(30)In order to assess the effectiveness of the national emission reduction commitments laid down in this Directive, Member States should also monitor the impacts of air pollution on terrestrial and aquatic ecosystems, and report such impacts. In order to ensure a cost-effective approach, Member States should be able to use the optional monitoring indicators referred to in this Directive and should coordinate with other monitoring programmes established pursuant to related Directives and, if appropriate, to the LRTAP Convention.