In 2012, there were an estimated 48,191 acres of underwater grasses in the Chesapeake Bay, achieving 26 percent of the 185,000-acre goal.
Analysis & Methods (100 KB) Bay Grasses (SAV) Restoration Goal Achievement: Single Best Year 2010-2012 Apr 17 2013 / Download
Analysis & Methods (100 KB) What are bay grasses and why are they important? Lee Karrh of the Maryland Department of Natural Resources takes us on the Chesapeake Bay to see some submerged aquatic vegetation (SAV) firsthand in this Bay 101 video.
Produced by Matt Rath
Music: “A Moment of Jazz” by Ancelin
Underwater grasses provide significant benefits to aquatic life and serve many critical ecological functions in the Bay and its tributaries, such as:
Scientists believe that having more grasses in the Bay and rivers will dramatically improve the entire ecosystem. The expectation is that as nutrient and sediment pollution decrease and water clarity improves, underwater grass acreages should expand. Experts closely monitor underwater grasses because their well-being is dependent on good local water quality. Therefore, their abundance is an excellent measure of the Bay’s health.
The goal is to have 185,000 acres of underwater grasses in the Chesapeake Bay. This acreage represents approximate historic abundance from the 1930s to present.
*Note: 2012 acreage is based on preliminary data provided 3/28/13.
Long-term Trend (1984-2012)
Short-term Trend (2003-2012)
Change from Previous Year (2011*-2012)
*Note: The 2011 data previously reported changed due to the finalization of preliminary data. Only 57,964 acres were mapped baywide in 2011. It is estimated that an additional 5,119 acres may have been present (for an estimated baywide total of 63,083). These acres could not be mapped due to excess turbidity present months after the passage of Hurricane Irene and Tropical Storm Lee. The regions that were not mapped are contained within nine CBP segments, including the Middle, Upper and Western Branch of the Patuxent River; the Middle and Upper Potomac River; Piscataway Creek; and the Anacostia River. The estimated additional acreage is based on acreages mapped in those regions in 2010.
Historic Bay Grass Data
Review of photographs 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 once grown along the Bay’s shorelines. However, by 1984, bay grass acreage had fallen to a low of about 38,000 acres. More nutrient and sediment pollution in the water has choked or eliminated bay grasses in many areas, contributing 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 bay grasses to 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 recovery rates 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 bay grasses. 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. The strategy included 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 that having more bay grasses in the Bay will dramatically improve the entire ecosystem. As nutrient and sediment pollution decreases and water clarity improves, bay grass acreage should expand.
Nita Sylvester
U.S. Environmental Protection Agency
(410) 267-5711
Virginia Institute of Marine Science
