Coastal zone conservation and management: a biological indicator of climatic influences

1. Management of new coastal conservation areas refocuses attention on the need to distinguish between the effects of natural and man‐made factors, and to ensure that global warming does not erroneously become a catch‐all explanation for future ecological changes. 2. With world distribution related to latitudinal temperature gradients the most sensitive responses to temperature will be seen at species’ geographical limits. 3. Northernmost populations often lack young age classes, and have a dominance of old individuals capable of surviving and reproducing after transfer to cold areas beyond their present limits. 4. Northern limits are therefore being set primarily by inadequate repopulation rates, which in poor seasons may extend many hundreds of kilometres to the south. 5. Confirmation of a warming trend here will reside in increasingly regular repopulation, reversal of the age structure and northward colonization by planktonic larvae. 6. Appropriate scenarios exist for southern limits and for species without planktonic stages. 7. A chain of north and south geographical limits along continental coastlines will indicate where temperature‐induced changes could be taking place generally. 8. Attempts to establish such a system in the 1980s failed for lack of financial support. Current attitudes, political will, etc., are discussed, and irrespective of its utility as a management tool such a project could form a fitting baseline for the century of climatic change. Copyright © 1999 John Wiley & Sons, Ltd.