From feral camels to ‘cocaine hippos’, large animals are rewilding the world



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Most of the world’s wild horses, such as the Australian brumby, are outside their historic native range.
Andrea Harvey

Erick Lundgren, University of Technology Sydney; Arian Wallach, University of Technology Sydney; Daniel Ramp, University of Technology Sydney, and William Ripple, Oregon State University

Throughout history, humans have taken plants and animals with them as they travelled the world. Those that survived the journey to establish populations in the diaspora have found new opportunities as they integrate into new ecosystems.

These immigrant populations have come to be regarded as “invaders” and “aliens” that threaten pristine nature. But for many species, migration may just be a way to survive the global extinction crisis.

In our recently published study, we found that one of the Earth’s most imperilled group of species is hanging on in part thanks to introduced populations.

Megafauna – plant-eating terrestrial mammals weighing more than 100kg – have established in new and unexpected places. These “feral” populations are rewilding the world with unique and fascinating ecological functions that had been lost for thousands of years.

Today’s world of giants is only a shadow of its former glory. Around 50,000 years ago, giant kangaroos, rhino-like diprotodons, and other unimaginable animals were lost from Australia.


Read more: Giant marsupials once migrated across an Australian Ice Age landscape


Later, around 12,000 years ago, the last of the mammoths, glyptodonts, several species of horses and camels, house-sized ground sloths and other great beasts vanished from North America.

In New Zealand, a mere 800 years ago, a riot of giant flightless birds still grazed and browsed the landscape.

The loss of Earth’s largest terrestrial animals at the end of the Pleistocene was most likely caused by humans.

Sadly, even those large beasts that survived that collapse are now being lost, with 60% of today’s megafauna threatened with extinction. This threat is leading to international calls for urgent intervention to save the last of Earth’s giants.

A wilder world than we think

Formal conservation distribution maps show that much of Earth is empty of megafauna. But this is only a part of the picture.

Many megafauna are now found outside their historic native ranges. In fact, thanks to introduced populations, regional megafauna species richness is substantially higher today than at any other time during the past 10,000 years.

Megafauna have expanded beyond their historic native range to rewild the world. Number of megafauna per region, in their ‘native’ range only (a) and in their full range (b)
Modified and reproduced from Lundgren et al. 2017

Worldwide introductions have increased the number of megafauna by 11% in Africa and Asia, by 33% in Europe, by 57% in North America, by 62% in South America, and by 100% in Australia.

Australia lost all of its native megafauna tens of thousands of years ago, but today has eight introduced megafauna species, including the world’s only wild population of dromedary camels.

Australia lost all of its native megafauna tens of thousands of years ago, but is now home to eight introduced species, including the world’s only population of wild dromedary camels. Remote camera trap footage from our research program shows wild brumbies, wild donkeys and wild camels sharing water sources with Australian dingoes, emus and bustards in the deserts of South Australia.

These immigrant megafauna have found critical sanctuary. Overall, 64% of introduced megafauna species are either threatened, extinct, or declining in their native ranges.

Some megafauna have survived thanks to domestication and subsequent “feralisation”, forming a bridge between the wild pre-agricultural landscapes of the early Holocene almost 10,000 years ago, to the wild post-industrial ecosystems of the Anthropocene today.

Wild cattle, for example, are descendants of the extinct aurochs. Meanwhile, the wild camels of Australia have brought back a species extinct in the wild for thousands of years. Likewise, the vast majority of the world’s wild horses and wild donkeys are feral.

There have been global calls to rewild the world, but rewilding has already been happening, often with little intention and in unexpected ways.

A small population of wild hippopotamuses has recently established in South America. The nicknamed “cocaine hippos” are the offspring of animals who escaped the abandoned hacienda of Colombian drug lord Pablo Escobar.

Colombia’s growing ‘cocaine hippo’ population is descended from animals kept at Pablo Escobar’s hacienda.

By insisting that only idealised pre-human ecosystems are worth conserving, we overlook the fact that these emerging new forms of wilderness are not only common but critical to the survival of many existing ecosystems.

Vital functions

Megafauna are Earth’s tree-breakers, wood-eaters, hole-diggers, trailblazers, wallowers, nutrient-movers, and seed-carriers. By consuming coarse, fibrous plant matter they drive nutrient cycles that enrich soils, restructure plant communities, and help other species to survive.

