If you’re preparing a planning application in Ireland, you’ve likely come across terms like biodiversity net gain survey and environmental impact assessment. While they may sound similar, they serve different purposes and knowing which one you need can save you time, money and headaches.
Here’s a quick breakdown:
- Biodiversity net gain (BNG) is about ensuring development leaves nature in a better state than before.
- Environmental impact assessment (EIA) assesses the broader environmental effects of a proposed development.
In England, BNG is now mandatory. In Ireland, it’s voluntary, but increasingly favoured by local authorities in planning decisions. Let’s unpack what each survey involves and when you might need one.
What is a biodiversity net gain survey?
A biodiversity net gain survey measures the ecological value of a site before and after development. The goal? To ensure that any new development results in a measurable improvement in biodiversity.
The survey typically includes:
- Baseline habitat assessment using a biodiversity metric
- Calculation of biodiversity units pre- and post-development
- Recommendations for habitat creation or enhancement
- Monitoring and management plans for long-term biodiversity gains
In England, BNG is now a legal requirement under the Environment Act 2021, with most developments needing to deliver at least a 10% net gain in biodiversity.
In Ireland, BNG is not yet mandatory, but it’s gaining traction. County councils like Dublin City, Fingal and Dún Laoghaire-Rathdown have already included BNG principles in their development plans. The National Biodiversity Action Plan 2023–2030 also encourages public bodies to integrate biodiversity into planning decisions.
What is an environmental impact assessment?
An environmental impact assessment (or Environmental impact survey) is a broader study required for certain large-scale developments. It evaluates the potential environmental effects of a project, including:
- Air and water pollution
- Noise and traffic
- Impact on flora and fauna
- Cultural and human health considerations
EIAs are legally required under EU and Irish law for developments likely to have significant environmental effects. They’re typically more comprehensive and time-consuming than BNG surveys.
When do you need a biodiversity net gain survey in Ireland?
While not legally required, a BNG survey can strengthen your planning application, especially in counties where biodiversity is a planning priority. BNG is also increasingly relevant for corporate ESG reporting, infrastructure projects, and public sector developments.
Why include a biodiversity net gain survey?
- Improve planning outcomes: Councils are more likely to approve applications that show environmental responsibility.
- Future-proof your project: BNG may become mandatory in Ireland, following the UK’s lead.
- Support sustainability goals: Align with Ireland’s National Biodiversity Action Plan and climate adaptation strategies.
A Biodiversity Net Gain (BNG) survey is a critical step in ensuring that new developments leave nature in a better state than before. Here is a high-level look at some of the considerations and requirements of undertaking such a survey in Ireland.
How to conduct a biodiversity net gain survey in Ireland
1. Understand the ecological baseline
The first step in a BNG survey is to assess the existing biodiversity value of the site. This includes:
- Identifying key habitats and species
- Mapping ecological features
- Evaluating habitat condition and connectivity
2. Survey Methodology
Surveys should follow best practice guidance from the National Biodiversity Data Centre, which includes:
- Standardised habitat mapping
- Vegetation data collection protocols
- Hedgerow appraisal systems
- Seasonal timing to ensure accurate species identification
These methodologies align with Ireland’s National Biodiversity Action Plan and support planning applications, EIAs and biodiversity reporting.
3. BNG metrics and assessment
Although Ireland lacks a statutory BNG metric, many consultants use adapted versions of the DEFRA Biodiversity Metric to calculate biodiversity units before and after development.
This helps demonstrate:
- Net biodiversity gain or loss
- Opportunities for habitat enhancement
- Feasibility of on-site vs. off-site compensation
Some organisations in Ireland, like IDEC, use the Wallacea Trust methodology, which includes peer-reviewed assessments of species, soil, water quality and ecosystem health.
4. Planning and policy context
BNG is increasingly embedded in Irish planning policies:
- Sligo County Development Plan requires BNG for sites over 0.5 hectares.
- Dublin City Development Plan encourages biodiversity enhancement in all new developments.
- Fingal and Dún Laoghaire-Rathdown councils are developing BNG guidance as part of their biodiversity strategies.
While not yet mandatory, presenting a BNG plan can streamline planning approvals and align with emerging ESG and sustainability standards.
5. Reporting and recommendations
A complete BNG survey should result in:
- A detailed ecological report
- Biodiversity unit calculations
- Recommendations for habitat creation or restoration
- A Biodiversity Gain Plan (if required by the local authority)
These outputs support planning applications and demonstrate a commitment to nature-positive development.
Final thoughts
If you’re planning a development or nature project in Ireland, it’s worth considering a biodiversity net gain survey, even if it’s not yet required. It’s a smart move that can improve your chances of planning approval and demonstrate your commitment to nature restoration.
For more technical guidance, check out the CIEEM Biodiversity Net Gain Report and Audit Templates and the CIEEM Briefing Paper on Biodiversity Enhancement in Ireland.
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