Hundreds of birch trees from the biggest Nazi death camp, at Auschwitz-Birkenau in Poland, are dotted around Berlin as a living memorial of this dark chapter in Germany's past.

The trees, called Birke in German, lent their name to the Birkenau camp where as many as 1.5 million people, mostly Jews, perished between 1940 and 1945.

The installation "Berlin-Birkenau" by Polish artist Lukasz Surowiec, 26, is part of the Berlin Biennale, a contemporary arts festival devoted this year to political art.

"This is an attempt to create a new kind of monument - a living monument," said Surowiec, who has had commemorative plaques erected in front of the trees. "With the help of nature, I try to continue a generational mission of deepening the memory of the victims of the Holocaust.

"My project is effectively based on giving back the 'inheritance' [of the camps] to its owners."

Biennale director Artur Zmijewski, also Polish, says it seems paradoxical to his compatriots that a place where Germans committed one of the worst crimes against humanity is not in Germany, but in Poland.

This installation, one of many at the Biennale which is not confined to a gallery or museum, is therefore partly about the "politics of history", he said.

The Holocaust and the Palestinian territories are strong themes at the Biennale this year, which is run by the contemporary art centre KW in former East Berlin but sprawls throughout the entire city.

The Berlin Biennale was founded in 1998, inspired by the Venice Biennale, and aims to showcase little established young artists and provide a forum for experimentation.

The seventh edition officially opens on April 27 and runs through until July 1, but many projects such as Surowiec's are already taking place. Zmijewski, 45, has said he wants "the exhibition to become a political space that resembles a parliament more than a museum".

Israeli, Palestinian Art

Israeli artist Yael Bartana, 41, will hold the "First International Congress of The Jewish Renaissance Movement", a symbolic project c a lling for the return of Jews to Poland that she created through video artwork.

"We call for the return of 3.3 million Jews to Poland to symbolize the possibility of our collective imagination - to right the wrongs history has imposed, Bartana says.

From May 11-13, she hosts a "parliamentary debate" on the questions: "How should the EU change in order to welcome the Other? How should Poland change within a re-imagined EU? How should Israel change to become part of the Middle East?"

Palestinian Khaled Jarrar, used the Biennale to develop his artist-activist project staking out Palestinians' right to a sovereign state.

Jarrar, 36, shot to international prominence last year by offering unofficial passport stamps of his own design to foreigners arriving in the occupied territories.

For the Biennale, he created a postage stamp for the "State of Palestine" with a drawing of the Palestine Sun Bird flying near delicate flowers.

The stamp was issued by Deutsche Post and can be used in the regular mail. More than 20,000 stamps have been sold so far.

"After I printed official post stamps in Germany and Netherlands, people started using these stamps to send letters all over the world," he wrote in an email.

"We are not allowed in the Palestinian post office to print postage stamps with the words 'State of Palestine'."

Jarrar said he felt artists should be politically engaged and not just leave it up to politicians to act.

"We should think and work hard to speak out against injustice," he said. "We should make art that will make a difference."

"Art is Politics"

Curator Zmijewski, who focuses on moral and political issues in his own video artwork, told Reuters he wanted to create an atmosphere "in which people start to fantasize about political issues and try to redefine politics".

He believes recent shocks like the financial and debt crises had made civil society more politically engaged, demonstrated by the eruption of protest movements like "Occupy".

This trend towards greater political engagement was reflected in art too, yet he still felt that artists today all too often offered only theoretical questions in their work rather than practical solutions to problems.

During his research for the Biennale, Zmijewski compiled a 400-page thick book on political engagement in culture today - the different strategies deployed and results achieved.

He interviewed artists and artistic-minded politicians or activists, from the Russian underground art collective Voina to a former mayor of Bogota, and entitled the book "Forget Fear".

"Art is politics," said the stern curator, who sports closely cut black hair, a beard and moustache, and rarely smiled during his interview. "We don't have to change existing politics, we can just propose our own politics and even propose a different kind of politician."

Zmijewski said he would prefer to talk politics with artists like Berlin-based Belarus activist Marina Naprushkina than with establishment figures.

When art must act

Naprushkina, whose work is showcased at the Biennale, campaigns with art against the authoritarian regime of Belarus President Alexander Lukashenko.

One of her main actions is the "anti-propaganda office" which gathers and archives "original propaganda material" from Belarus alongside the work of artists.

The office has already been shown in various museums around Europe but reaches Naprushkina's main audience in Belarus via a clandestine newspaper distributed by activists there.

"There is little free press, the state media controls everything," Naprushkina said in an interview. "It's difficult to have a critical view on what's going on so we felt the newspaper was a good way to do that."

Naprushkina said she did sometimes fear for her own safety. But greater than her fear was her instinct to speak out against the government of Lukashenko, who cracked down on the opposition after his re-election for a fourth term in 2010.

"After the election I just knew I had to do something," Naprushkina. "Art can change a lot."

"And when you see that people need that, it gives you a great feeling, a lot of energy," she said, noting that her anti-propaganda website has received as many as 20,000 visitors in one day.

Naprushkina was commissioned by the Biennale to create a special newspaper devoted to coming up with alternative future political models for Belarus "outside of the bloc-building confines of the EU or Russia".

Naprushkina, who now lives in Berlin and fears going back to Belarus, added: "I hope it pushes people to think more, to found cooperatives and ultimately, to get politically engaged."