Image copyright Olivier Jacquet Image caption Sorbonne lecture: Paris could have a mega-university, if those broken up after 1968 are re-united

Universities across Europe are talking about merging or forming alliances like never before.

Almost 100 mergers have taken place since the beginning of the century. The European University Association (EUA), representing universities in 47 countries, is mapping this changing landscape with an interactive merger map.

And the pace is accelerating, with eight super-universities or clusters identified in 2012; 12 in 2013 and 14 in 2014.

So what's driving the merger mania?

Is it a way of climbing world university rankings by concentrating the best brains and resources to attract more students and bigger research grants?

Or is it a way of responding to funding cuts?

Thomas Estermann, director for governance, funding and public policy development at the EUA, says bigger numbers of staff and students give these super-universities more clout.

Global reach

Bigger universities can gain higher profiles and boost global reputations, he says.

Mergers are also a way of "streamlining" and reducing duplication.

Image copyright Thinkstock Image caption Estonia has reduced the number of institutions by more than a quarter

In some cases it will be a way of coping with a demographic decline of young people.

The EUA says mergers gathered pace from 2005 onwards, with Denmark and Estonia being the early trendsetters.

More stories from the BBC's Knowledge economy series looking at education from a global perspective and how to get in touch

Estonia cut its number of higher education institutions from 41 to 29 between 2000-2012. The University of Tallin in the country's capital capital absorbed eight smaller institutes and colleges.

In Denmark, the number of universities was reduced from 12 to eight and government research centres integrated into the university sector.

French fashion

France now leads the way with mergers with a government-inspired initiative to gather universities and research centres into umbrella-like communities - "communes" - and then to consider full mergers.

One of the biggest amalgamations, the Paris-Saclay "federal university", includes the highly-ranked Ecole Polytechnique, the HEC business school and Universite Paris-Sud.

Image copyright Olivier Jacquet Image caption The Sorbonne could become part of a much bigger Paris university in the next few years

This has the explicit aim of creating a institution which will be in the top 10 of global rankings.

Now it looks like Paris will go one step further, following successful university mergers in Strasbourg, Bordeaux and Marseille.

In the heart of the Latin Quarter, two of the French capital's most prestigious institutions - Paris-Sorbonne and Pierre and Marie Curie (UPMC) Universities - are planning to recreate the spirit of the old unified University of Paris which was torn apart after the student riots of 1968.

Back then, the French government allowed the University of Paris - one of the oldest in the world, founded around 1150 - to split into 13 autonomous universities along faculty lines, often referred to as Paris 1, 2, 3 and so on up to 13.

The 'old Sorbonne'

Professor Jean Chambaz, president of UPMC - Paris 6 - said: "One of the limitations of French universities came about 40 years ago when they separated along disciplinary lines.

"One had all sciences, another only the humanities, another just law and economics.

Image copyright Andrea Fabry/KIT Image caption Karlsruhe Institute of Technology (KIT) is a German merger that has boosted research income

"We were the science and medical faculties of the Sorbonne, of the University of Paris, before the split in 1970."

"Today UPMC's focus is science, engineering and medicine; at Paris-Sorbonne it is arts and humanities. But to address the challenges of the world, we need to build a comprehensive university containing all these disciplines.

"At the moment in Paris, we don't have mergers, but autonomous institutions working in partnership, like our own Sorbonne University group, which includes research centres, the private INSEAD business school, as well as Paris-Sorbonne, UPMC and some other institutions.

"In February, we will have elections for presidents and boards of both Paris-Sorbonne and UPMC. Providing the new members agree, we will press ahead with a full merger and create the new university by 1 January 2018.

"In some ways we are recreating the old Sorbonne, but in the 21st Century."

Professor Barthelemy Jobert, president of Paris-Sorbonne University - Paris 4 - is enthusiastic about creating a powerful global research university covering all disciplines and capable of rivalling the best in the world.

"Success will be creating a new model of a global university in France, with independent autonomous faculties as well as a presidency who will speak for the whole university."

The French government favours such mergers, but is leaving it to the universities to decide.

Professors Jobert and Chambaz see eye-to-eye on the merger, but say it is vital to win support from academics, technical and administrative staff and students.

KIT a German MIT?

Prof Chambaz says they are learning from other European examples of successful government-backed mergers, such as Germany's Karlsruhe University and Karlsruhe Research Centre merging into Karlsruhe Institute of Technology (KIT).

Image copyright Pierre Kitmacher Image caption The University Pierre et Marie Curie could be part of the new Paris super-university

With the goal of repeating the success of the Massachusetts Institute of Technology (MIT) in the US, KIT has increased student numbers by 20% since 2009 and concentrated research on fields such as energy and mobility.

It enjoyed a 50% boost to research income between 2009 and 2013.

The new Aalto University in the Finnish capital, Helsinki, had government backing to combine institutions.

Helsinki School of Economics, Helsinki University of Technology and the University of Arts and Design, Helsinki were merged, with the aim of turbo-charging Finland's higher education system.

It wanted to tackle the relative poor performance of Finland's universities, compared with the country's top ratings at school level in the Pisa test rankings.

Image copyright Olivier Jacquet Image caption Prof Jobert (left) from Paris-Sorbonne and Prof Chambaz from UPMC are discussing a merger

"The new university was designed to put innovation and impact on the knowledge economy at the heart of things," said Aalto's vice president, Hannu Seristo.

And the new bigger university climbed almost 50 places in this year's QS rankings.

But not all mergers are so enthusiastically supported by government.

The University of Lisbon and Technical University of Lisbon, Portugal, had to "actively convince" public authorities to secure approval to merge into Universidade de Lisboa and justify the costs involved.

And that's just the point, says Mr Estermann. "Mergers need a lot of time and energy to be successful. Saving money should not be the main reason to merge as return on investment can take a long time.

"They shouldn't be forced. We're talking about autonomous institutions and not a company takeover."