Himalayan balsam is one of the UK’s most widespread invasive weed species, colonising river banks, wasteland, damp woodlands, roadways and railways. Research by CABI scientists has shown local invertebrate biodiversity is negatively affected by the presence of Himalayan balsam. This leads to fragmented, destabilised ecosystems, which has serious consequences on processes and functioning, and complicates habitat restoration unless remedial actions are implemented.
Increasingly we are seeing the terms ‘ecosystem services’, ‘ecosystem functioning’ and ‘ecosystem processes’ in the media and the scientific literature, to highlight the benefits the natural environment provides to our wellbeing. Invasive species, from bivalves to balsams, have the potential to impact on ecosystem services, though it is widely accepted that there are gaps in our understanding within this field.
Ecosystem services can be defined as the ecosystem processes that we as humans benefit from and they can be categorised into four groups:
Provisioning: The ecosystem provides products essential for our everyday needs including timber, fuel, food, genetic resources and medicine.
Regulating: We gain from natural services including pollination of wild plants and crops by bees, by rivers and floodplains providing natural flood management, and climatic regulation.
Cultural: We benefit from natural spaces for recreation and social activity. We find harmony in natural areas that are aesthetically pleasing.
Supporting: These services underpin all of those mentioned above. Biological diversity promotes stability and a healthy ecosystem, nutrient acquisition and flow through the ecosystem by fungal and invertebrate decomposers, and primary production.
Our river systems are undoubtedly one of the most diverse habitats found within the British Isles. They provide us with numerous benefits including areas for relaxation and recreation, they harbour high levels of biological diversity, act as natural flood management, provide water for consumption and irrigation, and act as corridors for the movement of nutrients and species in an otherwise fragmented landscape. However, our river systems are highly vulnerable habitats. Seasonal variations in hydrological processes render riparian habitats prone to high levels of disturbance which aid the invasion and colonisation of invasive plant species.
Himalayan balsam monoculture on the banks of the River Torridge, North Devon, UK (CABI)
The Global Invasive Species Programme (GISP) has recently published two publications on invasive species, Mainstreaming Gender into Prevention and Management of Invasive Species, and Invasive Species, Climate Change and Ecosystem-Based Adaption: Addressing Multiple Drivers of Global Change, both of which deserve a read. Both publications can be downloaded via the GISP website
After a long hot summer, many custodians of the countryside will be breathing a sigh of relief as the winter months will provide a rest bite from battling with infestations of non-native plant species. Unfortunately, the battle is too often one sided and the weeds are winning! Himalayan balsam (Impatiens glandulifera) is one of the UK’s most invasive non-native plant species and an incredibly difficult plant to control, due mainly to the inaccessible and sensitive habitats where it grows. As a weed of riparian habitats chemical control is often not a viable option, manual control is labour intensive, and for any control effort to be successful control must take place on a catchment scale else seeds from populations upstream will colonise cleared areas during the late summer months.
Himalayan balsam invading pasture-land in the Camel Catchment, Cornwall, UK (CABI)
Last month anglers at Grafham Water reservoir in Cambridgeshire, UK spotted the invasive killer shrimp Dikerogammarus villosus. The first sighting of this ferocious little beast in the UK has instigated the GB Non Native Species Secretariat (NNSS) to issue a species alert as part of the GB rapid response protocol in an attempt to contain and monitor its spread.
The Killer Shrimp Dikerogammarus villosus (Picture courtesy of Michal Grabowski)