Ecological Succession

Ecological succession is the sequence of community changes following disturbance. A cleared forest doesn’t stay bare. First come pioneer species — fast-growing, sun-loving, short-lived. They create shade. Shade-tolerant species establish beneath them. Over decades, forest returns. The sequence isn’t random; it’s patterned.

Henry Chandler Cowles documented succession in the Indiana Dunes in the 1890s. Different distances from Lake Michigan represented different ages since sand deposition. Near the lake: bare sand. Further: beach grasses. Further still: cottonwoods and pines. At the greatest distance: oaks and hickories. Space became a proxy for time.

Primary succession begins on substrate without soil — lava flows, retreating glaciers, newly formed islands. Life must build from nothing. Lichens crack rock. Mosses catch organic matter. Centuries pass before soil accumulates. Krakatoa, sterilized by eruption in 1883, took decades to develop forest.

Secondary succession follows disturbance that leaves soil intact — fire, logging, abandonment of agricultural fields. The process is faster because seeds remain in soil, root systems survive, nutrients persist. An abandoned New England farm may become forest within a century. The old stone walls remain beneath the trees.

The classic view held that succession led to stable “climax communities” determined by climate. Oak-hickory forest in the eastern US. Spruce-fir in the boreal north. The climax represented equilibrium — the community that would persist indefinitely without disturbance.

Modern ecology complicates this. Disturbance is normal — fire, storms, disease, herbivory constantly reset portions of landscapes. The notion of a single endpoint fades. Instead: shifting mosaics, multiple stable states, history-dependent outcomes. Succession describes trajectories rather than destinations.

The pattern reflects changing environmental conditions that organisms themselves create. Early colonizers tolerate harsh conditions but create conditions favoring later species. Shade, soil nutrients, moisture retention — the pioneers make the environment less suitable for themselves and more suitable for their replacors. Facilitation drives the sequence.

But not always. Sometimes early occupants inhibit later ones by monopolizing resources. Sometimes success is a lottery — whoever arrives first persists. The mechanisms vary by species and context. Succession describes a pattern; multiple processes produce it.

Go Deeper

Books

The Song of the Dodo by David Quammen — Island biogeography and extinction, with beautiful sections on ecological dynamics.
Reading the Forested Landscape by Tom Wessels — A field guide to decoding New England succession from stone walls, stumps, and forest structure.
Botany of Desire by Michael Pollan — On how plants exploit human preferences — a different angle on ecological relationships.

Essays

Henry Chandler Cowles’ 1899 papers on Indiana Dunes succession — The origin of the concept. Published in Botanical Gazette.
Eugene Odum’s work on ecosystem development — Mid-20th century synthesis of succession theory.

Places

The Indiana Dunes (now a National Park) — Where Cowles developed succession theory. Different zones still visible.
Mount St. Helens — Primary succession in progress since 1980, extensively studied.

Related: [[ecology]], [[keystone-species]], [[trophic-cascades]], [[scenius]]