Updated: Aug 29, 2019
Many thanks to Dr Matt Cowley from EAD Ecology, who has provided the below. Matt Cowley is a Design Review Panel member, attending Design Review Panels across the South West; in Cornwall, Devon (both Plymouth and Exeter), Somerset, Dorset, Wiltshire and Swindon. For more information on Matt Cowley please click here ...
In the Spring Statement 2019, the Chancellor announced that under the Government’s forthcoming Environment Bill it would become mandatory for new development to deliver a net gain in biodiversity. This blog article considers the detail behind this announcement and its implications for planning and design.
Biodiversity can be a confusing term, but essentially it refers to the diversity of plant and animal life - ‘wildlife’ in its broadest sense. On the face of it then, legislation that obliges developers to increase biodiversity, whilst at the same time providing housing or infrastructure (with its inherent land-take) sounds like a tall order and perhaps a radical step for a government perceived to have a pro-development agenda.
However, given the direction of recent Government policy, rather than a radical departure, mandating net gain appears to be a logical next step. In January 2018, the Government published its 25 Year Plan to improve the environment. The Government’s stated ambition was to leave the environment in a better state than they found it. This ambition was not considered incompatible with other stated Government objectives such as improving infrastructure, promoting economic growth and addressing the shortage of housing. The Government pledged to support development and the environment by embedding the principle of net gain within the planning system.
Environment Minister, Michael Gove: “Population growth and economic development will mean more demand for housing and this Government is committed to building many more homes. However, we will ensure that we support development and the environment by embedding the principle that new development should result in net environmental gain – with neglected or degraded land returned to health and habitats for wildlife restored or created”.
A key policy step towards embedding this principle came in July 2018 with the publication of the Revised National Planning Policy Framework (NPPF). This stated: ‘Planning policies and decisions should contribute to and enhance the natural and local environment by minimising impacts and providing net gains for biodiversity’. This strengthened the requirement for net gain relative to the previous NPPF, which included the significant caveat that net gain for biodiversity should be provided ‘where possible’. Even before the Environment Bill becomes law, there is a strong planning policy driver for net biodiversity gain.
The Revised NPPF refers to net biodiversity gain that is measurable. The obvious implication is that biodiversity losses and gains should be quantified and presented with a planning application to inform the decision-making process. It is no coincidence that Defra’s ‘Biodiversity Offset Metric’ will shortly be reissued (‘Defra Metric 2.0’). This is a spreadsheet-based metric that converts biodiversity into a single unit of measurement, a ‘biodiversity unit’. In essence, what is meant by development that provides a net biodiversity gain is development that provides a net gain in biodiversity units, as calculated by the Defra metric.
Wildflower meadow is a wildlife habitat that is relatively technically straightforward to create with low maintenance costs. It provides a good potential source of biodiversity units.
Biodiversity in units
As already mentioned, biodiversity is a complicated concept difficult to define, let alone objectively measure. So how are biodiversity units calculated? To simplify Nature’s complexity, Defra use habitat-type as a single proxy for biodiversity; individual species of plant or animal are not considered. The metric also does not consider indirect effects, only habitat that is directly lost, gained or modified.
The biodiversity units associated with a habitat-type are a function of its extent (area), distinctiveness (value to wildlife) and condition. For habitats being created or enhanced, unit values are modified according to risk factors including technical difficulty to create, length of time to the reach the target outcome, strategic location and the distance of the new or modified habitat from the development site. The unit values for different habitat-types and risk multipliers are pre-set within the metric. It is intended to be a standardised, transparent system.
How are biodiversity units applied to development?
Quantifying the effect of development using biodiversity units is therefore is a theoretical exercise that involves comparing biodiversity units associated with the habitat-types present on a site prior to development with those predicted to be present post-development. To meet their biodiversity net gain obligations (an increase in biodiversity units), the developer would be expected to:
provide the required number of biodiversity units on the development site;
secure the required number locally (e.g. through a legal agreement called a ‘conservation covenant’ with a local landowner);
pay a cash tariff toward a strategic delivery scheme; or
a combination of the above.
The price for securing a local agreement or for the cash tariff would reflect the costs of creating and managing the compensation habitat in a suitable location for 25 years. The Government’s estimate is that the tariff costs might be set at between £9000-£15000 per unit. At this stage, the recipients of the tariff and the mechanisms that would ensure delivery and appropriate auditing of implementation and outcomes remain unclear.
