… our marine parks are among the few places left with any reasonable fish populations, their protection is absolutely critical for your future. 

[Image - Morwong by Simon Mustoe. These fish are the elephants of the reef. They congregate to bulldoze through patches of weed and create dynamic gaps for other species to thrive. They grow to 15kg, about the weight of a Swamp Wallaby]. 

A recent history of decline

There has been an estimated 98-99% of resident reef fish decline since the 1950s [1]. By the turn of the century, most resident reef fish had been absent from rocky reefs in Port Phillip Bay. The consequence is imbalance that flows through almost every component of the ecosystem including the ecosystem services, affecting coastal communities.

In Australia, in particular the southeast, there has been massive decline in reef life, with severe consequences: a point made in recent articles and a 2022 paper led by Graham Edgar from the University of Tasmania[2]. The disappearance of large fish, which are particularly important, is blamed on excessive fishing.    

Edgar et al, place restoration of lost ecosystem structure, a ‘nature-based solution’ as the single greatest need, including to address the burden of nutrient overload and resilience to climate change and food security ([3].

Coastal communities, meanwhile, are largely unaware of the magnitude of the problem or indeed, empowered to be part of a solution. Without upfront community engagement, all other management solutions fail.

Fish hold the ecosystem together

As recently illustrated by Hammerschlag et al [4], aquatic predators function throughout the system, holding it together, and facilitating almost all the ecosystem services we depend on for our livelihoods.

Piecemeal conservation efforts pale into insignificance when compared to facilitative wholistic, natural ecosystem restoration, but this depends on stewardship by cooperative coastal communities – if you’re reading this, the Victorian government already recognises your importance in this process, as they have created a Marine Spatial Planning Framework (more on that in a later update).

The 15th meeting of the Conference of the Parties (COP) to the CBD brought together governments from 196 countries between December 7-19, 2022 in order to approve parts of the post-2020 Global Biodiversity Framework. One of the most substantial agreements is to protect 30% of the world’s land and sea by 2030 (the ’30 x 30′ policy). Victoria is a signatory to this. 

Less well-recognised is the role of wildlife as a foundation for ecosystem recovery and therefore, biodiversity restoration and achieving the Convention’s targets. 

Coastal reef fish defend against erosion and climate warming

There is a substantial and rapidly-growing body of evidence that animals are the main driver for ecosystem structure, function and stability through the transfer, amplification and concentration of energy [3, 5-19]. And that the absence of wildlife hampers or inhibits restoration efforts to adapt to, or build resilience against climate change, by declining human food security and other ecosystem services, through weakened and less certain ecosystem structures [20-27].

This is also well-established in term of reef fish [28-30]. One study has found, that even intermediate levels of species loss would greatly reduce plant production, compared to climate warming. Higher levels of extinction had effects rivalling ozone layer loss, ocean acidification and even nutrient pollution [31]. Meaning, decline in species, has already had a greater impact than most of the major environmental issues today (and therefore, also has a greater potential for restoration). 

The fish that would diversify and sustain the resilience of the ecosystem are the larger megafauna, such as wrasse, that can live for decades and grow to tens of kilos in weight.

A study in the Bahamas has shown, for example, for wrasse species that ‘Interactions between reef zone and size class were significant with the greater frequencies of larger individuals (≥21 cm) driving patterns (positive associations) on forereefs’ [32].

Rebuilding functioning food chains depends on recovering a diversity of wildlife which, in this region, includes the large resident reef fish. Equally, the most recent system-wide analysis of Australian reef life[2] and the global decline in ocean ecosystems points to the urgent priority to address fisheries issues, at all scales[33]. 

Marine ecosystems with fewer species are often functionally compromised, and those with more species are more likely to have functional redundancy[34-36]. Hence, human economies based on ocean ecosystems and their associated marine resources risk being less resilient where ocean ecosystems comprise fewer species diversity and/or low productivity.

People, shallow reef ecosystems and other marine vertebrates are all interdependent because stable ecosystems require structural biomass in the right proportions ([19, 37]). The resilience that brings can help to buffer economies against shifts in climate and other socio-economic change. 

Healthy fish populations are key to our coastal economy

In Australia, where eighty-five per cent of the population lives near the coast, the cost of sea defence construction, maintenance and upgrades has already been shown to be economically unviable[38].

Artificial structures for sea defence are mostly built on sandy substrate and cause ‘varied and severe ecological impacts on coastal habitats’[39]. Meanwhile, it’s been shown that reefs can mitigate most wave energy, ‘[providing] comparable wave attenuation benefits to artificial defences such as breakwaters’ but more importantly, can be enhanced cost effectively.[40]

The impact of natural reef systems is most pronounced when you consider high frequency, low-energy events. Sea defence tends to be focused around the worst events but reefs are far more resilient at addressing the everyday effects, because they don’t exacerbate erosion elsewhere. This offsets rising insurance costs, increasing taxes (to pay for costly engineering maintenance) and the risk of houses falling into the sea.

Analyses by re-insurance companies in the Caribbean, for example, have shown that reef restoration is significantly cheaper and always more cost-effective than breakwaters, across all nations.

Nature-based solutions are cheaper and easierGlobally, there has been a sharp movement towards Nature-based Solutions [3, 38, 41], effectively restoring natural processes that can deliver ongoing ecosystems services at little to no ongoing cost. Overall, coastal engineers have now concluded that “hard stabilization structures usually alter the natural environment of the coast, producing negative impacts.”  [42]

“The proliferation of defence works can affect over half of the shoreline in some regions and results in dramatic changes to the coastal environment. Surprisingly little attention has been paid to the ecological consequences of coastal defence.” [43]

The true value of our marine parks

Nature-based solutions and ecosystem-based management are new channels to faster, lower-cost and better methods for dealing with environmental problems. Because they address symptoms and causes by re-establishing natural pathways for resilience.

Without healthy fish populations we will never achieve this. Your cost of living will continue to rise and your wellbeing will decline. Since our marine parks are among the few places left with any reasonable fish populations, their protection is absolutely critical for your future.

 

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