What is habitat fragmentation and what does it mean for our wildlife?

Habitat fragmentation is a major problem for wildlife in the UK and across the world. But what exactly does it mean and why is it such a concern?

What is habitat fragmentation?

Fragmentation happens when parts of a habitat are destroyed, leaving behind smaller unconnected areas. This can occur naturally, as a result of fire or volcanic eruptions, but is normally due to human activity.

A simple example is the construction of a road through a woodland. For much of the wildlife that lives in the wood, the road is an obstacle that can only be crossed with difficulty, or not at all. A barrier has been created that effectively divides the wood. What was once one habitat has become two smaller habitats.

What are the effects of habitat fragmentation?

Habitat fragmentation can negatively impact wildlife in several ways.

Loss of total habitat area 

The destruction of habitat leaves species with less space to find everything they need to survive. For example, ancient woodland now covers just 2% of the UK. This means the many species that rely on this irreplaceable habitat have limited space in which to live.

Reduction in habitat quality 

Fragmented habitats are often lower quality. This is known as the ‘edge effect’. As a habitat is broken into smaller sections, the proportion of edge - where one habitat meets another - increases.

While some species can thrive along habitat edges, others struggle to survive. For instance, species that have evolved to live in the interior of a wood are less suited to its edge, where conditions are quite different. Examples of wildlife affected in this way are varied, ranging from birds like the treecreeper to lichens and mosses.

Increased extinction risk 

Fragmentation limits wildlife mobility. Individuals struggle to move between habitat patches, which can lead to inbreeding and a loss of genetic diversity. This reduces the long-term health of a population, making it more vulnerable to disease and at greater risk of extinction.

Habitat fragmentation in action

The dormouse (Muscardinus avellanarius) is a perfect example of a UK species affected by fragmentation. These tiny rodents spend most of their life among trees and can only travel small distances across open ground. As a result, the continued loss and damage of our native woods and the hedgerows that once connected them has been disastrous.

Unable to move between the fragmented pockets of habitat that remain, dormice are confined to isolated areas. Cut off, populations are at risk from inbreeding and loss of genetic diversity. This has contributed to dormice numbers falling by more than 50% since 1995.

How can you help?

We're addressing habitat fragmentation by taking a landscape-scale approach to conservation. This means we consider the role of woods and trees in the wider environment. We want to create a network of woods and trees that is bigger, better and more joined up by:

• fighting to prevent any loss of ancient woodland

• planting millions of native trees to buffer and extend ancient woodland, create new woods, and improve the connectivity of fragmented habitat across landscapes.

Do your bit to help combat habitat fragmentation by planting a tree - or several. Trees outside woods can provide habitat in their own right. They also serve as ‘stepping stones’ for species to move through landscapes.