Romania will suspend new hydropower projects in protected areas in a bid to preserve biodiversity, authorities and the conservationist group WWF said Tuesday.

The planned construction of thousands of small-scale hydropower stations across the Carpathian mountains in eastern Europe threatens hundreds of streams and rivers, the WWF has warned for years.

The building frenzy has been prompted by hefty government subsidies.

Around 20,000 Romanians have signed a petition over the last two months calling on the government to save mountain streams that are key to endangered species such as otters.

"We are not against investment in energy, but some streams have such an ecological value that we cannot destroy them for the sake of immediate profit," WWF director in Romania Magor Csibi told journalists.

Forests and Water Minister Lucia Varga promised that a joint commission would decide which natural areas should be free from hydropower plants to protect biodiversity.

These so-called "exclusion zones" should be established by May 31.

Small-scale hydroelectric production generally does not involve the construction of a dam. Instead, part of the flow is diverted through a pipe to a downstream turbine which generates the electricity.

In theory, this should not have a big impact on the environment.

But in many cases pipes have been installed in the bed of the stream and diverted water amounts to as much as 80 percent of the flow, posing lasting threats to biodiversity, environmentalists say.