The Great Barrier Reef and the bumphead parrotfish

When asking the question of whether wilderness is merely a luxury and whether Australia can afford to “lock up” areas as national parks, an important answer is found not on land, but in the sea: the Great Barrier Reef National Marine Park.

Established in 1975, the Great Barrier Reef National Marine Park extends for 2,300 kilometres along the northeast coast of Australia, from the tip of Cape York nearly to Bundaberg. Its area is 344,400 square kilometres, more than Tasmania and Victoria combined. Make no mistake, however, this area is not locked up, rather it is a multiple-use park. The park is explicitly managed for “ecologically sustainable use”, including commercial, recreational, and indigenous fishing. In 2004, however, the no-fishing (“no take”) areas of the park were expanded from 4.5 per cent to 33.3 per cent. Importantly, this protective action has not diminished - and indeed may have increased - the economic value of this park for Australia.

Protection for one-third of the Great Barrier Reef from fishing makes it one of the last best refuges for the “polar bear” of the South Pacific, the bumphead parrotfish. And the bumphead is not your average fish in the sea. Each adult, which can grow to 1.3m in length and 50kg in weight, consumes more than 5 tons of coral per year, which it then excretes as the white coral sands that make the region’s beaches so breathtakingly beautiful. Its coral-trimming action protects coral reefs by removing dead coral and opening up new areas for coral colonisation and making reefs more resilient to storms and other events.

Dr David Bellwood and other scientists examining the ecological roles of reef fishes single out the bumphead as the only one of 3,000 fishes studied that plays such a weighty role in structuring coral reef ecosystems. Ecosystem resilience, provided in part by the bumphead, may turn out to be the single greatest defence for the Indo-Pacific’s coral reefs in a world racked by climate change.

Coral reefs, in turn, provide abundant benefits to human economies. The Great Barrier Reef furnishes some $5.4 billion per year in revenue to Australia, according to a 2007 Access Economics report, with 94 per cent of this value derived from tourism. Globally, scientists estimate the value of ecosystems services of coral reefs at a staggering US$375 billion; these services take the form of providing fish habitat, tourism, and protection of coastlines.

Beyond the monetary realm, protection of coral reef ecosystems is vital to safeguarding human coastal populations from impacts of extreme weather events. Coral reefs are also the most diverse marine ecosystems globally, supporting one-third of the world’s fishes, while comprising less than 0.1 per cent of marine areas. Their value is incalculably high.

But coral reefs face numerous perils. The International Union for Conservation of Nature (IUCN) reports that more than one-quarter (27 per cent) of reef-building coral are threatened across the globe. The IUCN further estimates that more than half of the planet’s reefs have been lost or are under threat from overexploitation, destructive fishing practices, damaging land uses, and climate change. The latter ushers in escalating harms to coral reefs, including coral bleaching, rising sea levels, ocean acidification (which impedes some corals’ ability to grow), increasingly severe and frequent storms, and possibly coral diseases. While Australia’s reefs are faring better than reefs of South-East Asia, that is likely due, in part, to protection of the Great Barrier Reef.

The bumphead’s vulnerability to fishing has been well-documented by scientists. As the largest of all parrotfish, they are especially vulnerable to extinction due to their large body size. Compounding this is their habit of sleeping in groups on reefs at night, where they are vulnerable to spearfishing. In addition to being targeted by fishers, they possess other traits - especially slow maturation and low reproductive rates - that make them vulnerable to extinction. Compounding these factors are shrinking remnant populations and range reductions, which expose the species to elimination from random events.

Marine parks areas such as the Great Barrier Reef further the conservation of this species, but existing protected areas and fishing restrictions across their range (which includes portions of the Pacific and Indo-Pacific off Australia, Asia, and Africa) are not currently extensive or well-enforced enough to prevent the bumphead parrotfish from extinction. This is especially true in light of the burgeoning human population within the parrotfish’s range. Some countries within its range have astoundingly high fertility rates, of more than 5.0 children per adult female human: more than double the replacement rate. The US territory of Guam plans a massive influx of military personnel to the island. With more people in its range, and large numbers of those people targeting bumphead parrotfish for food or ceremony, or degrading its coastal reef habitat, this species requires maximum protections.

But the bumphead’s tale extends to other large fish as well, as big fish stocks have declined by 90 per cent since 1950. On the Great Barrier Reef, species to be concerned about include the humphead wrasse, white-tip and grey reef sharks, and groupers, according to scientists such as Dr Douglas Fenner. The humphead wrasse can grow to 2.3m in length and 191kg in weight. Giant groupers can reach 2.7m long and weigh up to 310kg. All of these large-bodied predators are generally slow to reproduce and often have high economic value. For example, humpheads may garner up to US$130 per kg in markets.

In addition to commercial value, sharks face another danger: they are often persecuted by humans because of generally exaggerated fears of shark attacks. Yet, while sharks cause only five human deaths across the globe every year, humans cause 100 million shark deaths. As a result of killing for commercial reasons or through persecution, the majority of sharks are now imperiled. A 2006 study headed up by Dr William D. Robbins found that on the Great Barrier Reef, sharks are fewer in areas where fishing is allowed; and no-go areas (the park’s Preservation Zones) are crucially important for safeguarding shark populations. Most concerning was their finding that white tip sharks are declining by 7 per cent every year on the Great Barrier Reef and grey reef sharks by 17 per cent. These scientists warn that enforcement of no-take regulations is imperative to prevent shark declines within the park.

Like the bumphead, apex predators such as sharks and groupers play important roles in maintaining a diverse reef ecosystem. But they are becoming increasingly imperiled world-wide. The reason is quite simple: us. On reefs that are nearly pristine, large fish comprise approximately one-half of the total reef biomass, whereas on reefs near human populations, big fish generally contribute only a small proportion of overall biomass.

If anything, the Great Barrier Reef Marine Park and its big fish deserve more safeguards, given their tremendous value and the many threats they endure. Climate change is an especial concern, as adverse effects from coral bleaching and ocean acidification have already been documented. The failure of the Copenhagen climate change talks to provide a global solution to greenhouse gas emissions and resulting climate effects underscores the need for nations, such as Australia and the US, to double up national efforts to reduce emissions. In the face of climate change and burgeoning human populations, no-take areas on the Great Barrier Reef and other locations within the bumphead’s range are imperative to ensure this key ecosystem actor and other big fish can persist.

The return benefits from such actions are manifold: from the tremendous and growing economic value of tourism, the safeguards healthy reefs provide for human coastal populations, to the moral imperative of ensuring that our actions help rather than hurt the diverse community of life in the sea.