Habitat destruction is the leading cause of extinctions (see graphic immediately below). Preserving habitat therefore helps to preserve biodiversity.
In addition to the many roles that diverse species play in ecosystems, humans directly benefit from biodiversity in many ways as well. Some reasons that we need biodiversity are summarized in the graphic below.
It is an area that is protected by law from human interference.
In all countries there are areas with ecosystems of special interest, like forests, coral reefs,oasis, and any other type of ecosystem. The country might be interested in that area because of an endangered species or a rare one. Or the area could be of an international interest.
In this case and in order to prevent any deterioration caused by human activity to it, regulations are set by the government to protect this area. Some times it is fenced, some other it has its own natural boundaries. Guards are contracted to monitor the application of the laws in this area, and of course there are penalties for the people who do not follow the rules. This area is a preserve.