The wide wanderings of megafauna move nutrients uphill that would otherwise wash downstream and into the oceans. These animals can be thought of as “nutrient pumps” that help maintain soil fertility. Megafauna also sustain communities of scavengers and predators.

In North America, we have found that introduced wild donkeys, locally known as “burros”, dig wells more than a metre deep to reach groundwater. At least 31 species use these wells, and in certain conditions they become nurseries for germinating trees.

Introduced wild donkeys (burros) are engineering the Sonoran Desert, United States.

The removal of donkeys and other introduced megafauna to protect desert springs in North America and Australia seems to have led to an exuberant growth of wetland vegetation that constricted open water habitat, dried some springs, and ultimately resulted in the extinction of native fish. Ironically, land managers now simulate megafauna by manually removing vegetation.

It is likely that introduced megafauna are doing much more that remains unknown because we have yet to accept these organisms as having ecological value.

Living in a feral world

Like any other species, the presence of megafauna benefits some species while challenging others. Introduced megafauna can put huge pressure on plant communities, but this is also true of native megafauna.

Whether we consider the ecological roles of introduced species like burros and brumbies as desirable or not depends primarily on our own values. But one thing is certain: no species operates in isolation.

Although megafauna are very large, predators can have significant influence on them. In Australia, dingo packs act cooperatively to hunt wild donkeys, wild horses, wild water buffalo and wild boar. In North America, mountain lions have been shown to limit populations of wild horses in some areas of Nevada.

Visions of protected dingoes hunting introduced donkeys and Sambar deer in Australia, or protected wolves hunting introduced Oryx and horses in the American West, can give us a new perspective on conserving both native and introduced species.

Nature doesn’t stand still. Dispensing with visions of historic wilderness, and the associated brutal measures usually applied to enforce those ideals, and focusing on the wilderness that exists is both pragmatic and optimistic.

After all, in this age of mass extinction, are not all species worth conserving?


The ConversationThis research will be presented at the 2017 International Compassionate Conservation Conference in Sydney.

Erick Lundgren, PhD Student, Centre for Compassionate Conservation, University of Technology Sydney; Arian Wallach, Chancellor’s Postdoctoral Research Fellow, Centre for Compassionate Conservation, University of Technology Sydney; Daniel Ramp, Associate Professor and Director, Centre for Compassionate Conservation, University of Technology Sydney, and William Ripple, Distinguished Professor and Director, Trophic Cascades Program, Oregon State University

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

I’ve always wondered: Why don’t hippos get cholera?


Julie Old, Western Sydney University

This is an article from I Have Always Wondered, a series where readers send in questions they’d like an expert to answer. Send your question to alwayswondered@theconversation.edu.au


Why don’t hippopotamuses get cholera? Why are some animals resistant to waterborne disease? – Phil Morey

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The short answer is that cholera has evolved to infect humans, not hippos. Cholera is a disease caused by a curved rod-shaped bacterium called Vibrio cholerae. The disease is characterised by a profuse diarrhoea that resembles “rice water”, and can lead to death within hours.

Transmission electron microsope image of Vibrio cholerae that has been negatively stained.
Dartmouth Electron Microscope Facility via Wikipedia

Humans contract the disease from water contaminated with human sewage containing the bacteria. As cholera is a waterborne disease, it is prevalent in areas where human sanitation is lacking or less than ideal. Unlike many other diseases, it can’t be passed to us from animals, as malaria is from mosquitoes.

Once ingested by humans, the bacteria attach to the small intestine wall. There they reproduce, and prodcue a toxin called choleragen. The choleragen toxin is made up of two parts, called A and B. The B portion attaches the toxin to the cells in the intestine and the A portion chemically forces electrolytes and water from the intestinal cells themselves, thus leading to massive dehydration, diminished blood loss and ultimately death.

Vibrio cholerae, the bacteria that causes cholera, only impacts humans, and can only be transmitted to new human hosts via contaminated water. It’s likely that the disease mechanism is precisely adapted to human-specific molecules in the cell walls of our small intestine, and the molecular structure of the bacteria’s toxins.

The annotation on this 19th century medical illustration reads. ‘A young woman of Vienna, 23. The same woman one hour after the onset of cholera, and four hours before death.’
Wellcome Library, London, via Flickr/the lost gallery

Over millennia, both the disease-causing organism (pathogen) and host have been evolving counter-strategies against each other: the host to evade the pathogen, and pathogen to invade the host. These battles have led to the bacteria becoming host-specific, and now only able to infect humans.

