From degradation to restoration: Using the past to shine the pathway to waterway recovery

BIO Web of Conferences 196, 02002 (2025) SMILS III https://doi.org/10.1051/bioconf/202519602002 From degradation to restoration: using the past to shine the pathway to waterway recovery Peter Gell1*, 2 1Future Regions Research Centre, Federation University, Ballarat, Australia; for Paleolimnology, Diponegoro University, Semarang, Indonesia. 2Cluster Abstract. Humanity has exceeded sustainability boundaries for factors that sustain aquatic ecosystems and so society is operating outside Safe Operating Spaces: those within which society has evolved over the long term. Our inland waterways have suffered through loss and degradation through the industrial revolution. The degree of biodiversity loss in inland waterways exceeds that of the oceans and the land and freshwater vertebrates are at great risk of extinction. The Ramsar Convention was established to arrest the loss and degradation of the world’s most significant wetlands. While the Convention has been effective in slowing this trajectory many wetlands have been lost or degraded since it was signed in 1971. The UN Decade of Restoration calls on nations to work to allow our ecosystems to recover from the impacts of industrialised people. This goal require us to identify desirable ecosystem states that act as targets for management. By characterising past, natural variability we can see the planetary boundaries we have exceeded, envision the factors that need addressing and acknowledge the magnitude of the challenge to return to sustainable states. The Society for Ecological Restoration identifies ‘appropriate native baseline’ as a target for restoration measures. This past condition of our inland waterways is readily identifiable through historical approaches including through paleolimnological techniques. The recognition of this past state is essential in assisting us to rebuild ecosystem resilience in the pursuit of a sustainable future within Planetary Boundaries. 1 Introduction By any measure it is clear that humanity has reached a fork in the road to sustainability. At a global level the recently revised assessment [1] of our position with respect to the boundaries for safe operating spaces suggests that our socio-ecological system has surpassed safe levels for six of nine life-support systems. Specifically, humanity is now in ‘unsafe’ territory with respect to: Climate Change – the concentration of CO2 in the atmosphere approaches 430 ppm at a rate of over 3 ppm/yr, leading to intense storms, widespread flooding and wildfire, and impacts at the coast from sea-level rise; *Corresponding author: © The Authors, published by EDP Sciences. This is an open access article distributed under the terms of the Creative Commons Attribution License 4.0 (https://creativecommons.org/licenses/by/4.0/). BIO Web of Conferences 196, 02002 (2025) SMILS III • • • • • https://doi.org/10.1051/bioconf/202519602002 Biospheric Integrity – the Living Planet Index reveals the index for biodiversity since 1970 declined by 30 with the decline of freshwater populations exceeding 80 [2]; Biogeochemical Flows – the flux of nitrogen and phosphorus is at unsustainable levels driving hazardous algal blooms; Novel Entities – invasive species continue to degrade ecosystems and now consume much of the world’s biodiversity conservation budget; Land-System Change – the clearance and degradation of native habitat continues largely unabated, even in developed countries such as Australia; Freshwater Change – Inland waterways continue to be impacted by impoundment, invasive species, poor water quality, wetland drainage and now suffer from emergent impacts such as microplastics [3]. Some of these measures have passed their boundaries since the first assessment and so the trajectory of change is negative. This has considerable implications for humanity with productivity in decline as the human population increases and our homes at direct risk from fire, drought and inundation. There are plans for an orderly retreat from rising seas. The very habitability of the Earth is under threat. The planet’s biodiversity is on track for catastrophe. This too has serious implications for humanity as nature provides services that are essential for human communities. The provision of safe food and water are fundamental and depend on these ecosystem services, as does our mental well-being. At the local level this decline can be felt in the heat domes that impact Europe and North America, the unprecedented Karenia bloom that is decimating coastal wildlife in South Australia, loss of life due to cyclonic storms and flooding in central America and Asia and coastal inundation with highest rates of subsidence in Jakarta and Semarang [4]. 2 Inland Waterways The Living Planet Index [2] identified the biodiversity of inland waters as among the most threatened on Earth. The index for freshwater vertebrates declines almost 4% p.a., a rate 4x that for terrestrial populations. He et al.[5] recognised freshwater vertebrates as the most threatened vertebrates at risk of extinction. Many of these were amphibians at risk through the spread of chytrid fungus however fish and turtles were also highly threatened. We are witnessing the pauperisation of the world’s aquatic fauna. Dudgeon et al. [6] identified 5 major drivers of decline in freshwater systems: 1. 2. 3. 4. 5. Overexploitation – increasing freshwater harvest of fish and bycatch; Water Pollution – increasing despite limited mitigation measures with new hazardous pollutants now recognised; Flow Modification – many dams are planned with little regard for ecological consequences; Destruction or Degradation of Habitat – accelerating as expanding human populations increase all threats; Invasion by Exotic Species – established populations are increasing as new invasives exploit increasing human mobility. These persist today although there has been some attempt to decommission impoundments and let some rivers run free. These measures are countered however by the construction of new impoundments such as Three Gorges Dam whose impacts will be realised over coming decades. Perversely, the call for more impoundments come as means to 2 BIO Web of Conferences 196, 02002 (2025) SMILS III https://doi.org/10.1051/bioconf/202519602002 overcome poor water quality and reduced water availability under drought. These threats are now regarded as persistent to freshwater systems and now act in concert with emerging threats whose impacts are recently being evaluated. The emerging threats [3] comprise: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. Changing Climates E-commerce and Invasions Infectious Diseases Harmful Algal Blooms Expanding Hydropower Emerging Contaminants Engineered Nanomaterials Microplastic Pollution Light and Noise Freshwater salinisation Declining Calcium Cumulative Stressors Humans have impacted freshwater systems for millennia [10]. Many of the world’s major rivers were seriously polluted in the 19th century with the (...truncated)