For more than 100 years, the US government has conducted lethal control of native wildlife, to benefit livestock producers and to enhance game populations, especially in the western states. Since 2000, Wildlife Services (WS), an agency of the US Department of Agriculture, has killed 2 million native mammals, predominantly 20 species of carnivores, beavers, and several species of ground-dwelling squirrels, but also many nontarget species. Many are important species in their native ecosystems (e.g., ecosystem engineers such as prairie dogs and beavers, and apex predators such as gray wolves). Reducing their populations, locally or globally, risks cascading negative consequences including impoverishment of biodiversity, loss of resilience to biotic invasions, destabilization of populations at lower trophic levels, and loss of many ecosystem services that benefit human society directly and indirectly.
You don’t have to look far to see the woolly influence of sheep on our cultural lives. They turn up as symbols of peace and a vaguely remembered pastoral way of life in our poetry, our art and our Christmas pageants. Wolves also rank high among our cultural icons, usually in connection with the words “big” and “bad.” And yet there is now a debate underway about substituting the wolf for the sheep on the (also iconic) green hills of Britain.
The British author and environmental polemicist George Monbiot has largely instigated the anti-sheep campaign, which builds on a broader “rewilding” movement to bring native species back to Europe. Until he recently relocated, Mr. Monbiot used to look up at the bare hills above his house in Machynlleth, Wales, and seethe at what Lord Tennyson lovingly called “the livelong bleat / Of the thick-fleeced sheep.” Because of overgrazing by sheep, he says, the deforested uplands, including a national park, looked “like the aftermath of a nuclear winter.”
Photo
CreditAnders Nilsen
“I have an unhealthy obsession with sheep,” Mr. Monbiot admits, in his book “Feral.” “I hate them.” In a chapter titled “Sheepwrecked,” he calls sheep a “white plague” and “a slow-burning ecological disaster, which has done more damage to the living systems of this country than either climate change or industrial pollution.”
The thought of all those sheep — more than 30 million nationwide — makes Mr. Monbiot a little crazy. But to be fair, sheep seem to lead us all beyond the realm of logic. The nibbled landscape that he denounces as “a bowling green with contours” is beloved by the British public. Visitors (including this writer, otherwise a wildlife advocate) tend to feel the same when they hike the hills and imagine they are still looking out on William Blake’s “green and pleasant land.” Even British conservationists, who routinely scold other countries for letting livestock graze in their national parks, somehow fail to notice that Britain’s national parks are overrun with sheep.
Mr. Monbiot detects “a kind of cultural cringe” that keeps people from criticizing sheep farming. (In part, he blames children’s books for clouding vulnerable minds with idyllic ideas about farming.) Sheep have “become a symbol of nationhood, an emblem almost as sacred as Agnus Dei, the Lamb of God,” he writes. Much of the nation tunes in ritually on Sunday nights to BBC television’s “Countryfile,” a show about rural issues, which he characterizes as an escapist modern counterpart to pastoral poetry. “If it were any keener on sheep,” he says, “it would be illegal.”
The many friends of British sheep have not yet called for burning Mr. Monbiot at the stake. But they have protested. “Without our uplands, we wouldn’t have a UK sheep industry,” Phil Bicknell, an economist for the National Farmers Union pointed out. “Farmgate sales of lamb are worth over £1bn” — or $1.7 billion — “to U.K. agriculture.” The only wolves he wanted to hear about were his own Wolverhampton Wanderers Football Club. A critic for The Guardian, where Mr. Monbiot contributes a column, linked the argument against sheep, rather unfairly, to anti-immigrant nativists, adding “sheep have been here a damn sight longer than Saxons.”
Mr. Monbiot acknowledges the antiquity of sheep-keeping in Britain. But the subjugation of the uplands by sheep, he says, only really got going around the 17th century, as the landlords enclosed the countryside, evicted poor farmers, and cleared away the forests from the hillsides and moorlands, particularly in Scotland. Britain is, he writes, inexplicably choosing “to preserve a 17th-century cataclysm.” The sheep wouldn’t be in the uplands at all, he adds, without annual taxpayer subsidies, which average £53,000 per farm in Wales.
