Invasive ants: federal budget takes aim but will it be a lethal shot?



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Argentine ants are a fact of life in many parts of Australia, but can still potentially be banished from Norfolk Island.
Davefoc/Wikimedia Commons, CC BY-SA

Lori Lach, James Cook University

Amid all the usual items we expect to see in the federal budget was one that raised eyebrows: A$28.8 million for three ant eradication programs.

Yet amid the inevitable media puns about the government “upping the ant-e”, we should note that these funds are for the continuation of existing programs that have already attracted significant funding and made substantial progress. Stopping now would have meant previous funding was wasted.

The funds will go a long way towards protecting Australia’s economy and environment from the damage wrought by invasive ants. But despite the apparent cash splurge, it nevertheless falls short of what is really needed.

Of the $28.8 million, $18.3 million was for the National Red Imported Fire Ant Eradication Program. These funds are part of a $411 million, ten-year program begun in 2017 to eradicate red imported fire ants from southeast Queensland, the only place they are found in Australia.




Read more:
Cannibalism helps fire ants invade new territory


Removing these pests will avoid an estimated $1.65 billion in total costs to 19 different parts of the economy. With previous funding, the program eradicated these ants from 8,300 hectares near the Port of Brisbane, making it the world’s largest ant eradication to date.

The Yellow Crazy Ant Eradication Program was allocated $9.2 million over three years. Yellow crazy ants have caused a cascade of ecological effects on Christmas Island, and at their peak abundance temporarily blinded a Queensland cane farmer with their acid spray.

The Wet Tropics Management Authority, which runs the program, had requested $6 million per year for six years to continue removing the ant from in and around the Wet Tropics World Heritage Area. The federal funding is $3 million short of this, and the authority is still waiting to hear whether the Queensland government will provide the remainder.

Since 2013, the program has received $9.5 million from the federal government (and $3 million from the Queensland government). No yellow crazy ants have been observed in about half of the target area in more than a year. A yet-to-be published analysis estimates the benefit-cost ratio for the program as 178:1.

“It’s a mop-up operation… we’ve got our foot on the throat of this thing.”

A further $1.3 million was allocated to the Argentine Ant Eradication Strategy on Norfolk Island in the South Pacific. Argentine ants have invaded places with Mediterranean-type climates all over the world, including southwestern Western Australia and parts of southern Australia, and become firmly established. But unlike those areas, the population on Norfolk Island is still considered small enough to be eradicable, and federally funded efforts to remove them began in 2010.

Yellow crazy ants in Queensland and Argentine ants on Norfolk Island directly threaten World Heritage Areas. The ants can have significant impacts on native birds, mammals, insects, reptiles, amphibians, and plants. Getting rid of them is important for meeting Australia’s international obligations to protect World Heritage sites.

What is ant eradication?

Ant eradication means removing all individuals of a particular ant species from a given area.

The first step is to define the extent of that area. Depending on the species, this may involve visual searches and/or placing lures such as sausages, cat food, or jam to attract the ants. The public can help by notifying relevant authorities of unusual ants in their gardens, and by not transporting materials that have ants on them.

The second step is treatment. Currently, the only way to eradicate ants is with insecticidal baits. Ants’ social structure makes this particularly challenging: killing the queens is vital for eradication, but queens typically stay sheltered in the nest – the only ants we see out foraging are workers.

Some of the most problematic ant species can have hundreds of queens and tens of thousands of workers per nest. They can reach extraordinarily high densities, partly because invasive ant species, unlike most of our native ant species, do not fight one another for territories.

Yellow crazy ants, proving it is possible to feel sorry for a cockroach.
Bradley Rentz/Wikimedia Commons, CC BY-SA

Beating ants means turning their biology against them. Bait needs to be attractive enough for workers to bring back to the colony and share, but not so deadly that they die before they get there. (And yes, this means if you’re spraying foraging ants in your kitchen you won’t get rid them for good, because the queens are somewhere hidden, laying more eggs and making more ants.)

Most ant eradication programs take three to four years to fine-tune their baiting regime because of a multitude of factors that need to be considered, such as seasonal changes in ant foraging behaviour and food preference, and the desire to avoid harming non-target species. Typically, two to six treatments are required, depending on the ant species, the size of the area, and the habitat type.

