Underwater bay grasses serve many essential ecological functions and are among the most closely monitored habitats in the Bay. Grasses:
Bay grass abundance is an excellent barometer of the health of the Bay because these grasses depend on good local water quality and provide significant benefits to aquatic life.
Learn more about bay grasses and bay grass restoration.
The goal is to have 185,000 acres of underwater bay grasses in the Chesapeake Bay by 2010, which represents approximate historic abundance from the 1930s to present.
*Note: The historic data featured in this indicator changed from that reported in the 2007 assessment. The 2007 data changed due to the finalization of provisional data.
Long-term trend (1984-2008)
- Bay-wide: Increased from 20.7 percent to 41.5 percent of goal achieved (38,228 acres in 1984 to 76,861 acres in 2008). Goal achievement has averaged 34.6 percent and has ranged from 20.7 percent to 48.5 percent.
- Upper Bay: Increased from 31.7 percent to 97 percent of goal achieved (7,498 acres in 1984 to 22,954 acres in 2008).
- Middle Bay: Increased from 13.6 percent to 30 percent of goal achieved (15,643 acres in 1984 to 34,521 acres in 2008).
- Lower Bay: Increased from 32.8 percent to 42 percent of goal achieved (15,086 acres in 1984 to 19,386 acres in 2008).
Short-term trend (10-year trend)
From 1999-2008:
- Bay-wide: Increased from 36.8 percent to 41.5 percent of goal achieved (68,100 acres in 1999 to 76,861 acres in 2008).
- Upper Bay: Increased from 37.1 percent to 97 percent of goal achieved (8,771 acres in 1999 to 22,954 acres in 2008).
- Middle Bay: Decreased from 31.8 percent to 30 percent of goal achieved (36,692 acres in 1999 to 34,521 acres in 2008).
- Lower Bay: No significant change; 41.8 percent, or 19,254 acres, in 1999 to 42 percent, or 19,386 acres, in 2008.
Change from previous year (2007-2008)
- Bay-wide: Increased from 35 percent to 41.5 percent of goal achieved (64,918 acres in 2007 to 76,861 acres in 2008).
- Upper Bay: Increased from 80.1 percent to 97 percent of goal achieved (18,922 acres in 2007 to 22,954 acres in 2008).
- Middle Bay: Increased from 26 percent to 30 percent of goal achieved (29,992 acres in 2007 to 34,521 acres in 2008).
- Lower Bay: Increased from 34.8 percent to 42 percent of goal achieved (16,004 acres in 2007 to 19,386 acres in 2008).
Historical Bay Grass Data
Review of photographic evidence from a number of sites dating back to 1937 suggests that close to 200,000 acres of bay grasses – also called submerged aquatic vegetation or SAV -- may have historically grown along the shoreline of the Bay. However, by 1984, the SAV community had fallen to a low of about 38,000 acres. Increasing quantities of nutrients, such as phosphorus and nitrogen, as well sediment in the water, have choked or eliminated the growth of SAV in many areas and contributed to declines in SAV acreage throughout the Bay.
Collecting Bay Grass Abundance Data
The aerial SAV survey is flown from late spring to early fall. The photography is processed in the fall and winter, and preliminary area totals are usually available the following spring. Visit the Virginia Institute of Marine Science website for additional information about the aerial survey and for segment-specific survey results.
Setting Bay-wide Goals for Bay Grass Restoration
In 1993, the Bay Program agreed to work to restore SAV to its historic levels. It set an interim restoration goal of 114,000 acres -- the total area vegetated at one time or another since the early 1970s. Based on rates of recovery at that time, the goal was expected to be achieved by 2005.
In the Chesapeake 2000 agreement, the Bay Program recommitted to the existing goal of protecting and restoring 114,000 acres of SAV. They also agreed to “revise SAV restoration goals and strategies to reflect historic abundance, measured as acreage and density from the 1930s to the present.”
In 2003, the Bay Program adopted the Strategy to Accelerate the Protection and Restoration of Submerged Aquatic Vegetation in the Chesapeake Bay, including a new Bay-wide restoration goal of 185,000 acres by 2010. This acreage represents approximate historic abundance from the 1930s to present.
Scientists believe increasing bay grass coverage beyond today’s acreages will result in dramatic improvements throughout the entire Bay ecosystem. As water clarity improves from nutrient and sediment pollution reductions, bay grass acreage should expand.
For more information contact: Mike Fritz at 800-968-7229 ext. 721