He proposes an end to this artificial foundation for the “agricultural hegemony,” to be replaced by a more lucrative economy of walking and wildlife-based activities. He also argues for bringing wolves back to Britain, for reasons both scientific (“to reintroduce the complexity and trophic diversity in which our ecosystems are lacking”) and romantic (wolves are “inhabitants of the more passionate world against which we have locked our doors”). But he acknowledges that it would be foolish to force rewilding on the public. “If it happens, it should be done with the consent and active engagement of the people who live on and benefit from the land.”
Elsewhere in Europe, the sheep are in full bleating retreat, and the wolves are resurgent. Shepherds and small farmers are abandoning marginal land at an annual rate of roughly a million hectares, or nearly 4,000 square miles, according to Wouter Helmer, co-founder of the group Rewilding Europe. That’s half a Massachusetts every year left open for the recovery of native species.
Wolves returned to Germany around 1998, and they have been spotted recently in the border areas of Belgium, the Netherlands and Denmark. In France, the sheep in a farming region just over two hours from Paris suffered at least 22 reported wolf attacks last year. But environmentalists there say farmers would do better protesting against dogs, which they say kill 100,000 sheep annually. Wolves are now a protected species across Europe, where their population quadrupled after the 1970s. Today an estimated 11,500 wolves roam there.
Lynx, golden jackals, European bison, moose, Alpine ibex and even wolverines have also rebounded, according to a recent study commissioned by Rewilding Europe. Mr. Helmer says his group aims to develop ecotourism on an African safari model, with former shepherds finding new employment as guides. That may sound naïve. But he sees rewilding as a realistic way to prosper as the European landscape develops along binary lines, with urbanized areas and intensive agriculture on one side and wildlife habitat with ecotourism on the other.
In northern Scotland, Paul Lister is working on an ecotourism scheme to bring back wolves and bears on his Alladale Wilderness Reserve, where he has already planted more than 800,000 native trees. He still needs government permission to keep predators on a proposed 50,000-acre fenced landscape. That’s a long way from introducing them to the wild, on the model of Yellowstone National Park. Even so, precedent suggests that it will be a battle.
Though beavers are neither big nor bad, a recent trial program to reintroduce them to the British countryside caused furious public protest. (One writer denounced “the emotion-based obsession with furry mammals of the whiskery type.”) And late last year, when five wolves escaped from the Colchester Zoo, authorities quickly shot two of them dead. A police helicopter was deployed to hunt and kill another, and a fourth was recaptured. Prudently, the fifth wolf slunk back into its cage, defeated.
Rewilding? At least for now, Britain once again stands alone (well, alone with its 30 million sheep) against the rising European tide.
Social species, such as the African wild dog, require strict participation from group members to be successful. This strategy can enhance fitness benefits for the group, but also a higher critical threshold for extinction. Awareness of life history needs to guide management strategy. “Failure to consider the impacts of group dynamics may result in underestimation of critical threshold population sizes or densities required for population persistence,” the researchers write.
Carnivore management is not just a numbers game, Virginia Tech wildlife scientists assert in response to an article in the Jan. 10 issue of the journal Science that urged “minimum population densities be maintained for persistence of large carnivores, biodiversity, and ecosystem structure.”
“This type of approach may fail in social carnivore species,” said Kathleen Alexander, an associate professor of fisheries and wildlife conservation in the College of Natural Resources and Environment. “Predator management is incredibly complex and we need to be extremely cautious in applying blanket approaches which rely on securing some target number or density of individuals in an ecosystem.”
The research-based argument appears in a letter in the March 14 issue of Science and an article abstract in the October 2013 issue of the journal Population Ecology.
“Life history strategy, including number of offspring, lifespan, diet, and behavior that evolves from ecological pressures of the species in question should also guide management approaches,” wrote Alexander and Claire E. Sanderson, a postdoctoral associate in fisheries and wildlife conservation, in the Science letter.