Beating the 1%

The hardest part of ant eradication is the end-game. Getting rid of the final 1% requires first finding them. This may mean painstaking searches through hundreds of hectares of bushland and residential areas, and the placement of hundreds of thousands of lures. Detector dogs can be very helpful, but they cannot be used in all environments and also need substantial resources for training, handling, and maintenance.

Ironically, it is at this stage that public and political support for eradication programs is most likely to wane, because ant numbers are too low to be seen as a threat to the public, economy or environment. Yet it is vital not to stop now, or else the remaining 1% will simply build up their numbers again. Experienced staff are also lost when programs suffer cuts or delays in their funding.




Read more:
Eradicating fire ants is still possible, but we have to choose now


Disappointingly not mentioned in the budget was funding for eradicating electric ants. Like red imported fire ants, electric ants have a painful sting, and when left to multiply will eventually turn gardens and swimming pools into no-go zones. They also pose a significant threat to native animals such as the southern cassowary, and can blind animals as large as elephants.

They are currently only found in the Cairns region. The National Electric Ant Eradication Program, funded by federal and state governments, ran from 2006 until 2017 and had likely reduced numbers down to that last 1%. The program has been running on state funding with reduced staff since then, but several new detections in the past three months demonstrate the cost of the gap in funding.

In those inevitable “federal budget winners and losers” lists, invasive ants have found themselves firmly in the losers column for 2019. But it’s worth remembering that most of the world’s roughly 15,000 known ant species provide vital services for the functioning of our ecosystems.

They aerate soil and redistribute its nutrients, protect plants from herbivores, disperse seeds, and repurpose dead organisms. They may even help slow down the spread of those pesky invasive ants that are much less friendly.The Conversation

Lori Lach, Associate Professor, James Cook University

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

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The summer bushfires you didn’t hear about, and the invasive species fuelling them



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Fire has burned through a swathe of the Tjoritja National Park.
Author provided

Christine Schlesinger, Charles Darwin University and Barry Judd, Charles Darwin University

In January 2019, fires burned across a 100-kilometre length of the iconic Tjoritja National Park in the West MacDonnell Ranges, from Ormiston Gorge nearly to the edge of Alice Springs.

These fires affected an area comparable to the recent Tasmanian fires, but attracted relatively little national attention. This is partly because the fires in Tasmania were so unusual – but we believe the fires in central Australia were just as unexpected.




Read more:
Dry lightning has set Tasmania ablaze, and climate change makes it more likely to happen again


In the past, fires of this magnitude have tended to come after heavy rain that powers the growth of native grasses, providing fuel for intense and widespread fires. But our research highlights the new danger posed by buffel grass, a highly invasive foreigner sweeping across inland Australia and able to grow fast without much water.

Far from being pristine, Tjoritja and the Western MacDonnell Ranges are now an invaded landscape under serious threat. Our changing climate and this tenacious invader have transformed fire risk in central Australia, meaning once-rare fires may occur far more often.

Buffel grass in Australia

Buffel grass is tough and fast-growing. First introduced to Australia in the 1870s by Afghan cameleers, the grass was extensively planted in central Australia in the 1960s during a prolonged drought.

Introductions of the drought-resistant plant for cattle feed and dust suppression have continued, and in recent decades buffel grass has become a ubiquitous feature of central Australian landscapes, including Tjoritja.

Buffel grass has now invaded extensive areas in the Northern Territory, Queensland, Western Australia and South Australia and is spreading into New South Wales and Victoria. It was legally recognised as a key threat in 2014, but so far only South Australia has prohibited its sale and created statewide zoning to enforce control or destruction.

Buffel grass crowds out other plants, creating effective “monocultures” – landscapes dominated by a single species. In central Australia, where Aboriginal groups retain direct, active and enduring links to Country, buffel grass makes it hard or impossible to carry out important cultural activities like hunt game species, harvest native plant materials or visit significant sites.

Buffel grass impacts on Anangu Pitjantjatjara Yankunytjatjara communities in central Australia.

But buffel grass isn’t only a threat to biodiversity and Indigenous cultural practices. In January the Tjoritja fires spread along dry river beds choked with buffel, incinerating many large old-growth trees. Much like the alpine forests of Tasmania, the flora of inland river systems has not adapted to frequent and intense fires.

We believe the ability of the fires to spread through these systems, and their increased intensity and size, can be directly attributed to buffel grass.

