Find out how weeds threaten biodiversity and what we are doing about it.

What are weeds?

Over 1,600 plant species have been identified as weeds in New South Wales. A weed is a plant growing where it is not wanted. Weeds can move into ecosystems where they have not previously existed and typically grow and reproduce rapidly. Weeds are invasive plants and are most often introduced species.

Weeds can thrive and persist in many different environments, from urban and rural areas to deserts, bushland, alpine, coastal and ocean habitats.

Why are weeds a problem?

Weeds pose a serious threat to our environment and farming industries. They can harm native plants and animals, natural landscapes, water catchments and agriculture and can impact the economy, human health and recreational activities.

Environmental weeds threaten the biodiversity of our native plants and animals by:

  • reducing the diversity and abundance of native species
  • upsetting the balance of natural ecosystems.

Weeds compete with native plant species for nutrients, water, sunlight and space. They can form dense areas of vegetation that shade and smother native species and may alter key environmental events such as the frequency of fire. This can threaten both native plants and the animals that rely on them for food and shelter.

Weed infestations can also reduce the aesthetic appeal of our natural environment for public recreation and appreciation and impact production land where they may reduce agricultural output.

The NSW Department of Primary Industries is the lead government agency for weed management in New South Wales and is responsible for implementing the Biosecurity Act 2015.

The Department of Climate Change, Energy, the Environment and Water develops and implements strategies for invasive species on lands managed by the National Parks and Wildlife Service (NPWS). The department also has an advisory role on environmental invasive species management across all of New South Wales. It is responsible for the Saving our Species program, which identifies specific strategies to address the key threatening processes that threaten biodiversity conservation and threatened species.

Statewide strategy

The key document guiding weed management is the New South Wales Invasive Species Plan 2023–2028.

The best way to manage the spread of weeds is to prevent them growing in the first place. The plan aims to prevent new incursions, contain existing ones and minimise the impact of widespread weed species.

As part of the Department of Climate Change, Energy, the Environment and Water, the National Parks and Wildlife Service (NPWS) manages weeds on national parks and reserves, in collaboration with other groups and agencies such as Local Land Services and local councils for a statewide, cross-tenure management approach.

We manage weeds using:

  • specific threat abatement plans
  • regional pest management strategies.

Under the Threatened Species Conservation Act 1995, NPWS developed threat abatement plans for weeds listed as key threatening processes. This legislation has been replaced by the Biodiversity Conservation Act 2016.

NPWS has also prepared regional pest management strategies to manage weeds and pest animals in national parks and reserves across New South Wales. These strategies provide a tactical approach to pest animal and weed management and follow the NSW Biosecurity Strategy and the Invasive Species Plan.

Weed management priorities

Weeds are prioritised based on the stage of invasion and the size of the area invaded. For new and emerging weeds, those which have a small number of localised populations or are rapidly increasing in abundance, the priority is to eradicate and/or contain the threat. For weeds which are widespread and abundant, asset-based protection is undertaken where weeds may threaten biodiversity, vulnerable species or ecological communities.

Climate change is predicted to be the greatest long-term threat to biodiversity in many areas. Human-caused climate change has been listed as a key threatening process. Given the current threat posed by weeds to the environment, agriculture and human health, there is significant interest in understanding the likely impact of climate change on weed abundance and distributions in Australia.

In 2010, we developed the Priorities for Biodiversity Adaptation to Climate Change report to highlight the likely effect of climate change on weeds.

We have also worked with Macquarie University to model the distribution of significant weed species in New South Wales and to predict the effects of climate change on their potential distribution. Over 1,600 plant species are known to be weeds in New South Wales, so a select group of weeds of national and state importance was selected for modelling. Visit the Weed Futures website for the results of this study.