The Ruataniwha water storage project could boost the region's GDP by $350 million but it could also result in a permanent loss of native plants, birds, lizards and bats changing habitats and ecosystems in the Central Hawke's Bay site forever.
One "at-risk" plant species found at the proposed dam site was the red mistletoe while nationally at-risk birds such as the pied stilt, New Zealand pipit, black shag and North Island fern bird were also living in the area. One pair of "nationally vulnerable" New Zealand bush falcon was nesting at the site during spring last year.
The total area affected by flooding and the dam structure was about 450ha and about 163ha or 36 per cent was covered in indigenous vegetation. A total of 37 bird species, 11 endemic, were identified at the proposed reservoir and of these birds, 55 per cent were native and 45 per cent introduced.
The ecological impact of the dam was measured in a study by consultants Kessels and Associated for the Hawke's Bay Regional Council and forms part of a feasibility report being discussed by the council tomorrow. "Long-tailed bats were found throughout the proposed reservoir during an ultrasonic survey completed between November 2011 and February 2012," the report said.
There were 11 lizard species known in the central and southern part of the Hawke's Bay region but only one was found during the field survey which was a southern North Island forest gecko not classified as being a nationally at-risk or threatened species. Detection devices found a "rich diversity of insects and land snails" however none were listed at threatened.
"A total of 184ha of ecologically significant indigenous vegetation and habitats would be flooded by the proposed reservoir.
"This comprises 80ha of mature and secondary indigenous forest, 22ha of secondary indigenous scrub and 73ha of gravel riverbed as well as 5ha of wetland and seep-zones."
To meet the problems, the report has put forward a plan which includes a two-year survey prior to construction to determine the size of the bat population, roosting sites and movement patterns. It would result in a "bat management plan".
A similar survey would gauge the extent of the lizard population and a weed hygiene and surveillance plan would be put in place as well as post-construction monitoring of key wader bird species.
The consultants also suggest recreating 46ha of riparian land with native vegetation to provide a new home for fauna and flora.
As well, there should be an avenue to restore and enhance at least 100ha of marginal farmland and existing forest above the dam to provide a refuge for species during and after flooding of the dam.
The regional council would have to control willows, lupins and other river weeds to provide a better habitat for wading birds such as banded dotterel within the Waipawa and Makaroro rivers and even help landowners with replanting and fencing to protect existing wetlands. There would be ongoing animal pest control targeting possums and rats.