Habitat creation within drainage features such as ponds and reedbeds would provide biodiversity units
One of the government’s key points when selling this approach to developers, is that it provides certainty and a ‘level playing field’. They also suggest that there may be cost savings due to it being a straightforward habitat-based process. However, as the Defra metric sits alongside, rather than replaces, other ecology planning inputs such as those concerning protected species and designated sites, such savings may be some time off. It is important to note that the current legal and policy protection given to designated wildlife habitats, ‘irreplaceable’ habitats and legally protected species remain in place.
The government are also at pains to stress that the ‘Mitigation Hierarchy’ must remain a core principle i.e. that adverse impacts to wildlife should be avoided where possible, and if not feasible, then mitigated, and only as a last resort compensated. The recently published CIRIA good practice guide on biodiversity net gain includes the mitigation hierarchy as a fundamental best practice principle for practitioners, including developers, local authorities and consultants. Advocates of offsetting principles might argue that an appropriate monetary value for biodiversity units also acts as a suitable incentive to apply the hierarchy.
Implications for design and planning
Ecological assessment has traditionally focused on ‘significance’: extensive areas of low-grade habitat or smaller areas of high-grade habitat could be removed with no mitigation or compensation if the loss fell below the threshold for a ‘significant’ effect. Using the Defra metric, the loss of any habitat-type will require compensation. This represents a major shift in focus with significant implications for design and development delivery.
With the new approach there becomes a financial incentive for developers to seek design solutions that minimise loss and maximise gains in biodiversity units, as measured by the Defra metric. This means retaining key wildlife habitats and incorporating new ones.
Invertebrates including the common blue (pictured) are likely to benefit from provision of wildflower meadow.
Biodiversity units as a design layer
Most development professionals are familiar with the ‘Ecological Constraints and Opportunities Plan’; such plans inform design by identifying the location of key ecological features, such as a legally protected species or notable habitat. The scope of such plans could now be extended to include the biodiversity unit value of the habitat-types across a project site. This is likely to become a key design layer through the evolution of a project, including at site selection / concept-layout stage, when net gain requirements could be factored in upfront and inform estimates of land value.
In relation to urban design, habitat-types such as wildflower meadow, pond, wet grassland and native woodland can generate high numbers of biodiversity units and could form a part of multi-functional greenspace or SUDS. Developments that incorporate wildlife habitats may bring other benefits: successful place making, opportunities for public access to nature and potentially an uplift in property values.
Habitat-types rather than wildlife species are used to calculate biodiversity units; species such as bullfinch (pictured) are likely to benefit from habitat creation.
Experience of using the Defra metric suggests that even with creative use of open space, for most typical greenfield development sites, it will be challenging to demonstrate ‘net gain’ without off-site compensation i.e. off-setting. Whilst the planning policy driver for biodiversity net gain has been around for some years, my experience to date is that finding suitable off-set providers is challenging and local authorities do not yet have mechanisms in place to facilitate this. By mandating net gain, the government are expecting off-set providers to come to the market-place; however, expect the system to take some time to run smoothly as local authorities, off-set providers and developers get to grips with the new reality.
Next steps and further information
The final release of Defra Metric 2.0 is expected soon; there are also future plans for a parallel metric concerning ecosystem services. The Environment Bill, when published, is expected to include exceptions to mandatory net gain, such as small sites and brownfield sites. Sources of further information include:
Introduction Defra Biodiversity Metric:
Biodiversity net gain guidance, including 2019 best practice principles guide:
Information from the recent government consultation on biodiversity net gain:
 HM Government 2018. Our 25 Year Plan to Improve the Environment.
 Paragraph 170, NPPF.
 Defra 2018. Net Gain Consultation Proposals.
Baker, J., Hoskin, R. and Butterworth, T. 2019. Biodiversity Net Gain. Good Practice Principles for Development. Part A: A practical guide. CIRIA, London.
EAD Ecology is a leading firm of ecological consultants. Based in Exeter, the company specialises in ecological survey and assessment to inform design, planning and management. The company currently employs over 20 ecologists and works for private and public-sector clients across the UK and overseas. The company was formed in 2003 and is owned and managed by Matt Jones and Matt Cowley.
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