Increasingly, the contribution of natural ecosystems to economic wealth, through their multi-use benefits to society, is being recognised. The concept of ecosystem accounting emerged as a useful tool to integrate such capital value as a component in the System of National Accounts, internationally used to track change in economic activity over time. Along our coasts, estuaries are especially valuable. Situated at the river-sea interface, these unique retention zones are incredibly productive and offer sheltered nurseries for numerous aquatic organisms. “No wonder they are often described as ‘super ecosystems’,” says Principal Researcher Prof. Lara van Niekerk.

Building on an earlier national ecosystem account for South Africa’s 290 estuaries, two principal researchers at the Council for Scientific and Industrial Research (CSIR), Profs. Susan Taljaard and Van Niekerk partnered in the first research study to apply ecosystem accounting at the individual estuary level. Supported by a Department of Science, Technology and Innovation Parliamentary Grant and the Community of Practice in the Western Indian Ocean regions’ Ocean Accounts Framework of the National Research Foundation, the duo teamed up with Prof. Janine Adams and Dr Tarryn Riddin of the Nelson Mandela University to apply ecosystem accounting in the Swartkops Estuary, now published in the South African Journal of Science.

Situated in the city of Gqeberha, the Swartkops Estuary has been the subject of numerous research studies for many years, generating a wealth of ecological information. Despite abundant data showing the estuary’s key role in supporting regional biodiversity and associated societal benefits, it is subjected to continued industrial and residential development transformation. Ecosystem accounting was therefore viewed as a new, innovative approach to communicate the critical importance of the Swartkops Estuary’s natural assets in a politically and managerially relatable manner.

Introducing pressure accounting

Ultimately, the protection and maintenance of natural ecosystems and their socioeconomic value involves the management of activities that threaten the integrity of these systems. In the case of estuaries, such pressures may include inappropriate freshwater flow modification, pollution, land use and development, over-exploitation of natural resources, and alien invasives. To address these pressures, the research team introduced the concept of pressure accounting in their suite of physical accounts. “These pressure accounts demonstrate a simple and practical manner to track change in possible causes of impact on individual estuaries, critical knowledge to inform future management efforts to recover or maintain ecosystem value,” says Van Niekerk.

Compromised, but opportunity remains for ecosystem service delivery

Physical ecosystem accounting primarily aims to quantify change over time in the extent and condition of an ecosystem as well as change in associated ecosystem services. Using a 79-year data record, the research team could estimate the change in extent and condition of an array of non-living and living habitats in the Swartkops estuary from 1942 to 2018 and in 2021. Results showed a marked loss of 42% in non-living habitats (floodplains, beaches, dunes, mud, sand banks, and open water areas) between 1942 and 2018, with a 42% decline in living habitats (intertidal, supratidal marshes, algae, reeds, sedges, and floodplain vegetation) during this same period. These losses accounted for a 47% decline in the overall condition of the Swartkops Estuary during this period, with incremental conditions losses even from 2018 to 2021. Matching these results with output from the pressure account, the research team could show that flow modification, land use and development, and pollution contributed most to the decline in the health of the Swartkops Estuary. “Because the pressure account is largely categorised on this sectoral basis, it becomes easy to identify and inform the responsible authority mandated to manage impacting activities,” says Van Niekerk.

Carbon sequestration and recreational use were used to inform change in key ecosystem services provided by the Swartkops Estuary. While the system still supports carbon sequestration, losses in intertidal and supratidal salt marsh habitats since 1942 have markedly reduced this value proposition. Suitability from recreational use also has been noticeably compromised during this period due to severe pollution, posing risks to human health. “Notwithstanding this decline in ecosystem service value, some of this can be restored through living habitat restoration and improved wastewater (pollution) management,” says Taljaard.

The urgency to maintain and restore natural capital

The urgency to maintain and restore the world’s natural capital is echoed in the United Nation’s Decade of Restoration (2021–2030). Ecosystem accounting provides a valuable tool to inform the required investment and resource needs to maintain or restore natural habitats, as well as acting as a monitoring and reporting tool to track progress.

Estuarine ecosystems continue to support societies with food and livelihoods even though they are more threatened than most other natural systems and still receive much lower levels of formal ecosystem protection. This is despite them being relatively small systems most vulnerable to global pressures, and offering disproportionally higher socio-economic benefits per unit area compared to other natural realms.

“By demonstrating the application of ecosystem accounting at the individual estuary level, we hope to offer a workable approach to inform local governance management and restoration efforts (‘bottom-up’) to contribute to the UN’s global Decade of Restoration initiative (‘top-down’) and that can be rolled out to other estuaries,” says Taljaard. “To better reflect the real opportunity cost of estuarine ecosystem decline, we hope to work with resource economists to develop monetary accounts for ecosystem services as well, linked to these physical accounts,” Van Niekerk adds.

Taljaard and Van Niekerk are also recipients of the Runner-Up Award for the annual Outstanding Article Award 2023 from the South African Journal of Science for their publication, acknowledging their contribution to valuing the country’s estuarine assets towards safeguarding future lives and livelihoods.

References

Taljaard S, Van Niekerk L, Adams JB, Riddin T. Advancing ecosystem accounting in estuaries Swartkops Estuary case study. S Afr J Sci. 2023;119(3/4), Art. #14303.

The published paper is available at https://doi.org/10.17159/sajs.2023/14303