Healthy environment

Biodiversity – the variety of plants, animals and micro-organisms in a region – delivers vital benefits to Victorians including clean air, fresh water and fertile soils.

Planned burning and bushfires can impact the health of the environment and also support plant and animals species that need fire for their survival.

We are charged with building the health of Victoria's biodiversity and this can sometimes involve the use of fire as a management tool. We balance this important obligation with a responsibility to manage bushfire risk to life, property and the environment.

To be successful we must reduce the risk of bushfire in a way that avoids unacceptable impacts.

Associate Professor Alan York of the School of Ecosystem and Forest Sciences from the University of Melbourne discusses the role of fire in ecosystem resilience at Science In Use, the DELWP Science symposium 2015.

Healthy ecosystems provide us with clean air, water, carbon storage, forest products and diverse plants and animals, as well as opportunities for recreation and enjoyment. Maintaining ecosystems that are resilient to external shocks is important in ensuring healthy environments that continue providing these benefits.

Our management approach seeks to maintain or improve ecosystem resilience. We are taking a whole-of-system approach that builds on our management of threatened and vulnerable species, as required under the Environmental Protection and Biodiversity Conservation Act (Cth) and the Flora and Fauna Guarantee Act (Vic), to focus on ecosystem stability, diversity and disturbance as a whole. This involves developing ecological models and measures of ecosystem resilience under different fire regimes.

We base our environmental management approach around the concept of ecosystem resilience, which is defined as:

An ecosystem’s capacity to absorb both natural and management imposed disturbance but still retain its basic structure – in terms of species abundance and composition – function and identity over space and time.

Understanding the impact of fire on ecosystems requires first being able to define and measure ecosystem resilience. This is complex and we can't directly measure all aspects of ecosystem resilience.

We use Tolerable Fire Interval (TFI) as a broad indicator of resilience at a regional level. We have also developed additional measures – Geometric Mean Abundance (GMA) and vegetation Growth Stage Structure (GSS) - to understand resilience and the impacts of fire. Other factors such as climate change, water availability and pest plants and animals also influence resilience.

We will continue to expand our understanding to develop more sophisticated measures of ecosystem resilience.

Groups of plants (vegetation communities) develop through growth stages that have distinguishing features, the same way humans do (e.g. juvenile, adolescent, mature).

The chart below shows the proportion of Victoria's vegetation within growth stages, at various times over the past 25 years.

Maintaining a diversity of growth stages (juvenile, adolescent, mature and old) in an ecosystem or landscape can help to improve ecosystem resilience. We can calculate a desired growth stage structure to maximise GMA for an ecosystem so that a range of species occur.

DELWP sets a goal of having a diverse range of growth stages, which provide habitats for lots of different species. Planned burning can be used to manage a landscape so that overall, it is moving toward a desired growth stage structure. It can also be used to minimise the risk that bushfires remove all the older vegetation. This is important because it takes decades for juvenile vegetation to become old-growth after a fire.

Find out more about GSS on the Fuel Management Report on the  Forest Fire Management  Victoria page.

Our management approach seeks to balance the need to reduce impacts to life and property and maintain ecosystem resilience. We currently use thresholds around the proportion of the landscape below minimum TFI and above maximum TFI that act as triggers in bushfire management planning processes. We will use similar thresholds for species diversity (Geometric Mean Abundance) and Habitat/Growth Stages (Vegetation Growth Stage Structure).

In the Barwon Otways Bushfire Risk region, we have trialled the use of GMA and GSS as measures of ecosystem resilience. Developing this approach has involved working with the University of Melbourne to determine what mix of growth stages would maximise the diversity of flora and fauna in the landscape. We then compared this ideal mix to the current distribution as well as proposed fire management strategies, to understand the impact of fire management.

By improving our understanding and ability to model how fire impacts ecosystem resilience, we can find the appropriate balance of fire in the region.

DELWP is also working with the University of Melbourne to develop tools to integrate measures of ecosystem resilience into bushfire management planning.

Click here to see how we're using Science and Technology to build knowledge of the relationship between fire and the environment.