It is therefore not surprising that a lot of farm, urban and roadside bushland has lost its native understorey. Understorey vegetation is vital for maintaining a balance in natural ecosystems. Many land degradation problems like dieback, erosion and salinity, and pest outbreaks, are linked to the loss of native understorey and trees. Shade from trees and shrubs can increase livestock productivity and survival. Shelterbelts also reduce wind speeds, which can improve stock performance, reduce lambing losses and improve crop and pasture growth by up to 50 per cent.
Shrubs help fill the gaps beneath the tree canopy, providing maximum shelter.
The understorey layer provides habitat for predators which are vital in maintaining an ecological balance between 'pests' and other species. These predators include wasps, birds, spiders, lizards and sugar gliders. Some wasp species lay their eggs in the larvae of Christmas Beetles and locusts. The adult wasps feed on nectar from native flowering shrubs and trees, and will not fly more than several hundred metres from a nectar source. These wasps cannot survive in areas cleared of understorey shrubs.