From Australia to Africa, fences are stopping Earth’s great animal migrations



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Wildebeest crossing the Mara River in Tanzania during their annual mass migration.
Jane Rix/Shutterstock

Bill Laurance, James Cook University and Penny van Oosterzee, James Cook University

For time immemorial, many wildlife species have survived by undertaking heroic long-distance migrations. But many of these great migrations are collapsing right before our eyes.

Perhaps the biggest peril to migrations is so common that we often fail to notice them: fences. Australia has the longest fences on Earth. The 5,600-kilometre “Dingo Fence” separates southeastern Australia from the rest of the country, whereas the “Rabbit-Proof Fence” stretches for almost 3,300 kilometres across Western Australia.

Emus attempting to cross the Rabbit-Proof Fence in Western Australia.
Western Australia Department of Agriculture & Food

Both of these enormous fences were intended to repel rabbits and other “vermin” such emus, kangaroos and dingoes that were considered threats to crops or livestock. Built over a century ago, their environmental impacts were poorly understood or disregarded at the time.

Since construction these fences have caused recurring ecosystem catastrophes, such as mass die-offs of emus and other species trying to find food and water in a land notorious for the unpredictability of its rainfall, vegetation growth and fruit production.

Fatal fences

The same thing is happening across much of the planet. While a nemesis for larger wildlife, nobody knows how many fences exist today or where they’re located. A study that mapped all the fences in southern Alberta, Canada, found there were 16 times more fences than paved roads.

Scientists are waking up to the peril of fences, realising that from an environmental perspective they’re grossly understudied — “largely overlooked and essentially invisible,” according to a recent global review.

A zebra noses a fence in Kenya.
Duncan Kimuyu

In Africa, home to some of the most spectacular wildlife migrations, scientists found that of 14 large-mammal species known to migrate en masse, five migrations were already extinct. Proliferating fences, along with habitat loss and wildlife poaching, has sent ecosystems such as the Greater Mara in Kenya crashing into ecological turmoil.

And a 2009 audit of Earth’s greatest terrestrial-mammal movements showed that of 24 large species that once migrated in their hundreds to thousands, six migrations have vanished entirely.

Many remaining migrations are mere shards of their former glory. For instance, Indochina once had mass migrations of elephants and other large mammals, big cats, monkeys and birds — often called the “Serengeti of Southeast Asia”.

Elephants and Banteng graze in Kuri Buri National Park in Thailand, vestiges of a once-massive fauna that migrated annually across Indochina.
Pattarapong/iStock

The thundering herds of American bison – some numbering up to 4 million animals – which once dominated the plains of North America have all but vanished today.

How to save mass migration

There are two main ways to destroy mass migrations: killing the animals outright by hunting and over-harvesting, or stopping the animals from accessing food or water, typically by fencing them out or clearing and fragmenting their habitat.

As the human footprint rapidly expands, scary things for wildlife are happening all over. Research that one of us (Bill Laurance) led revealed that 33 African “development corridors” would, if completed, exceed 50,000 kilometres in length and crisscross the continent, chopping its ecosystems into scores of smaller pieces.

Cost-benefit assessment for 33 massive ‘development corridors’ that are proposed or under construction in Sub-Saharan Africa.
William Laurance

Beyond this, over 2,000 parks and protected areas in Africa would be degraded or cut apart by the massive developments.

Migrations are vulnerable even in the seas. Recent research shows that growing shipping traffic is an increasing danger to migratory great whales, basking sharks, and giant whale-sharks – all highly vulnerable to collisions with fast-moving ships, as well as disruption of their sensitive hearing and vocal communications by shipping noise and sonar, and pollutants from vessels.

But the inspiring news is that, if you remove barriers such as fences, animal migrations can spontaneously resume – like a phoenix rising from the ashes.

A Red-Billed Oxpecker, which feeds on skin parasites of African mammals.
Fernando Quevedo de Oliveira/Alamy Stock Photo

In 2004, a fence that had blocked a former zebra migration in Botswana was removed. By 2007 it was one of the longest animal-migration routes in the world.

And a few places on Earth are still free from fencing and fragmentation. The world-famous Seregeti ecosystem of Tanzania is an iconic example. In war-torn South Sudan, a spectacular mass migration of a million antelope — known as white-eared kob — is still intact because there are no fences.

And caribou still migrate in great herds across large expanses of northern Canada and Alaska.

Alarming news for Botswana

Collapsing migrations are a global concern, but right now conservationists are most worried about Botswana.

This mega-diverse nation in southern Africa is considering profoundly changing its wildlife management by expanding fences and cutting off wildlife migrations not considered beneficial to the country’s current priorities.

