State of Chesapeake Forests 2.0
A follow-up to the 2006 State of Chesapeake Forests report.
![Aerial shot of Big Gunpowder Falls, with riparian coastline.](https://cdn.arcgis.com/sharing/rest/content/items/cb5b91c1c6fd43478f01cf8e8a7d6e9d/resources/w6qgfe06nxjPYXwSQTvLY.jpeg?w=20)
In September 2006, the State of Chesapeake Forests report provided a comprehensive watershed-wide snapshot on forests in the 206 counties that feed into the Chesapeake Bay. The report provides a history of forests in the watershed, describes their importance, and presents comprehensive data on forest extent, composition, health, products, trends, and more.
The recently released 2017/2018 1-meter resolution land use/land cover data and accompanying land use/land cover change data gives us an incredible opportunity to learn about Chesapeake forests at a finer scale than ever before.
![Screenshot of 2017/18 land use land cover data zoomed out showing a river flowing through a highly urbanized and parcelized landscape](https://cdn.arcgis.com/sharing/rest/content/items/cb5b91c1c6fd43478f01cf8e8a7d6e9d/resources/SWSuUxIwdWCL-udBMJclo.png?w=20)
![Screenshot of land use/land cover data zoomed in to a forest patch in a suburban area](https://cdn.arcgis.com/sharing/rest/content/items/cb5b91c1c6fd43478f01cf8e8a7d6e9d/resources/BB2Skj_VfPW7sBV2MkeHk.png?w=20)
This Storymap will use this new data to provide an updated understanding of the State of Chesapeake Forests and how they are changing. This evaluation will cover forests in more natural settings as well as tree cover in the cities and communities where many people live and play. As more complex analyses are conducted, this Storymap will be updated to reflect our growing understanding of Chesapeake Forests.
Healthy Forests, Healthy Watershed
Healthy forests are essential to the health of the Chesapeake Bay.
![An image with a perspective looking upwards, standing underneath a black gum tree covered in foliage.](https://cdn.arcgis.com/sharing/rest/content/items/cb5b91c1c6fd43478f01cf8e8a7d6e9d/resources/8Daw7IDIiyx6wHsJ1kBAr.jpeg?w=20)
The watershed’s forests provide habitat, clean air and water, prevent flooding and erosion, and allow for economic and recreational opportunities. By allowing trees to naturally provide these ecosystem services, communities save money and avoid harms to human health and the built environment.
![An image with a perspective looking upwards, standing underneath a black gum tree covered in foliage.](https://cdn.arcgis.com/sharing/rest/content/items/cb5b91c1c6fd43478f01cf8e8a7d6e9d/resources/looU0kNEtBN3aH40np-12.jpeg?w=20)
Based on estimates provided by i-Tree Landscape, across the Chesapeake Bay Watershed, trees are providing over $6 billion of benefits annually from air pollution removal, reduced stormwater runoff, and carbon sequestration. To learn more about the benefits trees are providing across the watershed, review the full i-Tree dataset here . To take a closer look at the benefits provided by tree cover in your county, check out the Chesapeake Tree Canopy Network’s County Fact Sheets .
![An image with a perspective looking upwards, standing underneath a black gum tree covered in foliage.](https://cdn.arcgis.com/sharing/rest/content/items/cb5b91c1c6fd43478f01cf8e8a7d6e9d/resources/hteX1EUHlQzeriVSfI2KI.jpeg?w=20)
Unfortunately, Chesapeake forests are being converted to development and fragmented into smaller areas. As work progresses to address pressing issues such as deforestation and environmental justice throughout the Chesapeake Bay Watershed, this Storymap will help inform decisionmakers so they can better target forest conservation, restoration, and management efforts.
Additional Resources
Where are there forests and trees in the Chesapeake Bay Watershed?
The new high-resolution data provides a detailed perspective on how forests and trees across multiple land use classes are distributed throughout the watershed. Every type of tree cover provides critical benefits in the watershed.
For the purposes of this Storymap, the Forest class is defined as areas with tree cover greater than one acre with a minimum patch width of 72 meters and an undisturbed or unmanaged understory.
Large, contiguous blocks of forests capture rain, reduce runoff, maintain the flow of streams, filter nutrients and sediment, stabilize soils, and pull carbon dioxide from the atmosphere, storing carbon in their roots, trunks, canopies, leaves, and surrounding soil. They provide critical habitat and migration paths for animals.
