One little bandicoot can dig up an elephant’s worth of soil a year – and our ecosystem loves it



Catching The Eye/Flickr, CC BY

Euan Ritchie, Deakin University; Amy Coetsee, University of Melbourne; Anthony Rendall, Deakin University; Duncan Sutherland, University of Melbourne, and Leonie Valentine, University of Western Australia

On Churchill Island, southeast of Melbourne, small cone-shaped, shallow holes (digs) puncture the grass. They’re widespread, and reveal moist soil below the surface. A soil heap at the entrance of a dig is a sign it was made recently.

Older digs are filled with leaves, grass, spiders, beetles and other invertebrates. They are made by hungry eastern barred bandicoots – small, roughly rabbit-sized digging marsupials – looking for a juicy worm or grub.




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It turns out these bandicoot digs are far from just environmental curiosities – they can improve the properties and health of soils, and even reduce fire risk.

But eastern barred bandicoots are under threat from introduced predators like foxes and cats. In fact, they’re considered extinct in the wild on mainland Australia, so conservation biologists are releasing them on fox-free islands to help establish new populations and ensure the species is conserved long-term.

Our recent research on Churchill Island put a number on just how much the eastern barred bandicoot digs – and the results were staggering, showing how important they are for the ecosystem. But more on that later.

A dig from an eastern barred bandicoot.
Amy Coetsee

Why you should dig marsupial diggers

Digging mammals – such as bettongs, potoroos, bilbies and bandicoots – were once abundant and widespread across Australia, turning over large amounts of soil every night with their strong front legs as they dig for food or create burrows for shelter.




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Their digs improve soil health, increase soil moisture and nutrient content, and decrease soil compaction and erosion. Digs also provide habitat for invertebrates and improve seed germination.

What’s more, by digging fuel loads (dry, flammable vegetation, such as leaves) into the soil, they can help bring down the risk of fire.

Rather than leaves and other plant matter accumulating on the soil surface and drying out, this material is turned over faster, entering the soil when the badicoots dig, which speeds up its decay. Research from 2016 showed there’s less plant material covering the soil surface when digging mammals are about. Without diggers, models show fire spread and flame height are bigger.

In fact, all their functions are so important ecologists have dubbed these mighty diggers “ecosystem engineers”.

How bandicoot digs affect soil.
Leonie Valentine, Author provided

Losing diggers leads to poorer soil health

Of Australia’s 29 digging mammals, 23 are between 100 grams and 5 kilograms. Most are at risk of cat and fox predation, and many of these are officially listed as threatened species by the International Union for Conservation of Nature.

Since European settlement, six of Australia’s digging mammals have gone extinct, including the lesser bilby, desert rat kangaroo and pig-footed bandicoots. Many others have suffered marked population declines and extensive range contraction through habitat destruction and the introduction of foxes and cats.




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Tragically, the widespread decline and extinction of many digging mammals means soil and ecosystem health has suffered as well.

Soils that were once soft textured, easy to crumble, rich and fertile are now often compact, repel water and nutrient poor, impeding seed germination and plant growth. Fuel loads are also likely to be much higher now than in the past, as less organic matter is dug into the soil.

To date, most research on digging mammals has focused on arid environments, with much less known about how digging influences wetter (mesic) environments. But our recently published study on eastern barred bandicoots provides new insights.

Just how much do bandicoots dig anyway?

In 2015, 20 mainland eastern barred bandicoots were released onto Churchill Island in Victoria’s Westernport Bay.

When eastern barred bandicoots were released on Churchill Island.

On mainland Australia, fox predation has driven this species to near extinction, and it’s classified as extinct in the wild. All Victoria’s islands are beyond the historic range of eastern barred bandicoots, but fox-free islands could be how we recover them.

Introducing bandicoots on Churchill Island presented the perfect opportunity to quantify how they influence soil properties when digging for food.




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To do this we recorded the number of digs bandicoots made each night and measured the volume of soil they displaced through digging. We also compared soil moisture and compaction within the digs, versus un-dug soil – and we didn’t expect what we found.