Fire and buffel grass

Because of the low average rainfall, widespread fires in central Australia have been rare in the recorded past, only following unusual and exceptionally high rainfall.

This extreme rain promoted significant growth of native grasses, which then provided fuel for large fires. There could be decades between these flood and fire cycles. However, since the Tjoritja (previously West MacDonnell Ranges) National Park was established in the 1990s, there have been three large-scale fires in 2001, 2011 and 2019.

What has changed? The 2001-02 and 2011-12 fires both came after heavy rainfall years. In fact, 2011 saw one of the biggest La Niña events on record.

Climate change predictions suggest that central Australia will experience longer and more frequent heatwaves. And although total annual rainfall may stay the same, it’s predicted to fall in fewer days. In other words, we’ll see heavy storms and rainfall followed by long heatwaves: perfect conditions for grass to grow and then dry, creating abundant fuel for intense fires.

The remains of a corkwood tree after an unplanned bushfire in an area heavily invaded by buffel grass near Simpsons Gap. Very few large old corkwood trees now remain in this area.
Author provided

If central Australia, and Tjoritja National Park in particular, were still dominated by a wide variety of native grasses and plants, this might not be such a problem. But buffel grass was introduced because it grows quickly, even without heavy rain.

The fires this year were extraordinary because there was no unusually high rainfall in the preceding months. They are a portent of the new future of fire in these ecosystems, as native desert plant communities are being transformed into dense near-monocultures of introduced grass.

The fuel that buffel grass creates is far more than native plant communities, and after the fire buffel grass can regenerate more quickly than many native species.

So we now have a situation in which fuel loads can accumulate over much shorter times. This makes the risk of fire in invaded areas so high that bushfire might now be considered a perpetual threat.

Changing fire threat

In spinifex grasslands, traditional Aboriginal burning regimes have been used for millennia to renew the landscape and promote growth while effectively breaking up the landscape so old growth areas are protected and large fires are prevented. Current fire management within Tjoritja “combines traditional and scientific practices”.

However, these fire management regimes do not easily translate to river environments invaded by buffel grass. These environments have, to our knowledge, never been targeted for burning by Aboriginal peoples. Since the arrival of buffel grass, there is now an extremely high risk that control burns can spread and become out-of-control bushfires.

Even when control burns are successful, the rapid regrowth of buffel grass means firebreaks may only be effective for a short time before risky follow-up burning is required. And there may no longer be a good time of year to burn.




Read more:
How invasive weeds can make wildfires hotter and more frequent


Our research suggests that in areas invaded by buffel grass, slow cool winter burns – typical for control burning – can be just as, or more, damaging for trees than fires in hot, windy conditions that often cause fires to spread.

Without more effective management plans and strategies to manage the changing fire threat in central Australia, we face the prospect of a future Tjoritja in which no old-growth trees will remain. This will have a devastating impact on the unique desert mountain ranges.

We need to acknowledge that invasive buffel grass and a changing climate have changed the face of fire risk in central Australia. We need a coordinated response from Australia’s federal and state governments, or it will be too late to stop the ecological catastrophe unfolding before us.


The authors acknowledge the contribution of Shane Muldoon, Sarah White, Erin Westerhuis, CDU Environmental Science and Management students, and NT Parks and Wildlife staff to the research at experimental sites and ongoing tree monitoring in central Australia.The Conversation

Christine Schlesinger, Senior Lecturer in Environmental Science and Ecology, Charles Darwin University and Barry Judd, Professor, Indigenous Social Research, Charles Darwin University

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

How we wiped out the invasive African big-headed ant from Lord Howe Island



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Not welcome: the African big headed ant might be small but it can be a pest if it gets in your home.
CSIRO, Author provided

Ben Hoffman, CSIRO

The invasive African big-headed ant (Pheidole megacephala) was found on Lord Howe Island in 2003 following complaints from residents about large numbers of ants in buildings.

But we’ve managed to eradicate the ant completely from the island using a targeted mapping and baiting technique than can be used against other invasive species.

Up to 15% of Lord Howe Island was thought to be infested with the ant.
CSIRO, Author provided

A major pest

The African big-headed ant is one of the world’s worst invasive species because of its ability to displace some native plants and wildlife, and adversely affect agricultural production.




