Starting in 2012, the Islands Trust and Islands Trust Fund in partnership with SeaChange Marine Conservation Society set out to map the shorelines of islands within the Islands Trust area with a particular focus on eelgrass beds. The study will provide baseline information that marine scientists can use to monitor marine habitats in the area. Kate Emmings, Ecosystem Protection Specialist with the Islands Trust Fund, presented the results of the Bowen mapping project to Council at a meeting in mid-January.
Emmings says that the SeaChange biologist and mapping team who conducted the mapping found eelgrass on 11.6 percent of Bowen's coastline. In many areas, the amount of cover was found to be patchy, but that is because eelgrass was found in places where it was not expected.
"There was a lot around Cates Beach and Mannion Bay, and that was expected," says Emmings, explaining that eelgrass normally grows in areas where the sea-bed is sandy or muddy. "But we were surprised to find quite a bit of eelgrass on the west side of the island, just north of Cape Roger Curtis, where it can be quite rocky. It seems that the eelgrass actually managed to take root in sandy and muddy sediments between pebbles and cobbles. We consider this to be a very positive result, as there is more eelgrass habitat than would be assumed."
Eelgrass (Zostera marina) is a flowering plant and it provides critical habitat to young salmon emerging from freshwater streams.
"They're able to hide from predators and bulk-up a bit on food they find in eelgrass beds before heading out into the open ocean," says Emmings. "Eelgrass blades also provide herring with a place to lay their eggs."
Emmings says that if the contributions eelgrass makes towards fisheries and carbon sequestration (eelgrass stores up to ninety times more carbon than the equivalent area of forest) are taken into consideration, the plant can be considered to have a significant monetary value.
"According to the David Suzuki Foundation, the estimated natural capital value of eelgrass is estimated to be between $21 thousand and $80 thousand per hectare per year," says Emmings. "If this was extrapolated to Bowen, where there are approximately 4.2 hectares of eelgrass, that would number would be somewhere between $90 thousand and $339 thousand per year.
Threats to eelgrass include boat motors, buoys, anchors and chains, shading from docks, sedimentation, dredging, changes to water quality and climate change.
Emmings says that previously, the Islands Trust was focused on terrestrial mapping in its approach to land use planning conservation, but after completing Terrestrial Ecosystem Mapping for the Islands Trust area in 2011, they have started to look at the way terrestrial activities affect the marine environment, and eelgrass is highly impacted by streams and shoreline activities, so is very connected to the terrestrial environment.
Last spring, Emmings presented results of the mapping project to Gambier, Lasqueti, Pender and Thetis Islands. She says that those islands have considered using the information to inform their official community plans and shoreline regulations, but none have actually put such regulations into place or changed existing regulations yet.
The Islands Trust eelgrass mapping is a three year project which is due to complete at the end of 2014. Emmings says the mapping of forage fish habitats will likely be the next undertaking.
