Invasive Species Week 2021

Invasive Species Week 2021

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Invasive Species Week

Invasive Species Week is an annual event led by the Non-Native Species Secretariat (NNSS) to raise awareness of invasive species and how everyone can help to prevent their spread.

Throughout the week lots of events and activities will be taking place that people can take part in online or socially distanced. We know that many have been finding solace in nature over the last year, and NNSS will be sharing some simple tips to help you protect the environment.

An alien species is an animal, plant or other organism that is introduced by humans, either intentionally or accidentally, into places outside its natural range. Some alien species – classed as ‘invasive’ – become established and negatively impact native biodiversity, as well as ecosystem services on which humans depend.

Invasive non-native species are considered to be the second greatest threat to native wildlife and they cost the UK up to £1.7bn a year.

UK Invasive Weeds
Non-Native Invasive Weeds in the UK

Global Impact of INNS

Invasive Non-Native Species (INNS) are considered a major driver of biodiversity loss. A research paper published in October 2020 predicted that the number of established alien species will increase across the globe by 36% between 2005 and 2050.

Additionally, a research paper published in July 2020, stated that an increase of 20-30% in INNS would lead to dramatic future biodiversity loss worldwide.

Some of these INNS have negative consequences for biodiversity and humans’ well-being, for example by displacing native species or transmitting diseases.

Experts identify three main drivers for the future spread of alien species:

  • Increasing global transport of goods
  • Climate change
  • Impacts of socio-economic development
Alien Species
Alien Species will Increase by 36% over 45 years

Wealthier regions of the World, with higher populations have the largest arrival of INNS a study found. The conclusion was that global trade and strong transport links were the main causes.

Climate change facilitates the spread and establishment of many INNS and creates new opportunities for them to become invasive. INNS can reduce the resilience of natural habitats to climate change. Conversely, climate change reduces the resilience of habitats to biological invasions.

Socio-economic activity represents many human-induced environmental changes. This can be related to diverse environmental changes relevant for biological invasions, like resource and energy use, consumption or land use.

Effect of INNS on UK Waterways and Ecology

Our waterway network is home to many invasive species, which cause a variety of problems. From interfering with navigation and water control to reducing water quality and habitat availability, invasive species can have a huge impact on our canals and rivers.

Himalayan balsam is now widespread along our waterways. It grows in dense thickets and projects its seeds up to four meters away, meaning it can quickly dominate any ecosystems it’s introduced to. These thickets can impede water flow, as well as leaving riverbanks vulnerable to erosion when dieback occurs over winter. Finally, Himalayan balsam pollen proves particularly enticing for visiting insects, which researchers believe may decrease the pollination of native plants.

The most effective control method is manual hand pulling; however, this is a time-consuming activity.

Himalayan balsam
Himalayan balsam is widespread along our waterways

In Britain alone, there are more than 3,000 non-native species. Not all of these are invasive, whereby the species has become established and thrives in a way that can pose a threat to native biodiversity. Invasive non-native species can cause problems for native species in several ways:

  • Predation - introducing new predators into an area can have devastating effects on the native wildlife and ecosystems. Biodiversity on islands and lakes is extremely susceptible to introduced predators, as native species have often evolved in the absence of predators and are not able to adapt quickly enough when they are introduced.
  • Competition for resources - introduced species can out-compete native species for resources such as nutrients, light-source, space, etc. This can change the habitat structure of an area, making it unsuitable for the other organisms that live there.
  • Introduction of new diseases - introducing new diseases can have serious consequences, as native species will not have developed immunity. Signal crayfish, an introduced species to the UK, is a carrier and host of the crayfish plague, which can kill our native crayfish.
  • Hybridisation - some species are capable of breeding with another related but distinct species, creating hybrids. Over time, the unique genetic diversity of one species can be lost and the species can become extinct.
  • Herbivory – As non-native species arrive in Britain they can damage the native ecosystem by over-grazing native flora, such as Canadian geese grazing on reed beds, saltmarshes and other vegetation, damaging the area.

The extent to which INNS affect our biodiversity has caused researchers to state that there are insufficient UK legislative provisions for the control of non-native species established in the wild. They have also summarised that there are no generalisations that can be made about the characteristics of INNS that hold for all cases.

Health & Safety Concerns of INNS

Rhododendron ponticum has potentially toxic chemicals, known as phenols and diterpenes. “Mad honey” is the toxic honey produced by bees feeding on nectar of Rhododendron ponticum. In 65BC, Pompey’s army were closing in to attack King Mithridates VI of Pontus’ troops. However, he placed the toxic honeycombs strategically along the roadside in advance of the invading army. While in their toxin-induced stupor they were helplessly slaughtered by the army of Mithridates VI which was lying in wait.