The cholera vaccine works by taking advantage of this close host/pathogen relationship. It inhibits the action of the B portion of the cholera toxin, hence it prevents the bacteria from attaching to the intestinal wall.

Other waterborne diseases are caused by other pathogens (although the specific mechanisms or molecules involved differ). In some cases, as in cholera, the molecules required for infection are host-specific. Whilst other pathogens are not species specific, they are often associated with more closely-related species than less closely-related species. For example, foot and mouth disease affects cattle, sheep, deer and pigs, because they are all cloven-hoofed animals (Artiodatyla) and thus closely-related species.

Hippopotamuses (Hippopotamus amphibious and Choeropsis liberiensis) are more closely related to cetaceans (whales and dolphins), than humans, and therefore it is not surprising that they have different pathogens. That being said, hippopotamuses, like other animals, are likely to suffer from loose stools (dung) from time to time, whether due to other pathogens, or the quality of the huge amounts of plant material they ingest on a daily basis.

Dung is super important in hippopotamus society. Hippopotamus defecation or “dung showering” involves flicking their tail at the same time as defecating to distribute their dung far and wide, hence dung is used to mark their territory and assert dominance.

If hippopotamus dung spread a disease like cholera, it could be rapidly fatal for large populations. It is likely that the individuals affected would be removed by natural selection. Those that were resistant, or only mildly affected, would overcome the disease and live on to produce disease-resistant offspring. Over time, it is therefore likely hippopotamuses have adapted to their aquatic environments and thus rarely, if ever, become infected with waterborne diseases.

The Conversation* Email your question to alwayswondered@theconversation.edu.au

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Julie Old, Associate Professor, Biology, Zoology, Animal Science, Western Sydney University

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

Debris from the 2011 tsunami carried hundreds of species across the Pacific Ocean



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Japanese vessel washed ashore on Long Beach, Washington being inspected by John Chapman.
Russ Lewis

Steven Chown, Monash University

When a foreign species arrives in a new environment and spreads to cause some form of economic, health, or ecological harm, it’s called a biological invasion. Often stowing away among the cargo of ships and aircraft, such invaders cause billions of dollars of economic loss annually across the globe and have devastating impacts on the environment.

While the number of introductions which eventually lead to such invasions is rising across the globe, most accidental introduction events involve small numbers of individuals and species showing up in a new area.

But new research published today in Science has found that hundreds of marine species travelled from Japan to North America in the wake of the 2011 Tōhoku earthquake and tsunami (which struck the east coast of Japan with devastating consequences).


Read more: Widespread invasive species control is a risky business


Marine introductions result from biofouling, the process by which organisms start growing on virtually any submerged surface. Within days a slimy bacterial film develops. After months to a few years (depending on the water temperature) fully formed communities may be found, including algae, molluscs such as mussels, bryozoans, crustaceans, and other animals.

Current biosecurity measures, such as antifouling on ships and border surveillance, are designed to deal with a steady stream of potential invaders. But they are ill-equipped to deal with an introduction event of the scale recorded along most of the North American coast. This would be just as true for Australia, with its extensive coastlines, as it is for North America.

Mass marine migration

Marine animals were transported vast distances on tsunami debris.
Carla Schaffer / AAAS

This research, led by James Carlton of Williams College, shows that over a few years after the 2011 earthquake and tsunami, many marine organisms arrived along the west coast of North America on debris derived from human activity. The debris ranged from small pieces of plastic to buoys, to floating docks and damaged marine vessels. All of these items harboured organisms. Across the full range of debris surveyed, scores of individuals from roughly 300 species of marine creatures arrived alive. Most of them were new to North America.

The tsunami swept coastal infrastructure and many human artefacts out to sea. Items that had already been in the water before the tsunami carried their marine communities along with them. The North Pacific Current then transported these living communities across the Pacific to Alaska, British Columbia, Oregon, Washington and California.

Japanese tsunami buoy with Japanese oyster Crassostrea gigas, found floating offshore of Alsea Bay, Oregon in 2012.
James T. Carlton

What makes this process unusual is the way a natural extreme event – the earthquake and associated tsunami – gave rise to an extraordinarily large introduction event because of its impact on coastal infrastructure. The researchers argue that this event is of unprecedented magnitude, constituting what they call “tsunami-driven megarafting”: rafting being the process by which organisms may travel across oceans on debris – natural or otherwise.

