Floods can be a disaster for humans – but for nature, it's boom time

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Wednesday, November 9, 2022

ShutterstockHumans, as a rule, do not like floods. And three years of La Niña rains have meant Australians have had more than enough of floods. But Australia’s plants and animals have evolved alongside periodic floods, as they have for fire. For them, floods are a boon. These pulses of water are vital to the health of most river floodplain ecosystems. For some native fish, floods create new habitat as the waters fill floodplains, wetlands and creeks. Many trees like river red gums need periodic flooding too. Floods trigger a huge spike in growth. Nutrient-rich sediment is washed downstream and out on to floodplains. This is a boon to algae and aquatic plants at first, and, once the water evaporates, to grasses, shrubs and trees. Herbivores such as wallabies and wombats feast on the new growth. Most of the time, rivers stay in their main channels and floodplains are dry. But in years like this one, so much rain falls that water spills over the banks and fills floodplains. This is a life-giving process which nourishes and replenishes. Without floods, rivers would not be rivers – they’d just be drains, unfit for all but the very hardiest of animals and plants. Herbivores like wallabies flock to the new growth after floods. Shutterstock Why does nature need floods? It’s not all good news for nature. Flooding is a disturbance for wildlife and plants, moving things around and shaking things up. Some animals may drown, high flows may rip out plants and even undermine and topple trees. Low-oxygen blackwater events and fish kills – heartbreaking for many – often follow floods, as they have recently on the Murray. But after the damage comes the boom. Once the initial pulse of water subsides, it often takes much longer for the water to evaporate or drain from the floodplains. Plants killed by the water will add to the organic matter load, which may later be used by other plants. The pulse of nutrients that goes with flooding is wonderful for freshwater phytoplankton (miniscule aquatic plants), as well as zooplankton which feed on them, such as tiny rotifers, known as wheel animals, and crustaceans. Some fish leave the main channel of the river and swim onto their new temporary habitat, feeding on the zooplankton. Waterbirds follow them. Read more: Beyond a state of sandbagging: what can we learn from all the floods, here and overseas? Should the timing be right, native fish like golden and silver perch may breed in floodplain wetlands. Their larvae are poor swimmers, and these still, food-rich water bodies are ideal nurseries. South Australia’s Kati Thanda-Lake Eyre has only filled a handful of times over the last century. But the unprecedented rains this year have partly filled the lake. When water covers the arid land, brine shrimp eggs hatch in their millions and start feeding and breeding. It’s a brief boom for fish, but as the water evaporates, the lake gets saltier and eventually kills the fish. Pelicans, cormorants, terns and gulls head inland to feast on shrimp and dying or dead fish. Birds like red-necked avocets flock to ephemeral lakes like Kati Thanda–Lake Eyre. Graham Winterflood/Flickr, CC BY In northern Australia, many rivers are not dammed, and widespread natural flooding occurs most years. Indigenous people here are accustomed to living alongside flooding and have been making use of the riches of floodplain productivity for more than 50,000 years. Tropical floodplains offer food and habitat to everything from aquatic plants and barramundi to saltwater crocodiles and magpie geese. Freshwater floodplain wetlands like this one on the Roper River floodplain in northern Australia are rich in species - but at risk from climate change. ` Keller Kopf, Author provided In Australia’s south-east, floodwaters generally don’t linger quite as long as they do in the tropical north. But they do rise rapidly – sometimes several metres over only a couple of days. Much of the water will never return to the main channel of the river but will evaporate slowly. Deeper remnants like billabongs, lagoons or oxbow lakes – actually old river channels – linger longest. The giant of Australia’s rivers, the Murray, takes longer to flood because Australia is mostly flat. Pulses of water move slowly down its tributaries to the main channel. It can take weeks to months for rain that falls on the Great Dividing Range to make it to the Murray’s mouth at Goolwa in South Australia. These lingering floodwaters are perfect for freshwater mussels, as well as frogs, lizards, platypus and snakes. Bottlebrushes, wattles, reeds, rushes and aquatic plants do well out of floods too. Of course, introduced species often thrive too. Common carp populations typically boom after floods. And willow trees and other invasive aquatic plants that spread through pieces breaking off, do well on the back of floods. Floodplain fertility can be seen with the naked eye, as in this image of the Murray River flowing through the Riverina in New South Wales. Shutterstock Our uneasy relationship with rivers Nature needs floods. But while you might not believe it, we need them too. Most of the world’s major cities were founded next to rivers, which gave their inhabitants water, fish, transport, and fertile farmland. But for all river cities, there are times when the river surges and can destroy houses and livelihoods. Many cities have tried to tame floods with levees and dams. But as we’re finding now, you can reduce the impact of smaller floods – but the big ones are all but unstoppable. Because we have farmed and settled so many floodplains, farmers are particularly vulnerable to floods. Floodwaters hitting bush will be slowed by trees and plants. But farms are often cleared, which can see more erosion take place. Whole farms can be devastated by flooding, leading to food prices spiking. With climate change, Australia is expected to experience bigger and more frequent floods. This may be a good thing for nature but means people will no longer be able to live safely in some places. It will also mean iconic ecosystems like Kakadu will be at risk, with sea level rise predicted to push saltwater into almost half of its famous wetlands by 2070. While floods bring pain in the short term, over the longer term both humans and nature need the benefits they bring. Read more: Floods play a vital role in ecosystems – it's time to get out of their way Paul Humphries has received funding from the Murray-Darling Basin Authority, the Australian Government’s Commonwealth Environmental Water Office and the Victorian Department of Environment, Land, Water and Planning. Keller Kopf receives funding from the Commonwealth Scientific and Industrial Research Organization, Australian Research Council and the Fisheries Research and Development Corporation.

