Tiny desert mice could help save Australia’s grasslands from invasion

Christopher Edward Gordon, University of Wollongong and Mike Letnic, UNSW Australia

You should stop skylarking about with those bloody desert mice and try and stop those woody weeds. I could see clear through that paddock in the ‘60s. Now look at it. That scrub costs us tens of thousands of dollars in lost fodder and it’s almost impossible to muster the livestock.

That blunt assessment of our research, first offered by a local farmer in Australia’s arid rangelands almost seven years ago, raised an irresistible question for us as field ecologists. Why are Australia’s (and many others around the world) grasslands becoming woodier?

It certainly was a question worth asking. Shrub encroachment – an increase in the cover of woody shrubs in areas once dominated by grasses – is not just an issue in Australia.

In two recent papers published in the journals Ecography and the Journal of Animal Ecology, we looked at one key reason why trees are invading grasslands, and how we could stop them. And it all comes down to tiny desert mice.

Shrub invasion

“Invasive native vegetation”, as bureaucrats call it, is a major problem for livestock producers in drylands throughout the world. This is because the shrubs compete for space and light with the grasses needed to feed their cattle and sheep.

Shrub encroachment ‘inside’ the Dingo Fence.
Dr Ben Moore

It is a hard problem to tackle. Clearing and fire are the most common methods of controlling woody shrubs. But these methods are laborious and often hard to implement on large scales.

Removing shrubs is also contentious because these are typically native species that provide important habitat for wildlife. The New South Wales parliament’s controversial relaxation in November of regulations governing vegetation clearing were designed partly to allow farmers to remove invasive native vegetation.

What’s going on?

The causes for the spread are complex and poorly understood. Shrub encroachment is often attributed to overgrazing by livestock, which favours the growth of shrubs over grasses. It has also been linked to a reduction in bushfires that wipe out the shrubs and an increase in atmospheric carbon dioxide, which can promote their growth.

However, we suspected another important factor could be at play. And it was those little desert mice that provided us with a big clue – and a possible solution.

Since European settlement, livestock grazing and the introduction of foxes, feral cats and rabbits have decimated Australia’s native mammals, especially in arid and semi-arid areas.

The bilbies, bettongs, native rodents and other small mammals that became rare or extinct across much of the continent in the early 20th century once played essential roles in Australian ecosystems, by shifting vast amounts of soil and consuming vegetation and seeds.

Historical accounts suggest that shrub encroachment quickly followed European settlement and mammal extinctions in many areas. This coincidence led us to ask: could the loss of native mammals be making Australia’s drylands woodier?

Hopping to it

To answer this question, we went to the northwest corner of NSW. Here the Dingo Fence marks the border with Queensland and South Australia.

The Dingo Fence.
Ben Moore

We wanted to know whether the local extinction of a native mammal, the dusky hopping mouse, which eats shrub seeds and seedlings, would allow more shrubs to grow. The Dingo Fence was the perfect study site because dusky hopping mice are common on the northwest side, “outside” the fence, where dingoes are present.

Dingoes keep fox numbers down, which are the mouse’s major predator. However, dusky hopping mice are rare on the “inside” of the fence (the NSW side), where dingoes are less common and foxes roam.

We first used historical aerial photographs to show that shrub cover was consistently higher inside the dingo fence (rodents rare) than outside (rodents common). We then did field surveys, which showed that the numbers of shrubs, their seedlings and their seeds were greater where rodents were rare.

We also showed that dusky hopping mice were major consumers of shrub seeds and capable of keeping the numbers of shrub seeds in the soil down.

Fieldwork in the Strzelecki Desert.
Dr Ben Moore

Going wild again

These results are exciting because they suggest that the loss of native mammals such as the dusky hopping mouse may be an important and overlooked driver of shrub encroachment, not only in arid Australia but also globally.

Perhaps more exciting, however, is how we can apply our work. Our research suggests that “rewilding” drylands by re-establishing rodents and other native mammal species that eat shrub seeds and seedlings, such as bettongs and bilbies, could curb the shrub invasion.