It’s not known how many of these new species will establish themselves and spread in their new environment. But, given what we know about the invasion process, it’s certain at least some will. Often, establishment and initial population growth is hidden, especially in marine species. Only once it is either costly or impossible to do something about a new species, is it detected.

Biosecurity surveillance systems are designed to overcome this problem, but surveillance of an entire coast for multiple species is a significant challenge.

Perhaps one of the largest questions the study raises is whether this was a once off event. Might similar future occurrences be expected? Given the rapid rate of coastal infrastructure development, the answer is clear: this adds a new dimension to coastal biosecurity that will have to be considered.

The ConversationInvestment in coastal planning and early warning systems will help, as will reductions in plastic pollution. But such investment may be of little value if action is not taken to adhere to, and then exceed, nationally determined contributions to the Paris Agreement. Without doing so, a climate change-driven sea level rise of more than 1 m by the end of the century may be expected. This will add significantly to the risks posed by the interactions between natural extreme events and the continued development of coastal infrastructure. In other words, this research has uncovered what might be an increasingly common new ecological process in the Anthropocene – the era of human-driven global change.

Steven Chown, Professor of Biological Sciences, Monash University

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

Renewables will be cheaper than coal in the future. Here are the numbers


Ken Baldwin, Australian National University

In a recent Conversation FactCheck I examined the question: “Is coal still cheaper than renewables as an energy source?” In that article, we assessed how things stand today. Now let’s look to the future.

In Australia, 87% of our electricity generation comes from fossil fuels. That’s one of the highest levels of fossil fuel generation in the world.

So we have important decisions to make about how we’ll generate energy as Australia’s fleet of coal-fired power stations reach the end of their operating lives, and as we move to decarbonise the economy to meet our climate goals following the Paris agreement.

What will the cost of coal-fired and renewable energy be in the coming decades? Let’s look at the numbers.

Improvements in technology will make renewables cheaper

As technology and economies of scale improve over time, the initial capital cost of building an energy generator decreases. This is known as the “learning rate”. Improvements in technology are expected to reduce the price of renewables more so than coal in coming years.

The chart below, produced by consulting firm Jacobs Group and published in the recent Finkel review of the National Electricity Market, shows the projected levelised cost of electricity (LCOE) for a range of technologies in 2020, 2030 and 2050.

The chart shows a significant reduction in the cost of solar and wind, and a relatively static cost for mature technologies such as coal and gas. It also shows that large-scale solar photovoltaic (PV) generation, with a faster learning rate, is projected to be cheaper than wind generation from around 2020.

Notes: Numbers in Figure A.1 refer to the average.
For each generation technology shown in the chart, the range shows the lowest cost to the highest cost project available in Jacobs’ model, based on the input assumptions in the relevant year. The average is the average cost across the range of projects; it may not be the midpoint between the highest and lowest cost project.
Large-scale Solar Photovoltaic includes fixed plate, single and double axis tracking.
Large-scale Solar Photovoltaic with storage includes 3 hours storage at 100 per cent capacity.
Solar Thermal with storage includes 12 hours storage at 100 per cent capacity.
Cost of capital assumptions are consistent with those used in policy cases, that is, without the risk premium applied.
The assumptions for the electricity modelling were finalised in February 2017 and do not take into account recent reductions in technology costs (e.g. recent wind farm announcements).

Independent Review into the Future Security of the National Electricity Market

Wind prices are already falling rapidly. For example: the graph above shows the 2020 price for wind at A$92 per megawatt-hour (MWh). But when the assumptions for the electricity modelling were finalised in February 2017, that price was already out of date.

In its 2016 Next Generation Renewables Auction, the Australian Capital Territory government secured a fixed price for wind of A$73 per MWh over 20 years (or A$56 per MWh in constant dollars at 3% inflation).

In May 2017, the Victorian renewable energy auction set a record low fixed price for wind of A$50-60 per MWh over 12 years (or A$43-51 per MWh in constant dollars at 3% inflation). This is below the AGL price for electricity from the Silverton wind farm of $65 per MWh fixed over five years.

These long-term renewable contracts are similar to a LCOE, because they extend over a large fraction of the lifetime of the wind farm.

