The Hidden Risks: Why BNG Baseline Surveys Demand a Professional Ecologist

I am not very risk averse. I don’t wear a helmet when I go skiing. I eat a lot of saturated fats, and when I am undertaking projects for hobbies (building extensions / forestry etc) then I don’t follow many safety precautions. My instinct of self preservation is set fairly low. . . . . .

BUT. One topic I am very careful with is Ecology. Because I don’t want to go to jail. . . . and please don’t think I am over-egging this 2 guys got sent to jail for chopping a tree down last year.

With mandatory Biodiversity Net Gain (BNG) now a core part of the planning process in England, the temptation for developers and landowners of smaller sites to fill out the baseline assessment themselves is understandable. After all, the Small Sites Metric (SSM) is marketed as being usable by a “competent person.”

However, to rely solely on a layperson’s judgment for the BNG baseline survey is to expose the entire project to significant risks—legal, financial, and planning—that far outweigh any initial cost savings. The BNG metric is a legal tool designed by ecologists, but only an expert can navigate the fine line between satisfying a planning condition and avoiding a criminal offence.

The above is just ones of the 100’s of figures contained within “Tracks and Signs of the Birds of Britain and Europe” it takes years of experience to be able to read these signs. I wouldn’t know which of the above are protected and which are not. That is why I would recommend getting an ecologist to do you BNG baseline survey.

1. The Critical Flaw: The Habitat Condition Trap

The BNG Metric, whether the full Statutory Metric or the simplified SSM, relies on accurately defining the type and condition of every habitat on site. This is where a layperson is most likely to fail the Local Planning Authority (LPA) check.

An ecologist is trained in the UK Habitat (UKHab) Classification system and uses standardised criteria to score habitat condition. For example, what looks like “long grass” to a layperson might be identified by an ecologist as Low-Quality Modified Grassland (low biodiversity value), or, critically, as Priority Habitat Lowland Meadow (high biodiversity value). Misclassifying a high-value habitat as a low-value one:

Massively underestimates the baseline biodiversity unit score.

Requires far more compensatory habitat creation (often making the development unviable).

Guarantees that the LPA will reject the submission, leading to months of expensive delays while a professional survey is commissioned and the metric is re-run.

2. The Legal Threat: Protected Species Liability

The BNG Metric and Protected Species Law operate on separate tracks, but they meet on the ground—your development site. The greatest risk is criminal prosecution under wildlife legislation.

Protected species (such as bats, badgers, and great crested newts) and their habitats are protected by law, primarily the Wildlife and Countryside Act 1981 and the Conservation of Habitats and Species Regulations 2017. Disturbing or destroying their resting places is a criminal offence, even if it is done accidentally.

A layperson’s baseline survey only focuses on the habitat units and cannot definitively rule out protected species. For instance, an old shed or a mature tree hole may be a bat roost. A pond may hold a population of Great Crested Newts. An ecologist, through a Preliminary Ecological Appraisal (PEA), specifically flags these features and identifies the need for mandatory, species-specific surveys. A layperson who fails to spot these signs and proceeds with demolition is committing a crime.

Recent Criminal Sentences

The risk is not theoretical. Criminal sentences for wildlife offences associated with development are becoming increasingly severe:

• Financial Penalties: Fines for companies and individuals can be unlimited for offences relating to Protected Species.
• Custodial Sentences: Individuals found guilty of intentional or reckless damage can face imprisonment. For instance, prosecutions have resulted in significant fines for developers found guilty of destroying badger setts or disturbing bat roosts, often running into the tens of thousands of pounds, alongside orders to pay massive remedial costs and prosecution costs.
• Somerset Example: A recent case in Somerset saw a caravan park owner ordered to pay over £116,000 for disturbing a Site of Special Scientific Interest (SSSI), demonstrating the courts’ willingness to issue punitive financial orders under the Proceeds of Crime Act where clear environmental harm and disregard for the law are found.

In conclusion, while the SSM is designed to be accessible, a layperson completing the BNG baseline is making critical ecological judgments that carry profound legal and financial weight.

An approved BNG plan is not a “get out of jail free” card for protected species law. Engaging a qualified ecologist is the only way to ensure the data is accurate, the project avoids criminal risk, and the planning process is delivered efficiently. Don’t risk a development delay or a criminal prosecution to save on an essential ecological report.