Environmental Weeds

• explain how habitat disturbance from soil degradation can advantage introduced species of plants and lead to the reduction or elimination of native flora and fauna species in affected areas

Weeds A weed is a plant that is out of place. Native plants could be classified as a

garden weed if, for example, they were growing in a vegetable garden.

Environmental weeds are plants that are growing outside of their natural habitat.

Environmental weeds Environmental weeds have usually been

introduced into new locations. Most environmental weeds are introduced from

outside Australia e.g. Camphor Laurel, Lantana Some environmental weeds are native to

different parts of Australia, e.g. Umbrella Tree, Fishbone Fern.

Some native plants have become established in new habitats due to human disturbance and become environmental weeds, e.g. Sweet Pittosporum.

Types of environmental weeds Annuals and groundcovers, e.g. Farmers

Friend, Fleabane. These tend to be shortlived and only do short term damage to an ecosystem.

Vines, e.g. Madiera Vine, Cats Claw Creeper. These can completely smother the canopy of even established trees and cause mid to long term habitat damage.

Woody trees, e.g. Camphor Laurel, Privet. These can permanently change the ecosystem.

Features of environmental weeds Because environmental weeds are

introduced into areas outside of their natural habitat they don’t have many of the pests and diseases that help keep native plants in balance, e.g. seed predators, etc.

Environmental weeds are often fast growing, prolific seeders and fast germinating.

Camphor Laurel is also allelopathic – oils from its leaves can inhibit the germination of native plants.

Habitat disturbance Environmental weeds rarely invade intact

habitats. The more degraded a habitat is, especially

through soil disturbance, the easier it is for environmental weeds to become established.

Soil disturbance can remove the seed bank of established native trees – some native seeds can remain dormant for tens of years.

Increased light levels will favour weeds in rainforest habitats while lack of fire will tend to favour weeds in sclerophyll habitats.

Impacts of weeds Environmental weeds tend to reduce

the diversity and abundance of native plants.

Some weeds can replace native plants in ecosystem processes, e.g. Camphor Laurel has replaced native laurels in the diet of many native birds.

Through lower plant diversity some faunal diversity may also be lowered, e.g. reduction in specialist species.

Camphor Laurel:Cinnamomum camphora

Small-leaved Privet:Ligustrum sinense

Madeira Vine:Anredera cordifolia

Cat’s Claw Creeper:Macfadyena unguis-cati

Umbrella Tree:Schefflera actinophylla