The tables and graph below show a selection of renewable energy long-term contract prices across Australia in recent years, and illustrate a gradual decline in wind energy auction results (in constant 2016 dollars), consistent with improvements in technology and economies of scale.

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But this analysis is still based on LCOE comparisons – or what it would cost to use these technologies for a simple “plug and play” replacement of an old generator.

Now let’s price in the cost of changes needed to the entire electricity network to support the use of renewables, and to price in other factors, such as climate change.

Carbon pricing will increase the cost of coal-fired power

The economic, environmental and social costs of greenhouse gas emissions are not included in simple electricity cost calculations, such as the LCOE analysis above. Neither are the costs of other factors, such as the health effects of air particle pollution, or deaths arising from coal mining.

The risk of the possible introduction of carbon emissions mitigation policies can be indirectly factored into the LCOE of coal-fired power through higher rates for the weighted average cost of capital (in other words, higher interest rates for loans).

The Jacobs report to the Finkel Review estimates that the weighted average cost of capital for coal will be 15%, compared with 7% for renewables.

The cost of greenhouse gas emissions can be incorporated more directly into energy prices by putting a price on carbon. Many economists maintain that carbon pricing is the most cost-effective way to reduce global carbon emissions.

One megawatt-hour of coal-fired electricity creates approximately one tonne of carbon dioxide. So even a conservative carbon price of around A$20 per tonne would increase the levelised cost of coal generation by around A$20 per MWh, putting it at almost A$100 per MWh in 2020.

According to the Jacobs analysis, this would make both wind and large-scale photovoltaics – at A$92 and A$91 per MWh, respectively – cheaper than any fossil fuel source from the year 2020.

It’s worth noting here the ultimate inevitability of a price signal on carbon, even if Australia continues to resist the idea of implementing a simple carbon price. Other policies currently under consideration, including some form of a clean energy target, would put similar upward price pressure on coal relative to renewables, while the global move towards carbon pricing will eventually see Australia follow suit or risk imposts on its carbon-exposed exports.

Australia’s grid needs an upgrade

Renewable energy (excluding hydro power) accounted for around 6% of Australia’s energy supply in the 2015-16 financial year. Once renewable energy exceeds say, 50%, of Australia’s total energy supply, the LCOE for renewables should be used with caution.

This is because most renewable energy – like that generated by wind and solar – is intermittent, and needs to be “balanced” (or backed up) in order to be reliable. This requires investment in energy storage. We also need more transmission lines within the electricity grid to ensure ready access to renewable energy and storage in different regions, which increases transmission costs.

And, there are additional engineering requirements, like building “inertia” into the electricity system to maintain voltage and frequency stability. Each additional requirement increases the cost of electricity beyond the levelised cost. But by how much?

Australian National University researchers calculated that the addition of pumped-hydro storage and extra network construction would add a levelised cost of balancing of A$25-30 per MWh to the levelised cost of renewable electricity.

The researchers predicted that eventually a future 100% renewable energy system would have a levelised cost of generation in current dollars of around A$50 per MWh, to which adding the levelised cost of balancing would yield a network-adjusted LCOE of around A$75-80 per MWh.

The Australian National University result is similar to the Jacobs 2050 LCOE prediction for large-scale solar photovoltaic plus pumped hydro of around A$69 per MWh, which doesn’t include extra network costs.

The AEMO 100% Renewables Study indicated that this would add another A$6-10 per MWh, yielding a comparable total in the range A$75-79 per MWh.

This would make a 100% renewables system competitive with new-build supercritical (ultrasupercritical) coal, which, according to the Jacobs calculations in the chart above, would come in at around A$75(80) per MWh between 2020 and 2050.

This projection for supercritical coal is consistent with other studies by the CO2CRC in 2015 (A$80 per MWh) and used by CSIRO in 2017 (A$65-80 per MWh).

So, what’s the bottom line?

The ConversationBy the time renewables dominate electricity supply in Australia, it’s highly likely that a price on carbon will have been introduced. A conservative carbon price of at least A$20 per tonne would put coal in the A$100-plus bracket for a megawatt-hour of electricity. A completely renewable electricity system, at A$75-80 per MWh, would then be more affordable than coal economically, and more desirable environmentally.

Ken Baldwin, Director, Energy Change Institute, Australian National University

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