Although an abstract and even controversial idea, rewilding of native mammals would provide a long-term solution to a problem that has affected pastoralists for more than a century.

Further, it would represent a natural and cost-effective strategy with enormous benefits for the conservation of imperilled native mammals.

Before we can do so, we have to control foxes and feral cats across vast areas, which is no small feat. However, the economic and conservation potential make it an approach that is well worth taking seriously.

The Conversation

Christopher Edward Gordon, Associate Research Fellow, University of Wollongong and Mike Letnic, Associate Professor, School of Biological, Earth and Environmental Sciences, UNSW Australia

This article was originally published on The Conversation. Read the original article.


Traditional hunting gets headlines, but is not the big threat to turtles and dugongs

Helene Marsh, James Cook University and Mark Hamann, James Cook University

Recent calls for a ban on legal traditional hunting of dugongs and marine turtles imply that hunting is the main threat to these iconic species in Australia. The science indicates otherwise.

While more is being done to address traditional hunting than any of the other impacts, the main threats to their survival often pass unnoticed.

The real threat to sea turtles

The draft Recovery Plan for Marine Turtles in Australia evaluated 20 threats to the 22 populations of Australia’s six species of marine turtle. Climate change and marine debris, particularly “ghost nets” lost or abandoned by fishers, are the greatest risks for most stocks.

If you’re a marine turtle, a likely cause of death is getting tangled in a discarded fishing net.
AAP Image/Department of Heritage and Government

Indigenous use is considered to be a high risk for three populations: Gulf of Carpentaria green turtles, Arafura Sea flatback turtles and north-eastern Arnhemland hawksbill turtles.

However, in each of these cases it is the egg harvest, not hunting, that causes concern. International commercial fishing is also a high risk for the hawksbill turtle, whose future remains uncertain. Traditional hunting of marine turtles in Australia is limited to green turtles.

Is hunting a threat?

The Torres Strait supports the largest dugong population in the world and a globally significant population of green turtles. Archaeological research shows that Torres Strait Islanders have been harvesting these species for more than 4,000 years and the dugong harvest has been substantial for several centuries.

Our research shows that the Torres Strait dugong population has been stable since we started monitoring 30 years ago and that the harvest of both species is sustainable.

The situation for dugongs is very different in the waters of the Great Barrier Reef south of Cooktown. The Great Barrier Reef Outlook Report classifies the condition of the dugong population in this region as poor.

Modelling indicates that the southern Great Barrier Reef stock of the green turtle, which live and breed south of Cooktown, is increasing.

Nonetheless, both green turtles and dugongs died in record numbers in the year after the extreme floods and cyclones of the summer of 2010-11. Dugongs stopped breeding in the Great Barrier Reef region south of Cooktown.

Thankfully, our current aerial survey indicates that dugong calving has resumed as inshore seagrass habitats recover. There is no evidence that the 2011 losses significantly affected green turtle numbers.

Working together

Traditional owners are the first managers of our coastal waters, with cultural practices extending back thousands of years. They have the most to lose from any loss of turtles and dugongs. It is therefore in their best interests, and the government’s best interest, to work in partnership to protect and sustainably manage these species.

Longstanding tensions between traditional owners and tourist operators are behind much of the opposition to traditional hunting in the Cairns area. Some of these tensions have been relieved by the Gunggandji Traditional Use of Marine Resources Agreement signed in June 2016.

Under this agreement, the traditional owners decided to cease hunting turtles and dugongs in the waters surrounding Green Island, Michaelmas Cay and Fitzroy Island.

The Gunggandji agreement is the seventh to be signed between the Great Barrier Reef Marine Park Authority and traditional owners. In addition, there are two Indigenous land use agreements that address hunting issues in the Great Barrier Reef.

In the Torres Strait, dugong and turtle hunting is managed through 14 (soon to be 15) management plans. There are similar agreements with traditional owners and management agencies in other regions in northern Australia.

Indigenous rangers are crucial to implementing all these agreements in collaboration with management agencies and research institutions. Rangers deliver the practical, on-the-ground arrangements to conserve these species in their Sea Country.

