Text Size: A  A  A

Underwater Bay Grass Abundance (Baywide)

In 2013, there were an estimated 59,927 acres of underwater grasses in the Chesapeake Bay, achieving 32 percent of the 185,000-acre goal.

Bay Grasses (SAV) Restoration Goal Achievement: Single Best Year 2011-2013

Map: Bay Grasses (SAV) Restoration Goal Achievement: Single Best Year 2011-2013

Date created: Apr 03 2014 / Download

This map shows progress toward achieving the Chesapeake Bay Program segment-specific underwater bay grass restoration goals. It is based on the single best year of acreage as observed through the most recent three years of data from the Chesapeake Bay underwater bay grasses aerial survey.

April 22, 2011

Bay grasses, also known as submerged aquatic vegetation, are an integral part of the Chesapeake Bay ecosystem. Lee Karrh from the Maryland Department of Natural Resources (DNR) explains what bay grasses need to grow and why their survival is important to Bay critters.

Produced by Matt Rath
Music: “A Moment of Jazz” by Ancelin

April 22, 2011

What is submerged aquatic vegetation, and why is it important to the Chesapeake Bay?  Commonly known as “bay grasses” they among the most critical inhabitants of the Bay’s ecosystem.  Find out more about submerged aquatic vegetation, and see what people around Baltimore’s Belvedere Square had to say about it.

Produced by Matt Rath
Music: “Neapolitan song” by Astrid & Ruediger Kramer
“2 percenter” by Williamson
“All of Me” by Double F


Underwater grasses provide significant benefits to aquatic life and serve many critical ecological functions in the Bay and its tributaries, such as:

  • Providing shelter for young striped bass, blue crabs and other species
  • Improving water clarity by helping suspended sediment particles settle to the bottom
  • Adding oxygen to the water
  • Reducing shoreline erosion

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.

Long-term Trend (1984-2013)

  • Increased from 38,958 acres to 59,927 acres. Acreage has averaged 65,468 and ranged from 38,958 acres to 89,659 acres.

Short-term Trend (2004-2013)

  • Decreased from 72,945 to 59,927 acres. Acreage has averaged 68,893 and ranged from 48,191 acres to 85,914 acres.

Change from Previous Year (2012-2013)

  • Bay-wide: Increased from 48,195 to 59,927 acres.

Additional Information

Changes to Goals Expected in 2014

The CBP SAV workgroup is in the process of recommending changes to the segment-specific goals to align them with water quality standards adopted by Bay jurisdictions.  This will result in revisions to the 185,000-acres baywide goal.

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.

Source of Data

Virginia Institute of Marine Science

410 Severn Avenue / Suite 112
Annapolis, Maryland 21403
Tel: (800) YOUR-BAY / Fax: (410) 267-5777
Directions to the Bay Program Office
Terms of Use | Privacy Policy
©2012 Chesapeake Bay Program | All Rights Reserved