This would be a shocking decision, because Botswana’s wildlife conservation is almost entirely dependent on its mass migrations.

For wildebeest, zebra, eland, impala, kob, hartebeest, springbok and many other large migrants, isolation is a killer – destroying their capacity to track the shifting patterns of greening vegetation and water availability they need to survive.

And it’s not just grazing and browsing animals that are affected: entire suites of large and small predators, scavengers, commensal and migratory bird species, grazing-adapted plants and other species are integrally tied to these great migrations.

Lions attacking an Angolan Giraffe, one facet of Botswana’s complex migratory ecosystems.
Michael Cohen

Botswana is already sliced into 17 giant “islands” by fences, erected in colonial times to protect the livestock of European farmers from foot-and-mouth disease.

But foot-and-mouth disease is far more likely to be spread by cattle, not wildlife. Fence-free strategies for managing disease risk also have have great potential.

And nature tourism in Botswana is a large, vibrant, and growing part of the national economy. Ecotourists will continue to favour the nation so long as it maintains untrammelled areas and spectacular animal migrations.

Botswana is expected to have over 40,000 tourism-related jobs by 2028, showing their key importance to the national economy.
Travel & Tourism Economic Impact: Botswana 2018

But you can kiss a lot of those tourism revenues goodbye if Botswana shatters its great migrations – killing off the spectacular living panoramas that are a magnet for the world’s nature lovers.

If we can avoid fencing and bulldozing critical parts of the Earth, we could hugely increase the chances that our most vibrant wildlife and ecosystems have a fighting chance to survive.The Conversation

Bill Laurance, Distinguished Research Professor and Australian Laureate, James Cook University and Penny van Oosterzee, Adjunct Associate Professor James Cook University and University Fellow Charles Darwin University, James Cook University

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

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The future is fenced for Australian animals



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Mala, also known as rufous hare-wallabies, will be protected behind an enormous cat-proof fence.
Donald Hobern/Flickr, CC BY-SA

Michael Bode, The University of Queensland

Many of Australia’s mammals spend their entire lives imprisoned, glimpsing the outside world through tall chain-link fences and high-voltage wires. There are dozens of these enclosures across Australia. Many are remote, standing alone in the endless expanse of inland Australia, but others are on the outskirts of our largest cities – Melbourne, Perth, Canberra.

Every year there are more of them, the imprisoned population growing, while the wild populations outside dwindle. These are Australia’s conservation fences.




Read more:
Let’s move the world’s longest fence to settle the dingo debate


The captives within our conservation fences are adorable – floppy-eared bilbies, tiny hare-wallabies, long-tongued numbats – and they all share an extreme susceptibility to introduced predators. At least 68 native mammal species cannot exist in the wild if either foxes or cats are present. Many of these species once numbered in the millions, ranging from the woodlands of Queensland to the deserts of Western Australia, but predation has driven them to the brink of extinction.

Fences offer these species a future in the wild, and conservation groups have risen to the challenge. Last week, the Australian Wildlife Conservancy completed a new cat-proof fence in their Newhaven Sanctuary, the largest conservation fence ever constructed.

Fences are extraordinarily successful

Make no mistake, these conservation fences work. Species that wilt at the sight of a fox, that have been exterminated from every corner of the Australian mainland, will explode in numbers behind fences. Along with offshore islands, inside these fences are the only places in Australia where these species can prosper – a few hundred square kilometres of safety, surrounded by 7.6 million lethal square kilometres.

Environmentalists have never particularly liked fences. Rather than hide behind walls, they repeatedly took the fight to the cats and foxes on the outside.

Their tactics have been diverse, innovative and brutal. Managers have rained bullets from helicopters and poison baits from planes. They have set cunning snares and traps, mimicked the smell and sound of their enemies, and have turned landscapes to ash with wildfire.

Nothing has worked for the most threatened marsupials. Some of the largest and most expensive management campaigns in Australian conservation history have ended in exhaustion and stalemate, and with a retreat back behind the fences.

Fences were once a source of vehement debate in conservation circles. Should they be permanent? Are fenced populations wild or captive? Should they contribute to species’ conservation status?

These arguments have effectively been abandoned. Scientific studies and painful experience has proven fences and offshore islands to be the only reliable method of protecting predator-threatened species http://www.wildliferesearchmanagement.com.au/Final%20Report_0609.pdf. In place of these debates, conservation organisations and governments have turned to more practical questions of fence height, electric wire voltage and skirt depth.

So now, on average, Australians are building a new fence every year, some of them truly enormous. The just-completed fence at Newhaven encloses a staggering 10,000 hectares of red sand and spinifex. By the time the project is complete, this fence will be home to 11 different threatened mammal species.

