Weed-covered Orari and Opihi riverbeds 'serious matter' for declining bird habitat
Forest and Bird has asked a South Canterbury water zone committee to consider the "serious matter" of two weed-covered riverbeds and its subsequent impact on indigenous birds and wildlife.
It said ensuring indigenous vegetation, such as tussock grasslands, was maintained on hill country "must" be part of the committee's Healthy Catchment Strategy.
In a letter to the Environment Canterbury (ECan) zone committee, Timaru man and Forest and Bird field officer Fraser Ross urged the committee to give the issue a "high level of consideration and action".
The Opihi and Orari riverbeds were becoming filled with weeds, such as broom and lupins, making them unsuitable for native birds, including black-billed gulls, terns, and dotterels.
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This was contributing to the decline in habitat for native wildlife and was a "serious matter" because some species were declining so much that they were now considered threatened, he said.
The letter is included in an agenda for the Orari-Temuka-Opihi-Pareora zone committee (OTOP), to be discussed on Monday.
Riverbeds provided an important habitat for many native birds and other wildlife species, the letter said.
In the past, the lower Opihi River bed saw "hundreds, if not thousands" of black-billed gulls.
"More recently, the beds of many of our local rivers have become covered in tall weeds, such as broom and lupins, making these areas entirely unsuitable," the letter says.
Recent development in hill country, such as the lower Rangitata Gorge, had seen the removal of tussock grasslands.
The native vegetation played an important role in controlling water run-off, providing consistent flow of water supply to downstream water bodies, such as streams, rivers, and lakes.
He noted scientific research by Otago University which supported this.
The letter questioned whether high country developments were "compliant" with ECan's rules and policies.
"And we feel that such hill country developments may also be contrary to what the healthy catchments exercise seeks to achieve by your zone committee."
The letter asked the committee, as part of its healthy catchments strategy, to ensure some areas on the river were free of weeds to open habitats for birds and wildlife, and that the committee put greater controls on conversion of local hill country vegetation.