The research published in Population Ecology evaluated 45 solitary and social medium and large carnivore species and their key life history attributes, population trends, and identified the presence of factors that increase the potential for extinction.
Disturbingly, 73 percent of carnivore species — both social and solitary — were declining, observed Sanderson, Sarah Jobbins, also a postdoctoral associate, and Alexander.
“Social carnivores appeared to be particularly vulnerable with 45 percent threatened by infectious disease but only 3 percent of solitary carnivores similarly impacted,” they report. “In this, increased contact between individuals, disease-related mortality, and loss of individuals below some critical threshold seems to be the issue, pushing social carnivores closer to the brink of extinction.”
Reporting on their research on social carnivores, Sanderson, Jobbins, and Alexander said in the article, “Highly cohesive social species, like African wild dog, require strict participation from all group members … in all areas of life, including predator avoidance, reproductive success, hunting, and survivorship. This life-history strategy can result in enhanced fitness benefits for the group, but also a higher critical threshold for extinction.”
“The number of individuals in the group then becomes the critical factor influencing population persistence,” said Sanderson.
For example, rabies and distemper have caused local extinction of African wild dog in regions of Africa. Even in a large population, transmission of an infectious disease from only a few infected individuals can result in sufficient mortality to push groups below a critical threshold, ultimately threatening population persistence, the researchers report.
It has been found in certain ecosystems that when wild dog packs are reduced to less than four individuals, they may be unable to rear pups because of trade-offs between specialized roles, such as pup guarding and hunting.
“While aggregation of conspecifics may be beneficial for reproduction, hunting, and vigilance, social living is a disadvantage when it comes to transmission of disease,” according to Alexander’s research.
Also a wildlife veterinarian, she cofounded the Centre for Conservation of African Resources: Animals, Communities and Land Use, in Kasane, Botswana and has been conducting research in Africa since the late 1980s.
“Failure to consider the impacts of group dynamics may result in underestimation of critical threshold population sizes or densities required for population persistence,” Sanderson, Jobbins, and Alexander write.
Alexander and Sanderson conclude in their letter in Science, “We urge consideration of life-history strategy and social behavior in the development of carnivore management strategy.”
Journal References:
W. J. Ripple, J. A. Estes, R. L. Beschta, C. C. Wilmers, E. G. Ritchie, M. Hebblewhite, J. Berger, B. Elmhagen, M. Letnic, M. P. Nelson, O. J. Schmitz, D. W. Smith, A. D. Wallach, A. J. Wirsing. Status and Ecological Effects of the World’s Largest Carnivores. Science, 2014; 343 (6167): 1241484 DOI:10.1126/science.1241484
Claire Elizabeth Sanderson, Sarah Elizabeth Jobbins, Kathleen Ann Alexander.With Allee effects, life for the social carnivore is complicated. Population Ecology, 2013; DOI: 10.1007/s10144-013-0410-5
Virginia Tech (Virginia Polytechnic Institute and State University). “Preserving large carnivores in ecosystem requires multifaceted approach.” ScienceDaily. ScienceDaily, 13 March 2014. <www.sciencedaily.com/releases/2014/03/140313142447.htm>.
Last week the kids and I found a wolverine track in the snow, just a few kilometres from my home. The sun was shining, the air was crisp and life suddenly felt different. The silent forest around me became transformed, from a bland backdrop to a dynamic living ecosystem. The encounter was unexpected, a rarity, a treasure; something that transformed just another family outing to “the day we saw that wolverine track”.
As both a scientist and a conservationist I have worked with large carnivore related issues for almost my entire professional life. Studying their prey (roe deer), studying the predator species themselves (including Eurasian lynx, leopards and jaguars), and studying their interactions with people, has taken me to study sites all across Europe, from the Barents Sea to the Adriatic, and beyond to India and Brazil.
