Author Archives: Euan Ritchie

About Euan Ritchie

I apply ecological theory with good doses of field work to seek solutions to the challenges of conserving biodiversity.

The Conversation: A numbers game: killing rabbits to conserve native mammals

Controlling rabbit populations has a key role in conserving Australia’s native plants and animals

By Euan Ritchie (Deakin University), Damien Fordham (University of Adelaide), and Miguel Lurgi, (Centre national de la recherche scientifique)

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

Invasive species have a devastating effect on biodiversity. In Australia, introduced red foxes and feral cats have been implicated in the majority of the extinctions of the native mammal fauna, which has been decimated since European arrival.

But there’s a herbivore that also causes eco-catastrophe. Rabbits both compete with native animals for food and shelter and act as easy prey for abundant populations of cats and foxes. By over-grazing vegetation and reducing habitat complexity, they make hunting easier for introduced predators.

Food webs are complex. Because of this, once an invasive species is embedded in a food web, simply eradicating them without considering the potential knock-on effects to other species they interact with, could cause unintended and undesirable consequences. We modelled different rates of rabbit population reduction to assess what level of control might be best for aiding the conservation of native mammals and not causing negative outcomes.

Rabbit numbers boom and crash

Rabbits, famously, reproduce rapidly and can cope with a relatively high predation rate. This can cause “hyper-predation”, where rabbit-inflated cat and fox populations indirectly increase the predation pressure on native mammals. This is especially so when rabbit populations intermittently crash due to, for example, extreme environmental events (like severe and prolonged droughts) or disease. This causes predators to switch their diet and eat more native mammals.

This logically suggests that reducing rabbit numbers might thus help reduce cat and fox populations, by removing their abundant prey. Collectively this should benefit native plants and animals, including many threatened mammal species. However, ecosystem and pest management is a complex game.

When controlling rabbits we need to look beyond one or two species. We should consider the potential consequences for the entire ecological community, which ultimately depend on how changes in one species percolate through the network of ecological interactions between them.

Our new research, recently published in the Journal of Applied Ecology, set out to examine these questions in more detail. We consider other key players in Australia’s arid regions, such as kangaroos and dingoes, when looking at the effects of rabbit control on small native mammals. Our aim was to provide a better understanding of how changes in rabbit populations might affect other species via the food web.

We developed a multi-species ecological network model to describe and quantify how changing rabbit abundance can affect species on different feeding levels. In addition to rabbits, small native mammals, and mesopredators (cats and foxes), our model also considers apex predators (dingo) and large herbivores (kangaroo) as part of the Australian arid food web. This model allowed us to examine changes in predator-prey interactions (including potential prey switching and hyper-predation) and how these could affect the survival of native prey through time.

We found that removing rabbits at rates between 30-40% appeared to benefit small mammals. This is approximately the rate at which rabbits are currently managed in Australia using biocontrol agents (introduced diseases).

Rabbit control in Australia typically involves a “press and pulse” approach. Rabbit populations are suppressed via biocontrol (press) and periods of warren destruction and poisoning (pulse). Finding that reducing rabbit populations by around 40% seems most beneficial to small mammals is important, as it informs how and when we combine these strategies.

The 40% rate corresponds well with the disease-induced (press) mortality rate in rabbit populations due to rabbit haemorrhagic disease and myxomatosis. These are the primary biocontrol agents used in arid Australia to control rabbit populations.

Our study supports rabbit-reduction strategies that involve sustained “press” control, that kill a moderate portion of a rabbit population, with less frequent removal at higher proportions of the population.

To effectively manage invasive species, it’s important to focus on entire communities. Targeting single species might not be enough – every animal exists within a complex web of interactions.

There has been much focus by the current government on controlling feral cats, as a way to conserve many of Australia’s unique and threatened mammal species.

However, more focus could be devoted to protecting habitat cover and complexity, by reducing the land clearing and over-grazing that makes hunting easier. We can also manage rabbits sensibly to reduce competition for resources, and indirectly control cats and foxes.
The Conversation

Eradicating abundant invasive prey could cause unexpected and varied biodiversity outcomes: The importance of multispecies interactions

Authors: Miguel Lurgi, Euan G Ritchie, and Damien A Fordham

Published in: Journal of Applied Ecology

Abstract

Abundant and widely distributed invasive prey can negatively affect co‐occurring native species by competing for food and/or shelter, removing vegetation cover and reducing habitat complexity (changing predation risk), and by sustaining elevated abundances of invasive mesopredators. However, information regarding the community and trophic consequences of controlling invasive prey and their temporal dynamics remain poorly understood.

