LEVELS of nitrogen in Poole Harbour are restricting food sources of a number of wading bird species, councillors have been told.

A nitrogen reduction plan for Poole Harbour looks likely to be adopted by Borough of Poole (BOP) later this year.

BOP’s place overview and scrutiny committee has already recommended full council agrees the plan, which essentially sets out ways to lessen the effects of prospective population growth in the borough.

According to the latest scientific research, nitrogen - or nitrates - in Poole Harbour are encouraging the growth of algae sheets, which, in turn, are restricting the growth of important food sources for wading birds.

The majority of this nitrogen - which has been causing algal mats to increase in Poole Harbour since the 1960s - comes from agriculture. However, a proportion is generated from human sewage.

While sewage treatment removes part of the nitrogen from human waste, some still enters the harbour from across its catchment.

The plan, backed by committee members at Poole Civic Centre on Tuesday, commits the council to upgrading sewage treatment works.

It also looks at ways of offsetting nitrogen generated from new development - for example, reducing the numbers of fields where nitrogen fertiliser is used.

A report from BOP planning policy manager Nick Perrins recommends councillors back the Poole Harbour Supplementary Planning Document (SPD).

This report concluded: “The SPD establishes a mechanism to secure contributions for the mitigation of adverse effects of Poole Harbour of nitrogen generated by population growth.

“It enables proposals for housing to be granted planning consent which otherwise would have to be refused and thereby having a significant effect on the delivery of housing and wider economy of the area.”

Figures given to BOP councillors showed a housing scheme of 100 homes (60 houses and 40 flats) generates 0.185 tonnes of nitrogen each year.

Therefore, the development of 100 homes can be mitigated through the change in management of 6.2 hectares of land from high nitrogen input use to low.

Poole Harbour is a designated Site of Scientific Interest, and a Special Protection Area.