Background Estuarine habitats of community interest in the Basque Country (Spain) are threatened by the presence of the exotic and invasive bushy shrub Baccharis halimifolia. The beneficiary has previously undertaken actions to improve the estuaries of Urdaibai and Txingudi, which included a pilot project to remove Baccharis halimifolia from the Urdaibai Biosphere Reserve. In 2008, actions to remove the invasive plant were carried out over 22.5 ha, with shrubs being felled and glyphosate herbicide being applied to the stumps. Additional work is now required to help regenerate degraded habitats cleared of Baccharis halimifolia. Objectives The objective of the Estuarios del Pais Vasco project was to address the problems that the invasive exotic plant species Baccharis halimifolia causes in the main estuaries of the Basque Autonomous Community. The main aims were to remove the invasive shrub and to regenerate habitats of Community interest, including lowland hay meadows, Spartina swards, Atlantic salt meadows, and Mediterranean and thermo-Atlantic halophilous scrubs. Other goals included contributing to the coordination of nature conservation actions in Europe’s Atlantic coastal estuaries. Results The Estuarios del Pais Vasco project implemented an ambitious control campaign for the target invasive species Baccharis halimifolia in protected areas of three Basque Country estuaries: Urdaibai, Lea and Txingudi. The eradication work entailed physical and chemical methods, and avoided the use of heavy machinery in order to reduce damage to the environment. It consisted of hand-pulling seedlings (over 590 ha) and cutting larger specimens by means of chainsaw and applying repeated brushings of herbicide (glyphosate) to the stumps (over 192 ha). In addition, herbicide was reapplied to re-sprouting shrubs and female specimens were selectively cleared before flowering. In all, about 570 000 adult specimens of Baccharis halimifolia were removed and more than 5 000 000 young plants were extracted by means of hand-pulling. In all, the invasive plant has been completely removed from around 212 ha. The habitat improvement in the three estuary areas was clearly evident. Better results were observed in Urdaibai and Lea, where it is not necessary to re-plant native vegetation. Reforestation was conducted in certain areas of the estuary of Txingudi, where more than 6 000 specimens of 13 different species, coming from a plant nursery operated by the regional government of Gipuzkoa, were used to reinforce the regeneration of the native vegetation. In addition to the improvements in the shrub and meadow habitats of Community interest, the amount of mudflat and sandflat habitat has also considerably increased. Significant increases recorded for both the area and quality of Phragmites australis (common reed) communities directly benefits bird species. The project’s monitoring programme showed that the removal of Baccharis halimifolia was effectively implemented in the three project areas. In Urdaibai, where the species is scattered over a marshy area, a significant though reduced re-sprouting rate was observed. In Lea and Txingudi, where the invasive species’ presence is more concentrated, the effectiveness of the control work has been high from the beginning, with very low re-sprouting rates in both areas. By the end of the project, the distribution of Baccharis halimifolia along the Basque coast had been mapped. During the four years of the project’s implementation, the Aranzadi Society of Sciences studied vegetation re-establishment in 45 plots and along 164 transects in the three project areas. In all three estuaries, a rapid development of the natural vegetation was observed, especially in Urdaibai. Nonetheless, despite the positive trend, Baccharis halimifolia continues to be a problem and project continuity is emphasised in the After-LIFE Conservation Plan, along with the need for preventive and corrective measures for other invasive plant species such as Cortaderia selloana, Spartina patents (Urdaibai), Aster squamatus (Lea) and Phytolaca americana (Txingudi). To ensure minimal negative effects on the environment from the use of the herbicide, GAIMAZ, the company contracted to do the eradication work, drafted protocols for the management of glyphosate. Researchers from the University of the Basque Country also conducted a study of glyphosate toxicity in the Mediterranean mussel (Mytilus galloprovincialis), while the Aranzadi Society of Sciences analysed soil samples from the experimental plots and showed herbicide concentrations far below the LC50 (median lethal concentration) established in a toxicity study. The project conducted various communication and awareness-raising activities, for example, through a website, information boards and leaflets, press releases, TV and radio features, guided visits, and Biodiversity Week activities. Project results were disseminated through the layman’s report, and at workshops and conferences. The project produced the ‘Manual for the Management of Baccharis halimifolia’, which arose from a specialised International Commission meeting held in the framework of the project. In addition, the beneficiaries organised two technical conferences on invasive species. The project’s findings relating to the control of invasive plant species have been integrated into conservation measures for the three estuaries and in the hydrological plan of the Basque Country, approved in 2012 in line with the EU Water Framework Directive. The best practice restoration techniques demonstrated can be readily implemented in other European estuaries experiencing similar problems. These project outcomes are a valuable support for the implementation of the new EU Regulation on Invasive Alien Species. Further information on the project can be found in the project's layman report and After-LIFE Conservation Plan (see "Read more" section).