In one night on Churchill Island, one bandicoot can make 41 digs an hour. That’s nearly 500 digs a night, equating to around 13 kilograms of soil being turned over every night, or 4.8 tonnes a year. That’s almost as much as the average weight of a male African elephant.

Bandicoots turn over huge amounts of soil in their search for food.
Amy Coetsee

So, an astonishing amount of soil is being turned over, especially considering these bandicoots typically weigh around 750 grams.

If you multiply this by the number of bandicoots on Churchill Island (up from 20 in 2015 to around 130 at the time of our study in 2017), there’s a staggering 1,690 kilos of soil being dug up every night. That’s some major earthworks!

However, we should note our study was conducted during the wetter months, when soils are typically easier to dig.

In summer, as soil becomes harder and drier on Churchill Island, digging may become more difficult. And bandicoots, being great generalists, feed more on surface invertebrates like beetles and crickets, resulting in fewer digs. So we expect in summer that soil is less disturbed.

Bandicoots might help agriculture too

All this digging was found to boost soil health on Churchill Island. This means eastern barred bandicoots may not only play an important role in ecosystem health and regeneration, but also potentially in agriculture by assisting pasture growth and condition, reducing topsoil runoff, and mitigating the effects of trampling and soil compaction from livestock.

One of 20 eastern barred bandicoots being released on Churchill Island.
Zoos Victoria

The benefits bandicoot digs have across agricultural land is of particular importance now that eastern barred bandicoots have also been released on Phillip Island and French Island, and are expected to extensively use pasture for foraging.

These island releases could not just help to ensure eastern barred bandicoots avoid extinction, but also promote productive agricultural land for farmers.




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So, given the important ecological roles ecosystem engineers like bandicoots perform, it’s also important we try to reestablish their wild populations on the mainland and outside of fenced sanctuaries so we can all benefit from their digging, not just on islands.


Lauren Halstead is the lead author of the study reported, which stemmed from her honours research at Deakin University. She also contributed to the writing of this article.The Conversation

Euan Ritchie, Associate Professor in Wildlife Ecology and Conservation, Centre for Integrative Ecology, School of Life & Environmental Sciences, Deakin University; Amy Coetsee, Threatened Species Biologist, University of Melbourne; Anthony Rendall, Associate Lecturer in Conservation Biology, Deakin University; Duncan Sutherland, Deputy Director of Research, Phillip Island Nature Parks; Research Fellow, University of Melbourne, and Leonie Valentine, Research Associate, School of Plant Biology, University of Western Australia

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Last summer’s fish carnage sparked public outrage. Here’s what has happened since



Graeme McCrabb/AAP

Lee Baumgartner, Charles Sturt University and Max Finlayson, Charles Sturt University

As this summer draws to a close, it marks just over a year since successive fish death events at Menindee in Lower Darling River made global headlines.

Two independent investigations found high levels of blue-green algae and low oxygen levels in the water caused the deaths. Basically, the fish suffocated.




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The conditions were caused by a combination of water extraction and extremely dry conditions which effectively stopped the river from flowing. Both investigations concluded that until more water flowed in the Darling, in western New South Wales, further fish kills were very likely.

So what’s happened since, and does the recent rain mean the crisis won’t be repeated?

Federal and state government action

In April last year the federal government committed A$70 million to improve the river’s health and prevent more fish deaths. Let’s examine what’s been done so far:

– Native fish management and recovery strategy: Parts of a draft native fish management and recovery strategy have been released for public consultation. The plan has included governments, academics, the community and indigenous groups.

– Native fish hatchery: Government hatchery facilities at Narrandera in NSW will be upgraded to hold and breed more fish. But reintroducing fish into affected areas is challenging and could be a decades-long program.

– Research: The government committed to new research into hydrology and climate change. A panel has been formed and the oversight committee is scoping the most effective research outcomes to better manage water under a changed climate.

