Chesapeake Bay Watershed Forests

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Chesapeake Bay Program Indicator Framework

Reporting Level Indicators

Indicator and Data Survey

A.  Category/Name/Source/Contact

(1) Category of Indicator

_x_ Factors Impacting Bay and Watershed Health

___ Restoration and Protection Efforts

___ Watershed Health

___ Bay Health

(2) Name of Indicator: Bay Watershed Forest Cover

(3) Data Set Description:  

For what purpose(s) were the data collected? (e.g., tracking, research, or long-term monitoring.) -  Long-term monitoring.

Which parameters were measured directly? N/A. 

Which were obtained by calculation? Estimates of Chesapeake Bay watershed forest cover were developed for 1650, 1750, 1800, 1830, 1850, 1880, 1900, 1930, 1953, 1963, 1970, 1977 ,1980, 1990 and 2003 (The State of Chesapeake Forests, 2006, pp 14-17,

(4) Source(s) of Data: The State of Chesapeake Forests, 2006, pp 14-17 (

Is the complete data set accessible, including metadata, data-dictionaries and embedded definitions? If yes, please indicate where complete dataset can be obtained. The State of Chesapeake Forests, 2006, Appendix A ( and Appendix B (

(5) Custodian of Source Data (and Indicator, if different): Sally Claggett 800-YOURBAY ext 706

(6) CBPO Contact: Sally Claggett 800-YOURBAY ext 706

B.  Communication Questions

(complete either part 1, 2, or 3)

3.  Factors Impacting Bay and Watershed Health indicators only

(7c) What is the long-term trend?  (since start of data collection)  In the 1600s, about 95 percent of the Chesapeake Bay watershed was forested.  Forests now cover only 58 percent, or 24 million acres.

(8c) What is the short-term trend? (10-year trend) The Bay watershed loses forestland at the rate of  approximately 100 acres each day. 

(9c) What is the current status? Forests now cover only 58 percent, or 24 million acres.

(10c) What does this indicator tell us?

•Since 1650 nearly all of the forested land in the basin has been cut at one time or another. Isolated remnants of 'virgin' forest (never cut) exist in very small quantities.  From 1750 to 1890 most land in the watershed was cleared for farming, timber and fuel. In the last 20 years, most deforestation has been due to urban sprawl and some agricultural conversion.

•More than 750,000 acres—equivalent to 20 Washington, DCs— have been developed since the early 1980s, and the Bay watershed now loses forestland at the rate of 100 acres each day.  If current trends continue, an additional 9.5 million acres of Chesapeake forests will be threatened by conversion to residential development by 2030.

•Some areas facing rapid growth or supporting intense agricultural uses have lost 80 percent of their historic forest cover.  Areas closest to the Bay have seen the most rapid forest loss. Recent findings suggest that fragmentation, created by urban sprawl and agriculture, can affect stream health, habitat quality and economic viability of forest patches.

 (11c) Why is it important to report this information?

•As forests and wetlands are destroyed to make room for roads and buildings, their ability to hold back pollutants and the important habitat they offer are lost as well.

•Forests protect and filter drinking water for 75 percent of the Bay watershed’s residents and provide valuable ecological services and economic benefits including carbon sequestration, flood control, wildlife habitat and forest products.

•Retaining and expanding forests in the Chesapeake Bay watershed is critical to our success in restoring the Chesapeake Bay.  Forests are the most beneficial land use for protecting water quality, due to their ability to capture, filter and retain water, as well as absorb pollution from the air.  In fact, our watershed forests are excellent assimilators of air pollution, retaining up to 85 percent of the nitrogen they receive from air emission sources such as motor vehicles and electric utilities.  Conversely, a reduction in forest area leads to a disproportionate increase in nitrogen loads to our waterways.

(12c) What detail and/or diagnostic indicators are related to this reporting level indicator? Bay Watershed Riparian Forest Buffer Cover

C.  Temporal Considerations

(13) Data Collection Date(s): Estimates of watershed forest cover were developed for 1650, 1750, 1800, 1830, 1850, 1880, 1900, 1930, 1953, 1963, 1970, 1977 ,1980, 1990 and 2003 (The State of Chesapeake Forests, 2006, pp 14-17).