We used multispecies ecological network models to simulate the consequences of changing European rabbit Oryctolagus cuniculus abundance in an arid mammalian community. We quantified how changes in the dominant prey (rabbits) affected multiple trophic levels, examining changes in predator–prey interactions through time and how they affected native prey persistence.

Our results suggest that removal of rabbits can benefit native biodiversity immediately at removal rates between 30% and 40%. However, beyond these levels, densities of small native mammals will decline in the short term. The processes underpinning these declines are: (a) increased competition for resources (vegetation) with kangaroos Macropus spp., whose numbers increase due to their release from competition with rabbits and (b) increased predation (prey switching) by feral cats Felis catus. Both effects are mediated by dingoes Canis dingo, a native apex predator.

Importantly, native mammal abundance recovers after a time delay, which is prolonged when high rates of rabbit control are applied. This is likely due to a reduction in hyperpredation by invasive feral cats and red foxes Vulpes vulpes following rabbit removal.

Continued eradication of rabbits in arid Australia will benefit native species due to a decrease in apparent competition for resources and by alleviating hyperpredation from invasive mesopredators. Furthermore, ecosystem‐level conservation benefits of reducing invasive prey abundance are as important as direct control of invasive mesopredators.

Synthesis and applications: Multispecies ecological network models provide wildlife managers with tools to better understand and predict the complex effects of species removal and control on both intact and modified ecosystems. Our results show that management of the Australian arid zone can benefit from controlling invasive prey as well as invasive predators. However, invasive species control can cause unexpected outcomes on native biodiversity. This extends to other systems where dominant prey may play fundamental roles in ecosystem structure and function.

Lurgi M, Ritchie EG, Fordham DA (2018) Eradicating abundant invasive prey could cause unexpected and varied biodiversity outcomes: The importance of multispecies interactions, Journal of Applied Ecology, PDF DOI 

Evaluating the efficacy of predator removal in a conflict-prone world

Authors: Robert J Lennox, Austin J Gallagher, Euan G Ritchie, and Steven J Cooke

Published in: Biological Conservation, volume 224 (August 2018)

Abstract

Predators shape ecosystem structure and function through their direct and indirect effects on prey, which permeate through ecological communities. Predators are often perceived as competitors or threats to human values or well-being. This conflict has persisted for centuries, often resulting in predator removal (i.e. killing) via targeted culling, trapping, poisoning, and/or public hunts. Predator removal persists as a management strategy but requires scientific evaluation to assess the impacts of these actions, and to develop a way forward in a world where human-predator conflict may intensify due to predator reintroduction and rewilding, alongside an expanding human population.

We reviewed literature investigating predator removal and focused on identifying instances of successes and failures. We found that predator removal was generally intended to protect domestic animals from depredation, to preserve prey species, or to mitigate risks of direct human conflict, corresponding to being conducted in farmland, wild land, or urban areas. Because of the different motivations for predator removal, there was no consistent definition of what success entailed so we developed one with which to assess studies we reviewed. Research tended to be retrospective and correlative and there were few controlled experimental approaches that evaluated whether predator removal met our definition of success, making formal meta-analysis impossible. Predator removal appeared to only be effective for the short-term, failing in the absence of sustained predator suppression. This means predator removal was typically an ineffective and costly approach to conflicts between humans and predators.

Management must consider the role of the predator within the ecosystem and the potential consequences of removal on competitors and prey. Simulations or models can be generated to predict responses prior to removing predators. We also suggest that alternatives to predator removal be further developed and researched.

Ultimately, humans must coexist with predators and learning how best to do so may resolve many conflicts.

Lennox RJ, Gallagher AJ, Ritchie EG, Cooke SJ (2018) Evaluating the efficacy of predator removal in a conflict-prone world, Biological Conservation, PDF DOI

Passing the brumby bill is a backward step for environmental protection in Australia

With the passing of the so-called “brumby bill” against scientific advice, feral horses will continue to damage the internationally significant Kosciuszko National Park.

