Australia Floods: The Human and Marine Toll

The recent Australian floods had an enormous impact on the lives of hundreds of thousands of people—including myself. And now that impact has been exacerbated by cyclone Yasi.

While the total damages from these natural disasters are still being assessed, there’s no doubt that the human toll is massive (read below for my personal story). But less publicized is how the floods will also wreak havoc on the marine ecosystems off the coast of Brisbane.

First, my story:

In mid-January, after years of intense drought, the state of Queensland in eastern Australia was devastated by one of the worst floods on record. A La Niña event brought unusually high rainfall to our state: at one point, two-thirds of Queensland was flooded and declared a disaster zone.

The floods started in the north before heading south along the catchment of the Great Barrier Reef to Brisbane—our state capital and my home.

My house is one block from the Brisbane River and was expected to flood. But I was lucky. The torrential rains stopped just before the flood waters were expected to peak and Wivenhoe Dam (constructed for flood mitigation) closed its gates, saving my house along with thousands of others.

Others were not so fortunate. More than 20 people lost their lives; thousands lost their homes or businesses. The economic cost of the floods will likely be in the billions.

When the rain finally stopped, it was eerily quiet. We had lost power and phone service, and most of my neighbors had evacuated.

In the worst-affected suburbs, the army and police closed off the roads that had become gridlocked. As people tried to get back to their homes on roads buried in sewage-infested mud, the smell, chaos, and helicopters over head made Brisbane feel like a war zone.

What followed was one of the greatest demonstrations of humanity and community spirit I’ve seen. Once the flood waters subsided, an army of volunteers rolled up their sleeves and started to clean up the mess. There were literally thousands of people, side-by-side, shoveling mud.

Since I was one of the lucky ones, I helped my friends Mark and Lexa clean up their lovely home, which had been inundated by water and was covered in mud. It was incredible how many people came to help—lots of friends, but also an endless stream of strangers who just turned up prepared to help in any way they could. (See Mark’s photos of the day.)

While I was wading through the mud, I couldn’t help but wonder what the flood had done to the marine environments downstream. Surely all that water, mud, debris and goodness-knows-what-else were damaging the marine environment in Moreton Bay (off Brisbane) and the Great Barrier Reef (GBR) further north. The human toll was immense—but what about the environmental cost?

I asked Jon Brodie, an expert in the effects of water quality on marine environments from the Australian Centre for Tropical Freshwater Research, to explain the likely impacts of the floods on Moreton Bay and the GBR.

Here’s what he said:

“Due to the early, prolonged and heavy wet season in Queensland, most east-coast rivers have had major flood events. And many of these rivers have deposited their overflow into Moreton Bay and the Great Barrier Reef.

“In some cases, the discharges have formed large flood plumes that extend up to 100km offshore and have headed north up the coast to distances of 250 km. [figure above]

“The river discharge contains freshwater but also, in the case of these highly developed catchments, heavy loads of pollutants. These include suspended sediment (from erosion), nitrogen and phosphorus compounds (from erosion and fertilizer losses), and pesticides (from agriculture) in amounts far greater than what would have been present in the rivers in pre-development times.

“From previous events of this type, we know that coral feel a direct effect. The influx of freshwater is damaging, but its impact is exacerbated by the debris the floodwater carries off. In 1991, a large flood in the Fitzroy River caused almost 100 percent coral mortality in the shallow parts of reefs about 50km from the river’s mouth.

We expect to see coral bleaching and mortality after these floods, too.

“Seagrasses will also be harmed by the floods. In 1992 and 1999, flood events in the Mary River caused extensive seagrass mortality offshore in Hervey Bay. Due to the lack of seagrass, dugongs subsequently experienced food shortages and large population declines. I believe we can expect to see similar effects from the recent floods.

“In addition to these acute effects, the delivery of this extreme load of pollutants will have severe long term effects on reef health along the GBR south of Cooktown. Coral cover has declined dramatically in the GBR over the last 40 years, from averages of near 55 percent to approximately 25 percent. This can be attributed to a combination of stresses, including climate change and water quality effects (including crown-of-thorns starfish damage). The current pollutant load will contribute to the continuation of this decline.

However there are some positives. Recent Australian Government initiatives like Reef Rescue are directing $200 million toward improving farming practices to protect the GBR. The Queensland Government has introduced reef protection legislation for the same purpose, and similar programs have been in place in the Moreton Bay catchment for several years. If these programs are prolonged over a few decades, we should see large improvements in water quality in the rivers discharging to the GBR and Moreton Bay.

“The outpouring of support Ali witnessed in Brisbane was inspiring. Hopefully, in the wake of this massive flooding, we’ll see similar efforts to help the offshore marine environments of eastern Australia recover.”

I received this response before Yasi struck. Jon is currently without power, but he has let me know he’s alright. The cyclone is likely to have profound effects on the GBR, and it’s been a rough few months for the marine ecosystems of Queensland.

Research into the impact of the floods on the GBR and Moreton Bay is just beginning and will continue for many years. You can follow the results of this research on the Great Barrier Reef Marine Park Authority’s website and Southeast Queensland Healthy Waterways website with the latest information available at and

(Image: Bleached corals in the Great Barrier Reef. Source: Flicker user mattk1979 via a Creative Commons license)

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