Invasive species data & legislation

Eight alien invasive species are listed on the Global Invasive Species Database (GISD), these are the alga - green fleece Codium fragile ssp. Tomentosoides, Pacific Oyster Crassostrea gigas, Japweed Sargassum muticum, Leathery sea squirt Styela clava, Asian kelp Undaria pinnatifid, Japanese kelp haijiecai, and the carrier pigeon Columba livia. The three native invasive species listed are Northern pike Esox lucius, stoat Mustela erminea and roack Rutilus rutilus.

The JNCC has a more comprehensive list of invasive species. The Biodiversity snapshot lists 27 invasive plant species, four invasive invertebrates, two invasive reptiles (Red-eared slider Trachemys scripta Elegans and Corn snake Elaphe guttata), one invasive reptile (Pool frog Rana lessonae), two invasive birds (Pheasant Phasianus colchicum and Red-legged Partridge Alectoris rufa), and two invasive mammals (feral cat Felis catus and feral ferret Mustela furo). As well as those recorded on the GISD, JNCC lists six further invasive marine species: Asian Shore Crab Hemigraspus sanguineus, Pacific Bryozoan Watersipora subtorquata, Manila Clam Venerupis Philippinarum, Slipper Limpet Crepidula fornicate, Australian Barnacle Elminius modestus,and Blue Mussel Mytilus edulis.

Bracken Pteridium aquilinum agg and western gorse Ulex europeaus are two native plant species which are very invasive in a range of habitats. A law in place preventing the spreading of injurious weeds is; Weeds (Jersey) Law 1961.

Problems with invasive non-native species

Bracken can replace other important habitats such as heathland, it harbours sheep ticks which may cause disease in livestock and humans, it is toxic and carcinogenic to stock and may have a negative impact on human health. Carrier pigeons cause damage to buildings and monuments because of their corrosive droppings. They can also transmit a variety of diseases to humans and to domestic poultry and wildlife.

Green fleece fouls shellfish beds and causes a myriad of impacts on shellfish communities. It has been documented to alter benthic communities and habitats, causing serious environmental implications. American limpet populations are well developed in bays, estuaries or sheltered sides of wave-exposed islands. It competes with other filter-feeding invertebrates for food and space, and often occurring in enormous numbers. Few management options are available to combat this species.

Dense stands of Japweed may reduce light, decrease flow, increase sedimentation and reduce ambient nutrient concentrations available for native kelp species. Leathery sea squirt can reach extreme densities and out-compete native organisms for food in the water column. It also predates on the larvae of native species causing population declines. Both Asian kelp and Japanese kelp form dense underwater forests, resulting in competition for light and space which may lead to the exclusion or displacement of native plant and animal species.

Spanish bluebell Hyacinthoides hispanica is widespread, hybridising with and outcompeting the native common bluebell Hyacinthoides non-scripta. White stonecrop Sedum album is a non-native stonecrop species. It is widespread in Jersey and may represent a threat to the native species.

Japanese knotweed is a very invasive plant it is widespread and even found on parts of the coast. Trying to clear it by strimming can cut it into thousands of pieces which might all grow up in to new plants. New Zealand pigmyweed Crassula helmsii is an extremely invasive aquatic plant that has escaped from garden ponds and is potentially a major threat to native aquatic life – including the agile frog Rana dalmatina. The agile frog population decline is also partly due to predator pressure from cats, birds and ferrets.

Priority invasive non-native species and actions

There has been a severe outbreak of the Oak Processionary Moth (external link) in Jersey which the government trying to control. Oak Processionary Moth is a risk to human health as its caterpillars are covered in hairs that contain a toxin and can cause skin irritation and allergic reactions in anyone who inhales them or comes into contact with them.

Holm oak Quercus ilex is widespread in Jersey, thousands of growing saplings are pulled up by hand each year. In 2011-2012, 258 man/days were dedicated to removing mature trees and saplings.

Cortaderia selloana is a highly invasive plant species, the grass that forms dense clumps is removed where possible but is difficult to totally eradicate. Purple dew plant Disphyma crassifolium is an invasive succulent that is spreading across the coast. 49.5 man/days were used removing succulents from Les Blanche Banques alone in 2011-2012.

Hottentot fig Carpobrotus edulis covers extensive areas of coastline to the detriment of the native flora and fauna, but due to the terrain, are extremely difficult to manage. On more accessible terrain large areas of the fig can be pulled up by hand. In 2011-2012, 64.5 man/days were spent removing fig plants.

The States of Jersey are gathering data on the spread of Japanese knotweed. This species is aggressive and there is no quick solution for its control.

The ‘Birds on the Edge’ project is using a herd of Manx Loaghtan sheep to help with the restoration of Jersey’s coastline. The extensive grazing helps prevent the spread of invasive scrub and bracken, opening up areas for more sensitive plants to grow, allowing a mosaic of heathland vegetation to develop.

Thin strip of image show tree trunk and bark