By Don Driscoll, Euan Ritchie, and Tim Doherty (Deakin University)

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

Late on Wednesday night the so-called “brumby bill” was passed without amendment in the New South Wales Parliament. The controversial Coalition bill, supported by the Christian Democrats and the Shooters, Fishers and Farmers Party, means that feral horses must be kept in Kosciuszko National Park.

It also creates a community advisory panel, with no scientific experts appointed, to advise the minister on how to manage the horse population in the alpine ecosystem.

The NSW government has attracted accusations of a conflict of interest. Former Nationals member Peter Cochran, who now runs a commercial venture offering brumbie-spotting rides through the National Park (and who has donated extensively to Deputy Premier John Barilaro) reportedly commissioned lawyers to draft the bill. Peter Cochran, John Barilaro and Gladys Berejiklian have denied all accusations of conflict of interest and underhanded conduct.

The bill has also been criticised by scientific bodies. In a letter to NSW Premier Gladys Berejiklian this week, the Australian Academy of Science noted that the legislation removes consideration of scientific advice, and called for the bill to be withdrawn or substantially amended.

In a rare move, the International Union for the Conservation of Nature has also written to the NSW government, expressing concern over the potential degradation of this internationally significant national park.

Out of step with other states

The NSW Labor Party does not support the bill and has pledged to repeal the legislation if elected next March. The legislation represents a radical change in NSW’s management of feral horses, coming after a 2016 draft strategy that recommenced reducing their population by 90% over 20 years.

NSW now stands in contrast to other Australian states. Last Saturday, Victoria launched its Feral Horse Strategic Action Plan. That plan aims to protect native species and ecosystems in national parks by removing or controlling feral horses and is a welcome step in the right direction. Victorian environment minister Lily D’Ambrosio called on the NSW and federal governments to support a unified approach to feral horse management in Australia’s alpine regions.

Is culling in or out?

The Victorian plan excludes aerial culling but will revisit horse control methods if the proposed trapping methods don’t reduce environmental impacts. Aerial culling is widely practised throughout Australia, including Western Australia, the Northern Territory, Queensland (where culling was used to improve road safety), and the Australian Capital Territory, which borders Kosciuszko National Park.

Barilaro argued against aerial culling when he presented the Brumby bill to parliament, calling it cruel and barbaric. He reiterated that the bill is meant to prevent lethal control in his response to Victoria’s announcement. But surprisingly, the draft legislation makes no mention of control methods, lethal or otherwise.

The deputy premier also referred to the Guy Fawkes National Park horse cull in northern NSW in 2000 to support his argument against aerial culling. But an independent enquiry found that the cull was an appropriate humane response to the situation, where horses were starving to death and causing environmental damage after a fire. The RSPCA and independent reports show that aerial culling is an acceptable and humane way to manage horse numbers.

Further, the brumby bill now locks in the predictable outcome that thousands of horses are likely to starve to death in the next drought or after large fires. It is therefore puzzling that actions likely to increase horse suffering are not of great concern to many within the pro-brumby lobby.

Greater emphasis, instead, has been put on a cultural argument for protecting feral horses: for example, by claiming that feral horses made enormous contributions to Australia’s World War One effort. However, the cultural heritage report prepared for the NSW National Parks Service says “there is no definitive evidence that remount horses were directly taken from the brumby population of what is now Kosciusko National Park”.

The Sydney Olympics opening ceremony was also offered as evidence that brumbies are integral to Australian culture. However, Australian Stock horses, not brumbies, were showcased at the Sydney Olympics – a distinct breed, established by horse enthusiasts in the 1970s.

That said, it is true that horses in the snowy mountains do have local cultural value. But so too does the native fauna and flora threatened by feral horses, many of which only occur in Australia’s high country. This includes species such as the southern corroboree frog, alpine she-oak skink, broad-toothed rat, Raleigh sedge and mauve burr-daisy.

Can we compromise?