Large carnivores are not an easy career path. For the scientist part of me, they are difficult and expensive to study. Working on rodents would certainly have allowed me to gain more scientific kudos. For the conservationist part of me they are associated with a constant round of challenges and conflicts. So why do I do it?
Fascination is clearly amajor part of the answer. The more I learn about how these animals live their lives the more I appreciate them as masterpieces of evolutionary adaptation. They also trigger some emotional responses deep inside.
The combination of grace, power, silence, resilience and adaptability in such a beautiful packaging can only induce a sense of awe. These animals demand your respect simply by looking at you. They are also truly wild.
Completely independent of us humans, unapologetic about their actions, their persistence in our modern urbanised world provides a refreshing reminder that there is still some wildness left in nature. Predators above all other species remind us that nature is still something of a dynamic process and made up of interactions rather than just being static scenery. The idea that nature is something bigger than us humans and that it still not tamed provides a refreshing tonic to human arrogance and egotism.
However, many of these characteristics are also the source of conflicts. The sources of my fascination can easily become another person’s frustrations or fears. Predators don’t always make easy neighbours, and many rural people living in their proximity experience very real problems.
Working for the conservation of these species involves confronting these conflicts and trying to find ways to minimise them. And the challenge of responding to this is probably my second motivation to work with these species. The challenge is even greater considering that most of my work is in Europe. Europe is a crowded continent, with 500 million people, and no true wilderness areas. There is no “over there” with more space. If we want large carnivores, they have to be “here”; in the same landscape where people live, work and play.
Integrating these species into the fabric of our modern landscape is probably the greatest example of land sharing that has ever been attempted in conservation. The Large Carnivore Initiative for Europe, of which I am a member, is trying to find ways to facilitate this integration of large carnivores into multi-use landscapes that simultaneously provide for the needs of human food production, recreation and biodiversity conservation.
And judging by present trends, the carnivores are succeeding, although there is still a long way to go. Many conflicts persist, and some are escalating. Finding solutions is going to require patience, ingenuity and a willingness to make compromises. Although research can provide some guidance, there is going to be a lot of trial and error because quite simply this experiment has never been tried before. For almost the entirety of human history we have been at a state of war with these species. We are now trying to find a way to coexist with them, although nobody knows how this coexistence is going to look in the end. Who could resist being a part of such a process?
John Terborgh, Research Professor in the Nicholas School of the Environment and Earth Sciences at Duke University; Director of the Duke University Center for Tropical Conservation
In this presentation, Dr. Terborgh draws on his decades of ecological research in the Neotropics to explain how biological interactions intricately regulate biodiversity. Hypotheses on the maintenance of tropical forest diversity abound, but it is becoming increasingly recognized that interspecific interactions are vital to sustaining the rich diversity the tropics are famous for. Dr. Terborgh offers ecological insights on the regulation of biodiversity and describe how interactions between primary producers, herbivores, and their predators contribute to the richness of tropical forests.
PGE’s interdisciplinary Spring conference, “Conserving More Than Carbon: Valuing Biodiversity in a Changing World”, addressed the current state of knowledge of tropical forest diversity and outlooks for its protection.
In addition to preserving biodiversity for future generations, the Natura 2000 Network provides a wide range of other important benefits to society and the economy via the flow of ecosystem services.
Healthy freshwater ecosystems, for instance, provide clean water and help remove pollutants from the surrounding countryside. Intact wetlands act as natural buffers against floods, soaking up excess rainwater. Peat bogs help fix and store carbon dioxide, the number one cause of climate change, whilst forests improve air and soil quality.
In addition, Natura 2000 helps to conserve natural pollinators, preserve landscape and amenity values, as well as support tourism and recreation. By offering attractive breathing spaces, it provides ample opportunities for economic activities based on these valuable natural assets.
Healthy and well-functioning ecosystems sustained within protected areas can increase not only the range of ecosystem services, but also the resilience of ecosystems to resist and adapt to natural disasters and disturbances (e.g. climate change) also beyond the site level.