Floods upend the plans of humans and wildlife – but after the water calms, it’s boom time for nature.

Shutterstock

Humans, as a rule, do not like floods. And three years of La Niña rains have meant Australians have had more than enough of floods.

But Australia’s plants and animals have evolved alongside periodic floods, as they have for fire. For them, floods are a boon. These pulses of water are vital to the health of most river floodplain ecosystems. For some native fish, floods create new habitat as the waters fill floodplains, wetlands and creeks. Many trees like river red gums need periodic flooding too.

Floods trigger a huge spike in growth. Nutrient-rich sediment is washed downstream and out on to floodplains. This is a boon to algae and aquatic plants at first, and, once the water evaporates, to grasses, shrubs and trees. Herbivores such as wallabies and wombats feast on the new growth.

Most of the time, rivers stay in their main channels and floodplains are dry. But in years like this one, so much rain falls that water spills over the banks and fills floodplains. This is a life-giving process which nourishes and replenishes. Without floods, rivers would not be rivers – they’d just be drains, unfit for all but the very hardiest of animals and plants.

wallaby eating
Herbivores like wallabies flock to the new growth after floods. Shutterstock

Why does nature need floods?

It’s not all good news for nature. Flooding is a disturbance for wildlife and plants, moving things around and shaking things up. Some animals may drown, high flows may rip out plants and even undermine and topple trees. Low-oxygen blackwater events and fish kills – heartbreaking for many – often follow floods, as they have recently on the Murray. But after the damage comes the boom.

Once the initial pulse of water subsides, it often takes much longer for the water to evaporate or drain from the floodplains. Plants killed by the water will add to the organic matter load, which may later be used by other plants.

The pulse of nutrients that goes with flooding is wonderful for freshwater phytoplankton (miniscule aquatic plants), as well as zooplankton which feed on them, such as tiny rotifers, known as wheel animals, and crustaceans. Some fish leave the main channel of the river and swim onto their new temporary habitat, feeding on the zooplankton. Waterbirds follow them.


Read more: Beyond a state of sandbagging: what can we learn from all the floods, here and overseas?


Should the timing be right, native fish like golden and silver perch may breed in floodplain wetlands. Their larvae are poor swimmers, and these still, food-rich water bodies are ideal nurseries.

South Australia’s Kati Thanda-Lake Eyre has only filled a handful of times over the last century. But the unprecedented rains this year have partly filled the lake. When water covers the arid land, brine shrimp eggs hatch in their millions and start feeding and breeding. It’s a brief boom for fish, but as the water evaporates, the lake gets saltier and eventually kills the fish. Pelicans, cormorants, terns and gulls head inland to feast on shrimp and dying or dead fish.

red necked avocet
Birds like red-necked avocets flock to ephemeral lakes like Kati Thanda–Lake Eyre. Graham Winterflood/Flickr, CC BY

In northern Australia, many rivers are not dammed, and widespread natural flooding occurs most years. Indigenous people here are accustomed to living alongside flooding and have been making use of the riches of floodplain productivity for more than 50,000 years. Tropical floodplains offer food and habitat to everything from aquatic plants and barramundi to saltwater crocodiles and magpie geese.

roper river wetland
Freshwater floodplain wetlands like this one on the Roper River floodplain in northern Australia are rich in species - but at risk from climate change. ` Keller Kopf, Author provided

In Australia’s south-east, floodwaters generally don’t linger quite as long as they do in the tropical north. But they do rise rapidly – sometimes several metres over only a couple of days. Much of the water will never return to the main channel of the river but will evaporate slowly. Deeper remnants like billabongs, lagoons or oxbow lakes – actually old river channels – linger longest.

