BambApp: a citizen science project for the re-evaluation of the invasive potential of bamboo species in North-West Italy.
Several bamboo species, suitable for temperate climates, have been introduced from southern China as ornamental plants in Europe and in Italy since the XIX century. Bamboos were appreciated also for other commercial purposes afterwards (e.g., food and structural applications) and nowadays in NW Italy (Piedmont and Aosta Valley Regions) the interest in their plantation has been growing. Consequently, many public authorities responsible for environment and biodiversity protection expressed a precautionary attitude for the commerce of bamboos. 'BambApp' project was implemented to scrutinize the invasive potential of naturalized bamboo species with a 'citizen science' approach, which implied the support of volunteers to collect scientific information through the use of "iNaturalist" app for smartphones. Citizens described each recorded bamboo clump in terms of maximum height, maximum stem diameter, and clump size. The coordinates and a description of the habitat type on the border of the four sides for each clump were required to volunteers as well. Moreover, surveyors had to upload four pictures of the clump, which were used to identify the bamboos at species level. In a ten-month period, 871 validated bamboo populations were recorded in the two regions and nine different species identified. The most widespread species was Phyllostachys aurea (67%), followed by Phyllostachis viridiglaucescens (16%), Pseudosasa japonica (6%), Phyllostachys reticulata (5%), Phyllostachys nigra (2%), Phyllostachys flexuosa (2%), Phyllostachys sulfurea (2%), and Phyllostachys edulis (1%). To quantify the invasive potential of bamboo species a Principal Component Analysis was carried out by using variables related to clump growth. Average elevation ranged between 252 m and 431 m a.s.l. and the clump size ranged between an average of about 27 m2 and about 2160 m2. Phyllostachis reticulata and P. sulfurea were the tallest species with the largest stem diameters, whereas P. aurea was the species forming the largest clumps in terms of occupied surface. The 82% of populations bordered for at least one side with anthropic habitats, 60% with agricultural habitats, and 45% with natural habitats. 'BambApp' project, through a citizen science network, successfully provided reliable and comprehensive information to public authorities for re-evaluating the invasive potential of bamboo species in NW Italy and for regulating their commerce.