However, for the Natura 2000 Network to deliver its full economic and biodiversity potential, it is essential that every effort is made to restore the sites to a more favourable condition. Positive conservation action is vital if we are to safeguard Europe’s biodiversity for future generations and maximise the socio-economic benefits that flow from healthy
well-functioning ecosystems.
As human populations expand and use the land differently, they are having an impact on the plants and animals that share that land with them. Conservation biologists have been working for decades to try and document the ways in which these changes are affecting species, and to try and develop indicators that can be used to monitor these changes over time. However, previous work has tended to focus on certain species (e.g. bats, birds), neglecting other important groups such as insects, and have been biased towards certain habitats (e.g. tropical rainforest).
A new project in partnership between University College London, Imperial College London, the University of Sussex, UNEP World Conservation Monitoring Center and Microsoft Research, aims to improve on previous studies and develop a model for understanding how whole biological communities respond to human pressures across the globe. Collating high-quality data from hundreds of peer-reviewed papers, in addition to unpublished data direct from field researchers, the PREDICTS team hope to investigate local patterns of biodiversity at a global scale, and improve our understanding of how whole ecosystems respond to human pressures such as land-use change.
Biodiversity Declines Major global loss of biodiversity is underway, and we have good reason to believe humans are responsible. The current extinction rate of species is estimated to be 1000 times higher than long-term historical averages, although large fluctuations in this in the past were also common. Humans have altered the world enormously, converting forests and savannas into farmland and housing. Virtually all ecosystems have been changed substantially – most biomes have lost between 20 and 50% of land to human uses. Humans have also exploited natural resources for wood, food, medicine and social reasons, and in many cases overexploitation has lead to major species declines and extinctions. Globally, it is estimated that 12% of bird species, 23% of mammals and 32% of amphibians are threatened with extinction, with many of these species suffering population declines and a reduction in genetic diversity, which may exacerbate the effect of human impacts. Even optimistic projections indicate continued human pressure on biodiversity from a range of different sources including hunting and habitat destruction. Many of the pressures currently placed on global biodiversity, such as land-use change, pollution and the introduction of invasive species, are set to continue or intensify over coming decades.
Ecosystem Services
Biodiversity is a valuable asset to humans for many reasons, not least its considerable economic value. Biodiversity contributes to human well-being by providing ecosystem services such as food (crops and livestock), fresh water, timber, natural hazard protection, air quality, climate regulation, prevention of erosion, as well as cultural benefits such as the aesthetic and recreational use of biodiversity. The exact relationship between biodiversity and ecosystem services is still relatively poorly understood, as it represents a complex interaction of many factors, which may vary from habitat to habitat. Many researchers suspect there may be threshold effects, with a sudden collapse of ecosystems, and a consequent loss of the services they provide, once a threshold number of species is lost. Others suggest certain ‘keystone’ species may be more important for ecosystem function. What is clear, however, is that healthy, functioning ecosystems are key to human health and well being. A greater understanding both of how biodiversity contributes to ecosystem function and ecosystem services, and of how biodiversity is likely to respond to continued anthropogenic pressures is sorely needed.
Improving Indicators One central issue to studying and increasing our understanding of how ecosystems respond to human pressures is selecting species, populations or ecosystems to act as indicators of overall trends. It is simply not possible to monitor all populations of all species, and conservationists have traditionally relied upon indicator species and ecosystems as a measure of the overall health of biodiversity. In many cases these indicators were initially selected out of convenience meaning that well-studied species, communities and biomes are hugely overrepresented in the data available. However, species’ traits are likely to influence how they respond to human pressures, and a broader geographical and taxonomic view is needed to take the next step in our understanding.