The giant of Australia’s rivers, the Murray, takes longer to flood because Australia is mostly flat. Pulses of water move slowly down its tributaries to the main channel. It can take weeks to months for rain that falls on the Great Dividing Range to make it to the Murray’s mouth at Goolwa in South Australia.

These lingering floodwaters are perfect for freshwater mussels, as well as frogs, lizards, platypus and snakes. Bottlebrushes, wattles, reeds, rushes and aquatic plants do well out of floods too.

Of course, introduced species often thrive too. Common carp populations typically boom after floods. And willow trees and other invasive aquatic plants that spread through pieces breaking off, do well on the back of floods.

riverina murray floodplains
Floodplain fertility can be seen with the naked eye, as in this image of the Murray River flowing through the Riverina in New South Wales. Shutterstock

Our uneasy relationship with rivers

Nature needs floods. But while you might not believe it, we need them too. Most of the world’s major cities were founded next to rivers, which gave their inhabitants water, fish, transport, and fertile farmland. But for all river cities, there are times when the river surges and can destroy houses and livelihoods.

Many cities have tried to tame floods with levees and dams. But as we’re finding now, you can reduce the impact of smaller floods – but the big ones are all but unstoppable.

Because we have farmed and settled so many floodplains, farmers are particularly vulnerable to floods. Floodwaters hitting bush will be slowed by trees and plants. But farms are often cleared, which can see more erosion take place. Whole farms can be devastated by flooding, leading to food prices spiking.

With climate change, Australia is expected to experience bigger and more frequent floods. This may be a good thing for nature but means people will no longer be able to live safely in some places. It will also mean iconic ecosystems like Kakadu will be at risk, with sea level rise predicted to push saltwater into almost half of its famous wetlands by 2070.

While floods bring pain in the short term, over the longer term both humans and nature need the benefits they bring.


Read more: Floods play a vital role in ecosystems – it's time to get out of their way


The Conversation

Paul Humphries has received funding from the Murray-Darling Basin Authority, the Australian Government’s Commonwealth Environmental Water Office and the Victorian Department of Environment, Land, Water and Planning.

Keller Kopf receives funding from the Commonwealth Scientific and Industrial Research Organization, Australian Research Council and the Fisheries Research and Development Corporation.

Read the full story here.
Photos courtesy of

Ministers ‘ignored’ own adviser over weak targets for restoring English nature

Government accused of hypocrisy for pushing global target but not following Natural England’s advice at homeThe UK government ignored scientific warnings from Natural England that its nature restoration target was inadequate and would not meet its commitments, new documents show, undermining efforts to protect threatened species.In December the environment secretary, Thérèse Coffey, unveiled targets at the biodiversity Cop15 in Canada to reverse the decline of nature in England. They included plans to improve the quality of marine protected areas, reduce pollution and nitrogen runoff in the river system, and restore more than half a million hectares of wildlife-rich habitat outside protected areas by 2042. Continue reading...

Government accused of hypocrisy for pushing global target but not following Natural England’s advice at homeThe UK government ignored scientific warnings from Natural England that its nature restoration target was inadequate and would not meet its commitments, new documents show, undermining efforts to protect threatened species.In December the environment secretary, Thérèse Coffey, unveiled targets at the biodiversity Cop15 in Canada to reverse the decline of nature in England. They included plans to improve the quality of marine protected areas, reduce pollution and nitrogen runoff in the river system, and restore more than half a million hectares of wildlife-rich habitat outside protected areas by 2042. Continue reading...

Killing dingoes is the only way to protect livestock, right? Nope

For more than 200 years, European farmers have killed dingoes to protect livestock. But living alongside dingoes benefits nature - and actually helps graziers