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In an ant’s world, the smaller you are the harder it is to see obstacles


It’s also a serious domestic nuisance. People can become overwhelmed by the large number of ants living in their buildings – you can’t leave a bit of food lying around, especially pet food, or it will be covered in ants.

It remains unclear how long the ant had been on Lord Howe Island, in the Tasman Sea about 770 km northeast of Sydney, before being found. But it is likely to have been present for at least a decade.

Because of the significant threat this ant posed to the conservation integrity of the island, an eradication program was started. But on-ground work done from 2003 to 2011 had many failings and was not working.

In 2011, I was brought in to oversee the program. The last ant colony was killed in 2016, but it is only now, two years later, that we are declaring Lord Howe Island free from the ants.

No African big-headed ants have been seen on the island for two years.
CSIRO, Author provided

A super colony

The ability to eradicate this ant is largely due to its relatively unique social organisation. The queens don’t fly to new locations to start new nests – instead, they form interconnected colonies that can extend over large areas.

This makes the ant’s distribution easy to map and treat. The ant requires human assistance for long-distance transport, so the ant will only be found in predictable locations where it can be accidentally transported by people.

From 2012 to 2015, all locations on the island where the ant was likely to be present were formally inspected. Priority was given to places where an infestation was previously recorded or considered likely. The populations were mapped, and then treated using a granular bait available at shops.

In the latter years we found 16 populations covering 30 hectares. Limited by poor mapping in the early years, we estimate that the ant originally covered up to 55 hectares, roughly 15% of the island.

Stopping the spread

The widespread distribution of the ant through the populated area of the island is thought to have been aided by the movement of infested mulch and other materials from the island’s Waste Management Facility.

To prevent any more spread of the ant, movement restrictions were imposed in 2003 on the collection of green waste, building materials and other high risk items from the facility.

The baiting program used a product that contains a very low dose of insecticide that has an extremely low toxicity to terrestrial vertebrates such as pet cats and dogs, birds, lizard etc. The toxicant rapidly breaks down into harmless chemicals after exposure to light.

No negative impacts were recorded on any of the native wildlife on the island.

Importantly, the African ant usually kills most other ants and other invertebrates where it is present, so there are few invertebrates present to be affected by the bait.

Ecological recovery of the infested areas was rapid following baiting and the eradication of the African ant.

Another ant invader

One of the main challenges was getting the ground crew to correctly identify the ant.

It turns out there was a second (un-named) big-headed ant species present, also not native to the island, that created a lot of unnecessary work being conducted where the African ant wasn’t present.

CSIRO and Lord Howe Island Board team tackling the African big headed ant problem.
CSIRO, Author provided

Like numerous other exotic ant species present, this second species was of no environmental or social concern, so there are no plans to manage or eradicate it.

The protocols used in this program are essentially the same that are being used in other eradication programs against Electric ant in Cairns and Browsing ant in Darwin and Perth, because those two species also create supercolonies.




Read more:
We’ve got apps and radars – but can ants predict rain?


It is highly likely that those programs will also achieve eradication of their respective species, the first instance where an ant species has been eradicated entirely from Australia.

The fire ant program in Brisbane has many similarities, but there are distinct differences in that the ants there don’t form supercolonies that are so easy to map, and the area involved is far greater.The Conversation

Ben Hoffman, Principal research scientist, CSIRO

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

We’ve cracked the cane toad genome, and that could help put the brakes on its invasion



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Cane toads are on the march, but new genetic research could slow them down.
Michael Linnenbach

Peter White, UNSW; Alice Russo, UNSW, and Rick Shine, University of Sydney

We and our international colleagues have deciphered the genetic code of the cane toad. The complete sequence, published today in the journal GigaScience, will help us understand how the toad can quickly evolve to adapt to new environments, how its infamous toxin works, and hopefully give us new options for halting this invader’s march across Australia.

Since its introduction into Queensland in 1935, the cane toad has spread widely and now occupies more than 1.2 million square kilometres of Australia. It is fatally poisonous to predators such as the northern quoll, freshwater crocodiles, and several species of native lizards and snakes.

Previous attempts to sequence the cane toad, by WA researchers more than 10 years ago, were not successful, largely because the existing technology could not assemble the genetic pieces to create a genome. But thanks to new methods, we have succeeded in piecing together the entire genetic sequence.




