EUPHRESCO – DeCLAIM: a decision support system, for control of alien invasive macrophytes

This report contains the result of a research programme on four invasive aquatic macrophytes, Cabomba caroliniana (Fanwort), Hydrocotyle ranunculoides (Floating pennywort) , Myriophyllum aquaticum (Parrott’s feather) and Ludwigia grandiflora (Water primrose). The collaborative project was intended to generate a prototype decision support system for optimising control measures for these species, considered to be the four most troublesome invasive alien aquatic weeds at present in the UK and NL. A further reason for selecting these species is that they are widely sold in the horticultural trade and are therefore the number of invaded sites is likely to increase in the short term. C. caroliniana, was selected as a representative of the Myriophyllids growth form, representing 35% of the import volume of aquarium plants in The Netherlands. In 2009 it is found at three sites in The Netherlands, posing serious problems at one. It has been present at two sites in the UK recent past and was collected from one site again in autumn 2011. H. ranunculoides, was selected as a representative of the Stratiotids s.l. growth form, is at present the most troublesome invasive alien aquatic weed in the United Kingdom and The Netherlands, and is showing increased distribution in neighbouring countries, including Belgium and Germany as well as in Australia, Uganda and Zimbabwe. A second representative of the Stratiotids s.l. growth form, L. grandiflora, has proven to have a severe detrimental ecological impact in France and is gaining importance in The Netherlands. In the UK promising management strategies have already been developed using and the infestation in the wild has responded well to rapid application fo control measures. The third representative of the Stratiotids s.l growth form is M. aquaticum. This species has been sold extensively by the aquatic nursery trade as an ornamental species for domestic ponds. It is now present in many natural lowland static water sites in the UK. The species is still very popular in The Netherlands, and the number of occurrences is increasing. The project was divided into several work packages in order to prioritise the order in which data were derived and used in the project. The first stage was to collect all published data on the individual species, in order to gain information on various physiological parameters of the species to put into the model CHARISMA, a model that predicts biomass of a species given both physiological and environmental data. We found that although the species were relatively common in the UK and the Netherlands, data on physiology were not widely available and we had to estimate some of the more important model parameters to get a realistic output. This is an area of possible experimental error and can only be corrected by actual field and laboratory measurements on net photosynthetic rate, light compensation point, biomass production related to nutrient availability and other indices, including shoot to root ratios, leaf area indices etc.. The literature survey also provided information on the native range of the species from which we were able to derive optimum environmental conditions for growth in Europe and the effect of any management techniques already in use. The literature survey also produced information on the main reproductive strategies, either by vegetative means such as fragmentation, or by seed production, or a combination of both. Most species have very effective reproductive strategies using vegetative fragmentation and seed production in both countries was considered to be relatively unimportant. Stage two of the project involved an assessment of the areas at risk of colonisation by the four species in both countries. For the Netherlands it was assumed that if the site of an occurrence shared both physical and chemical characteristics, then it should be classed as at risk. The low altitudes and low slopes of most watercourses in the Netherlands create a situation in which the whole country can be considered at risk. For the UK, we used the elevation data for known occurrence and plotted an area at risk based on this altitude plus 100m, to account for any unknown sites. This produced different maps for each species as some had been found at higher altitudes than others. We do not consider this to be as accurate as possible and the integration of temperature data, especially a day degree index could improve the prediction of at risk areas for each species in the UK. This is an important topic for inclusion in future work. The third area of work was to assess current methods of control and to develop or optimise new techniques. This was carried out in conjunction between all four project partners. Considerable improvements in the management of C. caroliniana were made during this project and have been implemented by water boards in the Netherlands. A consistent approach to management of H. ranunculoides has been adopted in this project and the approaches to management of the two other species have been shown to be effective in the current regulatory conditions. The spatially explicit model CHARISMA was developed for two native macrophytes species in the Netherlands and was used in this project to model growth and biomass accumulation of the four nonnative invasive macrophyte species. Some of the input parameters used in the original model were not valid for the new species, and estimates or adjustments had to be made. However, for three out of four of the new species, the predictions of biomass and dominance were quite accurate and the model could be developed for these species without excessive modification. The only species that did not comply well with the model was C. caroliniana, but only in the degree of overwintering biomass required for dominance in the following season. This is probably due to a lack of any data for physiological characteristics of this species in winter in Europe and this data gap should be addressed for this species and others in order to accurately model the behaviour of other species in European conditions. The main objective of this project was to produce a draft Decision Support System that could be used by field operatives and office based managers to identify the species accurately, and to enable a rapid risk assessment to be made in the field that could be reported in a consistent manner, enabling a rapid response to be made against the species with the aim of preventing further spread and eventually eradication the species from the affected watercourse. In order to make the response to aquatic non-native species consistent and proportionate a pictorial field and office guide has been produced that provides descriptive photographs of characteristic features, areas at risk, typical habitat types, and available management techniques. We have deliberately left out costs of management as these vary within each country and certainly between countries. In addition, each species chapter will be made available at www.declaim.eu . The DSS was submitted to the Non Native Species Secretariat in the UK for comment before being used by managers. In the Netherlands the DSS was submitted to representatives of various water boards that are actively involved in trials to control invasive macrophytes. The comments received were positive and helpful and led to developments in the current version