woensdag 30 juni 2010

From complex regions to complex worlds, C.S.Holling

Living systems both persist and innovate at the same time.

A pattern of two phases of growth is generated, followed by two phases of reorganisation. The first two form a familiar, slow, fairly predictable pattern of growth called the “forward loop”; the second two constitute a less familiar, unpredictable and – in ecosystems – more rapid “back loop” of reorganization.

It is the two together that make the cycle adaptive. Novel elements can accumulate, largely unexpressed during the forward loop. Then – in the back loop – they become the seeds for the novel combinations that launch the next cycle. However the ecosystem cycle is embedded in a set of those cycles that cross scales in space and time from leaves, to trees, to patches, to stands, to forests, to biomes.

Finally an important aspect of the adaptive cycle concept lies in the cross-scale effects. Scales ranging from leaves to biomes and from centimeters and days to hundreds of kilometers and millennia. The structures along that hierarchy affect one another by opening up the possibility of the appearance of small-scale novelty during a back loop, followed by a cascade to larger scales. At the same time, persistence is encourages by the memory of large-scale properties such as seeds stores, institutional structures that influence the renewal of a smaller-scale cycle as suggested.