Invasive Species

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What are the main invasive species impacting the River Sid catchment?


The primary invasive species causing significant issues in the River Sid catchment are Himalayan Balsam, Japanese Knotweed, and Signal Crayfish. Himalayan Balsam and Japanese Knotweed are problematic plants found along the riverbanks, while Signal Crayfish are an invasive freshwater crustacean present in the river itself.

How do invasive plant species like Himalayan Balsam and Japanese Knotweed affect the River Sid environment?

Himalayan Balsam and Japanese Knotweed are considered "significant issues" and can form dense stands that out compete native plant species. This leads to a reduction in the diversity and structure of plant communities, which are crucial habitats for native wildlife. Himalayan Balsam is particularly widespread, infesting over 50% of the River Sid's length.

What are Signal Crayfish and why are they considered a serious invasive species in the River Sid?

Signal Crayfish (Pacifastacus leniusculus) are a large freshwater crayfish species native to North America, introduced to the UK in the 1970s. They are considered a serious invasive species because they out compete the native white-clawed crayfish, are larger and more aggressive, and carry crayfish plague which is deadly to native populations. They also cause ecological damage by burrowing into riverbanks, causing erosion and siltation, and disrupting the food chain by preying on invertebrates and eating aquatic vegetation.

What is the connection between invasive species and the decline of native wildlife in the River Sid?

The presence of invasive species is directly linked to the loss of native species such as water voles, snipe, water rail, salmon, and sea trout. Invasive plants degrade habitats by out competing native flora, reducing shelter and breeding areas. Signal Crayfish prey on native invertebrates and fish eggs, compete with native crayfish, and spread disease, all of which contribute to the decline of native animal populations.

What efforts are being made to address the invasive species issue in the River Sid catchment?
Efforts include a programme targeting the Himalayan Balsam infestation in the upper reaches to prevent downstream spread through re-seeding. There is also potential consideration for using herbicide to control Japanese Knotweed. The total eradication of invasive non-native species is identified as a goal    

Beyond typical invasive species, what other 'invader' is causing adverse effects on the River Sid?

While controversial, dogs owned by human beings are also highlighted as having adverse effects on the River Sid. At peak times, their presence in the river disturbs bird species and stirs up the riverbed, impacting insect larvae. Additionally, chemicals from dog grooming products and issues with faeces and urine can contribute to water toxicity.

How do dogs in the river impact native bird populations and the river's water quality?

Dogs in the river cause an obvious disturbance to bird species that could use the river, which is reflected in limited bird sightings. Their presence stirs up the riverbed where many insect larvae live, impacting aquatic life. Chemicals used for flea treatment and dog grooming, along with faeces and urine, can also add to the toxicity of the water.

What challenges exist in addressing the issue of dogs impacting the River Sid environment?
A significant challenge is the lack of awareness among dog owners regarding the negative impacts of their dogs on the river. Suggestions for keeping dogs on leads are often met with derision and are seen as unenforceable. This issue was notably overlooked in a recent public review of the river, its uses, and problems, despite being a major issue along certain stretches.