And Australia is not alone: around the world, from New Zealand to Hawaii to South Africa, an archipelago of fences is emerging from an ocean of predators. It is one of the great achievements of modern conservation and has already averted the extinction of critically endangered species. Although it’s much smaller than our network of protected areas, it offers refuge to species that are long-gone from our national parks and wilderness areas.

Red foxes have been extraordinarily successful in Australia.
Harley Kingston/Flickr, CC BY

A troubling pattern

However, in recent years a concerning pattern has begun to emerge. While the number and size of fences continue to increase, the number of new species being protected has stalled. In fact, the last five fences haven’t included any new species – they have only offered additional protection to species that were already protected behind existing fences https://www.nature.com/articles/s41559-017-0456-4.

As an example, the first two marsupials planned for introduction behind the Newhaven fence will be the mala (Lagorchestes hirsutus) and the burrowing bettong (Bettongia lesueur). These two species undeniably deserve more protection. Both are highly susceptible to foxes and cats and will derive tremendous benefit from the protection of this enormous fence. However, both species are already found elsewhere behind fences (four different fences for burrowing bettongs). Meanwhile, yet-to-be-published research from the National Environmental Science Program has found 41 other species that are desperately vulnerable to introduced predators are not protected by any fence.

This problem is not new to conservation. In the 1990s, Australian researchers suddenly realised that our national park system was failing to protect the full range of Australian ecosystems. Despite our best efforts, we had created a system of reserves that was biased towards mountainous landscapes and deserts, and away from the fertile valley floors. The solution was to create new national parks using systematic and mathematical methods.

This discovery – the theory of systematic conservation planning – revolutionised global conservation. In 2018, conservation fences need their own systematic revolution.

Unfortunately, the national park system had natural advantages that fences lack. The vast majority of Australia’s protected areas belong to the state and federal governments. The centralised nature of the protected area network is perfect for systematic thinking and top-down optimisation – picture the Soviet Union’s Politburo. In contrast, the conservation fencing sector is diverse and decentralised – picture the third day of Woodstock.




Read more:
All cost, little benefit: WA’s barrier fence is bad news for biodiversity



Fences are built by governments at the state, federal and municipal levels, by multimillion-dollar NGOs like the Australia Wildlife Conservancy, by tiny local environmentalist groups and by profit-making corporations. This diversity is a fundamental strength of the fence network, giving it access to a spectrum of funding and ideas. But it makes it almost impossible to plan in a systematic manner. You can’t tell a small bilby conservation group in western Queensland that they should protect the central Australian rock-rat instead (Zyzomys pedunculatus). It doesn’t necessarily matter to them that bilbies are already protected behind four different fences and the rock-rat has none.

While conservation science tries to work this problem out, new and larger fences will continue to be built at an accelerating rate into the foreseeable future. True, the absence of coordination will make mathematicians break their slide rules, but each fence will do its job. The furry denizens will hop, and scurry, and bounce around, heedless of their precarious safety.

The ConversationAnd for us, from the outside looking in, these fences will help us forget the parlous state of Australian marsupial conservation. It will be possible to forget our record-breaking rate of extinctions, to forget the empty forests and deserts, and to imagine what a bushwalk might have been like before Europeans unleashed foxes and cats onto Australia.

Michael Bode, Associate Professor of Mathematics, The University of Queensland

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

Fences are an increasing threat to Africa’s migratory wildlife


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In the Serengeti wildebeest will move more than 2000km during their annual migration.
Sarah Durant

Sarah Durant, Zoological Society of London

Wildebeest rarely stay still for long. With sloping hindquarters, and an easy loping gait, their bodies are designed to move. In the Serengeti ecosystem, for instance, a wildebeest will move over more than 2,000 kilometres during their annual migration.

Migratory or nomadic animals, like wildebeest, that live in drylands need to move over vast distances to find sufficient water and nutrients. They follow localised and variable rainfall and food resources.

The Serengeti wildebeest spends the wet season, November to April, on the short grass plains of the southern Serengeti National Park and adjoining Ngorongoro Conservation area in Tanzania. Here they feed on nutritious grass shoots that grow in response to the abundant rain. But even here, they do not stay still. They constantly move across the short grass plains in search of the fresh grass that grows after each new rainfall. This allows mothers to maximise milk production for their calves, born during a simultaneous calving of more than a quarter a million, peaking in February.

When the rains cease at the end of April, the wildebeest start their long journey to their dry season grazing areas. They first move west, and then head north, following the remaining water in the rivers before moving on as they dry out. Eventually they reach the only permanent water found in the Mara River on the Kenyan border. The dry season is hard, and many wildebeest die of starvation during this period.