(14) Planned Update Frequency (e.g. - annual, bi-annual): every 5 years

(a) Source Data: high resolution imagery and semi-automated GIS tool (still in development)

(b) Indicator:  forest cover

(15) For annual reporting, month spatial data is available for reporting: N/A

D.  Spatial Considerations

(16) Type of Geography of Source Data (point, line polygon, other): imagery

(17) Acceptable Level of Spatial Aggregation (e.g. - county, state, major basin, tributary basin, HUC):

All of the above.

 (18) Are there geographic areas with missing data?  If so, where?


(19) The spatial extent of this indicator best described as:

(a) Chesapeake Bay (estuary)

(b) Chesapeake Bay Watershed

(c) Other (please describe): _______________________

Please submit any appropriate examples of how this information has been mapped or otherwise portrayed geographically in the past. Several maps are featured in The State of Chesapeake Forests, 2006

(20) Can appropriate diagnostic indicators be represented geographically? yes

E.  Data Analysis and Interpretation

(Please provide appropriate references and location of documentation if hard to find.)

(21) Is the conceptual model used to transform these measurements into an indicator widely accepted as a scientifically sound representation of the phenomenon it indicates?  (i.e., how well do the data represent the phenomenon?)   Yes, it is a indicator for forest cover and a partial indicator for forest health.

(22) What is the process by which the raw data is summarized for development and presentation of the indicator?    Semi-automated GIS tool

(23) Are any tools required to generate the indicator data (e.g. - Interpolator, watershed model) yes

(24) Are the computations widely accepted as a scientifically sound?  No computations are necessary--- this is a direct indicator

(25) Have appropriate statistical methods been used to generalize or portray data beyond the time or spatial locations where measurements were made (e.g., statistical survey inference, no generalization is possible)?  

1) Historic interpretation of forest cover was taken from Grace Brush’s palenology work such as Reconstruction of Late Glacial and Holocene Forests in Middle Atlantic United States. 

2) The past 40 years of data on forest cover were derived directly from Forest Inventory and Analysis, a research branch of the US Forest Service that uses fixed sampling plots on a grid.  Appropriate statistical sampling was involved for the region, but somewhat specious at a resolution as fine as the county scale.  

3) The new method to determine forest cover would be relevant at the county scale, and use high-resolution imagery as the source data.

(26) Are there established reference points, thresholds or ranges of values for this indicator that unambiguously reflect the desired state of the environment? (health/stressors only)   It has been stated that the desired forest cover for a generic watershed is 70%.

F.  Data Quality

(Please provide appropriate references and location of documentation if hard to find.)

(27) Were the data collected according to an EPA-approved Quality Assurance Plan?  

If no, complete questions 28a – 28d:


(28a) Are the sampling design, monitoring plan and/or tracking system used to collect the data over time and space based on sound scientific principles? Yes

(28b) What documentation clearly and completely describes the underlying sampling and analytical procedures used?

(28c) Are the sampling and analytical procedures widely accepted as scientifically and technically valid?  Yes

(28d) To what extent are the procedures for quality assurance and quality control of the data documented and accessible? QA/QC are well-documented for data displayed up to this point.  

(29) Are the descriptions of the study or survey design clear, complete and sufficient to enable the study or survey to be reproduced?  Yes

(30) Were the sampling and analysis methods performed consistently throughout the data record? Yes

(31) If datasets from two or more agencies are merged, are their sampling designs and methods comparable? n/a

(32) Are uncertainty measurements or estimates available for the indicator and/or the underlying data set? Yes

(33) Do the uncertainty and variability impact the conclusions that can be inferred from the data and the utility of the indicator? No

(34) Are there noteworthy limitations or gaps in the data record?  Please explain.  Only with the historical data as documented by Brush et al.

G.  Additional Information


(35) Please provide any other information about this indicator you believe is necessary to aid communication and any prevent potential miss-representation.


1.  The State of Chesapeake Forests, 2006

2.  Bibliography from The State of Chesapeake Forests:

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