Mr Dougherty joined a team of about 10 "grand old conservationists" to plant about about 400 natives along one of the remaining tidal arms of Kaikorai Stream and the estuary on Saturday.
The project was part of a year-long push to plant about 1500 native plants next to the waterway, to extend the habitat for waterfowl and to reinvigorate a "severely degraded" ecosystem in the shadow of the Green Island landfill.
Mr Dougherty yesterday said the area was home to about 23 species of birds, including the rare black-billed gull, but that black-backed gulls - attracted to the area by food scraps in the landfill - were top of the pecking order.
Those gulls competed with other bird species that were also threatened by predators, such as rats and feral cats, on the ground.
"That is what happens when people continue to throw out their food scraps instead of composting them.
They attract pests, which proliferate and threaten our native birds - and all because of what some people throw away."
Recent heavy rain sent a wave of plastic refuse down the stream and on to the estuary, while sediment washed from subdivisions or other land uses compounded the assault on the ecosystem.
"People need to understand that there is a link between the estuary and what they do on land."
The project group will soon to replant the four islands in the area.
Conservation Corps workers will continue the planting programme today.
