Succession and Intervention

If human activity over the last 5,000 years has transformed Britain so that nothing is truly "natural," why do we bother designating nature reserves? The answer lies in understanding the natural process of succession.

What is Ecological Succession?

Succession is the process by which nature recolonises a cleared area. If left alone, most land in Britain will undergo a series of stages to return to woodland. 

The Stages of Succession:

• Stage 1: An open area is first colonised by hardy grasses and flowering plants.

• Stage 2: Over time, shrubs appear, and the area becomes "scrubby."

• Stage 3: Trees begin to develop within the scrub, signalling the final transition toward woodland.

The Climax Habitat

Eventually, an area reaches a point where no further succession is possible; this is called the climax habitat. While this is usually woodland, environmental factors like soil or climate can create different climax states. 

• Example: In boggy areas, the ground is too wet for trees to grow, so the "climax" remains a wetland.

Why Isn’t Britain Covered in Trees?

If succession is constant, why is our countryside a patchwork of different habitats? The process is frequently halted or reversed by interventions: 

Type of Intervention

• Natural Events: Storms (falling trees) or lightning strikes (fires).

• Human Activity: Felling trees for fuel or grazing livestock

This "permanent cessation" of succession is actually beneficial. It allows specific plants and animals to find a niche and prosper in habitats that would otherwise disappear.

Managing for Biodiversity

Many of our nature reserves are actively managed to keep succession at bay. To a casual observer, cutting down trees or clearing scrub can look like habitat destruction, but it is actually a vital effort to maintain unique, ancient habitats. 

Common Managed Habitat Types

The type of habitat created depends on when the intervention occurs in the succession cycle: 

• Grassland & Heath: Created by very early intervention (e.g., heavy grazing). 

• Scrub Habitat: Formed if intervention occurs after shrubs like hawthorn or bramble take hold but before trees mature. 

• Broadleaf Woodland: Formed if succession is allowed to continue, creating a rich environment of mosses, fungi, and birds. 

Mosaics and Transitions

Nature rarely has clear lines. You may find:

• Transitions: A gradual shift from one habitat to another where species from both areas overlap. 

• Mosaics: A mix of habitats in the same area, such as a heathland that contains patches of acid grassland. 

The Lesson: Chalk grasslands and heaths are not "natural," but they are ancient and stable. They only remain biodiverse if we continue the human interventions that created them.