Instructions: This task is about writing a correct answer for the reading comprehension task. Based on the information provided in a given passage, you should identify the shortest continuous text span from the passage that serves as an answer to the given question. Avoid answers that are incorrect or provides incomplete justification for the question.
Input: Passage: Deforestation and forest fires are a problem in many areas, as is the continual spread of the eucalyptus tree, a species imported from Australia, actively promoted by the paper industry since the mid-20th century. Galicia is one of the more forested areas of Spain, but the majority of Galicia's plantations, usually growing eucalyptus or pine, lack any formal management. Massive eucalyptus, especially Eucalyptus globulus plantation, began in the Francisco Franco era, largely on behalf of the paper company Empresa Nacional de Celulosas de Espana (ENCE) in Pontevedra, which wanted it for its pulp. Wood products figure significantly in Galicia's economy. Apart from tree plantations Galicia is also notable for the extensive surface occupied by meadows used for animal husbandry, especially cattle , an important activity. Hydroelectric development in most rivers has been a serious concern for local conservationists during the last decades. Question: What kind of development on rivers are conservationists concerned about?
Output:
Hydroelectric