Forests promote human health by providing clean air and water and abundant opportunities for recreation such as hiking, camping, and fishing. They contribute to the Chesapeake Bay watershed economy by providing clean air and water, wood and paper, jobs and income, higher property values, improved physical and mental health, and recreational opportunities.
Early Successional Forest includes Natural Succession and Harvested Forest, which are barren, herbaceous, scrub-shrub, or harvested forest lands that are presumed to be undergoing either natural or managed succession and will eventually become forested.
Early successional forests are an important transitional tree cover class. These forests provide valuable habitat, comprised of grasses, forbs, perennial herbs, woody shrubs and shade-intolerant trees like river birch and yellow poplar. These habitats are especially important for pollinators and for a variety of forest birds, such as the golden-winged warbler and American woodcock, that rely on early successional forests for foraging and breeding grounds.
Declines in early successional forests, due to a lack of sustainable forest management, has negatively impacted early successional plants and animals.
Other Tree Cover is smaller or irregularly shaped patches of tree cover that are not big enough to be classified as forest, but are presumed to have an undisturbed or unmanaged understory. This tree cover class includes riparian forest buffers and agricultural windbreaks.
Riparian forest buffers reduce erosion and filter excess nutrients, sediments, and pathogens from runoff entering waterways. They stabilize stream banks and restore in-stream conditions of temperature, oxygen, and food that supports aquatic ecosystems.
Agricultural windbreaks, silvopasture (lands managed for trees and livestock), and other agroforestry practices serve many of the same functions while providing additional benefits to farmers, like protecting crops, conserving soil, and acting as a barrier to dust, odor, and pesticide drift.
Urban tree cover, including Tree Canopy Over Turf Grass and Tree Canopy Over Impervious Surfaces cleans the air, mitigates heat, reduces stormwater runoff, and provides critical greenspaces for people living in cities.
This viewer aggregates the original 54-class, 1-meter data into a 10-meter, 6-class thematic map to display the following comprehensive landcover classes: tree cover, early successional forest, development, agriculture, non-forested wetlands, and water. Tree Cover includes Forest (contiguous tree cover patches greater than one acre with a minimum patch width of 72 meters and an undisturbed/unmanaged understory), Other Tree Cover (smaller or irregularly shaped patches of tree cover that do not qualify as forest, but are presumed to have an undisturbed/unmanaged understory), Tree Canopy Over Turf Grass (tree cover adjacent to structures or turf grass in developed areas), and Tree Canopy Over Impervious Surfaces (tree cover that overlaps with roads, structures, or other impervious surfaces). Early Successional Forest, includes Natural Succession and Harvested Forest (barren, herbaceous, scrub-shrub, or harvested forest lands that are presumed to be undergoing either natural or managed succession and will eventually become forested).
How much tree cover is in the Chesapeake Bay Watershed?
It is important to understand tree cover where people are. Urban tree cover provides countless benefits to communities. Trees in communities are not only aesthetically pleasing, but they also create green spaces where people can go outside and enjoy nature, which can help improve mental health and reduce crime. Trees provide clean air and shade, decreasing energy costs and heat and air pollution-related illnesses.
Tree Cover includes all mature tree cover, both natural and urban. Overall, sixty-three percent of the Chesapeake Bay Watershed is covered by trees. More rural states display higher amounts of contiguous, forested tree cover. The state of West Virginia stands out with the greatest amount of tree cover (75%). Pennsylvania, New York, and Virginia also have relatively high amounts of tree cover. The Monongahela National Forest and the George Washington & Jefferson National Forests in West Virginia and Virginia support high amounts of forest cover in these areas.
More localized information can be used to better understand whether there is adequate tree cover to provide clean water to streams and waterways. For example, the Chesapeake Healthy Watersheds Assessment provides data that can be explored at the watershed or catchment scale. Although there is significant variation, the Assessment found that on average, healthy watersheds are 63.6% forested (Roth et al., 2020).
In coldwater habitat areas, forest cover is particularly important for providing clean and cool water. An analysis from Maryland found that watersheds where brook trout were present had 70% forest cover on average. Riparian tree cover, which will be evaluated in the next iteration of this Storymap, is also critical for cooling streams and providing clean water.
Looking across the watershed, areas with agriculture and major, population-dense cities are centrally concentrated and have significantly less tree cover.
However, there is oftentimes an uneven distribution of tree cover within cities. Areas with relatively low tree cover can experience the urban heat island effect, where high concentrations of impervious surfaces can lead to elevated temperatures.
