Biosecurity and Non-Native Aquatic Plants

Biosecurity measures are essential on all construction sites even if they are not known to be present on site, some may ask why? One reason may be that invasive plants may completely die back and disappear in winter or become hard to identify, therefore they may have been missed in surveys; or in cases where rapid growth is seen, they may have entered the site and spread in just the last growing season. Another reason is that biosecurity measures also aim to stop the introduction of species onto a site. While some invasive non-native species (INNS) spread by seeds, many spread by tiny vegetative fragments. Smalls seeds and vegetative fragments can easily catch a ride on plant, equipment or in the treads of shoes and tyres. Once on site they can be easily spread across the site, potentially even only being discovered post construction when new growth is discovered, leaving the contractor liable for potentially costly remediation. If discovered during works, a fast response for containment and management can be vital to minimise spread, delays and costs spiralling.

Aquatics are often less known about yet there are more aquatics listed on Schedule 9 of the Wildlife and Countryside Act 1981 then terrestrial plants! Maybe aquatics appear to pose less of an immediate threat to construction, however once introduced, their spread on a site can be incredibly rapid. In this article we will explore the key terrestrial aquatic plants to be aware of, all of which are listed on Schedule 9:

Floating Pennywort can be free-floating or rooted and can spread rapidly. It can grow up to 20cm per day and may quickly dominate a waterbody forming thick mats. As a result, it impedes water flow and amenity use, out-competes native species by blocking out light, causing deoxygenation, obstructs air breathing insects from reaching the water surface and reduces water temperatures.

Water Fern is a very small free-floating water plant that forms dense mat leading to similar issues as those above, however it may also pose a safety hazard as the dense and continuous stands cause the water surface to appear solid.

Curley, Canadian and Nuttall’s Waterweed perennial, mostly submerged aquatic plants that spread mainly by vegetative propagation through detached stem fragments that become easily established. Waterweeds can overwhelm ponds and outcompete native vegetation as well as choke up waterways, exacerbating flood risk. They also replace native aquatic plant species and reduce biodiversity in lakes and ponds and interfere with recreational activities such as angling and boating.

New Zealand Pigmyweed can be submerged, emergent and terrestrial. It forms dense mats and can impede drainage, causing flooding. It also displaces other aquatic plant species and reduces amenity use of the waterbody.

Parrot’s Feather Emergent growth that is blue-green colour with feather-like leaves make this a distinctive water plant, spreading by vegetative fragments. It displaces native species, rapidly dominating water bodies and causes flooding by blocking watercourses and drainage channels

Creeping Water Primrose only currently known in a few places in the UK, it can alter water chemistry through allelopathic activity (production of biochecmicals) leading to multiple knock-on effects to other trophic levels, including aquatic invertebrates.

It is vital that any engineering works in watercourses, drainage systems or waterbodies where these species may be present or could be easily spread to ensure pre-construction surveys are undertaken and biosecurity and invasive management plans are implemented to reduce the risk of spread or introduction of INNS. It is always worth remembering, if the construction activities facilitate the spread to ‘the wild’ or to a ‘location outside its native range’ (Scotland), it would constitute an offence under Schedule 9 of the Wildlife and Countryside Act 1981 (in England and Wales) or Section 14 of the Wildlife and Natural Environment (Scotland) Act 2012). As a minimum, a ‘clean, check, dry’ method should be implemented on all sites.

Naturally complaint can undertake invasive species surveys and advise on how to manage them on your site, the earliest involvement of an environmental professional can often help to reduce any delays and costs due to INNS. prior