Statewide study examines health of forestland in Maryland

MARYLAND – A recent study from the University of Maryland’s Harry R. Hughes Center for Agro-Ecology (HHCAE), Chesapeake Conservancy, and the University of Vermont is revealing data about the health of Maryland’s forestland.

Calling For Collaboration

The study was born from two pieces of legislation passed by the Maryland General Assembly in 2019 and 2021. Senate Bill 729 called for a technical study on changes in forest cover and tree canopy in the state. Two years later, House Bill 991 established the Tree Solutions Now Act of 2021.

“To satisfy the provisions of that legislation, the Hughes Center helped several stakeholder events where we talked to stakeholders throughout Maryland. Then we issued an open request for proposals in 2020,” said HHCAE Executive Director Dr. Kate Everts.

The Chesapeake Conservancy and University of Vermont answered that call with a proposal. Dr. Everts says the research team was then awarded a grant to develop their data. From there, the information gathering began.

“Forests represent one of Maryland’s most important natural resources. They’re critical to our economy, and our environmental sustainability, as well as the health of our citizens,” said Dr. Everts.

Diving Into The Data

“We took a comprehensive look at Maryland’s forests over decades of data, and used three independently developed and managed data sets to examine trends in forests,” said Vice President of Climate Change Strategy for Chesapeake Conservancy, Susan Minnemeyer.

Minnemeyer says the data was collected through six different tasks: restoration and planting efforts, forest and tree canopy extent, forest health, progress in Chesapeake Bay Program restoration work, forest and tree canopy change, progress in tree planting, mitigation banking through the Forest Conservation Act, and a survey of forest and tree planting programs across the set.

The team used three data sets, starting with the Chesapeake Bay Program’s high resolution data. Minnemeyer says it’s the longest data stream they have available on a national scale.

“It’s information collected through field sampling, and it’s been ongoing for nearly 90 years. It provides the greatest long record of change. It has a few drawbacks in terms of what we were looking at in this study, in that the sampling isn’t dense enough to provide regional patterns within the state,” said Minnemeyer.

Researchers also utilized the National Land Cover Dataset. “This has data for the last 20 years, and they have a more limited set of data that goes back in to the 1990s. But, we used the data from 2001 to 2019. It’s based on satellite data monitoring. It makes the advance of being spatially explicit. You see maps of where change is happening,” said Minnemeyer.

Lastly, Minnemeyer says high resolution data from the Chesapeake Conservancy, University of Vermont, and the United States Geological Survey was also used.

“It provides a high level of detail. So, we can monitor individual trees within this data set. And, it provides all those details in urban an suburban areas that we’re not quite able to get to with the NLCD data,” said Minnemeyer. “It’s for the first time we can comprehensively look at tree canopy outside of forests across the state.”

Forest Cover and Tree Canopy Outside Forests

“With cities and suburbanization, there were steep levels of forest loss in the state. Looking into the 90s and 2000s, you see that curve bend, where the amount of forestland begins to stabilize. We’re seeing much less rapid rates of forest loss,” said Minnemeyer.

As forest loss rates decline, researchers also noted a drop in the amount of forestland used to harvest timber. “That is a pattern continuing along with the changes in forest cover we see here,” said Minnemeyer.

Minnemeyer says the greatest amount of forestland was found in Western and Southern Maryland. However, Southern Maryland saw low amounts of tree canopy cover outside of designated forests. Meanwhile, North Central and Central Maryland saw increasing amounts of canopy cover outside of forests. On the Eastern Shore, greater amounts of land are in agricultural or wetlands. For that reason, Minnemeyer says overall forest extent was lower. And, the Eastern Shore saw lower amounts of urbanized tree canopy outside of forests.

“We’re seeing an overall decline of 4.6% of forest cover, and an annual change of -0.23%,” said Minnemeyer. “We’re seeing smaller rates of overall change, and a smaller rate of annual change, as well. All three of these independent data sets are seeing declines in forest cover, but the rate of decline has decreased over time.”

Health of the Forests

Forest health was assessed through two lenses, says Minnemeyer; fragmentation of forests over time.

“Fragmentation is increasing over time. The amount of forest in small, medium, and large areas is declining. Increasingly, we have isolated patches and those patches are also getting fragmented until they no longer meet the forest definition,” said Minnemeyer.

Researchers also looked at invasive species found in forests across the state. “12% of forestland showed disturbances, and the leading cause of those disturbances was invasive species. That includes suppression of trees by vines and other invasive species, like Oriental Bittersweet, or Chinese Wisteria,” said Minnemeyer.

Meeting Goals

The study also surveyed how well each of Maryland’s 24 counties are doing when it comes to meeting restoring forestland and tree planting goals. “We saw progress across the state, and wanted to note that there is extensive variation county by county,” said Minnemeyer.

Somerset County had the lowest amount of work done. However, Minnemeyer says it can be harder to find space for the trees in coastal areas. “There’s not an opportunity area for tree planting to reach a 70% goal in individual counties,” said Minnemeyer.
Areas of the state that saw gains include Baltimore City and other smaller, urban areas. “In areas where we’re seeing housing development from agricultural land, you often do see tree canopy increases. But, I would also expect that a significant part of that is related to Chesapeake Bay restoration,” said Minnemeyer.

Counting Change

In Maryland, between 36% and 38% of forested areas that experienced change were converted into developed area, says Minnemeyer. Central Maryland saw the most net forest change, as development continues in the area. Minnemeyer says forests in Prince George’s and Montgomery Counties were frequently changed into impervious surface, or turf and low vegetation.

However, another thing that Minnemeyer says is changing, is the increasing commitment to restoring forestland and canopy cover. In a survey, researchers found that about 1,854 total acres of trees were planted in 2019 and 2020. Protected areas were a significant source of gains, with about a third of Maryland’s forests under protective status. Researchers estimate that there are about 400,000 acres of areas suitable for tree planting across the state.

“Maryland is really accelerating the amount of total land protected. As of 2021, we’ve reached 29%, and Maryland is really approaching the 30 by 30 goals of protecting land and achieving that rate of protection,” said Minnemeyer.

Read The Study

To read the full, study click here. A digital StoryMap of the study is also available here.

Categories: Delaware, Environment, Local News