Is a compromise possible, in which both cultural and conservation goals can be accommodated? We think so. The feral horse population can be removed from the national parks and sensitive ecosystems. Brumby herds can thrive on extensive private property in the region, an approach already proven in South Australia’s Coffin Bay National Park.

The brumby bill was written and presented to parliament by groups with at best a perceived conflict of interest, and promoted by using inaccurate information about culling and heritage. It has been roundly criticised by leading national and international scientific bodies for not taking adequate account of science and the key role of national parks in conserving biodiversity.

That this bill has now passed the NSW upper house is a further backward step for conservation goals and Australia’s international reputation for environmental protection, and sets a dangerous precedent by undermining prominent national and state environmental policy. It remains to be seen how this legislation aligns with the federal Environment Protection and Biodiversity Conservation Act, given that it literally tramples over several matters of national environmental significance.

The Conversation

The Conversation: Killing sharks, wolves and other top predators won’t solve conflicts

Black tip sharks swim with tropical fish in a lagoon in French Polynesia.

By Robert Lennox (Carleton University), Austin Gallagher (University of Miami), Euan Ritchie (Deakin University) and Steven J Cooke (Carleton University).

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

In French Polynesia, fishing is an integral part of everyday life. The people living here fish on the flats and along the reef using nets, hooks and line, harpoons, spearguns and traditional artisanal traps.

They fish for food. They are also seeing the benefits of using their traditional knowledge to guide recreational fishing tourists — a business with potential to improve long term employment security.

Abundant sharks in the lagoon led to questions about their contribution to the fishery and whether it would help the fishery if they were targeted. This is a question that is often on the minds of humans when they encounter predators.

As an ecologist working with the fish populations in French Polynesia, I went looking for research about what happens to an ecosystem when a predator is removed. Are the responses predictable? Does it work? Can we make generalizations?

Our new study, published in Biological Conservation, surveyed the research on predator removal and identified several interesting — and perhaps unexpected — trends.

Humans and other predators

Predators are among the most charismatic animals on Earth — lions, eagles and sharks adorn many human symbols. On land, in the air and in water, predators fascinate and inspire, they are quintessential representations of nature’s majesty and might.

In spite of their ecological, economic and cultural significance, predators are among the most heavily persecuted animals, due to conflict with humans and their assets.

Predators attack and kill livestock, hunt economically important prey and can kill or injure people or be perceived as a threat to human safety. These conflicts may motivate humans to try to manage predators to lessen the damages.

One of the oldest and most rudimentary methods is to cull or remove them, even though predators are already rare and some are threatened with extinction.

The motivation to remove predators is easy to understand, but what if predator removal does not even achieve the desired outcomes?

In balance

Predators are essential to ecosystems because they regulate prey populations. Without predators, prey can become over-abundant. This can result in damage to local plants, as well as disease outbreaks that can spread to domesticated animals.

Top predators like wolves dominate small predators like coyotes, keeping those populations in check too. Without predators, ecosystems become unbalanced in many ways because plants, herbivores and small predators change in response to their loss.

In a perfect scenario, successful predator removal would strike a balance. It would reduce conflict and be sustainable, but not cause the predator population to disappear entirely. However, our review of 141 studies of predator removal revealed that success is rarely achieved.

Livestock attacks weren’t always reduced when predators were removed, and the human-wildlife conflict remained. On top of that, new predators often moved into vacated territory and recolonized areas where others had been removed. For example, when caracal (a type of wild cat) and leopard were culled in South Africa, predator conflicts on farms increased.

A small number of studies have shown successful removal of predators without harming the predator population, and led to increases in the prey population. However, these examples of success were generally from the Arctic where wolves were removed to increase caribou or moose numbers. In that scenario, there are fewer links in the food web, possibly making responses more predictable.

Generally, however, the responses were unpredictable and removing predators often failed for one reason or another.

Coexistence, not conflict

Ecosystems are complex networks of species. They include plants, decomposers, naturally subordinate predators (such as feral cats, foxes and coyotes), pathogens, predators and their prey. Together, they all play vital roles in regulating each other.

When humans remove predators, the effects are consistently negative. The action can, for example, fracture wolf packs into smaller units, or increase the reproductive rates of coyotes to produce even more offspring. This can have knock on effects, including an increase in disease, plant damage if herbivore populations explode and even an increase in the number of collisions between large herbivores, such as moose, and vehicles.

