A Site of Special Scientific Interest is England’s national conservation designation, and the thing to understand before you offer on land is that it reaches beyond its own boundary. Natural England publishes Impact Risk Zones around every terrestrial SSSI, and a scheme inside one triggers formal consultation even where the site itself is untouched.
Protected areas on land in England cover about 1.03 million hectares, roughly 7.8% of the land area, on Defra’s biodiversity indicator published 25 February 2026 using data to 31 March 2025. This guide covers the planning test that actually applies, the criminal liability that sits underneath it, and how to establish your exposure before you spend anything.
What an SSSI is, in legal terms
SSSIs are notified by Natural England under section 28 of the Wildlife and Countryside Act 1981 for their flora, fauna, geological or physiographical features. Notification does two things that matter commercially.
- It creates a consent regime for the owner and occupier. Section 28E lists operations likely to damage the special interest, and carrying one out without Natural England’s consent is an offence. The list is site-specific and published with the notification. Ordinary farming can be on it.
- It creates a duty on public bodies. Under section 28G a local planning authority must take reasonable steps, consistent with its functions, to further the conservation and enhancement of the features. That duty is why a council will not simply take your word for it.
Many SSSIs also underpin a Special Area of Conservation, Special Protection Area or Ramsar site. Where they do, the stricter habitats regime applies on top — a separate test, covered in the Special Areas of Conservation guide.
The planning test
Policy N6(1)(b) of the National Planning Policy Framework published on 17 August 2026 says development affecting an SSSI should only be supported if one of three things holds:
- there would be no adverse effect, alone or in combination with other development, on the site’s features of special scientific interest; or
- the benefits of the development in the location proposed clearly outweigh both the likely impact on those features and any broader impact on the national network of SSSIs; or
- the impact is being addressed through an Environmental Delivery Plan which has been made and the developer has committed to paying the nature restoration levy.
The second limb is the real difference between an SSSI and an SAC. An SSSI is a balance, not a prohibition — a scheme can be approved on benefits where a habitats site could not be. But note the words “and any broader impact on the national network of Sites of Special Scientific Interest”. You are not only arguing about your field, and a precedent argument is available to the council.
Policy N6(3) closes the obvious gap: the policy applies to development inside or outside the designated area, if it would have an impact on the biodiversity or geodiversity value of the area concerned.
The Environmental Delivery Plan route is new and not yet available. It comes from Part 3 of the Planning and Infrastructure Act 2025, which received Royal Assent on 18 December 2025. Natural England is preparing the first plans; as at September 2026 none had been made.
The penalty is an unlimited fine, not £20,000
A lot of published guidance still quotes a £20,000 maximum in the magistrates’ court. That cap was removed on 12 March 2015. Under section 28P of the Wildlife and Countryside Act 1981 a person who, without reasonable excuse, intentionally or recklessly destroys or damages the features for which land is of special interest — knowing it was within an SSSI — is liable on summary conviction, or on conviction on indictment, to a fine. Unqualified, in either court. Natural England’s own guidance says you can get an unlimited fine and be required to pay for repairs to the damage.
The practical exposure is not usually the prosecution. It is site clearance carried out by a contractor who did not know, in a strip of land whose boundary nobody checked.
SSSI Impact Risk Zones: the check that actually answers the question
An SSSI boundary tells you whether you are inside. It does not tell you whether your scheme is in scope. Natural England’s SSSI Impact Risk Zones (England) dataset does. It draws zones around each site reflecting what that site is sensitive to, and lists which categories of development inside each zone need to be consulted on — residential above a stated number of units, discharges, combustion, infrastructure, and so on. Councils use it to decide when to consult Natural England, and the zones also cover the SACs, SPAs and Ramsar sites that those SSSIs underpin.
Two practical consequences. First, an Impact Risk Zone hit is not a refusal; it is a trigger for consultation, which is a timetable item and an evidence requirement. Second, the trigger is often a unit threshold — so the same field can be in scope at 15 dwellings and out of scope at 9. That is worth knowing before you fix a scheme size.
Biodiversity net gain does not answer an SSSI
Statutory BNG and SSSI protection are separate obligations. Delivering the mandatory 10% gain does not discharge the policy test, and being exempt from BNG does not exempt you from it. The exemption for sites of 0.2 hectares or below, in force from 6 August 2026, is disapplied in any case where on-site priority habitat is impacted — which is common on and around a designated site.
Where BNG and an SSSI do interact usefully is in the design. Habitat creation on the part of your site nearest the designation can serve both the gain plan and the ecological case, and a scheme that buffers the SSSI rather than abutting it is easier to defend on both counts.
How to check a site before you commit
- Map the designation at appraisal, not at application. In BOOM! SSSIs are a Data Studio layer and a SiteSeeker constraint, so affected land can be excluded from a search rather than checked one title at a time. Impact Risk Zones are a separate Natural England dataset and need checking directly.
- Read the citation and the operations list. Both are published on Natural England’s Designated Sites system. The citation tells you what the site is notified for, which tells you what your assessment has to address. The operations list tells you what the owner cannot do without consent, which matters if you are structuring an option over the land.
- Check condition. A site already in unfavourable condition for a reason your scheme could worsen — nutrients, hydrology, air quality, recreation — is a much harder case than one in favourable condition.
- Go to pre-application with a position, not a question. Where Natural England is a consultee, its response usually decides the outcome. Getting its view before you buy converts an unpriceable risk into a cost.
Why an SSSI is not automatically a bad deal
An SSSI on the land is a hard problem. An SSSI near the land is a process, with a known set of documents and a known consultee. The second category is much larger than the first, and it is systematically underpriced by buyers who see the designation and stop reading.
The same is true of the constraints that tend to sit alongside it. If your site is in a river catchment serving a designated site, read the nutrient neutrality guide next, because that is the constraint most likely to decide whether the scheme is viable.