Supplied, Author providedSince European colonisation, farmers have often viewed dingoes as the enemy, waging war against them to protect their livestock. Farmers felt they had no option but to eradicate dingoes using traps, shooting, poisoned baits (such as 1080) and building a 5,600km long dingo fence, the world’s longest. Killing dingoes costs millions of dollars each year. But it hasn’t resolved the conflict. In many cases it has made the threat to livestock worse by breaking up dingo families and removing experienced adults which hunt larger, more mobile prey. The alternative? As some farmers are discovering, there are unexpected benefits of learning to coexist with dingoes instead. As Western Australian cattle grazier David Pollock told us: I reckon my dingoes are worth $20,000 each, probably more. So, killing them would be the last thing that I did. Can dingoes really help graziers? Yes. In many cases, they can be allies for graziers by reducing the competition for pasture from wild herbivores such as kangaroos and goats, as well as killing or scaring off foxes and feral cats. As our understanding of the importance of predators has grown, a new approach has taken root: human-wildlife coexistence. Recently recognised by the United Nations Convention of Biological Diversity, this field offers a path to stem the global loss of biodiversity by balancing the costs and benefits of living alongside wildlife. Our new research lays out seven pathways to shift from the routine killing of dingoes towards coexistence. What does coexistence look like? One path to coexistence is supporting graziers to adopt effective tools and strategies to reduce the loss of livestock while capitalising on the benefits of large predators. This is known as predator-smart farming Our research on this area has led to a new Australian guide. This approach relies on a variety of effective non-lethal tools and practices to protect livestock three main ways: humans or guardian animals such as dogs and donkeys watch over and defend livestock from dingoes, as well as using fencing to create a physical barrier using knowledge about dingo biology and behaviour to find better deterrents, such as the use of lights, sounds or smells stronger land management and livestock husbandry to increase the productive capacity of pastures and livestock resilience. This approach helps ensure the livelihoods of farmers remain resilient and makes the most of the benefits of dingoes for productive agricultural landscapes and ecosystem health. This artist’s impression of a predator smart farm shows many different deterrent methods. Amelia Baxter As one New South Wales cattle producer found, these approaches work. He told us: Three years ago, we were losing 53% of our calves to dingoes. We started looking into alternatives that were cost and time effective and decided to try guardian donkeys. We purchased two jacks (male donkeys) and now we have 94% calving rate. Donkeys saved our business. Guardian donkeys are effective dingo deterrents. Author provided So what’s stopping us? We now know it’s entirely possible to live and farm alongside dingoes. So why do we still resort to lethal control? Inertia is one barrier to change. The default option is to kill dingoes. Laws, policies and funding by government and industry have institutionalised lethal control. But there are other barriers, such as a lack of funding for different approaches from government and a lack of support from the community and graziers. Despite this resistance the number of graziers adopting predator smart farming is growing. To overcome these barriers, we believe it’s important to undertake research alongside graziers to field-test and demonstrate how these methods actually work, and which combinations work best. Changes like this take time. We also have to build connections and rapport through agricultural networks, as well as tackle the institutional infrastructure built up around dingo control. It’s natural for farmers, graziers and state government representatives to be sceptical of such a big change. But the status quo isn’t working. Living alongside dingoes could help us make some of the fundamental changes needed to stop the loss of biodiversity. To that end, public awareness and talking about this openly can help bring something which has long gone unquestioned into the spotlight. Our research emerged from in-depth interviews with Australian livestock producers, ecologists, conservation and animal welfare groups, industry representatives and policy makers as well as field observations and analysis of Australia’s wild dog action plan. Coexisting with dingoes could be a win-win for livestock farmers. Shutterstock If we do make progress towards coexisting with dingoes, we could embed predator-smart techniques in the way we farm to boost biodiversity, landscape resilience, food security and livelihoods. We would bring back dingoes as apex predators and regulators of healthy ecosystems. Politics would take a step back, in favour of scientific, evidence-based approaches and First Nations input into environmental policies. This is not hypothetical. Graziers and landholders already using predator-smart tools and strategies report many benefits. They include: fewer animals injured or killed by dingoes less time spent stalking and killing dingoes lower total grazing pressure from feral grazers such as goats boosting pasture growth and livestock profitability. Landholders for Dingoes promotes the work of landholders who are coexisting with dingoes. It’s time to modernise Australia’s approach to dingoes. This approach offers a potential win-win for farmers and dingoes, as well as significant gains for nature. But to make this happen, we will have to shift our attitude towards dingoes, gain support from graziers and other stakeholders, and make non-lethal coexistence tools and approaches the new standard practice. Read more: From the dingo to the Tasmanian devil - why we should be rewilding carnivores Louise Boronyak was funded by the University of Technology Sydney under the UTS Research Excellence Scholarship. She is is a research affiliate of the University of Technology Sydney and Humane Society International AustraliaBradley Smith is an unpaid director of the Australian Dingo Foundation, a non-profit environmental charity that advocates for dingo conservation. He also serves as a member of the International Union for the Conservation of Nature (IUCN) dingo working group, which is part of their Species Survival Commission (Canids Specialist Group).

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