No conservation restriction held by any governmental body or by a charitable, educational or other corporation, association, trust or other entity whose purposes include conservation of land or water areas or of a particular such area, no preservation restriction held by any governmental body or by a charitable, educational or other corporation, association, trust or other entity whose purposes include preservation of structures or sites of historical significance or of a particular such structure or site and no agricultural preservation restriction held by any governmental body or charitable corporation, trust or other entity whose purposes include preservation of land or water areas predominantly in their agricultural state shall be unenforceable against any owner of the restricted land or structure on account of lack of privity of estate or contract or lack of benefit to particular land or on account of the benefit being assignable or being assigned to any other governmental body or to any entity with like purposes. This section shall not be construed to imply that any restriction, easement, covenant or condition which does not have the benefit of this section shall, on account of any provisions hereof, be unenforceable. Any doctrine of law which might otherwise cause the termination of such a restriction shall not be affected by the provisions of this subdivision.