* Green Party keeps distance under new premier Valls
* Royal's pro-environment record could keep Greens on board
* Nuclear, shale, growth pressures will test her pro-renewables credentials
By Andrew Callus and Benjamin Mallet
PARIS, April 2 (Reuters) - Former French presidential candidate Segolene Royal brings green credentials, a high profile and strong political ambition to her new role as energy and environment minister at a crucial time for industry and government.
The naming in Wednesday's government reshuffle of Royal, an ex-partner of President Francois Hollande, is seen partly as an attempt to maintain Green Party support for an unpopular Socialist government with a thin parliamentary majority.
In 2011, Royal responded to a Greenpeace policy questionnaire with a call for a complete exit from nuclear power within 40 years. She also backed the ban on hydraulic fracturing techniques - or fracking - for shale gas development, and in her constituency of Poitou-Charentes in western France she has pushed hard for renewable power, sustainable farming and energy efficiency.
But environmental activists and politicians are sceptical about whether this record will survive her political ambition in a role that is traditionally occupied by lesser-known figures than Royal, who announced her split from Hollande after losing the 2007 election to Nicolas Sarkozy.
"This appointment will make a noise, which is no doubt the intention," said Greenpeace in a statement. "We hope the personality of the minister will not eclipse the crucial issues linked to the environment portfolio, most specifically energy."
Hollande has promised anti-nuclear and environmentalist campaigners a reduction in France's heavy dependence on nuclear power to 50 percent from 70 by 2025 and a cut in fossil fuel use by 30 percent by 2030 - backed up by a carbon tax.
He has also presided over a ban on the use of the shale gas extraction techniques that have helped to revitalise the U.S. economy and which other European governments are encouraging to reduce their energy bills and boost growth.
Business groups said they hoped that Royal's nomination would not mean they would have to start from scratch in difficult talks undertaken with her predecessor Philippe Martin.
"We had worked closely with the former minister lately. I hope we won't have to start it all over again (and) that we will be able to jump on the train while it's moving," said Jean-Louis Schilansky, head of oil-sector lobby UFIP.
Pro-environment groups already accuse Hollande of foot-dragging on his commitments since he took power in 2012. They now fear the new prime minister Manuel Valls and economy minister Arnaud Montebourg will put growth before ecology.
Experts say nuclear policy in particular is approaching a crucial point, at which decisions need to be taken soon on whether to extend the lives of ageing plants, commit to building new ones, or allow gas-fired stations to fill the gap.
Royal will also be a major player in deciding a replacement for Henri Proglio, head of the state-backed power utility EDF , whose term ends in November, and who is seen as too close to conservative former President Nicolas Sarkozy to stay in his post.
Hollande has enjoyed Green Party support in parliament, where his Socialist Party has a 3-seat majority.
Until Tuesday's reshuffle, which followed a crushing defeat by the right in municipal elections, there were Greens among his ministers. However, the Greens are unwilling to serve in a government led by Valls due to his conservative stance on social issues such as immigration.
With Royal as energy and environment minister though, Valls may still be able to carry their support in big votes such as on new public spending savings and cuts to payroll taxes for business that he wants to pass in the next few weeks.
Taking office, Royal said she was a strong advocate of "social ecology" including water cleanliness, affordable energy, and action on air pollution. She pledged her support for projects ranging from electric cars to ecological construction.
"We see in all that, in this ability to innovate and to create, the amazing capacity France has to face up to the challenges in this area," she said.
Denis Baupin, a Green member of parliament for Paris, said Royal had "undeniable competences" and noted her record in Poitou-Charentes, saying the appointment "signifies clearly that this question of ecology and energy transition is considered important by the government of Manuel Valls".
But Corinne Lepage, environment minister from 1995 to 1997 under the conservative government of Alain Juppe, said she expected the politically ambitious Royal to adhere to the fundamentally pro-nuclear line pursued by France for decades.
"She is a politician before everything else. She's a powerful woman within the Socialist Party." (Additional reporting by Gus Trompiz, Geert de Clercq and Sybille de La Hamaide; editing by Mark John and David Stamp)