Land use, watershed processes, and coastal biodiversity can be strongly coupled. Land-sea interactions are ignored, however, when selecting terrestrial and marine reserves with existing models, with the risk that reserves will fail to achieve their conservation objectives. The conceptual model underlying existing reserve selection models presumes each site is a closed ecological system, unaffected by inputs from elsewhere. As a short-term objective, we recommend extending land conservation analyses to account for effects on marine biodiversity by consideration of linkages between them. This level of integration seems tractable and directly relevant to agencies and conservancies engaged in protecting coastal lands. We propose an approach that evaluates terrestrial sites based on whether they benefit or harm marine species or habitats. We then illustrate the approach with an example on the Central Coast of California, USA. Whether the effort will produce more effective terrestrial reserves needs to be proven.