Common ragwort poses real threats to horses, causing liver damage and even failure. In 2002, veterinary surgeons reported 284 cases of suspected or confirmed cases of liver failure in horses due to ragwort poisoning.

Giant hogweed arguably poses the greatest health risk as it can cause severe skin burns and even blindness. The sap of Giant hogweed is phototoxic and causes phytophotodermatitis in humans, resulting in blisters and scars. If the sap is rubbed into the eyes, it can cause blindness. Contact with the sap can be caused by just brushing against the hairs on the stalks and underside of the leaves.

The affected area of the skin may remain sensitive to UV light for some years after the original burn and blisters and can be left with scars.

Mad Honey is produced from Rhododendron ponticum
"Mad Honey" is produced from Rhododendron ponticum

INNS Effects on the Built Environment

Japanese knotweed has long been associated with having a negative impact on the built environment. Its highly resilient and fertile underground rhizome if disturbed is tolerant to a great many environments and can regrow and colonise ground easily. This has meant that since its introduction to the UK human disturbance and distribution has made knotweed present in urban and rural locations alike.

Due to knotweed thriving on disturbance, its presence on a property results in a restriction of amenity use and the free enjoyment of the property. This in turn affects the property desirability and value. Allowing knotweed to spread and impacting another property is an actionable private nuisance. When selling a property affected by knotweed, it’s now a standard requirement for the property to have a specialist Knotweed Management Plan with an Insurance Backed Guarantee.

Leaving knotweed uncontrolled can result in a great many problems and in the built environment this can include exploiting weakness in structures resulting in instances of structural damage. It requires great care in developing a site with knotweed to identify and remove the plant correctly. Duty of care regulations require waste containing knotweed to be handled and disposed of correctly and ignoring and spreading knotweed during construction can add significant costs and unwanted problems.

House of Commons Science and Technology Committee: Japanese knotweed and the built environment

In 2018, the Science and Technology Committee commenced a review, including an oral evidence session in early 2019 with relevant experts, specifically to explore the science behind the effects of Japanese knotweed on the built environment. Witnesses from the Environment Agency, RICS, AECOM, Property Care Association and Japanese Knotweed Ltd (represented by Ben Lindley, Sales & Marketing Director ) were called to give evidence, as well as other noted experts.

The outcome will help mould a more evidence-based risk assessment to Japanese knotweed and request mitigation rather than litigation where possible to private nuisance claims in connection with knotweed.

Ben Lindley in Parliament
Ben Lindley Giving Evidence in Parliament

Whilst Bamboo is not listed in Schedule 9 Part II of Section 14 of the Wildlife and Countryside Act 1981, it is an incredibly invasive plant. We are being contacted by concerned homeowners who have a bamboo infestation that is out of control. We’re also seeing some court cases emerge where neighbours are pursuing Private Nuisance claims for bamboo encroachment.

The plants are categorised as either running or clumping; running bamboo rhizomes spread away from the original plant, and clumping bamboo rhizomes form in circles that grow larger in diameter as more rhizomes develop.

Both types have the ability (in a similar way to knotweed) to cause structural damage to buildings.

Running bamboo’s rhizomes spread out from the plant, and although they will find the path of least resistance to grow, they can grow into and exploit weaknesses in structures.

Cracks in patios can be expanded, driveways heaved and buckled from underlying rhizome, and weakness in walls and foundations aggravated.

Clumping bamboo might not spread outward as aggressively, but it too will grow without stopping. That growth can put pressure on the built structures if the bamboo is planted right next to them.

Invasive Running Bamboo
Running Bamboo

Contact the Invasive Weed Experts

Japanese Knotweed Ltd is the UK's largest, dedicated Japanese knotweed removal and invasive weeds control company. We have a proven track record in working successfully for developers, construction companies, local authorities and private landowners. Our highly knowledgeable and skilled staff provide a comprehensive service and are committed to providing the highest level of customer care.

We provide Knotweed Surveys and Knotweed Management Plans, which include immediate excavation and/or long-term chemical treatment options with Insurance Backed Guarantees. Our remedial methods are tailored to each site and provide sensible and efficient eradication solutions to meet all requirements.

The company employs staff across the UK to provide an efficient and responsive service. It enables us to deliver an average of 150 excavations and over 8,000 herbicide visits per year for more than 6,000 customers. Our services cater for project values in the range of £250 up to £1.5M and we had an annual turnover of £4.6M in 2020.

Above all else Japanese Knotweed Ltd is a ‘safety first’ contractor, holding a range of safety SSIP and industry related accreditations that support our commitment to employee training and always working safely. We are dedicated to raising awareness of invasive and injurious weed issues and a proud members of the PCA’s Invasive Weed Control Group.

Contact us today for an industry-leading Japanese knotweed remediation service that includes support if you need legal assistance in cases of Japanese knotweed litigation.

Call us on 0333 2414 413 or email us at

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