Storing and Sequestering Carbon: Pennsylvania’s Forest Resource

Imagine the Opportunity of a Smaller Carbon Footprint

At the 2020 Pennsylvania Farm Show the Hardwoods Development Council (HDC) hosted the Pennsylvania Hardwoods exhibit. The exhibit’s theme was Imagine the Opportunities of a Smaller Carbon Footprint. The exhibit was made possible by a collaboration between the HDC and the three Pennsylvania Hardwood Utilization Groups (HUGs): Allegheny Hardwood Utilization Group, Keystone Wood Products Association, and the Northern Tier Hardwood Association.

The Hardwoods exhibit featured educational displays, all pertaining to how implementing sustainable forestry practices and the use of hardwood products can help reduce one’s carbon footprint. These articles will provide information pertaining to each of the themes that were displayed. This is the sixth, and final, in the series of articles.

Article 6: Storing and Sequestering Carbon: Pennsylvania’s Forest Resource 

By Jonathan Geyer and Dave Jackson

Let us start by taking a closer look at Pennsylvania’s forest resource. Based on the U.S. Department of Agriculture’s (USDA) Forest Inventory & Analysis (FIA) program, 2019 data, Pennsylvania has more than 16.6 million acres of forest land and is 58% forested. From this data we also know that Pennsylvania has the largest hardwood forest volume of any state. The Commonwealth has historically provided about 10% of the nation’s supply of hardwood lumber and leads the U.S. in lumber exports.

In addition, the Commonwealth’s has 121.6 billion board feet of standing sawtimber volume. It has increased 7% since 2013, with an estimated 7,600 board feet per acre. Despite the increased mortality brought about by pest outbreaks, net growth has remained relatively stable, between 3.0 and 3.1 billion board feet per year. Timber harvests in Pennsylvania account for the removal of roughly 1-1.3 billion board feet in wood products annually. Considering growth, mortality, and harvesting (removals) Pennsylvania’s sawtimber volume is increasing by approximately 2 billion board feet annually!

To put into perspective what one billion board feet of wood looks like – one board foot is a piece of lumber 12 inches wide by 12 inches long and 1-inch thick – one billion board feet is a stack of lumber 2½-feet high by 5-feet wide, spanning from Harrisburg to Houston, Texas (Figure 1).

Figure 1: Pennsylvania’s forest products industry harvests between 1 and 1.3 billion board feet of wood volume annually.

Using FIA data, we can also research the history of Pennsylvania’s standing wood volume (Figure 2). This graph illustrates the standing sawtimber volume of Pennsylvania’s forests from 1955-2019. In just 64 years the Commonwealth wood volume has increased over 5 times! This is due to a variety of reasons, sustainable forest management practices, farmland conversion to forest, and our forest rebounding from the previous centuries’ land clearing and unsustainable harvesting practices. 

Figure 2: Since 1955, the sawtimber volume in Pennsylvania has increased more than five times all while harvests continued to remove approximately 1 billion board feet of lumber annually.

What does all this mean for carbon storage and sequestration in Pennsylvania’s forests? Forests both store carbon, in carbon pools, and sequester carbon from the atmosphere. Carbon storage is the amount of carbon retained within the forest. Typically, carbon storage levels increase with forest age and peak in NE forests when they are greater than 200 years old.

 

Carbon sequestration on the other hand, is the process of removing carbon from the atmosphere. Trees do this through photosynthesis. The rate at which forests sequester carbon changes over time. In NE forests carbon sequestration typically peaks when forests are around 30-70 years old. Forest-level sequestration rates generally decline with age, regardless of tree species or soil conditions.

 

Figure 3: In NE forests, carbon sequestration typically peaks when forests are around 30-70 years old.

The age of the forest not only influences the rate at which they sequester carbon but also the amount of carbon they store. A forest’s maximum rate of carbon sequestration happens when trees range in size from sapling, approximately 4 inches in diameter, through medium sawtimber, trees up to 16 inches in diameter. The maximum amount of carbon storage happens when trees are large sawtimber in size, greater than 18 inches in diameter. A forest composed of both young trees and old trees will have high rates of sequestration from the younger trees while maintaining the storage capacity and sequestration rates of the surviving older trees.

Maximizing carbon storage and sequestration is only part of the global carbon picture. To understand the full role forests play in the carbon cycle, one must consider both the amount of carbon stored in forest products and the amount of carbon saved when wood is used in place of more carbon-intensive materials, such as aluminum, plastic, steel and concrete. All carbon removed from the forest during a timber harvest is not immediately returned to the atmosphere. Approximately one-third of the forest products harvested in the NE United States are made into products with long life spans, such as furniture, flooring, and cabinets (Figure 4).

Figure 4: Approximately one-third of the forest products harvested in the NE United States are made into products with long life spans such as this red oak floor.

If we decide to continue using wood because it is the most environmentally friendly choice, but do not use wood harvested in Pennsylvania, then it must be imported from somewhere. If it comes from outside the state, it takes energy and carbon emissions to bring those wood products to our region. Using locally sourced wood not only increases the overall carbon sequestered, but also adds to the local economy.

It is important to understand the whole forest carbon story. This necessitates looking beyond the local level to both the regional and global scale and includes considering the role forest products play. The land-use decisions of Pennsylvania’s landowners will have a profound impact on our forests’ ability to sequester and store carbon and therefore the role they play in mitigating climate change. The greatest impact forest owners can have on carbon is to ensure their land remains a forest, i.e., keep forests as forests.

Reference: Forest Carbon:An Essential Natural Solution for Climate Change, By Paul Catanzaro, University of Massachusetts and Anthony D’Amato, The University of Vermont