Need an Invasive Species Survey?

The Impact of Invasive Species

Across the UK, invasive non-native species are an increasingly common issue on development sites. Whether you are planning a residential scheme, commercial development or infrastructure project, the presence of invasive species can have a serious impact on planning timescales, construction costs and legal compliance if not identified and managed correctly from the outset.

An Invasive Species Survey allows potential risks to be identified early: it will assist developers and planners when it comes to taking the right action, avoiding unexpected delays and demonstrating compliance with UK legislation and planning policy.

With the correct survey and mitigation strategy in place, land development projects can proceed lawfully while protecting the surrounding environment.

What are Invasive Species?

Invasive species, also known as invasive non-native species (INNS), invasive alien species, or non-indigenous species, are plants or animals that have been introduced outside of their natural range and subsequently cause harm to native biodiversity, the economy or human health: they can also introduce new diseases.

Many invasive species thrive because they lack the natural predators, diseases or controls that keep them in balance in their native habitat. Once established, such species can have significant impacts: they may spread rapidly, out-competing native species for space, light, water and nutrients.

While invasive species can include animals, insects and aquatic organisms, invasive plants are the most common concern on development sites and the primary focus of invasive species surveys.

Examples of Invasive Non-native Species in the UK

The UK hosts a wide range of invasive species that pose risks to native biodiversity, habitats and development projects. Some invasive animals that are well known include:

• American mink threatening water voles
• Grey squirrels displacing red squirrels
• Asian hornets impacting pollinators
• Signal crayfish out-competing native crayfish

However, it is invasive plant species that most frequently affect planning and construction. Common invasive plants found on development sites include:

• Japanese Knotweed (Fallopia japonica / Reynoutria japonica)
• Giant Hogweed (Heracleum mantegazzianum)
• Himalayan Balsam (Impatiens glandulifera)
• Floating Pennywort (Hydrocotyle ranunculoides)
• Water Hyacinth (Eichhornia crassipes)

Many of these species are listed under Schedule 9 of the Wildlife and Countryside Act 1981, making it an offence to allow them to spread into the wild.

Why Invasive Species matter for Land Development Projects

Ecological impacts

Invasive plant species are highly competitive. Often originally introduced as ornamental plants, they can rapidly spread, displacing native plants and altering habitats. Dense stands of invasive plants can reduce biodiversity, disrupt food chains and introduce new plant diseases.

For example, the introduced species Himalayan balsam can dominate river banks, suppressing native flora and increasing erosion once it dies back in winter. Over time, this can significantly degrade ecosystems.

Economic and structural impacts

Invasive species can also have major financial consequences. Japanese knotweed, in particular, is well known for exploiting structural weaknesses in hard surfaces, drainage systems and building structures. It can take root in the smallest cracks and rapidly spread to colonise large areas of natural or man made habitats: as root fragments can quickly take hold when disturbed, early detection is advantageous when it comes to controlling this species.

For developers, landowners and homeowners, the cost of managing, treating or removing such species, especially if discovered late, can be substantial. Mortgage restrictions, insurance issues and planning delays are all common consequences, making appropriate risk assessments important.

Invasive Species and the Law

Managing invasive species is not optional. A number of UK laws and regulations place responsibilities on landowners, developers and contractors.

Key legislation includes:

• Wildlife and Countryside Act 1981 (Schedule 9)
• The Conservation of Habitats and Species Regulations 2017
• Environmental Protection Act (Duty of Care) Regulations 1991
• Controlled Waste (Registration of Carriers and Seizure of Vehicles) Regulations 1991

Regulatory bodies involved in invasive species control include:

• DEFRA
• The Environment Agency
• Local planning authorities

Failure to comply can result in enforcement action, fines or prosecution, particularly if invasive species are allowed to spread beyond a site boundary.

What is an Invasive Species Survey?

An Invasive Species Survey is a detailed assessment of land to determine whether regulated or problematic invasive species are present, and if so, their location, extent and density.

The survey provides evidence to assist developers to:

• Meet planning conditions
• Inform remediation and management strategies
• Prevent the spread of invasive species
• Protect neighbouring land and watercourses
• Avoid costly construction delays

The ultimate goal is to ensure invasive species are identified early and managed effectively, allowing development to proceed safely and legally.

When is an Invasive Species Survey required?

Invasive species surveys apply if:

• There is existing knowledge or records of invasive species or injurious weeds on or near the site
• The site includes riverbanks, brownfield land, railway corridors or disturbed ground
• A previous ecological report has flagged invasive species risk
• A local planning authority requests confirmation that invasive species will be managed
• You want to reduce the risk of legal or financial issues later in the project

Even where invasive species are not obvious, surveys are often commissioned as a precautionary measure during early site assessments.

Types of Invasive Species Surveys

Depending on site conditions and project requirements, surveys may include:

• Japanese Knotweed Surveys
• Giant Hogweed Surveys
• Himalayan Balsam Surveys
• Injurious Weed Surveys
• Problematic Species Audits
• Biosecurity Assessments
• Invasive Species Management Plans
• Expert Witness and Planning Support Services

Invasive species survey methods are tailored to the site and its planning context. In some instances, A Problematic Species Management Plan may be required.

How Invasive Species Surveys are carried out

1. Desk study

The survey begins with a review of historical and ecological records, aerial imagery and previous reports to assess the likelihood of invasive species being present.

2. On-site inspection

An experienced ecological consultant visits the site to identify invasive species, record their location, estimate extent and assess density.

3. Mapping and photography

All findings are accurately mapped and photographed to provide clear evidence for planners, contractors and regulators.

4. Sampling (if required)

In rare cases, plant samples may be taken to confirm identification where species are difficult to distinguish.

Invasive Species Survey report

Following the survey, a comprehensive report is produced. This typically includes:

• Confirmation of species presence or absence
• Maps showing infestation extent
• Legal and planning implications
• Clear recommendations for control, containment or removal
• Advice on next steps to allow development to proceed

This report can be submitted to the local planning authority as part of a planning application or to discharge planning conditions.

Invasive Species Management and Solutions

Discovering invasive species on a site does not mean development cannot proceed. With the right strategy, impacts can be effectively managed to:

• Prevent further spread to other areas
• Protect surrounding habitats and wildlife
• Minimise disruption to construction
• Support long-term ecological health

Where large infestations are present, management plans and control methods are carefully designed to avoid impacts on nesting birds, watercourses and sensitive habitats.

Best time of year for invasive species surveys

Timing is crucial. Most invasive plant surveys are best carried out between late spring and early autumn, when species are visible and identifiable.

Early engagement is strongly recommended to ensure surveys are completed within the optimal seasonal window and without delaying planning or construction programmes.

Arrange an Invasive Species Survey

If you require an Invasive Species Survey to support a planning application, it’s important to engage a specialist team. Identify an ecological consultancy with the right experience. Consultants must have specialist knowledge of the invasive species present in the UK and have the necessary qualifications to deal with specific species.

Expert guidance will enable you to comply with the required legislation and fulfil your planning obligations.