"Let Bosnia and Herzegovina's rivers run free," DiCaprio tweeted underscoring that the construction mini hydropower plants presents a grave risk to thousands of kilometres of wild rivers in that country.
DiCaprio was supporting the start of a campaign by environmentalists and nongovernment organisations aimed at protecting Bosnia and Herzegovina's rivers.
The NGO called Foundation for Social Change recalled that Wednesday in fact was the deadline when a resolution adopted by the the Croat-Bosniak Federation parliament in June was to be implemented to completely ban the construction of mini hydropower plants in that entity.
"We are sending an urgent call to Federation authorities to permanently ban this type of construction by turning the resolution into law otherwise thousands of kilometres of wild rivers in Bosnia and Herzegovina, and the lives of animals and people will be gravely jeopardised," the NGO said in its call.
The parliament in the Serb entity - Republika Srpska - had previously rejected the initiative.
Several NGOs have formed a coalition to protect the rivers and recalled that 430 small hydropower plants had already been constructed in the country and several more are planned, which would devastate some of the most preserved and most diverse rivers and forests in Europe.
The coalition believes that rivers between Slovenia and Albania, including those in Bosnia and Herzegovina, are the most important hubs for endangered biological diversity of fresh water species in Europe while 69 species that live in those rivers cannot be found anywhere else in the world.