Biodiversity is on the agenda. Over 40% of our native species of plants, animals and pollinators are in severe decline due to habitat loss, including hedgehogs, songbirds and bumblebees.
With 50% of property development still taking place on greenfield sites, the government has become sufficiently concerned about the cumulative impact of development to take action on reversing biodiversity decline. From autumn 2023, planning applications for most mid to large sized developments in England will be required to provide a 10% increase in biodiversity compared to condition of the site prior to development. This will require a change in thinking around density and the design and management of green spaces.
The new biodiversity provisions will apply to residential developments over 0.5 hectares, and other developments over 1 hectare. Sites with no existing vegetation are exempted, as are brownfield development sites where the new provisions would make the development unviable.
Early adopters
The requirement for biodiversity net gain has already been adopted by a handful of local authorities, including Cornwall, Wiltshire, South Oxfordshire and Warwickshire, as well as urban areas including Greater Manchester, Leeds, Tunbridge Wells and Solihull. This has provided a glimpse into how these new planning requirements will work once they are implemented in national legislation.
New risks
The new requirements present a number of potential pitfalls for developers. Incorporating biodiversity into developments will will likely involve both loss of development value and additional development costs. As such, the impact of biodiversity legislation will need to be factored into the price which is paid for the land. In most cases land is sold on a 'full and final offer' basis so the land may be sold to a purchaser who is not aware of the new biodiversity requirements and who will struggle to make their development stack up financially.
Measuring biodiversity
The methodology for providing the 10% biodiversity increase is intricate and detailed. It requires an ecologist to survey the development site to establish what habitats are currently present, and what condition they are in. Habitats are scored according to how rare they are and whether they support protected animal species (distinctiveness), what condition they are in, whether they are identified locally as significant for nature, and whether they are connected to similar or related habitats nearby.
It is absolutely vital for the baseline habitat survey to be done before the site is cleared, as a developer recently found out. The developer was refused planning permission because he had cleared the site of scrub vegetation prior to undertaking a habitat survey, resulting in a low biodiversity baseline. Local ecological records showed a number of plant and animal species previously present on the site. The development was refused permission because it was no longer possible to quantify an accurate habitat baseline, meaning that the site is blighted and cannot be developed.
The higher the baseline biodiversity score, the more difficult it will be to achieve a 10% net gain while developing the site sufficiently to generate an investment return. Therefore it is vital to for the developer to know whether a high scoring habitat is likely to be found on the site when making an offer. Habitat surveys can only be undertaken at specific times of the year, but there is an increasing amount of information available digitally which an ecologist can use to provide indicative advice.
Scores for replacement habitats are calculated similarly to the baseline, but the scores are discounted to take account of the time and effort required for the replacement habitat to reach target condition. High distinctiveness habitats, including woodlands, heath and specific types of grassland, take decades to establish so any loss of a high distinctiveness habitat is difficult to offset. Habitats are grouped into broad categories including grasslands, woodlands, hedges and rivers, and some net gain must be achieved in each category to make up the total 10%.
Adjusting the development scheme
The landscape plan for the development will need to be designed with biodiversity in mind. Domestic gardens carry a low biodiversity score as occupants are free to chop and change the planting or even put in patios in place of greenery. Communal amenity landscaping is also likely to carry a relatively low biodiversity score. Therefore land will need to be put aside for more natural forms of green space, such as a meadow, wood or wetland. This could incorporate paths to make it suitable for recreational use. We will therefore be seeing recreational natural green spaces incorporated into developments. This has a knock-on effect on dwellings per hectare as a portion of the land is used for natural green space rather than development. Developers will need to ensure that their architects, landscape architects and ecologists collaborate to optimise both the development value and the biodiversity score of the proposed development.
Typically, it will be possible to achieve a 10% biodiversity net gain on a greenfield site at 25 dwellings per hectare with a Garden Suburb style of development with tree lined avenues and a mix of recreational and natural green space.
Planners will require land which is set aside for biodiversity to be managed and monitored to achieve its target condition. The new legislation will require the developer to enter into a 'conservation covenant' to enhance and maintain habitats for at least 30 years. Conservation covenants are a new type agreement which will bind future owners of the land, and will include a provision for monitoring by the local authority or a local wildlife trust.
Managing land for biodiversity
It is not enough to simply leave the land alone, because habitats left to their own devices tend to be dominated by the most vigourous plant species. Grasslands require low intensity grazing to achieve their maximum potential, while woodlands require different management actions at different stages of growth. The developer will need an ecologist to prepare a Landscape and Ecology Management Plan detailing a calendar of management activities from planting to full establishment and beyond. In leasehold developments it would be possible to recover the maintenance and monitoring costs via the annual service charge.
Staying ahead of the curve
Developers will need to make sure that their development managers and consultants are fully briefed on the new biodiversity requirements, that scheme designs include recreational green space and the development appraisal takes account of both realistic densities and the multiple new costs involved in measuring, creating and maintaining habitats for biodiversity.
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