Three little culverts are all it should take to return 5.8ha on Rough Island back into its original salt marsh habitat.
Tasman District Council’s project manager, George Daly, says the causeway at the northernwestern end of the equestrian park was built in the 1960s with a small culvert that has never enabled enough seawater to flow into the area which has become largely tall fescue grass with little tidal water. That altered the original salt marsh habitat for fish, marsh birds and the native fauna that once grew on and around the intertidal flat.
Now the incoming tide is expected to flow further into the marsh which is wedged between Tic Toc Rd and the equestrian park, enabling it to return to a salt marsh, which are described as one of the most productive ecosystems on Earth.
Though the Waimea Inlet still has about 278 hectares of salt marsh, George says it is estimated that 70 percent of salt marsh in the Waimea Inlet has been lost, primarily through roading and urban developments, or conversion to farmland.
“What remains is extremely important for marsh birds, but also coastal birds. It provides for a whole food web below them, like invertebrates and crabs and shrimps.”
The causeway at the base of the salt marsh is part of a popular walking track around the outside of the equestrian park and now the single, small culvert has been replaced that part of the causeway has been reinstated. The next step is planting the area with salt marsh species, as well as coastal forest planting such as ngaio and manuka above the tide line.
“We’ll have more salt water and more vegetation to get the birds back.”
George says an improved fence with sheep netting will be erected around the salt marsh to keep dogs out and the taller trees and shrubs are intended to provide privacy for the often-shy birds that he hopes will take up residence, including the Australasian bittern and fernbird. He says some marsh birds and coastal birds already nest there.
Though the tide will flow further into the area between Tic Toc Rd and the equestrian park, George says it is not expected to flow on to the road or the park, apart from during storm events which already affect low-lying areas on the island.
The project is being funded by the Ministry for the Environment and Tasman District Council through the Jobs for Nature – Mahi mō te Taiao programme.
