Marine ecologists have been remarkably successful in advancing our knowledge of how strong local interactions affect the composition of communities, yet it is not yet clear how the results of small-scale experiments can be scaled up into broad scale generalizations. This is one of the major challenges of rocky intertidal ecology since practical, everyday concerns of management, commercial harvesting, biodiversity, and restoration demand answers on the scale of square kilometers of habitat, not square meters of experimental site. One current approach has been to use teams of researchers undertake identical small-scale experiments over a broad geographical region (e.g., EuroRock in Great Britain and Europe) or over similar oceanographic conditions (e.g., the ongoing studies of rocky shore in upwelling systems on the Pacific Rim by PISCO). Another approach has been the integration of 'real time' physical, chemical, biological data from in situ and remote sensors (e.g., satellites that can reveal near shore temperature and primary productivity) with experimental studies on community dynamics.
Neither approach solves the difficulties of working with large mobile consumers such as mammals, whose importance is under appreciated because of the difficulties inherent with studying mammals. Even the rat (Rattus norvegicus) - the most widely recorded introduced intertidal mammal with the broadest documented intertidal diet - likely remains underreported as a rocky intertidal consumer from many coastal locations where it is known to be established. It is likely that rocky intertidal organisms supply terrestrial consumers significant amounts of energy, yet there are few data on intertidal-terrestrial linkages and how intertidal shores serve as important subsidies for terrestrial habitats.
It is also unclear if detailed information from one area can be informative about another area. For example, rocky intertidal shores on both sides of the Atlantic Ocean look surprisingly alike with not only the same species of plants and animals present but also similarities in their abundances and distributions. The similarity is so striking that a good marine ecologist, knowing little more than the direction of the prevailing swells, can list the 20 most common species on any 100 m stretch of shoreline. The average beachcomber could not tell if he or she were in Brittany, Ireland, Nova Scotia or Maine. The causes of this similarity are not well understood. Rocky shores in Europe and North America may look similar because of strong biological interactions maintain species in balance or because of historical accident, and these opposing views are endpoints on a continuum but represent one of the major intellectual debates in ecology today.
Finally ecosystems are not static, and rocky intertidal systems, which lie at a land-sea boundary, will be doubly affected by climate change as both oceanic conditions such as storm frequency and surge extent, and terrestrial conditions, such as air temperatures, are altered. Such changes could affect local communities by altering the disturbance dynamics and changing the geographic limits of intertidal species.
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