Causal networks

Overview

What are causal networks?

Causal networks are models that describe the relationships between climate, adaptation options and outcomes for environmental, cultural, social, and economic values and assets (adapted from (Peeters et al. 2022)). They include the links which form the basis of the Driver-indicator-response models (e.g. EWR tool: hydrology to indicators), in addition to the links that connect indicators to objectives that are defined for key values.

Tip

In HydroBOT (and hence, this website), we use the word ‘theme’ to refer to the dimension described by the causal network, scaling typically from proximate, granular values (e.g. fish spawning) to larger-scale values such as species, groups of species, or decadal management targets. In the paper describing HydroBOT, this dimension is referred to as ‘value’, representing the use of ‘value’ defined in the sense of an ‘ecological value’, i.e. any social, economic, environmental or cultural asset or function of significance, importance, worth, or use. While that use of ‘value’ is closest to the meaning of this dimension, we do not use it in HydroBOT or here because in describing the functioning of HydroBOT, the word ‘value’ is too easily confused with its meaning as ‘a number’ or even more generally a state, such as the ‘value’ of a function argument.

Causal networks can show many relationships and outcomes. To illustrate here, we show the links between EWRs (hydrologic indicators), proximate environmental objectives, larger-scale objectives, and finally broad-based ecological groupings.

Where do they come from?

The causal networks for environmental values relevant to the EWR tool, and so along the environmental ‘theme dimension’, are derived from specific documents detailing the relationships between indicators and objectives for those bottom-line elements. Other ‘theme’ dimensions, e.g. cultural, social, or economic would have separate causal networks linking different values relevant to those themes. For the present example, we focus on environmental values in two catchments of the Murray-Darling Basin and so we draw the causal relationships from the Long Term Water Plans (LTWPs) produced by the states (e.g. DEW 2020; DRDMW 2022; DELWP and Department of Environment, Land, Water, and Planning 2022; Planning, Environment, and State of NSW 2023). The LTWPs report the environmental water requirements (EWRs) for spatially explicit objectives to be achieved. These objectives are aimed to support the completion of all elements of a lifecycle of an organism or group of organisms (taxonomic or spatial). Objectives are described for five target groups and are associated with long-term targets (5, 10, and 20 year) of the LTWP’s management strategies. The links from EWRs to environmental objectives to long-term targets are captured in the causal networks to enable assessment of outcomes in direct equivalence to the LTWPs’ management strategies.

How are they useful?

The causal networks enables 1) visual representation of the complex inter-relationships between scenario inputs (hydrographs) and river-related outcomes and 2) assessment of outcomes aggregated along the thematic dimension. The former, aids transparency, elucidating the targets and causal relationships behind the Driver-indicator-response models and is a useful device for communication about HydroBOT and its outputs. The latter allows outcomes to be assessed for individual (or sets of) environmental objectives, target groups, long-term targets, or at larger theme groupings to identify synergies and trade-offs among values.

In HydroBOT

HydroBOT provides various functions for creation and manipulation of causal networks, depending on what needs to be plotted or investigated, and the causal plots page provides some examples of various ways they can be visualised with HydroBOT.

HydroBOT provides the causal network for the EWR tool in the HydroBOT::causal_ewr data. Until recently, this was the only source. More recently (early 2025), the EWR tool itself provides its own causal networks. These are brought over to HydroBOT and become HydroBOT::causal_ewr after testing. This process happens frequently, but if there is any question about whether the networks are current, the network in the installed version of py-ewr can be accessed with HydroBOT::get_causal_ewr().

Other networks can be supplied by the user to all functions that require them. In this case, the network requirements are to be a data frame or list of dataframes with the relevant mapping between levels and any other grouping variables. I.e. there might be columns for spatial units if the network varies in space, and then the ‘level1’ column might contain several rows with different values that all have the same value in the ‘level2’ column. See the structure of causal_ewr for an example.

References

DELWP, and Department of Environment, Land, Water, and Planning. 2022. “Environmental Water Management Plan Guidelines for Rivers and Wetlands.” https://www.water.vic.gov.au/waterways/water-for-the-environment/how-we-manage-water-for-the-environment/environmental-water-management-plans.

DEW. 2020. “Long-Term Environmental Watering Plan for the South Australian River Murray Water Resource Plan Area.”

DRDMW. 2022. “Warrego Paroo Bulloo and Nebine Long-Term Watering Plan.” https://qldgov.softlinkhosting.com.au:443/liberty/OpacLogin?mode=BASIC&openDetail=true&corporation=DERM&action=search&queryTerm=uuid%3D%22035ea76f0a0200f06b1dc0e0000be0d7%22&editionUuid=035ea76f0a0200f06b1dc0e0000be0d7&operator=OR&url=%2Fopac%2Fsearch.do.

Peeters, Luk J. M., Kate L. Holland, Cameron Huddlestone-Holmes, and Andrew J. Boulton. 2022. “A Spatial Causal Network Approach for Multi-Stressor Risk Analysis and Mapping for Environmental Impact Assessments.” Science of The Total Environment 802 (January): 149845. https://doi.org/10.1016/j.scitotenv.2021.149845.

Planning, Department of, Environment, and State of NSW. 2023. “NSW Long Term Water Plans: Background Information a Description of the Development of the 9 LTWPs in NSW Part c: Environmental Water Requirements.” Parramatta. https://www.environment.nsw.gov.au/sites/default/files/long-term-water-plans-background-information-part-c-230052.pdf.