Poole Harbour is defined as a Special Protection Area and Ramsar site which is protected by the Habitats Regulations. Sites which are protected by the Regulations are important for nature or protecting threatened habitats and species. The regulations require the councils to assess environmental impacts of plans (including local plans) and projects (including planning applications) on these sites. The councils may only grant planning permissions that will not adversely affect a protected habitat site or ensure that any adverse effects are mitigated. As part of the decision-making process the councils are obliged to get advice from Natural England.
High levels of nitrogen discharged into Poole Harbour has caused increases in algal growth with resulting losses in biodiversity. An overall reduction is needed to bring the harbour back into a favourable condition. Agriculture is a significant contributor to nitrogen loading and schemes like the Poole Harbour Nutrient Management Scheme (PHNMS) have been set up to address this. Nitrogen in treated waste effluent from sewage plants also contributes to the pollution effecting the harbour. Planned upgrades at Wastewater Treatment Plants will deliver improvements over the long term. In the short term before the condition of the harbour is improved, any new development which contribute to nitrogen pollution must demonstrate nitrogen neutrality (this means demonstrating that there is no net increase in nitrogen discharged into the harbour after new development is occupied). Typically, nitrogen neutrality is achieved by reducing nitrogen loading on the harbour elsewhere in the catchment to offset the impacts of development.
A map showing the extent of the Poole Harbour Catchment (PHC) can be found on the last page. All mitigation needs to be delivered within the catchment boundary.
It is the responsibility of Dorset Council and Bournemouth Christchurch and Poole (BCP) Council as the planning authorities to assess the impact of planning applications and plans on the harbour to ensure there are no negative effects. Where it is not possible to deliver mitigation on development sites, developers will need to investigate other options (potentially including working with other third-party providers) to deliver the necessary nitrogen reductions equivalent to the increased loading from their development proposal. The councils have also committed to working together to invest a government grant to deliver projects to provide another mitigation option for developers.
The council would like to work with farmers and landowners in the catchment to help identify and fund appropriate mitigation projects. This mitigation may take several different forms and could be both temporary or permanent.
The upgrade of wastewater treatment works through the Levelling Up and Regeneration Act 2023 will improve the performance of certain wastewater treatment works (WWTW) to achieve a higher permitting requirement (known as a technically achievable limit) by April 2030. For developments linked to a WWTW where upgrades are anticipated, the mitigation requirement will decrease after 2030. Therefore, there may be an option to provide land-use change that delivers temporary mitigation only.
Dorset Council has been awarded funds from government’s Local Nutrient Mitigation Fund (LNMF) to increase the supply of nitrogen mitigation to enable sustainable development. The projects the council fund will need to meet the terms of the grant which is on a cost recovery basis. This will enable the funds to be recycled into further mitigation projects and in the longer term will be used to secure the restoration of Poole Harbour to a favourable conservation status. The council will ensure credits are available for certain priorities such as affordable housing and brownfield development sites.
Dorset Council also deliver mitigation in the PHC for developments in the BCP area.
Mitigation projects will be delivered by Dorset Council’s nutrient delivery team after consideration by a steering group. There will be additional sign-off from senior officers in the council, depending on the level of spend. This governance will ensure transparency, accountability, and that effective and value-for-money mitigation projects are funded. It will also ensure there is fair return for the farmer or landowner based on what is required. Whether the mitigation involves acquisition of land, or management of the land in accordance with a planning obligation management agreement, the council will take account of market rates and where appropriate seek professional guidance to help inform decisions. The full cost of any works and on-going management/maintenance will also be taken into account in any offer made to a farmer and landowner. This will be reflected in the price of the nitrogen credits the council will seek to sell in order to recycle the funds into further mitigation.
The steering group includes representatives from Natural England to ensure the mitigation proposed and the nitrogen credit delivered will be suitable for development.
Funding from the LNMF will vary depending on the nature of the site and the management change required. Each project will be reviewed against assessment and prioritisation principles outlined below.
These principles will apply to all mitigation land whether purchased by the council or that which is managed for the council by a farmer or landowner in accordance with a planning obligation, effectively a Nitrogen Mitigation Agreement (NMA).
