Stream ecosystems offer us a whole array of basic ecosystem services like water, cultivatable land, food, raw materials, biodiversity, aesthetics, ecotherapy or leisure, among others. For that, it is very important these very necessary and, at the same time, delicate ecosystems are maintained in a good state of conservation.

The ailanthus (Ailanthus altissima) and the black locust (Robinia pseudoacacia) are two invasive exotic species considered to be amongst the 100 worst on the planet.
The ailanthus is a deciduous tree originally from China that was introduced to Europe during the 19th century as an ornamental species. The black locust is also deciduous but comes from the United States. It was introduced in 18th century, also for gardens.