Invasive Species

While the River Sid appears picturesque, it faces significant ecological challenges. From aggressive non-native plants to modern human impacts, the river's biodiversity is currently under threat.

1. Invasive Non-Native Plants

Invasive plants are a "big" issue for river management, often out competing native flora and destroying essential habitats.

• Himalayan Balsam: This is the most widespread invader, infesting over 50% of the river's length. It forms dense stands that reduce invertebrate populations and spreads rapidly via seeds that travel downstream during floods.

• Japanese Knotweed: A highly problematic species within the catchment, including a known "Japanese Knotweed Forest" in the valley.

• Winter Heliotrope: Another non-native plant frequently found colonizing the riverbanks.

Management Efforts: Programs are underway to target Himalayan Balsam in the upper reaches to prevent re-seeding downstream, while herbicides are being considered for Japanese Knotweed.

2. The Signal Crayfish Invasion

Introduced to the UK in the 1970s, the Signal Crayfish (Pacifastacus leniusculus) has caused widespread ecological damage.

• The "Signal": They are identified by a distinctive pale blue-green or white patch near the joint of each claw.

• Outcompeting Natives: They are larger and more aggressive than the native white-clawed crayfish, which is now in serious decline.

• Crayfish Plague: They carry a fungal disease that is deadly to native populations.

• Bank Erosion: These crayfish dig deep burrows that destabilize riverbanks, increasing erosion and siltation.

3. The Impact of Human Disturbance (Dogs)

A controversial but significant "invader" to the river ecosystem is the domestic dog.

• Physical Disturbance: At peak times, numerous dogs in the water stir up the riverbed, disturbing the insect larvae living there.

• Wildlife Impact: Constant disturbance deters bird species; aside from the occasional grey wagtail or mallard, bird records in heavily used areas like The Byes are limited.

• Chemical Pollution: Flea treatments and grooming products on dogs can add toxicity to the water, alongside issues from urine and faeces.

4. Loss of Key Native Species

The combination of habitat loss and invasive pressure has led to a decline in iconic British wildlife along the Sid.

• Mammals: Water voles.

• Birds: Snipe and water rail.

• Fish: Salmon and sea trout.