The structure of a hedge
From the herbaceous vegetation at the bottom, to the woody shrubs that make up the structure and the trees that tower above the hedge canopy, all the parts that make up a hedge play a role for wildlife.
1. Hedgerow trees
especially old trees, benefit birds, bats invertebrates and more.
- We are seeing the loss of hedgerow trees and also a lack of recruitment of young trees. Current rates of young tree recruitment are less half the number we need to maintain the tree population.
- Trees are important for many bird behaviours, and are used as song-posts and territory markers.
- Oak and willow trees can support over 400 insect species each.
- Old trees can also contain dead wood, a rare habitat, home to a number of rare specialist species.
- Over half of our priority species associated with hedgerows are dependent on hedgerow trees
2. A diverse shrub layer
Hedges with a greater diversity in shrub plant species, have a higher diversity of invertebrate and birds. Greater variety in woody species increases the variety and year round availability of food sources. Native shrubs and woody species provide a better habitat for insect and animal species than introduced ones as more of our native wildlife have adapted to eat them.
3. Hedgerow height and width
Increasing the width and height of a hedgerow increases the diversity and abundance of wildlife within it. Many farmland birds depend on hedgerows for nesting. Larger and more complex hedges provide better shelter for foraging birds and reduced predation for nesting birds
4. Structural complexity
Some species need several hedge features throughout their lifecycle. E.g a song thrush nests in the bush shrub of a hedge, sings from hedgerow trees and eats snails living in the base of the hedge before swapping to hedgerow berries later on in the season.
The extent to which a hedgerow is connected to other hedges and to the wider landscape influences how useful it is as a corridor for wildlife. Corridors play a vital role for many species that are at risk from habitat fragmentation. Fragmentation is the limiting factor for the distribution of some of our species in the UK and thought to be a treat to survival of others.
Dormice, bats, hedgehogs, birds and butterflies can all depend on hedgerows for dispersal.
6. A hedge margin
A margin between the base of the hedge and any cultivation or disturbance will protect the roots of the structural hedge shrubs and trees. This area can also be very herb rich when it is protected from drifting spray and fertilizer.
Birds, small mammals and insects all use this valuable habitat. The larvae of many butterflies and other invertebrates feed on the grasses and herb layer in the margin.
7. Hedge base vegetation
Dense vegetation at the base of a hedge is crucially important to wildlife. This includes nesting birds, insects, reptiles and small mammals. The vegetation at the base of a hedge can grow thin through herbicide spraying, over grazing or shading if the hedge has become over-grown. In the latter case, laying the hedge will help restore it