the sheer scale of its timber resources. Understanding the number of trees requires appreciating the scientific methodology used to quantify this vast natural asset. Data collected by federal forest agencies provides a reliable picture of the density, composition, and extent of the forests that shape Pennsylvania’s landscape.
The Current Estimate of Individual Trees
The U.S. Department of Agriculture (USDA) Forest Service’s Forest Inventory and Analysis (FIA) program estimates that Pennsylvania is home to approximately 7.75 billion live trees. This figure is a statistically derived estimate from a vast sampling network, not a literal count of every plant.
To be included in this total, a plant must meet the FIA’s minimum size threshold for a tree. The estimate includes all live trees with a diameter of at least 1.0 inch, measured at breast height (DBH). This definition includes saplings and smaller trees, providing a comprehensive measure of the entire standing forest population.
Forest Land Coverage and Density
This massive tree population covers approximately 16.6 million acres of forest land, blanketing about 57% of the entire state. The FIA program defines forest land as requiring a minimum of 10% tree canopy cover on at least one acre of land.
Combining the total number of trees with the total acreage determines the average stocking density across the state. The 7.75 billion trees spread over 16.6 million acres translates to an average density of around 467 live trees per acre of forest land.
This density is a dynamic figure, fluctuating based on the specific forest type, the age of the stand, and past management activities. Younger forest stands often have a much higher number of smaller trees per acre than mature stands composed of large, older growth trees.
Dominant Species and Forest Composition
The vast majority of the trees are hardwoods, making up about 95% of the total forest land. The two most prevalent forest types are the Oak/Hickory group and the Maple/Beech/Birch group, which dominate the composition of Pennsylvania’s woodlands.
The Oak/Hickory forest type is the largest, covering about 54% of all forest land, or approximately 9.0 million acres. This group is found predominantly in the southern two-thirds of the state. The Maple/Beech/Birch group accounts for another 31% of the forested area, roughly 5.2 million acres.
When analyzing the population by individual species, Red Maple is the most common tree, accounting for about 20% of all trees 5.0 inches or greater in diameter. Black Cherry is the second most abundant, valued for its commercial timber. Sweet Birch follows as the third most abundant species. The remaining 5% of the forest is composed of softwoods and other minor hardwood groups.
How Forest Resources Are Inventoried
The figure of 7.75 billion trees is generated by the USDA Forest Service’s Forest Inventory and Analysis (FIA) program, which acts as the nation’s continuous forest census. The foundation of the inventory is a systematic network of fixed, permanent sampling plots distributed across the entire state.
These plots are spaced out on a precise grid, ensuring the sample is representative of all forest conditions across the landscape. Field crews visit and measure a subset of these plots annually in an annualized inventory. On each plot, the crews collect detailed data, including species identification and the diameter of every tree that meets the minimum 1.0 inch DBH requirement.
By extrapolating the measurements observed on these fixed plots to the entire area of forest land, the FIA program produces the statewide estimate of tree numbers and other metrics. This continuous, plot-based methodology provides a consistent way to track changes in the forest resource over time, including growth, mortality, and removals.