1. Bay Grass Abundance 42% Bay Grass Abundance of Goal Achieved
Data and Methods:
Percent of
Goal Achieved
42%
of Goal Achieved
Bay Grass Abundance
Goal (185,000 acres)
Bay Grass Abundance
Status: In 2008, there were 76,861 acres of bay grasses throughout the Bay, which was 42 percent of the goal and an increase of 11,984 acres from In 2008, grasses in the Upper Bay covered about 22,954 acres (97 percent of the area’s 23,630-acre goal). Middle Bay grasses covered 34,521 acres (30 percent of the 115,229-acre goal for the area) and grasses in the Lower Bay covered 19,386 acres (42 percent of the area’s 46,030-acre goal).
Additional Information:
Importance: Underwater bay grasses serve many essential ecological functions and are among the most closely monitored habitats in the Bay. Grasses provide critical shelter to many key species such as young striped bass and blue crabs, improve water clarity by helping sediment settle to the bottom, add oxygen to the water, and reduce shoreline erosion. 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.
Goal: 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.
Trends:
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.
What is the long-term trend? (since start of data collection)
Bay-wide: : increased from 20.7% to 41.5% goal achievement (38,228 to 76,861 acres). Goal achievement has averaged 34.6% and has ranged from 20.7% to 48.5%.
Upper Bay: : Increased from 31.7% to 97% goal achievement (7,498 to 22,954 acres).
Middle Bay: : increased from 13.6% to 30% goal achievement (15,643 to 34,521 acres).
Lower Bay: : increased from 32.8% to 42% goal achievement (15,086 to 19,386 acres).
What is the short-term trend ? (10 year trend)
Bay-wide: : increased from 36.8% to 41.5% goal achievement (68,100 to 76,861 acres).
Upper Bay: : increased from 37.1% to 97% goal achievement (8,771 to 22,954 acres).
Middle Bay: : decreased from 31.8% to 30% goal achievement (36,692 to 34,521 acres).
Lower Bay: : no significant change 41.8% to 42% goal achievement (19,254 to 19,386 acres).
Change from previous year:
Bay-wide: : increased from 35% to 41.5% goal achievement (64,918 to 76,861 acres).
Upper Bay: : increased from 80.1% to 97% goal achievement (18,922 to 22,954 acres).
Middle Bay: : increased from 26% to 30% goal achievement (29,992 to 34,521 acres).
Lower Bay: : increased from 34.8% to 42% goal achievement (16,004 to 19,386 acres).
Aside from the water itself, underwater bay grasses are one of the most important habitats in the Chesapeake Bay. As their health is closely related to the quality of local waters, grasses serve as an excellent barometer for the overall health of the estuary. Bay grass abundance has a profound effect on the Bay and its aquatic life, as it provides critical habitat to key species such as striped bass and blue crabs while improving the clarity of local waters.
As water clarity improves from nutrient and sediment pollution reductions, bay grass acreage should expand.
Bay grasses, or submerged aquatic vegetation (SAV), are important to the complex Chesapeake Bay ecosystem because they produce oxygen, supply food for many species (especially waterfowl), offer shelter and nursery habitat for fish and shellfish, reduce wave action and shoreline erosion, absorb excess nutrients such as nitrogen and phosphorus, and trap sediments.
Review of photographic evidence from a number of sites dating back to 1937 suggests that close to 200,000 acres of 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.
Bay grasses are a unique yardstick for measuring the progress of Chesapeake Bay restoration efforts because they are not under harvest pressure and their health is closely linked to water quality. Increases in Bay grasses are expected in areas where water quality conditions are improving.
In 1993 the Chesapeake Bay Program (CBP) agreed to work to restore SAV to its historical levels. They 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 CBP 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. The revised goals will include specific levels of water clarity which are to be met in Strategies to achieve these goals will address water clarity, water quality, and bottom disturbance.”
In 2003, the CBP adopted the Strategy to Accelerate the Protection and Restoration of Submerged Aquatic Vegetation in the Chesapeake Bay including a new Baywide restoration goal of 185,000 acres by 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.
The aerial 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. For additional information about the aerial survey and for segment specific survey results, go to
Chesapeake Bay Health and Restoration Assessment:
Ecosystem Health
031709