Some options will be easier to deliver measurable nitrogen reduction and the council may prioritise these due to the need to unlock housing quickly and because of the conditions imposed by the LNMF grant award. However, long-term mitigation projects will be necessary and will also be taken into consideration.
Taking suitable land out of production to create woodland is a simple mitigation option, provided the above principles are adhered to. There will be no need for pre monitoring of nitrogen levels provided a history of land-use can be demonstrated. A minimum of 100 trees per ha will be required but there may be an option to consider natural regeneration or a combination of both as agreed in an NMA.
As above. The minimum tree planting which the councils will seek to achieve is at a rate of 100 trees per ha.
The mosaic of wetland habitats and the degree of year-round wetness required will be agreed on a site-by-site basis, but the measures taken to rewet the land will need to create conditions that permanently preclude future agricultural production.
The use of grazing animals (e.g. hardy ponies) as part of an extensive grazing schemes with no supplementary feeding or fertiliser inputs for the purpose of promoting biodiversity and nature recovery may be acceptable in limited circumstances (e.g. where the land will be managed as a publicly accessible nature reserve) but would need be agreed by Dorset Council and Natural England.
Buffer strips comprise bands of vegetation planted to intercept run-off before it enters a water course. Natural England have approved guidance on establishing the nitrogen removal efficiency of buffer strips without the need for pre and post monitoring. The buffer strips will need to be a minimum of 10 metres, but the highest efficiencies are achieved from buffers of 30 metres, and these would be prioritised for funding.
Projects to reprofile and vegetate drainage channels have the potential to deliver reductions in nitrogen. Further guidance is expected from Natural England on calculating the nitrogen reduction benefits from various in channel interventions. It is anticipated the guidance will not require pre or post water quality monitoring.
Wetlands in appropriate locations can be highly cost and land efficient for delivering nitrogen reductions but have significant design and set up costs. They can vary in their degree of intervention and construction; however, a good understanding of all inputs and outputs and variations across the year is essential. The design and evaluation of treatment wetlands will require specialist advice. See further details on treatment wetlands.
The councils will also work to develop other mitigation projects. For example, river channel re-naturalisation can deliver nitrogen reductions. Typically, these will require a robust pre and post monitoring scheme to determine the inputs and outputs and scale of nitrogen reduction achieved and so are likely to be longer-term mitigation options, which are possibly more suited to other funding sources.
Where the land will be maintained for mitigation by a farmer or landowner a simple planning obligation/ Nitrogen Mitigation Agreement (NMA) will be used to secure this. Planning obligations run with the land and are legally binding and enforceable. A template agreement drawn up by the council sets out comprehensively what is required by the farmer/landowner and the payment that they will receive. The agreement also includes appropriate clauses to ensure the mitigation is delivered, the necessary monitoring arrangements are in place and what would happen in the event the agreement is not adhered to.
The council will cover any legal costs by the landowner/farmer incurred to secure the NMA up to a maximum value. No access requirements beyond the management plan will be required unless agreed as part of stacking credits– see below. But it will not be possible to use the land in any way which conflicts with achieving nitrogen reductions. If the land is sold it will be subject to the earlier agreement for duration specified in the NMA.
The NMA will reflect whether the land-use use change is temporary or permanent.
A one-off payment will be made as agreed in the NMA as soon as the land is available for mitigation.
Stacking is when multiple credits or units from different nature markets are sold separately from the same activity on a piece of land.
On land which is delivering nutrient mitigation it is possible to stack additional biodiversity derived from land use change in the form of Biodiversity Net Gain (BNG) units. The baseline for establishing the biodiversity uplift secured will be the original land-use and must be demonstrated by use of the Statutory Biodiversity Metric. Entering a NMA on the land will not preclude the selling of BNG units by the farmer/landowner and this will be made clear in the NMA. You may find the links below helpful.
If your holding is included in the Poole Harbour Nutrient Management Scheme, any land which is entered into a mitigation agreement with the council will be removed from the PHNMS.
If you already have well developed ideas and are seeking a funding mechanism or if you want to explore possible options further, we welcome you getting in contact. Decisions will be based on the principles and governance arrangements summarised above. You may want to contact us directly at mitigationdelivery@dorsetcouncil.gov.uk or register your interest through our website, making it clear you would like the land considered for nitrate mitigation.
