Just had some news about the farm I am buying.

Is this common practice in Catalonia that government can take away part of your land just because nobody worked on the land for years and some pines managed  be seeded from neighboring natural park????? 

A proper sytem for land registration is quite new in Spain. That is why a lot of land is not properly registered. Often land is used by a private owner, but not registred on his or her name. Formally the land will then be registred as owned by the government.

My finca was partly registered as private and partly not registred. The non-registred part was in a natura 2000 area and -because of the lack of private registred owner-, registered on the governement.

In the process of buying and registering my finca there was made a public delaration to give anyone the option to claim the unregistered part. No one made a legal claim within in a month and so it become legally mine.

As Rita already pointed out: a solicitor (or a notary) can tell you what to do in your case.

Good luck,
Mark

Just to update and put closure to this topic.
I have waited for couple of months for reply only to find out that the place been advertised again so I have gave up on this.

Still on the look out for a decent finca with Legal house.