Instead of killing predators, there are other measures we can take to reduce conflict and learn to live with wildlife. In parts of Alberta, biologists are encouraging landowners to use electric fencing around bee hives and chicken coops to fend off bears. These types of non-lethal solutions can be tested and may often be more effective than removing the predator.

Other studies have suggested that “rewilding” an ecosystem — that is, reintroducing species into the ecosystem — can reduce conflicts. When their prey are abundant, the predators have less interest in nearby livestock. One study showed that lynx conflict with farmers increased when their natural prey, roe deer, were scarcer.

Essential elements

Instead of removing predators to manage human-wildlife conflict, we should be looking towards non-lethal alternatives. Using deterrent devices (lights, sounds or flapping material) can keep predators away from homes, fields and livestock.

The services that predators and functioning ecosystems provide to humans are of enormous value, and we would be wise to work hard to conserve and maintain them for the benefit of all.

Predators aren’t only symbols, they are essential parts of healthy terrestrial and aquatic landscapes. And beyond what we value, we should feel an imperative to preserve the diversity of life we share Earth with, most of which precedes our own evolution.

Of course, there will be times when predator removal may be necessary to protect people and their interests. Interventions that champion the principles of coexistence between humans and predators may be more successful and justifiable approaches to managing wildlife.

Efforts to protect predators or proactively promote their return, rather than continue contributing to their decline and extinction, are among the greatest conservation challenges we face.
The Conversation

Crowdfunded campaigns are conserving the Earth’s environment

Crowdfunded campaigns to save the orange-bellied parrot are a rare ray of hope. Image credit: Fatih Sam

By Eduardo Gallo-Cajiao (University of Queensland), Carla Archibald (University of Queensland), Euan Ritchie (Deakin University), Rachel Friedman (University of Queensland), Richard Fuller (The University of Queensland), Rochelle Steven (University of Queensland), and Tiffany Morrison (James Cook University)

This article was originally published on The Conversation. Read the original article, including reader comments.

If not for the public’s generosity, the iconic Statue of Liberty might not have the solid and impressive footing she does today. In the late 1800s, government funds for the monument were exhausted. Yet through a fundraising campaign, the New York World newspaper garnered support from over 160,000 residents to cover the pedestal costs.

Just as large monuments need solid bases to ensure their long-term existence, so too does the environment. In the case of nature conservation, it requires money to support diverse research projects, on-ground activities, and outreach aimed at protecting and managing species and habitats.

While the health of the environment continues to decline globally, in most regions government funding falls short of what is required to stem the losses. Crowdfunding plays an important and under-appreciated role for biodiversity conservation.

Our new research presents a global analysis of how crowdfunding, still a relatively novel and minor financial mechanism in the conservation community, is contributing to conservation around the world.

Show me the money. What’s being funded and why?

Crowdfunding offers a powerful mechanism for mobilising resources for conservation across borders. We recorded 577 conservation-oriented projects (from 72 crowdfunding platforms), which have raised around US$4.8 million since 2009. The people leading these projects were based in 38 countries, but projects took place across 80 countries.

This pattern has important implications for conservation, because there is often a mismatch between high-priority areas for global conservation and countries with the greatest financial and technical capacity. For instance, we discovered that a third of the projects were delivered in different countries to where their proponents were based. The USA, UK and Australia were the countries with the highest outflow of projects (“project exporters”). Indonesia, South Africa, Costa Rica and Mexico had the highest inflow (“project importers”).

Crowdfunding could be supporting conservation work of actors that do not have as much capacity for raising funds.

The people leading projects were primarily from non-governmental organisations (35%) or universities (30%), or were freelancers (26%). Importantly, among non-governmental organisations, we discovered organisations operating at sub-national levels proposed a majority of projects.

Additionally, crowdfunding for conservation is not all about research. While most of the projects we reviewed focused on research (40%), many tackled raising awareness of conservation-related issues (31%) or boots-on-the-ground activities (21%). This expands the sphere of anecdotal evidence and commentary about crowdfunding related to conservation, which has so far revolved around research. For the first time, we’ve systematically unpacked how these funds are being used for additional activities to support conservation.