Read more:
Yes, you heard right: more cane toads really can help us fight cane toads


Our team, which also featured researchers from Portugal and Brazil, worked at the Ramaciotti Centre for Genomics at UNSW. This centre played a key role in decoding the genomes of other iconic Australian species, including the koala.

Sequencing, assembling and annotating a genome (working out which genes go where) is a complicated process. The cane toad genome is similar in size to that of humans, at roughly 3 billion DNA “letters”. By using cutting-edge technology, our team sequenced more than 360 billion letters of cane toad DNA code, and then assembled these overlapping pieces to produce one of the best-quality amphibian genomes to date.

We deduced more than 90% of the cane toad’s genes using technology that can sequence very long pieces of DNA. This made the task of putting together the genome jigsaw much easier.

Toxic toads

The cane toad has iconic status in Australia, with many Aussies loving to hate the poisonous invasive amphibian. This is a little unfair. It’s not the cane toad’s fault – it was humans who chose to bring it to Australia.

Our obsession with sugar in the 1800s led to the toad’s introduction to many countries around the world. Wherever sugar cane was planted, the cane toad followed, taken from plantation to plantation by landowners as the warty interlopers travelled from South America to the Caribbean and then on to Hawaii and Australia.

But unlike most other places to which the cane toad was introduced, Australia lacks any native toads of its own. The cane toad’s powerful poisons are deadly to native species that have never before encountered this amphibian’s arsenal.

The cane toad has therefore been subject to detailed evolutionary and ecological research in Australia, revealing not only its impact but also its amazing capacity for rapid evolution. Within 83 years of its introduction, cane toads in Australia have evolved a wide range of modifications that affect their body shape, physiology and behaviour.

For example, cane toads at the invasion front are longer-legged and bolder than those in long-colonised areas and invest less into their immune defences (for a summary, see Cane Toad Wars by Rick Shine).

The new genome will give us insights into how evolution transformed a sedentary amphibian into a formidable invasion machine. And it could give us new weapons to help stop, or at least slow, this invasion.

Cracking the cane toad genome.

Viral control

Current measures such as physical removal have not been successful in preventing cane toads from spreading, so fresh approaches are needed. One option may be to use a virus to help control the toad population.

Viruses such as myxomatosis have been successfully used to control rabbits. But the cane toad viruses studied so far are also infectious to native frogs. The new genome could potentially help scientists hunt for viruses that attack only toads.

In a study published this month, we and other colleagues describe how we sampled genetic sequences from cane toads from different Australian locations, and found three viruses that are genetically similar to viruses that infect frogs, reptiles and fish. These viruses could potentially be used as biocontrol agents, although only after comprehensive testing to check that they pose no danger to any other native species.




Read more:
Come hither… how imitating mating males could cut cane toad numbers


The full cane toad genome will help to accelerate this kind of research, as well as research on the toads’ evolution and its interactions with the wider ecosystem. The published sequence is freely available for anyone to use in their studies. It is one of very few amphibian genomes sequenced so far, so this is also great news for amphibian biologists in general.

As the cane toads continue their march across the Australian landscape, this milestone piece of research should help us put a few more roadblocks in their path.The Conversation

Peter White, Professor in Microbiology and Molecular Biology, UNSW; Alice Russo, PhD candidate, UNSW, and Rick Shine, Professor in Evolutionary Biology, University of Sydney

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

South Africa should sort out the bad from the really bad on its invasive species list



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Managing trout is a contentious issue with conflicting views about whether they pose a risk, or are beneficial.
Shutterstock

Tsungai Zengeya, South African National Biodiversity Institute

This article is the third in a series The Conversation Africa is running on invasive species.

Alien species have been introduced to Africa for a variety of reasons. They provide food, raw materials for industry, ornamental plants, recreation in the form of sport fishing, hunting and pets. Some that are highly valued have been moved around widely. And in some areas they now form prominent components of societies and ecosystems like the domestic cat for example.

Many alien species bring considerable benefits. But some have become invasive, causing a loss of biodiversity, changes to ecosystems, economic losses and, in some cases, even affecting people’s health.

The shrub Prosopis or mesquite is an example. It was introduced to South Africa to provide fodder, firewood and shade in arid parts of the country. But it’s also a major water user. And two trout species (S. trutta and O. mykiss) are used for recreational angling and commercial aquaculture. But they’ve also been implicated in having a negative effect on the environment.

