Environmental-economic accounting for the Mitchell River

Environmental economic accounts are a way to integrate environmental and economic information about an area to better understand the relationships between the environment and the economy, particularly how environmental contributions benefit humanity.

The United Nations’ System of Environmental Economic Accounting – Ecosystem Accounting (SEEA EA) provides a framework for organising data about habitats and landscapes, measuring ecosystem services, tracking changes in ecosystem assets, and linking this information to economic and other human activity.

This project used the SEEA EA framework to develop a set of pilot ecosystem accounts for the Mitchell River catchment in Far North Queensland.

Read more in the project’s final report, methodology report and data inventory.

Layout of the ecosystem accounts for the Mitchell River catchment. 

The Mitchell River is located in Far North Queensland and flows into the Gulf of Carpentaria. Image: Resilient Landscapes Hub.

For tens of thousands of years prior to European invasion and settlement, the ancestors of today’s Traditional Owners of the Mitchell River catchment socialised the landscapes of the region as they managed land and water, fulfilled custodial responsibilities under customary law and maintained an economic system that sustained their way of life. This active management by Traditional Owners continues in many localities today, albeit under constrained conditions.

Three ecosystem types make up 94% of the 71,722 km² of the Mitchell catchment – pyric tussock savannas (78%), subtropical–temperate forested wetlands (10%) and hummock savannas (6%).

There has been only modest change in the areas of most ecosystem types between the pre-clearing era (~1750) and post-clearing (~2015). In total, approximately 916 km² of predominantly pyric tussock savannas, subtropical–temperate forested wetlands and tropical–subtropical montane rainforest have been cleared for grazing, agriculture and horticulture.

Ecosystem extent in the Mitchell River catchment post-clearing (~2015), by ecosystem type. 

An ecosystem condition account was compiled using 39 variables covering ecosystems’ biotic (e.g. species richness, tree cover, fire frequency), abiotic (e.g. erosion, above-ground carbon, number of waterholes) and landscape-level characteristics (e.g. area burned each year, landscape fragmentation).

Key findings from the ecosystem condition account:

• Several ecosystem types are subject to considerable gully erosion.
• The catchment’s ecosystems store large amounts of carbon in above-ground and below-ground biomass, and in the top 30 cm of soils.
• The catchment contains large areas of woody and sparse woody vegetation.

Data on human pressures affecting ecosystems were compiled alongside the condition account. These data showed that:

• Considerable areas of many ecosystem types are burnt more frequently, or less frequently, than recommended for the ecosystems concerned.
• Habitat fragmentation is relatively modest across most of the catchment.
• Episodic land clearing has occurred in some areas of the catchment, although the total area cleared is a small proportion of total catchment area.
• Priority invasive species are widespread across the catchment, with cane toad, feral cat, feral pig, wild dog and rubber vine present in all ecosystem types. The aquatic weeds cabomba, olive hymenachne, salvinia, sagittaria, water hyacinth and water lettuce are present in all aquatic ecosystem types.

Spatial coverage of woody vegetation in 2018, categorised into 3 classes: non-woody vegetation, sparse woody vegetation and woody vegetation (forest). This is an example of a biotic ecosystem condition variable.

Ecosystems in the Mitchell River catchment supply services to humans in the following categories:

• provisioning services (e.g. food, drinking water, timber)
• regulating services (e.g. climate regulation, erosion prevention)
• cultural services (e.g. tourism, recreation).

Provisioning services reported by this research:

• Crop provisioning services into irrigated agriculture (e.g. naturally occurring soil nutrients, trace minerals and soil water that support the production of cultivated crops) were valued at $79 million per year.
• Grazed biomass provisioning services into cattle rearing on cattle stations were valued at $18 million per year.
• Wild fish provisioning services into the commercial barramundi fishery in the Mitchell River delta and coastal zone were valued at $0.2 million per year.

Regulating services reported by this research:

• Global climate regulation services from carbon storage in biomass and soil were valued at $110 million per year and $391 million per year, respectively.
• Global climate regulation services from carbon sequestration from savanna fire management were valued at $3.5 million per year.
• Soil and sediment retention services were acknowledged but not quantified.

Cultural services reported by this research:

• Recreation services provided to domestic and international visitors were valued at $48 million per year.
• Other cultural services that were acknowledged but not quantified include visual amenity services; education, scientific and research services; and spiritual, artistic and symbol services.

Total monetary value per hectare ($/ha) of selected ecosystem services from ecosystem types in the Mitchell River catchment.

Ecosystem accounts can be useful for informing policy direction in the following ways.

• ‘Past-to-present’ trajectories of ecosystem extent, condition, and supply and use of ecosystem services could help identify emerging problems and inform possible policy directions for addressing those problems.
• Accounts can be used to track the effectiveness of policy interventions against pre-defined targets for ecosystem extent, condition or biophysical service supply.

However, because ecosystem accounts only report the values of services that are supplied by ecosystems, they are not well suited for informing decisions on alternative development proposals at specific locations.

We considered various potential methods for including Indigenous-related cultural ecosystem services in the ecosystem accounts for the Mitchell River. Significant challenges arise between SEEA EA’s ‘linear, transactional use value-based’ paradigm and the ‘reciprocal, relational value-based’ paradigm of Traditional Owners. Access issues related to COVID-19 prevented full consultation with Traditional Owners on these topics. Consequently, without endorsement (or otherwise) of potential methodologies, Indigenous-related cultural ecosystem services were not included in our ecosystem account for the Mitchell River. This remains an opportunity for future research.