When the rains start in November, the wildebeest lope down south once again. They make the journey to the short grasslands nearly 200km away in just a few days. Here they graze, recover their strength and the cycle begins again.

If these Serengeti wildebeest were to face a barrier at any point in their journey, they would die, either of starvation or thirst. Sadly, this has happened to migratory animals elsewhere in Africa. For example, over 30 years ago, after a fence was erected as a veterinary cordon to separate wildlife from cattle in the Kalahari, 80,000 wildebeest and 10,000 hartebeest died when they were no longer able to access permanent water during a drought. The fence was built to satisfy European Union livestock disease regulations, and allow southern African countries to export meat into the European Union.

Unfortunately, the ability of wildlife in Africa to continue to move across landscapes is still being threatened by linear barriers, and this is particularly a problem in Africa’s drylands.

African drylands

African drylands are home to most of its large mammal species. These include semi-arid and arid savannahs, found across much of eastern and southern Africa, which support spectacular wildlife migrations, such as those found in the Serengeti. But drylands also include hyperarid deserts, such as the vast Sahara, home to distinctive nomadic species such as the critically endangered Addax and dama gazelle.

Because mobility is key for large mammals in these systems, subdividing land reduces the numbers of animals areas can support. To the extent that 300km2 of land in Laikipia will support 19% fewer cattle if subdivided into 10km2 parcels.

Large carnivores, which depend on wide-ranging herbivore prey, also need to range widely, and live at even lower densities than their prey. The Saharan cheetah, for example, occurs at one of the lowest densities ever documented for a big cat, with only one individual per 4,000km2.


Sarah Durant

The recent human migration crisis and growing insecurity in many dryland areas across the Sahara-Sahel has led to calls for large-scale border fencing in Africa, some of which stretch over several hundreds of kilometres.

There are also growing calls for large scale boundary fencing of protected areas as well as infrastructure developments, such as oil pipelines and railways, that cut across wildlife movement pathways. Kenya’s new Standard Gauge Railway line is a recent example.

On top of this is the problem of boundary fences erected around smaller plots of land. In southern Kenya fences put up around private farms have meshed together to form a large-scale barrier to wildlife movement.

International action

In the face of these pressures, migratory, nomadic and wide ranging species depend on trans-boundary action for their long term survival.

The UN Convention on the Conservation of Migratory Species of Wild Animals , also known as the Bonn Convention, lays the legal foundation to safeguard species that need to move across international boundaries. It also provides for internationally coordinated conservation measures throughout their migratory range.

Africa is not alone in facing barrier threats. In central Asia, linear barriers also threaten this region’s migratory wildlife. For example, the border fence and railroad between Kazakhstan and Uzbekistan bisects the Saiga antelope migration between these countries. It has helped to put this population on the brink of extinction.

In response to barrier threats, the Convention on the Conservation of Migratory Species established the Central Asian Mammals Initiative This produced an important set of guidelines to inform fencing interventions and to help sustain migration corridors for migratory ungulates in Asia.

These guidelines are now being followed up with action. A project has been initiated to partially remove and modify the fences along the Trans-Mongolian Railway. This had formed a major barrier to movement for kulan (wild ass) and Mongolian gazelles. Furthermore, border fence modifications recommended by the Bonn Convention on the Conservation of Migratory Species are being implemented to enable Saiga to move, once again, between Kazakhstan and Uzbekistan.

African issues on the table

The Bonn Convention on the Conservation of Migratory Species has just held the Second Meeting of the Sessional Committee of its Scientific Council. This is in the run up to the Conference of the Parties in October where countries will come together to agree on new actions to save migratory species. Under discussion was a new African Carnivore Initiative, which seeks to develop a framework for the trans-boundary conservation of existing Bonn Convention listed large carnivore species, cheetah and African wild dog, and to add two as yet unlisted species, lion and leopard, to the initiative.

Also on the table was an important new initiative to maintain connectivity for terrestrial species, including an additional decision requested by the Zoological Society of London to address the problem of linear barriers in Africa, building on the experiences under the Central Asian Mammals Initiative.

If Africa to avoid catastrophic impacts of large scale fencing on its wildlife in the future, we must avoid repeating past mistakes. This will require further scientific research to better understand potential negative impacts of fencing and other linear barriers, and how best to mitigate such impacts, not just for wildlife, but also for ecosystem services and local communities.

The ConversationAt the Bonn Convention’s next Conference of Parties, nations will need to decide whether to implement important decisions to safeguard migratory species, including maintaining terrestrial connectivity. The fate of many wide ranging species hangs in the balance, and depends on governments supporting and, importantly, implementing, these decisions.

Sarah Durant, Senior Research Fellow, Zoological Society of London

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