Unfortunately, these urban heat islands are often located in historically underserved communities. Tree planting efforts in these areas, when supported by local communities, can be particularly beneficial for ensuring the benefits of trees can be enjoyed by everyone.
Please use the ‘open live content in a new tab’ feature in the upper right had corner of the viewer and then zoom in to select a single county and visualize the data for that county. The viewer displays a county-by-county map of tree cover, with a pie chart showing the breakdown of tree cover by each tree cover class, and bar graphs showing how tree cover in the jurisdiction compares with tree cover across the the state and the watershed. A full, watershed-wide dataset of county-level tree cover is available here . State-level tree cover data (within the Chesapeake Bay watershed) can be accessed here .
Additional Resources
Roth et al. 2020. Chesapeake Healthy Watersheds Assessment Report
How much forest is in the Chesapeake Bay Watershed?
While Tree Cover includes all mature tree cover in both natural and developed areas, forested extent includes all stages of natural forest development: recently harvested, early successional, and forest. It is critical that we look at all stages because recent harvests can look like tree canopy loss on the surface. Some recent harvests may be converted to other uses, like development or windfarms, but many are simply harvests – a planned stage in sustainable forest management.
Sustainable forest management is an important part of the healthy forests, healthy watershed connection.
Different stages of forest and tree canopy development provide different benefits. Natural disturbances, such as wind, fire, and tree mortality, as well as human disturbances, such as sustainable forest harvests, create a mosaic of habitats across the landscape. Forests with a diversity of age, structure, and species composition help support a multitude of wildlife species across the landscape.
Sustainable timber harvesting helps keep forests as forests by incentivizing regrowth and reducing economic pressure to convert land to development. Harvested forests, even when first cut, still provide important ecological benefits such as habitat for early successional species, like the golden-winged warbler which relies on early successional forests for habitat and breeding. Early successional forests are relatively rare, accounting for only 3.7 percent of land in the Chesapeake Bay.
Timber harvests also provide a wealth of other benefits – they can improve forest health, reduce fuel buildup (and therefore potential wildfire risk), improve resiliency to climate change, and provide wood fiber and lumber for forest products.
The greatest density of forest occurs in the western part of the watershed, with the agricultural and population-dense center of the watershed having the least amount of forest. Early successional forests, which include harvested areas, are difficult data to categorize. It takes more than a few years to detect if a harvested area is reverting to managed forest or transitioning into a new land use, like cropland or development. Our understanding of these areas will improve as we monitor land use change over longer time periods and evaluate additional sources of reported timber harvest data.
Please use the ‘open live content in a new tab’ feature in the upper right had corner of the viewer and then zoom in to select a single county and visualize the data for that county. The viewer displays a county-by-county map of forested extent, with a pie chart showing the breakdown of forested extent by each forested extent class and bar graphs showing how forested extent in the jurisdiction compares with forested extent across the the state and the watershed. A full, watershed-wide dataset of forested extent in every county is available here . State-level forested extent data (within the Chesapeake Bay watershed) can be accessed here .
Additional Resources
C.H. Greenberg et al. (eds.), Sustaining Young Forest Communities, 1 Managing Forest Ecosystems 21, DOI 10.1007/978-94-007-1620-9_1, © US Government 2011. https://www.nrs.fs.usda.gov/pubs/jrnl/2011/nrs_2011_greenberg_001.pdf
How is Chesapeake tree cover changing?
Although the Chesapeake Bay Watershed still contains a relatively large amount of tree cover, the new land use change data has demonstrated that areas of tree cover loss are clear and significant.
Trees in communities and urban areas provide numerous benefits to people, but urban forests and trees are under increasing pressure as development expands to support growing populations. A recent analysis of tree cover change by the Chesapeake Bay Program using the new high-res data shows a net loss of over 25,000 acres of tree canopy in urban and community areas alone.
However, when you look beyond the footprint of urban and community areas, across the watershed there has been a net loss of over 106,000 acres of tree cover on developed and developing lands.
According to estimates from i-Tree Landscape, this loss of tree cover has resulted in a reduction of over $871 million in benefits from air pollution removal, reduced stormwater runoff, and carbon sequestration. It is therefore critical to focus additional attention on conserving and maintaining mature trees and forests.
Equation for calculating Urban Tree Canopy (UTC) change. (Luley and Bond 2002, A Plan to Integrate Management of Urban Trees into Air Quality Planning. Naples, NY: Davey Resource Group), Graphic by John Damm Graphics).