Managing invasive species is therefore critical. In South Africa the movement and use of 552 listed invasive species are managed under the Biodiversity Act and regulations attached to it. But not all the species on the list are equally harmful. Several may in fact be relatively harmless.

All the listed species under these regulations require management. Given that the capacity is limited, regulations should arguably focus on priority species because not all are necessarily harmful to the extent that would justify spending large amounts of time and effort on keeping them under control.

The question then is: are there some species that could be removed from the list? In our recent study we set out to answer this question by classifying species as inconsequential, beneficial, destructive or conflict generating species. This was done by assessing the relative degree of benefit they brought and their negative effects.

Beneficial and harmful species

The classification was done by using a simple scoring system. It had two categories for the negatives (ecological and socio-economic) and two for the benefits (economic and intrinsic).

  1. Inconsequential species: these make up 55% of the species listed under the act and in the regulations. They were associated with relatively low costs and low benefits to society. Species in this group had limited distribution or no known impact and were largely introduced as ornamentals or pets. Some examples include the eastern grey squirrel (Sciurus carolinensis), European perch (Perca fluviatilis), and the Père David’s Deer (Elaphurus davidianus).

  2. Destructive species: these make up 29% of the list. They don’t bring substantial benefits to society or the environment, but they have a highly negative impact. Many were introduced accidentally and are regarded largely as pests and weeds. Examples include invasive rodents like the black rat (Rattus rattus) which causes damage to infrastructure and transmission of zoonotic diseases and pitch canker (Fusarium circinatum) a growing threat to pine plantations and forests worldwide.

The jacaranda is an iconic tree species in the city of Pretoria where it’s regarded as part of the identity.
Shutterstock
  1. Beneficial species: they make up 10% of the list and have clear social or environmental benefits. For example the jacaranda (Jacaranda mimosifolia) is an iconic tree species in the city of Pretoria where the species is regarded as part of the identity and “sense of place” of the city. Active management is not necessary or should only be done in particular cases.

  2. Conflict-generating organisms: these can be either beneficial or destructive, depending on one’s perspective or what value is placed on them. They make up only 6% of the list. There’s huge disagreement about whether these species should be controlled, or how they should be controlled. Examples include woody plants introduced for forestry, erosion control, sand dune stabilisation, agriculture and as ornamentals. Acacias and pines are examples. Animal examples include species like the Himalayan tahr which was introduced to the Table Mountain National Park. The goat has been the focus of eradication attempts, despite strong opposition. It also includes species introduced for aquaculture like maroon and brown trout. Managing trout has been highly contentious with conflicting views about whether they pose a risk, or deliver a benefit. This has led to them being listed and delisted. The trout fraternity refuse to acknowledge that trout are invasive species and highlight the lack of scientific evidence of the risks they pose.

Finding common ground

We need to keep sight of the fact that there is general agreement on 94% of listed species. By identifying the small number that are generating the greatest tension, it’s more likely discussions can be held to reach common ground on regulation.

Most countries in Africa don’t have invasive species regulations. But there’s growing recognition that they’re needed. South Africa offers useful lessons on how this could be done.

The control of species listed under the country’s biodiversity act is compulsory. This means that plans to manage them have to be drawn up and implemented. But this doesn’t seem sensible given that not all are equally harmful and resources are limited. Our study suggests that some of the species currently regulated could be removed from the list.

Countries wanting to set up a system of managing invasive species could start by classifying a prospective list of candidates. Policymakers could then quickly bring out legislation against the most damaging and destructive ones. At the same time, discussions could be had on the ones that generate conflict with the aim of reaching consensus.

The ConversationThis would allow managers and regulators to focus on the most destructive species – as well as those that are at the centre of fierce disagreement.

Tsungai Zengeya, Researcher at the South African National Biodiversity Institute, South African National Biodiversity Institute

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

Alien animals and plants are on the rise in Africa, exacting a growing toll



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The larger grain borer beetle attacks crops like maize and cassava, threatening food security.
Shutterstock

Katelyn Faulkner, University of Pretoria; Brett Hurley, University of Pretoria, and Mark Robertson, University of Pretoria

This article is the first in a series The Conversation Africa is running on invasive species.

Let’s say you’re travelling from Uganda to South Africa for business. You finally arrive at your hotel after a long day and decide to change before dinner. You unlock and unzip your luggage, but there’s something in your bag that you didn’t pack. As you reach for a clean shirt, a moth flies out. Did that come with you all the way from Uganda? It’ll be fine, right? Surely, something so small won’t cause any harm.

