Eco-1: Challenges with calculating change in ecological value

Modelling is fundamental to sustainability, particularly when measuring the impacts of development on the environment and society. But when your compliance requirements need you to model impacts to say, kangaroos and trees, and provide a single number as your output, what do you do?

ISCA’s Infrastructure Sustainability (IS) rating scheme (version 1.2) emphasises protecting and enhancing ecological areas affected by projects and assets.

The Eco-1 Ecological Value credit requires projects to quantify the percent change to ecological value. For projects adjacent to sensitive habitats, an ecologist must conduct an ecological impact assessment (EcIA) to determine this change. Although this appears conceptually straightforward, verification can be challenging.

An EcIA quantifies and evaluates the predicted impact on individual ecological attributes from a development activity—usually in terms such as hectares of endangered vegetation cleared, or high risk of adverse impactdjndxg on species. Although an EcIA predicts changes to individual attributes, it does not produce a number that quantifies the overall change to the ecological value of an entire site.

This partly arises from the fact that, for example, you can’t add kangaroos and trees together and average them to get a meaningful number. In addition to this ‘apples/oranges’ problem, the Technical Manual (TM) provides a very generalised requirement for calculating ecological value change, making this approach difficult to apply, especially in the absence of an established scientific method.

To address this gap, the IS scheme requires a suitably qualified professional ecologist to conduct this assessment and provide assurance. However, the guidance in the TM is open to interpretation. Given the significant number of points for Eco-1 and the expense of an ecological assessment, this is a high-risk credit.

IS Version 2.0 approach

Although version 2.0 has redesigned the Eco-1 credit, it still requires projects to develop metrics to demonstrate a net gain, or no net loss, in ecological value. Of the six methods it provides, four evaluate a single metric (i.e. vegetation condition) compared to a benchmark. The two remaining methods use metrics to estimate the suitability of offset sites through a ‘balance sheet’ approach. However, these methods may not suit all projects due to inflexible calculation methods, differences in spatial and temporal impacts, or the inability to capture some benefits (e.g. water quality improvements or fauna connectivity structures).

Potential methods for version 1.2 and 2.0

In May 2018, the Building Research Establishment (BRE) released a new method for calculating the change to ecological value for its BREEAM and CEEQUAL rating tools. It employs the change in ‘Biodiversity units’ pre and post development as an indicator of the change to ecological value. Biodiversity units are based on three main attributes:

  • the area or length of habitats
  • their condition, and
  • their distinctiveness.

Each attribute is scored against criteria, and the percent change in overall ecological value is calculated by comparing the change in score pre and post development.

This method can provide a consistent and comparable approach for projects to estimate ecological value change. It also addresses the issue of averaging change across different attributes.

Although designed for British environments, the approach could be adapted to Australian environments. Unfortunately, IS v2.0 was finalised before the BRE method became available.

The NSW Biodiversity Assessment Methodology (BAM) calculates offsetting requirements for projects proposing to clear vegetation or affect biodiversity values in NSW. BAM contains an extensive list of equations for calculating the change to various ecological attributes, such as threatened vegetation, pre and post development, although is only suited to NSW. Coincidently, the equations have similarities to the BRE method and could be adapted to create an Australian equivalent.

BRE’s standardised approach to ecological value may offer those preparing to respond to these credits a good place to start.


Oliver Mitchell is an Environment and Sustainability Consultant with Losee Consulting Pty Ltd. These are his personal thoughts.

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