The Great Barrier Reef Marine Park Authority has implemented an Indigenous Compliance Program that authorises trained Indigenous rangers to respond to suspicious and illegal activities that they encounter as part of their work.

Indigenous rangers and community members from Badu Island in Torres Strait help JCU scientists fit a dugong with a satellite tracking device.
Takahiro Shimada/James Cook University

Indigenous rangers also remove marine debris from remote beaches. The community-based organisation GhostNets Australia has worked with 31 coastal Indigenous communities to protect over 3,000km of northern Australia’s saltwater country from ghost nets. These community projects have been instrumental in rescuing turtles, clearing ghost nets off beaches and identifying key areas to aid management agencies to better understand the impact.

Traditional owners from the Torres Strait and the northern Great Barrier Reef also play a valuable role in intervention works at Raine Island, one of the world’s most significant green turtle rookeries. This includes rescuing stranded turtles, using fences to stop turtles from falling over cliffs, and altering beach profiles.

What about welfare?

Traditional hunting raises animal welfare issues. The turtle and dugong management plans developed by the Torres Strait communities explicitly address animal welfare. The Torres Strait Regional Authority has been working with a marine mammal veterinarian and traditional owners to develop additional methods of killing turtles humanely.

Indigenous hunters who breach state and territory animal welfare laws can be prosecuted. But more widespread animal welfare problems, not associated with hunting, are largely hidden and ignored. The Queensland Strand Net Program reported that 879 turtles died of their wounds from vessel strike between 2000 and 2011.

An immature female loggerhead turtle severely injured by a boat strike near Gladstone. This turtle was determined to be unrecoverable and was euthanased by a local veterinarian in May 2016.
Takahiro Shimada/James Cook University

Other serious animal welfare issues are associated with animals drowning in nets and being caught in and ingesting marine debris. In addition, the potential impact of emerging threats like underwater noise pollution and water quality remain as substantial knowledge gaps. These matters tend not to make the headlines.

Australian waters are home to some of the world’s largest populations of marine turtles and dugongs. A comprehensive and balanced approach to their conservation and management is required to enable our grandchildren and their children to enjoy these amazing animals.

The Conversation

Helene Marsh, Dean, Graduate Research, James Cook University and Mark Hamann, Senior Lecturer in Environmental Science (marine focus), James Cook University

This article was originally published on The Conversation. Read the original article.

Great Barrier Reef needs far more help than Australia claims in its latest report to UNESCO

Jon C. Day, James Cook University; Alana Grech, James Cook University, and Jon Brodie, James Cook University

At first glance, the progress reports on the Great Barrier Reef released last week by the Australian and Queensland governments might seem impressive.

The update on the Reef 2050 Plan suggests that 135 of the plan’s 151 actions are either complete or on track.

The Australian government’s apparent intention in releasing five recent reports is to reassure UNESCO that the Great Barrier Reef should not be listed as “World Heritage in Danger” (as the World Heritage Committee has previously threatened).

Sadly, behind the verbosity and colour of these reports, there is disappointingly little evidence of progress in the key areas needed to make a significant difference to a World Heritage Area that is in crisis.

Poor baseline

The government framework for protecting and managing the Reef from 2015 to 2050, the Reef 2050 Plan, has been widely criticised as failing to provide a sound basis for the necessary long-term protection of the Reef.

As well as providing a shaky basis to build effective actions, the Reef 2050 Plan has few measurable or realistic targets. It is therefore not easy to report on the actual progress.

Several of the actions that will have the greatest impacts on the overall health of the Reef are shown in the progress reports as “not yet due”. In some cases, such as climate change, the Reef 2050 Plan is silent, instead simply referencing Australia’s national efforts on climate change.

Instead, the plan is to “[improve] the Reef’s resilience to climate change by reducing local pressures”. Besides addressing water quality, there are many things that should also be considered but they involve making some really hard decisions, such as choosing between coal and coral.

Progress versus reality

The overview of progress claims that 135 of the 151 actions in the Reef 2050 Plan are either completed (dark green) or are on track for their expected milestones (light green), as shown below.