– Fish passage infrastructure: Fish ladders – structures that allow fish to travel around obstacles on a river – are needed at sites on the lower and upper Darling. Fish ladder concept designs have progressed and are also part of the NSW government’s Western Weirs project.

-In-stream cameras: Live-stream feeds of the Darling River are not yet available.

-Meter upgrades and water buybacks: Discussions have begun as part of a commitment to buy back A-class water licenses from farmers and return water to the rivers. Rollout of improved metering is due over the next five years.

Progress on these actions is welcome. But the investigation panels also recommended other actions to help fish populations recover over the long term, including ensuring fish habitat and good water quality.

Further fish deaths

In 2003, basin native fish communities were estimated to be at 10% of pre-European levels and the spates of fish deaths will have reduced this further.

Over spring and summer in 2019, conditions in the Darling River deteriorated. A series of smaller, but significant, fish deaths prompted government agencies and communities to conduct emergency “fish translocations”.. Aerators were deployed in a bid to improve the de-oxygenation. Fish were moved to more suitable water bodies, or to hatcheries to create insurance populations.

By spring, once-mighty rivers such as the Darling and Macquarie had dried to shallow pools. As summer progressed, more than 30 fish die-offs occurred in the Macquarie, Namoi, Severn, Mehi and Cudgegong rivers and Tenterfield Creek.

What about the rain?

Strong recent rainfall means upper parts of the Darling catchment are now flowing for the first time in more than two years. Flows are passing over the Brewarrina Weir and associated fishway.

A flowing Darling is great, but it raises questions over future water management. Farmers have been waiting for years for the Darling to flow and will be eager to extract water for agricultural productivity. Likewise, the environment has been awaiting a “flush” to reset the system and restore ecological productivity.




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After the rains, the NSW government allowed irrigators to harvest floodwaters to reduce the threat of damage to private infrastructure. Now that threat has subsided, governments are working together to “actively manage” the event – meaning water rules will be decided as the flow progresses, in consultation with water users and environmental managers.

But there is still significant debate on how best to manage water over the longer term.

Water use on the Darling River remains highly contested.
Dean Lewins/AAP

Is a flowing Darling a return to normal?

The current flows in the Darling are far from a return to normal conditions. NSW is still in drought, and the river flows are yet to reach the Lower Darling. Many children in the Menindee township have not seen a flowing Darling in their lifetime.

Indigenous elders and recreational fishers – those who remember when the river flowed freely and was full of fish – are lamenting the recent declines. In parts of the system, dry riverbeds and isolated pools are still begging to be connected so fish can move about, spawn, and naturally recover.




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River flows could take up to six weeks to reach the lower Darling, and follow-up rain is urgently needed to avoid another summer of fish carnage. Future water sharing strategies must protect both upstream and downstream communities. Some people are lobbying for the Menindee lakes to be listed as internationally important under the Ramsar Convention on Wetlands to ensure biodiversity and water management work together.

Undoing over 200 years of fish declines will require a sustained effort, with a significant investment in recovery actions over a long period. We must recognise Australia is a country of long droughts and flooding rains, and develop a proactive native fish strategy that reduces the probability of a similar disaster in future.

But unfortunately, as history has shown that when we transition from drought to flood, our memories can be short.The Conversation

Lee Baumgartner, Professor of Fisheries and River Management, Institute for Land, Water, and Society, Charles Sturt University and Max Finlayson, Adjunct Professor, Charles Sturt University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Vital Signs: a 3-point plan to reach net-zero emissions by 2050



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Richard Holden, UNSW

Every January Larry Fink, the head of the world’s largest funds manager, BlackRock, sends a letter to the chief executives of major public companies.

This year’s letter focused on climate risk. “Climate change has become a defining factor in companies’ long-term prospects,” Fink wrote. To put sustainability at the centre of its investment approach, he said, BlackRock would stop investing in companies that “present a high sustainability-related risk”.




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Now business leaders – even big money managers – express opinions all the time, and major companies keep doing what they are doing. But this was different.

