Journal on Policy and Complex Systems
have been involved in the loss of the kingdom . Alchin ( 2003 ) describes the rhyme as " often used to gently chastise a child whilst explaining the possible events that may follow a thoughtless act " ( p . 21 ). It is not used to gently explain that it is impossible to say what effect a thoughtless act will have on possible events .
The Keystone and the Topstone
Robert Paine discovered the phenomenon of the keystone species in an experiment during which he removed a single species of sea star from a small area of shoreline and found that it had far-reaching effects on species diversity . Significantly , the effect produced by the removal of the sea star was out of proportion to its relative abundance in the community .
Keystone species , by definition , are nearly impossible to identify without observing what happens when they are removed . Said Paine ( 1969 ):
The two keystone species discussed above have little in common . Pisaster is abundant and is somewhat of a trophic generalist ; Charonia is rare and a food specialist . ... Both are starfish feeding on a variety of prey . ... The significance of these carnivores could not have been guessed beforehand , since other carnivores coexist with them . ( pp . 92 – 93 )
As with the butterfly effect , this first story is about a system in which complex relationships among small influences produce large difficulties in prediction . Again , a second story arose , and again it favors certainty . What I have come to call the topstone story discards the inconvenient aspects of the keystone concept , those having to do with retrospective discovery .
Soon after Paine introduced about his concept , wildlife conservationists started trying to identify keystone species ( without removing them ) in order to wisely use limited conservation budgets . Political , cultural , and special-interest complexities joined the mix , and the keystone species concept widened and weakened as the second story rose up to counter the first . For environmental study , retrospective discovery might suffice , but for environmental action , people wanted predictive certainty .
In the mid-1990s , a group of scientists self-dubbed the " Keystone Cops " was concerned enough about erosion of the concept to convene a special session ( Power et al ., 1996 ). They restored the keystone species concept to intellectual rigor with a new definition , as follows :
[ W ] e define a keystone species as one whose impact on its community or ecosystem is large , and disproportionately large relative to its abundance . ( p . 609 )
Soon after , Piraino and Fanelli ( 1999 ) reminded ecologists to adhere to that definition :
Putting keystones and key species in the same melting pot , as Khanina ( 1998 ) does , should be
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