Protocols for prioritizing invasive plants with a view to their management: state of the art and possible improvements in France

Abstract

Risk assessment is an essential tool for the control of invasive species. It allows to qualify the risk and define preventive measures to be put in place. Regional, national or international lists of invasive species can be produced. The process can be more or less long, depending on the objectives sought. There are two ways to perform a risk assessment: a Phytosanitary Risk Analysis (PRA) which is very lengthy but is accepted by the World Trade Organization (WTO) and can consequently provide a legal ban on the sale of certain species for the whole Europe, and other much shorter methods that are sometime more suitable for nature conservation or land settlement. Several agencies under the Ministry of Agriculture and the Ministry of the Environment (MAAPRAT and MEDDTL) have developed hierarchical lists of invasive species using different assessment processes. These lists divide species into categories that distinguish those that are most harmful and those with more moderate and low impacts. The aim of the study is to find one or several methods to determine priorities for national and regional control programs. Two approaches have been tested here and compared with previous studies: the "EPPO Prioritization Process" (EPPO = European Plant Protection Organization) which can be used in over 50 European countries and which has been tested here for France, and the prioritization process developed by Weber & Gut, is - able to rank species and very simple to perform - which has been tested for the Mediterranean part of France and also used in comparison with the EPPO process for the whole country. Over 370 species were assessed for the MAAPRAT. The EPPO prioritization process identified about 30 species, which should be targeted for priority prevention measures. The results from the Weber process are consistent with these results. Over 70 species have been tested for the MEDDTL, the results are in line with the experts' opinion and the score allows to order and prioritize the species and to better take into account the impacts of these species on ecosystems.