Projecting Responses of Ecological Diversity in Changing Terrestrial Systems
The PREDICTS project aims to address some of these issues by performing a meta-analysis of species responses to different human pressures, covering as broad a taxonomic and geographical data set as is available. The PREDICTS team are collecting data from published papers; however, they also hope to draw on rich datasets held by ecologists which are simply too large to have been published in full. If you are an ecologist and believe you may have data that could be used for this project, please visit the PREDICTS website to find out more. They have already collated over 800,000 biodiversity records covering more than 15,000 species. These data are being combined to form a database that will be used to answer a number of key questions about biodiversity and anthropogenic change. In particular, the PREDICTS project is interested in investigating how different taxonomic groups respond, how responses differ in different biomes and with different intensities of human pressure. They also plan to investigate how different measures of biodiversity (e.g. species richness, evenness, abundance etc) may respond differently in different species, regions and for different human pressures.
By combining data from many species and sites, across a variety of different intensities of human pressure, PREDICTS hopes to develop a deeper understanding of how different factors interact to determine species responses. From this they hope to make predictions about how biodiversity may respond to different projected future scenarios, and thus provide insights for science policy.
Turning Science into Policy
We are faced with an increasingly difficult global situation, as human populations expand, the climate changes and biodiversity declines. What makes this situation more difficult still is that we need to make decisions now and over the next few years that will impact a generation, but for which we still have insufficient data to know for sure what’s best. Making projections for climate change, human population expansions and changes in the exploitation of biodiversity is difficult. Making projections for how biodiversity will respond to those changes is even more difficult still, but it is a task we must attempt if we are to make informed decisions about the future of our planet. PREDICTS hopes to utilise what data we do have to make synthesise a more in depth and holistic understanding of how ecological communities respond to human impacts, which can be used to make predictions that will help inform science policy makers globally.
Of the 17 species of butterlies found in Europe, eight have declined, including the common blue, above. Photograph: Getty
Europe‘s grassland butterfly population has plummeted in the past two decades, new research published on Tuesday shows, with a near halving in the numbers of key species since 1990.
The precipitous decline has been blamed on poor agricultural practices and pesticides, by the European Environment Agency, which carried out the research. Falling numbers of butterflies are bad news not just for nature-lovers and for biodiversity, but have a knock-on effect on farming, as – like bees – they act as pollinators, and their disappearance harms birds and other creatures that need them for food.
Butterfly populations are a leading indicator of the health of other insect species. The new study therefore suggests many other species of insect, which are also food sources for birds and small mammals, and which play a key role in the health of the countryside, are also under threat.
Scientists from the EEA, the European Unoin’s environment watchdog, looked at 17 key species of grassland butterflies, of which seven were common species and 10 more specialist, using data gathered from 1990 to 2011 in 19 European countries. Of the total 17 species, eight have declined, including the common blue, which has suffered a serious fall in numbers; two species remained stable, including the Orangetip; and only one increased. The trend for the remaining six species is still uncertain, including the much-appreciated Lulworth skipper, beloved of butterfly watchers.
Grassland butterflies make up the majority of butterflies in Europe, with over 250 species out of the more than 400 found in Europe. Others species prefer to colonise woods, wetlands, heaths and other habitats. Chris van Swaay, one of the authors of the report, from the Dutchconservation organisation De Vlinderstichting, said that the same pesticides that affect bees – leading to the EU to ban certain products, at least temporarily – also have an effect on butterflies. “The pesticide problem is especially a problem in the intensive agricultural areas of western Europe,” he said. “In eastern Europe, it is less of a problem.”
Grassland species are also particularly important because so much of EU land is given over to agriculture: if butterflies cannot thrive on farmland, they will suffer dramatic declines. The EEA warned that as a result of intensive practices, with the aggressive use of pesticides and other chemicals, the loss of hedgerows, field margins and other semi-wild areas, as well as the monocultures prevailing in many areas and the rapid turnover of land, many large areas of farmed land are becoming “sterile” in terms of biodiversity.
The EEA, which worked with conservation charities such as Butterfly Conservation Europe to put together the European grassland butterfly indicator, said that in some areas of affluent north-western Europe, agriculture had become so intensive that butterflies are now confined to marginal land such as road and rail verges and even urban gardens, as well as the small proportion of farmland that is managed with environmental aims in mind.
