A Eurasian beaver that was reintroduced in Devon, UKNature Picture Library/AlamyBetween 1990 and 2014, forests in Europe expanded by 13 million hectares, an area roughly equivalent to the size of Greece but that came with a cost. Crops consumed in the European Union had to be grown somewhere, so, in other countries mainly tropical nations around 11 million hectares of forest was chopped down to make up for the drop in EU production.Such biodiversity leakage is a major problem with conservation and rewilding projects, particularly schemes in higher-income, industrialised countries that tend to have lower biodiversity, says