What have we learned about ecological recovery from liming interventions of acid lakes in Canada and Italy?

The idea of launching another special issue of the Journal of limnology on Lake Orta was born in 2014, on the 25^th anniversary of its liming intervention, during an International symposium on Lake Orta organized and hosted by the Pallanza Institute (http://www.ise.cnr.it/vb). The conference did not simply celebrate the past. While the liming of Lake Orta was undoubtedly a great national and international success, the speakers at the conference, instead sought to enlarge and deepen knowledge of patterns and mechanisms of lake ecosystem responses to the water quality improvements, or chemical recovery, that accompanied Lake Orta’s liming.