Reef 2050 Plan: Update on Progress, 2016, CC BY

The reality, however, is that many of the 103 of the actions described as “on track/underway” have not progressed as initially proposed when the Reef 2050 Plan was submitted to UNESCO, and that the definition of “underway” is far too loose to be meaningful.

Our rapid assessment of the status of actions indicates that the level of progress reported for at least 32 of these 151 actions (around 21%) has been overstated. The following are just some examples:

The unfortunate truth is that neither UNESCO nor the IUCN has the time or resources to conduct their own comprehensive assessment of the Great Barrier Reef. They rely heavily on these reports when deliberating on what to recommend to the World Heritage Committee, including whether the Reef should be placed on the World Heritage in Danger list.

Our rapid assessment indicates there are real concerns with relying on the government to self-report accurately. It would appear the only way that UNESCO will receive an accurate update is if that assessment is done independently of government. Fortunately, UNESCO and IUCN do consider other evidence.

It is also concerning that the members of the government’s Independent Expert Panel and the Reef 2050 Advisory Committee were not involved in making the final assessments for the 2016 update report.

Despite pronouncements that the Great Barrier Reef remains healthy, the evidence of the 2015 Water Quality Report Card, along with numerous expert opinions (for example, Jon Brodie on water quality; Terry Hughes on coral health; the Queensland government on scallops; and the Marine Park Authority on inshore dolphins) shows that the real situation is not as rosy as UNESCO and the Australian public are being told.

Some real progress, but not enough

It is important to recognise some progress is being made – but sadly too little and not enough to reverse the declining trend for many of the values for which the Reef was listed as World Heritage.

We should also question some of the priorities in the Reef 2050 Plan given the widely acknowledged critical issues (see page 252 in the government’s 2014 Outlook Report). Adopting best practice for water quality from point sources such as sewage discharge (action WQA11 under the plan) and protecting habitat for coastal dolphins (BA12) should be immediately addressed.

Whether we have the money to do what’s necessary is another question. The government’s pledge to spend A$2 billion over 10 years is the current collective yearly spending (A$200 million) of four federal agencies, six state agencies and several major research programs, extrapolated over the coming decade.

While the level of funding is significant compared with many other World Heritage areas, the amount and priorities must be questioned, given that many of the Reef’s values are continuing to decline.

So far most funding has been spent on addressing water quality, and while this has achieved some positive results, it has not managed to stop the deteriorating trends.

As Jon Brodie recently wrote on The Conversation:

The best estimate is that meeting water quality targets by 2025 will cost A$8.2 billion … If we assume that … A$4 billion is needed over the next five years, the amounts mentioned in the progress report (perhaps A$500-600 million at most) are … totally inadequate.

More action needed

The Reef is unquestionably of global significance. Given its sheer size and location, no other World Heritage Area on the planet includes such biodiversity.

The worst-known bleaching event in the Great Barrier Reef demonstrates the limitations of the Reef 2050 Plan, which is silent on the impact of greenhouse emissions from Queensland’s coal mines and the effects of climate change more generally.

Governments have an obligation to protect all the Reef’s values for future generations. To do this they must recognise growing global moves to address climate change, and the widespread national and international expectations that more needs to be done to protect the Reef.

Australia is a relatively rich country and has the technical capability to address the issues. This provides an opportunity to show some global leadership for managing such a significant part of the world’s heritage.

Listing the reef as World Heritage in Danger won’t in itself fix the problems – but it will certainly focus the spotlight on the issues.

As the World Heritage Committee prepares for its next meeting in July 2017, and considers once again whether to officially list the reef as in danger, it will need to study all the evidence, not just the government’s reports.

Certainly the true picture is more complicated and dire than the most recent government reports imply.

The Conversation

Jon C. Day, PhD candidate, ARC Centre of Excellence for Coral Reef Studies, James Cook University; Alana Grech, Assistant Director, ARC Centre of Excellence for Coral Reef Studies, James Cook University, and Jon Brodie, Professorial Fellow, ARC Centre of Excellence for Coral Reef Studies, James Cook University

This article was originally published on The Conversation. Read the original article.