Species are intentionally or accidentally transported by humans between continents to regions where they are not native. With the help of humans or by natural means like flight, these alien species can also spread within continents.

Their spread within continents can be rapid, affecting both the ecology as well as societies and the economy. Unfortunately, it’s really challenging to prevent species from spreading. Given the vast amount of people and goods that are transported between and around continents they can easily be moved across oceans as well as between countries.

The spread of alien species within Africa is increasing. Since 2000 more alien insect pests of eucalyptus trees have spread to other African countries from South Africa, than have been introduced to these African countries from other continents. To manage the spread of these alien species countries need to co-operate, communicate and share information and skills..

The spread of alien species

Many alien plants and animals have been introduced to Africa from other regions and then have spread from country to country, often having devastating effects.

Take the larger grain borer beetle, (Prostephanus truncatus) which is thought to have arrived on the continent in imported grain from Mexico and central America. The beetle was introduced to Tanzania before 1984, Togo before 1981 and Guinea before 1987. It then spread across the continent and within 20 years could be found further south in South Africa.

The beetle attacks crops such as maize and cassava, threatening food security and the livelihoods of the poor. Infestations often destroy maize that’s been stored by farmers, forcing them to buy maize as well as lose income they could have earned from selling any excess.

But alien species don’t just arrive from abroad. Many that are native to parts of Africa have also spread to countries on the continent where they are not native.

An example is the fish commonly known as the Mozambique tilapia (Oreochromis mossambicus) which is native to rivers on the east coast of southern Africa. Fishermen have transported the Mozambique tilapia to other areas and it is now found in river systems in southern and western South Africa and Namibia.

The Mozambique tilapia is a popular species for fishing but it can pose a threat to native fish and has been responsible for the disappearance of native species in some regions.

The spread of alien species within Africa is by no means a new thing. For instance, the bur clover (Medicago polymorpha), a plant from northern Africa, might have been accidentally transported by humans to South Africa as early as 760 AD.

A high and increasing threat

Recently a number of alien species have spread extremely rapidly across the continent, posing a particularly high threat to food security and livelihoods.

The fall armyworm, native to the Americas, was first recorded in west and central Africa in early 2016 and then in South Africa in January 2017.
Shutterstock

One is a caterpillar known as the fall armyworm (Spodoptera frugiperda). The species, native to the Americas, was first recorded in west and central Africa in early 2016 and then in South Africa in January 2017.

The moths of the armyworm are strong fliers and the species may have spread through flight to South Africa from other African countries. Although the species attacks a wide range of crops, it poses a particularly serious threat to grain farmers. It is extremely difficult to manage.

Another example is a wasp known as the bluegum chalcid (Leptocybe invasa), which is native to Australia. In 2000 it was detected in Israel and shortly afterwards it was reported in Uganda and Kenya. From there it spread rapidly to many African countries including Zimbabwe, Mozambique, and Tanzania and was finally detected in South Africa in 2007. The insect probably reached Israel on live plant material and spread into Africa the same way, or was carried by people travelling between countries.

The wasp causes swelling or growths on eucalyptus trees, which can lead to decreased growth and tree death. As eucalyptus trees are an important source of income and fuel, this species could have an impact on the livelihoods of locals in these countries.

Preventing the introduction and spread

Once a species is introduced to one African country it’s highly likely it will spread to others on the continent because borders checks are weak.

The introduction and spread of species could be reduced if countries introduced biosecurity systems. These are used extensively in countries like Australia and New Zealand and involve using technology to check for alien species when people and goods enter a country. In Australia this involves inspecting goods, vehicles and luggage before they enter the country.

But even these systems aren’t a guarantee that species won’t spread. African countries would need to work together and share information and skills. This would also allow countries to prepare for the arrival of species, and to draw up plans to reduce their impact.

The ConversationThis is a tall order. But as a country’s defence against alien species introductions is only as strong as that of its neighbours, such action would benefit all of the countries involved.

Katelyn Faulkner, Postdoctoral research fellow, University of Pretoria; Brett Hurley, Senior Lecturer Zoology and Entomology, University of Pretoria, and Mark Robertson, Associate Professor Zoology & Entomology, University of Pretoria

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