European project investigates the spread of alien invasive plants
The EU funded Giant Alien project is investigating the causes and mechanisms of the giant hogweed spread and its effects on native vegetation in Europe and the Caucasus. The final goal is to develop an integrated management strategy for the control of this and other alien invasive plants. Named after the mythical Hercules due to its immense size of approximately three metres, Heracleum mantegazzianum is commonly known as 'giant hogweed'. It appears that, due to its tenacious and invasive nature, getting rid of this noxious weed could prove as difficult as one of the twelve labours given to the Greek hero. This member of the parsley family, originally indigenous to the Caucasus mountains and southwestern Asia, was first introduced to Europe as an ornamental garden curiosity. The invasive nature of the species meant that it soon become a pest, and is currently considered a significant threat to floral and faunal biodiversity in a wide range of habitats across Europe in which it is becoming established. The plant has large leaves that create so much shade that few other plants can grow around it. As a result, when the giant hogweed dies in the autumn, large areas remain bare and erosion takes place. It multiplies by seed propagation, a single plant producing up to 100,000 seeds that can survive for more than seven years before germinating. 'It has a remarkable invasion potential. On top of this, efficient reproduction makes it extremely difficult to control or eradicate this species,' explains Petr Pyek from the Botanical Institute of the Academy of Sciences of the Czech Republic, a partner in the project. Moreover, giant hogweed proliferating populations in urban and suburban areas represent an increasing public health hazard: its clear, watery sap has toxins that sensitise the skin to ultraviolet radiation. Skin contact with the sap followed by exposure to sunlight causes photo-dermatitis, provoking painful, burning blisters that may develop into purplish or blackened scars. The fact that the giant hogweed and other alien invasive plants can become a problem is beyond questioning. But so far, no sustainable solutions have been found to stop the spread and prevent future invasions. Moreover, with globalisation and global trade there is an increased risk that new plants - so-called neophytes - will further spread in the EU and lead to an imbalance in the old ecosystems. In an attempt to overcome this gap, eight universities and research institutes from Germany, the UK, Denmark, the Czech Republic, Latvia and Switzerland joined efforts, and set up the Giant Alien project in January 2002. It is funded under the 'energy, environment and sustainable development' programme of the European Commission's Fifth Framework Programme (FP5). The partners of the project bring together contributions on all aspects of Heracleum mantegazzianum, with a particular emphasis on its biology and ecology, management and control, as well as the development of best practice on the basis of research dealing with alien invasive plants. The overall objective of the project is therefore to develop an integrated management strategy that comprises effective, practicable and sustainable means of controlling an alien non-agricultural weed. This will provide a generic control strategy to safeguard the biodiversity of Europe from the increasingly serious threat of other alien invasive species. In addition to the effective control of this species, a concept will be produced, which could serve as a template by which other exotic species could be controlled, or prevented from reaching the invasive phase. To achieve this overall objective, the project is developing a comprehensive knowledge base for H. mantegazzianum, including genetics, taxonomy, biology and ecology in order to establish a thorough understanding of the life-cycle, population dynamics, seed and recruitment ecology, fecundity and regeneration. To study the temporal dynamics of the invasions, both at the local and continental scales, scientists use computer models. It is difficult to gather empirical data over a time span that is appropriate for the temporal scale in question. This way they capture the key processes of ecological systems and by developing a model suitable for describing the invasive dynamics of a plant, it is possible to understand the population dynamics of the giant hogweed and its invasive strategy and potential. Thus, the spread of invading species can be predicted. Nana Nehrbaß from the Centre for Environmental Research (UFZ) at the University of Leipzig, Germany, another partner in the project, is investigating the spread of giant hogweed, focusing on the factors that favour or hinder the plant's spread. 'Linear structures like rivers and roads appear to be the main dispersal methods. The seeds are transported along them in the water or attached to the tyres of vehicles,' she says. On her computer, she analyses aerial photographs to study the spread of the plant with the aim of producing computer models that will make it possible to predict the spread of invading species. The current models developed within the project already take into account local factors, like land use or roads. Another aspect of the project focuses on searching for, and assessing, potential biological control agents within the area of origin of H. mantegazzianum for potential future use in Europe. This includes a risk-benefit analysis, an evaluation of existing European guidelines for the import of exotic organisms, and an implementation plan. Giant Alien is also investigating current mechanical and chemical control methods together with possible measures to reduce and prevent further dispersal of H. mantegazzianum and other alien invasive weeds. Radical solutions provide for mowing and digging out the roots - naturally only with protective clothing including gloves, eye and mouth protection. However, in her doctoral thesis, Nana Nehrbaß suggests a much simpler solution, which is already being implemented in Scandinavian countries: 'A large proportion of the local dispersal potential is defined by fallow land. In areas where lots of meadows and fields cannot be used, the giant hogweed can spread easily. The best control measure is therefore agricultural land use or grazing.' The scientists hope that they will be able to produce forecasts for other immigrant species in the future using the computer models, and all knowledge and experience created and gathered during the project is being integrated into a set of best practice guidelines and an integrated control strategy, which will be disseminated around Europe.
Countries
Germany