Spontaneous reforestation of mountainous landscapes: global lessons from Europe

Spontaneous reforestation of vast former pastoral and agricultural lands may occur in mountainous regions due to socio-economic, political, and climatic factors. As a consequence, several animal and plant species will undergo changes in their habitat quality, behaviour and demography, which finally may reduce connectivity. Historical sources attest that such trends have cyclically occurred in Europe. Once again, Europe is largely affected by the abandonment and spontaneous reforestation of mountainous old-fields. Similar trends in other continents might be underestimated due to long-term effects, time lags in ecological responses, and absence of economic interest towards the land uses which are being lost. Moreover, landscapes where these changes take place are a mixture of open and closed tree and shrub canopies, hence the shrinking of fragmented habitats is rather difficult to be appreciated, unless long-term monitoring is available. In addition to those being threatened, some of the affected species may be of interest for humans, hence a reduction of services' provision is possible. As a conclusion, it is important to raise awareness of the issue and to develop a forum of scientists and practitioners also from regions outside Europe.