This chart displays the acres and percentage of tree cover change on developed/developing lands within the watershed for each state. Developed/developing land use classes include roads, impervious surfaces, turf, pervious developed lands, and extractive lands. Note there are slight discrepancies with the change data reported in the Tree Canopy Fact Sheets, as extractive lands were not included in the Fact Sheet change calculations. Washington D.C. recently conducted a more localized and robust Lidar tree cover analysis, which can be viewed in this Storymap . More detailed state-level data on change for each tree cover class can be found here .
Although it is clear that tree cover loss is widespread, it is important to remember that tree cover loss shows up quickly in remotely sensed imagery, whereas gains in tree cover take years to appear. While tree cover losses heavily outweigh tree cover gains overall, the data nonetheless shows areas with tree cover gains. These areas can provide examples of successful policy and restoration strategies that could be applied elsewhere in the Chesapeake Bay watershed to generate additional tree cover gain.
Please use the ‘open live content in a new tab’ feature in the upper right had corner of the viewer and then zoom in to select a single county and visualize the data for that county. The viewer displays tree cover change on developed/developing lands by county and by census places as a percentage of land area. Bar charts show how tree cover change in a selected jurisdiction compares with other tree cover change across the state and the watershed. Developed/developing land use classes include roads, impervious surfaces, turf, pervious developed lands, and extractive lands. Select a county to access a fact sheet containing more detailed land use and land use change data for that county. Note there are slight discrepancies with the change data reported in the Tree Canopy Fact Sheets, as extractive lands were not included in the Fact Sheet change calculations. A full, watershed-wide dataset of county-level tree cover change is available here .
Additional Resources
Case studies: Vibrant Cities Lab , Chesapeake Tree Canopy Network Community Spotlight
How are Chesapeake forests changing?
As populations expand beyond the footprint of more densely populated urban areas and communities, forested land is also being converted to make way for new housing developments and commercial shopping centers. Pressure comes not only from residential development, but from new forms of development which are becoming increasingly widespread. Conversion of forest to utility-scale solar installations and data warehouses are emerging challenges that increase the urgency of conserving forests and developing land use policies to minimize impacts to intact forests.
These larger tracts of intact forest store and sequester carbon, provide essential habitat, mitigate flooding, and serve as valuable sources of drinking water, so their loss and fragmentation has major implications for climate resiliency, biodiversity, and other ecosystem services we rely on.
Like with mature tree cover, when we look across all stages of forest development, forest loss is also widespread, with nearly 100,000 acres of net loss on developed/developing lands watershed-wide.
However, due to limitations in consistently classifying remotely sensed imagery, there may be some areas where the change in forest is overestimated due to a misclassification of timber harvest as a pervious developed class.
This chart displays the acres and percentage of forested extent change on developed/developing lands within the watershed for each state. Developed/developing land use classes include roads, impervious surfaces, turf, pervious developed lands, and extractive lands. Note: Washington D.C. recently conducted a more localized and robust Lidar tree cover analysis, which can be viewed in this Storymap . More detailed state-level data on change for each forested extent class can be found here .
Please use the ‘open live content in a new tab’ feature in the upper right had corner of the viewer and then zoom in to select a single county and visualize the data for that county. This viewer displays a map of forested extent change on developed/developing lands by county as a percentage of land area. Zooming in will display forested extent change as a percentage of land area per 1km 2 . Bar charts show the breakdown of forested extent change by each forested extent class for a selected jurisdiction and how forested extent change for a jurisdiction compares with forested extent change across the state and the watershed. A full, watershed-wide dataset of county-level forested extent change is available here .
Additional Resources
Next Steps
Although forests and trees are under increasing threat in the Chesapeake Bay watershed, there are many opportunities for local leaders, policy makers and communities to get involved with conserving and restoring Chesapeake forests.
Source: A Local Government Guide to the Chesapeake Bay: Capitalizing on the Benefits of Trees
As we continue to explore and analyze the high-resolution land use data, we plan to update this Storymap with new information, analyses, and case studies. In upcoming iterations of this Storymap, we plan to add new data on riparian land use, identify plantable areas in the watershed, evaluate forest fragmentation, and consider the implications of tree cover trends for social equity.
We would also like to improve the Storymap based on user feedback, so please let us know what you think!
Contact Katie Brownson ( Katherine.brownson@usda.gov ) with any suggestions.