Crowdfunding can also support innovative projects that traditional funding agencies deem too risky or unconventional. For example, one project supported buying and training two Maremma sheepdogs to protect penguins against predatory foxes in southeastern Australia. (That might sound familiar to those who’ve seen the movie Oddball.)

Such opportunities for innovation can have important consequences for conservation worldwide; crowdfunding could be considered an incubator for novel ideas before widespread dissemination.

More than half of the projects we recorded (around 58%) largely focused on species. These included a disproportionate number of threatened bird and mammal species.

Prominent projects to save orange-bellied parrots or Papua New Guinea’s endangered tree kangaroos are important success stories.

This is not to underplay crowdfunding’s importance for ecosystems – whether land-based (20%), marine (9%) or freshwater (4%). Crowfunding is supporting projects ranging from protection of wilderness areas in remote Tasmania to research informing the conservation of the Californian coast.

Crowdfunding benefits extend beyond dollars and cents

The amount of money for conservation via crowdfunding has so far been relatively modest compared to more traditional conservation finance mechanisms. However, the benefits of crowdfunding extend well beyond dollars and cents. Crowdfunding helps communicate environmental issues and empower researchers and communities.

The figure below shows the reach of a single tweet during the Big Roo Count campaign. It shows how conservation-related messages can spread widely and engage communities via social media.

Crowdfunding is an exciting new tool in the conservation toolbox. But, ultimately, traditional funding sources, like government agencies, still have a major role and duty to invest adequately in environmental protection and nature conservation. Considering the current extinction crisis, governments must avoid further outsourcing of such responsibilities.

The discussion over novel sources and recipients of conservation funding continues. At the same time, transparency and oversight remain critical for managing expectations and overall effectiveness of funding. Crowdfunding contributes one more building block to democratising conservation funding and increasing transparency.

The authors would like to acknowledge the contribution of Edward Game.
The Conversation

Crowdfunding biodiversity conservation

Authors: Eduardo Gallo-Cajiao, Carla Archibald, Rachel Friedman, Richard A Fuller, Edward T Game, Tiffany Morrison, and Euan G Ritchie

Published in: Conservation Biology

Abstract

Raising funds is critical for conserving biodiversity and hence so too is scrutinizing emerging financial mechanisms that might help achieve this goal. In this context, anecdotal evidence indicates crowdfunding is being used to support a variety of activities needed for biodiversity conservation, yet its magnitude and allocation remain largely unknown.

We conducted a global analysis to help address this knowledge gap, based on empirical data from conservation‐focused projects extracted from crowdfunding platforms. For each project, we determined the funds raised, date, country of implementation, proponent characteristics, activity type, biodiversity realm, and target taxa.

We identified 72 relevant platforms and 577 conservation‐focused projects that have raised US$4,790,634 since 2009. Whilst proponents were based in 38 countries, projects were delivered across 80 countries, indicating a potential mechanism of resource mobilization. Proponents were from non‐governmental organizations (35%), universities (30%), or were freelancers (26%). Most projects were for research (40%), persuasion (31%), and on‐ground actions (21%). Projects have focused primarily on species (57.7%) and terrestrial ecosystems (20.3%), and less on marine (8.8%) and freshwater ecosystems (3.6%). Projects have focused on 208 species, including a disproportionate number of threatened bird and mammal species.

Crowdfunding for biodiversity conservation has now become a global phenomenon and presents signals for potential expansion, despite possible pitfalls. Opportunities arise from its spatial amplifying effect, steady increase over time, inclusion of Cinderella species, adoption by multiple actors, and funding of a range of activities beyond research.

Our study paves the way for further research on key questions, such as campaign success rates, effectiveness, and drivers of adoption. Even though the capital input of crowdfunding so far has been modest compared to other conservation finance mechanisms, its contribution goes beyond funding research and providing capital.

Embraced with due care, crowdfunding could potentially become an increasingly important financial mechanism for biodiversity conservation.

Gallo-Cajiao E, Archibald C, Friedman R, Steven R, Fuller RA, Game ET, Morrison TH, Ritchie EG (2018) Crowdfunding biodiversity conservation, Conservation Biology PDF DOI