Invasive species can create a serious problem, not only on development sites, but also in ecologically sensitive areas. Current legislation means that landowners and developers are responsible for ensuring that any invasive species which are on their property do not spread outside the boundary.
Teams at Thomson environmental consultants provide specialist invasive species consultancy, remediation and treatment services. We pride ourselves on providing a bespoke service, and we take the time to understand how the invasive species are impacting on the site and any development works.
In-house specialists can undertake a range of invasive species works, including initial walkover surveys, herbicide spraying, excavation, on-site burial, and off-site removal.
We have experience in providing solutions to invasive species on a wide variety of projects, including flood defence, rail, housing, highways, renewables, and commercial development sites as well as for domestic customers.
We provide advice on suitable approaches for invasive species remediation, which can take into account the project programme, and aim to minimise time and costs.
Invasive species services we provide include
- Initial advice and consultation
- Initial site survey to map and identify specific invasive species and any associated site constraints
- Production of priced remediation strategies, detailing the findings of the surveys, and methods for treatment
- Clerk-of-work services for remediation
- Herbicide treatment
- Excavation and on-site bunding
- Excavation and on-site burial, often involving encapsulation in a heat-welded cell
- Excavation, haulage and off-site disposal
- Hand-pulling and cutting of Himalayan balsam
- Clearance and treatment of aquatic invasive species
Types of invasive species
Japanese knotweed can regenerate from any small piece of material – root, rhizome, crown or stalk – so it can very easily be spread if the plants are disturbed. It can grow through cracks in walls, tarmac and concrete, greatly reducing land and building values. Even after treatment, the rhizome can remain dormant in the soil for years, growing again if disturbed. The EA advises that 3 to 5 years should be allowed for eradication.
Australian swamp stone crop
Australian Swamp Stone Crop was introduced from Australasia in 1911 and has spread at an alarming rate. This plant forms dense carpets across the water surface, so excluding all other competitors and reducing the biodiversity of the water body. There are various methods to control the plants, including physical removal of the plant from the watercourse, chemical application, or covering the plants with soil, rock or even black polythene to starve them of sunlight.
Bamboo is often planted in gardens, but, left unmanaged, it can spread beyond the boundaries and become invasive. It spreads via its rhizomes, and weed-suppressant membrane will not stop it spreading. The roots can run underneath hard surfaces like concrete, and the shoots will pop up elsewhere. The leaves are more resilient than the leaves of Japanese knotweed and so bamboo can be more difficult to treat effectively.
Floating Pennywort originated in North America. The plants form dense mats of floating vegetation on the water surface, altering the ecology of the water body, deoxygenating the water, killing fish and invertebrates, causing problems with drainage systems and sluices, causing extensive localised flooding, and crowding out native plants.
This plant can dominate vegetation, and can be harmful to skin or eyes. Under the Wildlife and Countryside Act 81 it is an offence to “plant or otherwise cause (GHW) to grow in the wild.” Its seeds are spread by wind, traffic,or on water and can remain viable for 7 – 15 years. Giant hogweed can reduce land values and, if it grows across pathways, can effectively close them.
Growing 2-3m in height, Himalayan balsam is often found along river banks, and out-competes native species leaving the ground bare in winter and susceptible to erosion. The seeds can spread by air, water, on feet or car tyres, and can remain viable for 18 months, so a two year programme is the minimum to control it. Ongoing management is essential.
Ragwort is an injurious weed which is dangerous to livestock, especially horses where it can cause liver damage. It can also be dangerous to humans through direct contact with skin and if the pollen is inhaled. The plant is more difficult to kill the larger it is and seeds can remain dormant and viable for years (up to 15 years has been suggested). Treatment is usually ongoing and needs a minimum 2 year programme.
Introduced to the UK as seed in the 1760s, it soon became readily supplied by the nursery trade, becoming popular as soil and weather conditions in the UK are ideal for its growth. Seed dispersal and growing branches putting down roots where they touch the ground mean that it has reached invasive levels in many parts of the country. Its foliage shades out native flora, and wildlife populations can be greatly reduced by the dense foliage.