Fink, who’s in charge of US$7 trillion (that’s not a typo – $7,000,000,000,000), says in his letter: “In the near future – and sooner than most anticipate – there will be a significant reallocation of capital.”

It’s emphasised in bold type. That’s something to which chief executives pay attention.

Even before the letter was sent – but knowing what was coming – major US companies like Amazon, Delta Air Lines and Microsoft announced new climate action plans.

These three companies are in different industries with different abilities to take action. But the plans they’ve outlined illuminate the three key strategies needed to achieve net-zero carbon emissions by 2050.

Delta Air Lines

Delta, being an airline, burns a lot of fossil fuels. Bar an extraordinary technological shift in aircraft, it will burn a lot of fossil fuels well into the future.




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The airline’s goal by 2050 is to cut its carbon emissions to half the levels they were in 2005. It plans to do this through a combination of fuel-efficiency measures and helping spur the development of more sustainable jet fuels. In the medium term (up to 2035), its goal is “carbon-neutral growth”, buying carbon offsets for any increases in emissions from jet fuel due to business growth.

Delta Air Lines operates about 5,000 flights a day. Jet fuel accounts for about 99% of its total emissions.
Shutterstock

Let’s consider the economics of the Delta plan – at least up to 2035.

Buying carbon offsets increases the airline’s costs. These are passed on to customers – in which case it is simply a form of carbon tax – or paid for by shareholders through lower profits. I’m betting it’s not the shareholders who will pay.

So Delta is essentially imposing its own carbon tax in the hope customers who care about the environment will be more attracted to its brand or that other airlines follow suit.

Amazon

Amazon, which reported a carbon footprint of 44.4 million metric tons in 2018, is doing two broad things.

The company has a fleet of about 30,000 delivery vans. It plans to have 100,000 electric vehicles by 2024. This will reduce the company’s carbon footprint so long as the vans are charged with power from sustainable sources.

Amazon’s founder, Jeff Bezos, has also announced the Bezos Earth Fund, which will give away US$10 billion in grants to anyone with good ideas to address climate change or other environmental issues.

Again, let’s consider the basic economics at play here.

Moving to electric vehicles is a smart hedge against rising fuel costs from a price on carbon – something that already exists in California.

The Bezos Earth Fund, meanwhile, is an excellent example of taking money generated from maximising shareholder value – Amazon is valued at about US$1 trillion and Bezos’s personal fortune (pre-divorce) was about US$130 billion – and redistributing it to socially productive causes.

Microsoft

Finally, Microsoft – the least-carbon-intensive business of the three mentioned here – plans to be carbon-negative by 2030, and by 2050 to have offset all the emissions it has been responsible for (both directly and through electricity consumption) since its founding in 1975.

Since 2012 it has had an “internal carbon tax”, which in April 2019 was doubled to US$15 a tonne. This price mechanism is used to make Microsoft’s business divisions financially responsible for reducing emissions.

On top of this, Microsoft has developed the AI for Earth program, which provides cloud-computing tools for researchers working on sustainability issues to process data more effectively.

Lessons for Australia

Australia’s Coalition government and Labor opposition would do well to heed the lessons of these three companies.

Together they show three clear strategies:

  • a technological push to lower emissions
  • a price on carbon to drive technological innovation and uptake
  • clear goals to reduce emissions.

Our political parties both have one out of three. Right now Labor has announced a goal. The Coalition is promising a technology plan some time soon.

Prime Minister Scott Morrison is right to criticise Labor for not having a plan. Opposition Leader Anthony Albanese is right to criticise the Coalition for not having a suitable goal.

But neither of them advocates a price on carbon, without which neither technology road maps nor ambitious goals will translate into sufficient emissions reductions.




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Technology investment, a carbon price and clear goals are all necessary to effectively reduce carbon emissions. Without all three we are bound to fail.

And we no longer have time for that, according to climate scientists.The Conversation

Richard Holden, Professor of Economics, UNSW

This article is republished from The Conversation under a Creative Commons license. Read the original article.