Scientists and coastal resource managers rely heavily on eelgrass maps derived from remote sensing methods when making management, planning, and construction project siting decisions. Remote sensing methods often use imagery to detect and delineate habitats, however, their accuracy and detection limitations are not well known, and confidence is especially low at the meadow’s edge.
Diving is considered the most reliable method for determining the boundaries of eelgrass meadows, but it is also the most time- and resource-intensive.
Since 1995, MassDEP has conducted aerial surveys to observe and track the spatial extent of eelgrass beds in coastal Massachusetts waters, obtaining data for a given area every 5 years. More recently, advances in technology are making more survey methods available, including drones, boat-based side-scan sonar, and satellites. All of these methods have some limitations on the data quality gathered however, and if portions of eelgrass meadows are underrepresented in the maps, there is greater risk of inadequate resource protection.
Study design and purpose
Download the detailed MassBays Eelgrass Mapping Quality Assurance Project Plan 2022.
In October 2021, MassBays and CZM kicked off their new eelgrass mapping study. The project will compare meadow edge-detection capabilities across several remote sensing methods and compare their accuracies against diver surveys. We will look at data from side scan sonar, drones, fixed-wing manned airplanes, and satellites to assess each method’s ability to detect the edge and low-density areas of five eelgrass meadows in northern Massachusetts.
The goal is to better understand if and by how much each method underestimates the meadow, and in terms of management, if there are appropriate buffers that can be applied to delineations from each method for better resource protection. Ultimately, we hope to also develop a process by which the data generated from different methods can be more reliably integrated. We are working with many partners, both agency and nonprofit, in an effort to build capacity and fluency for this type of work.
Coming soon: Eelgrass Mapping Project Story Map. Check back so you can follow along with project progress.
Project contact: Jill Carr, MassBays Coastal Data Scientist.