Hans Bruyninckx, executive director of the EEA, said: “This dramatic decline in grassland butterflies should ring alarm bells – in general Europe’s grassland habitats are shrinking. If we fail to maintain these habitats we could lose many of these species forever. We must recognise the importance of butterflies and other insects – the pollination they carry out is essential for both natural ecosystems and agriculture.”
Perhaps surprisingly, intensive agriculture is not the only threat to butterflies – the abandonment of previously cultivated agricultural land, in central and southern Europe, is also a problem when it results in the neglect of key grassland habitats. When farmland is abandoned, it rapidly turns to scrub, and Europe’s grassland butterfly species have evolved over millennia to live on grassland, including land under old forms of cultivation that were less intensive.
Paul de Zylva, nature campaigner at Friends of the Earth, said: “Bees, butterflies and pollinators in general are facing decline across Europe for the same reasons – loss of habitat, intensive farming and the use of pesticides. Unfortunately the recently reformed Common Agricultural Policy is worse for wildlife than its predecessor. European governments must stop using tax-payers’ money to prop up a farming system that isn’t doing enough to protect nature and biodiversity.”
Two years ago, a stellar cast of ecologists changed the way conservation scientists think about biodiversity. As we tumble headlong into the sixth great extinction, biologists have focused largely on protecting regions with the highest number of species. By saving the most species, the thinking goes, you’ll conserve the greatest number of ecological interactions and so the greatest biodiversity. But in a study that drew on ecological theory and contemporary studies of apex predators like wolves and pumas, the all-star team of ecologists found that some species matter more than others. Losing top predators, they argued, can have far-reaching, irreversible effects on the structure, function and biodiversity of ecosystems.
Ecological theory predicts that changes in the abundance and distribution of top predators can cause substantial shifts in ecosystems. And recent studies—many published in the new millennium—have shown how theoretical predictions play out on the landscape. The collapse of sea otter populations on Amchitka Island in the Aleutian Islands decimated kelp forests by allowing unfettered expansion of sea urchins, the otters’ main food. The loss of wolves in Yellowstone’s Lamar River Valley famously allowed elk to forage with abandon, arresting the development of streamside willows and other riparian vegetation. In Venezuela, forests without jaguars, pumas and eagles had almost no vegetative underbrush compared to the lush understory in forests where predators kept ungulate herbivores in check.
But, according to the study, the loss of large top predators can also lead to soaring rates of wildfires, infectious disease and carbon emissions, and degrade water quality and nutrient cycles.
These “top down” trophic cascades, which the ecologists dubbed “trophic downgrading,” have been documented from the poles to the equators and every major biome in between, making the loss of top predators, they wrote, “arguably humankind’s most pervasive influence on the natural world.” Earth has weathered five mass extinctions but never before at the hands of one species—human beings. And we humans seem hell bent on clearing the Earth of larger bodied apex predators.
I considered all this as I read a new paper from wildlife ecologist Chris Wilmer’s lab (published last week in PLOS ONE) that looks at how human development affects pumas. Like most large carnivores, pumas need vast territories to hunt, find mates and raise young. Pumas living in the San Francisco Bay Area have no such luck. Wilmers, an associate professor of environmental studies at the University of California-Santa Cruz, has been studying the effects of habitat fragmentation on the behavior, ecology and even the physiology of pumas around the Santa Cruz Mountains. He develops cutting-edge GPS collars to track both the location and behavior of his animals.
Fragmented landscapes often pave the way to extinction for wide-ranging large carnivores like pumas, with cascading effects. Freed from the threat of top predators, smaller carnivores like foxes increase in number, driving declines in birds and small mammals. But habitat fragmentation can produce effects similar to extinction because large predators tend to avoid small fragmented parcels. Given the heterogeneous patterns of human developments—with houses and other structures interspersed among natural areas—predicting how animals might respond, and with what consequences, presents a serious challenge.
Since pumas make risk-benefit calculations just like the rest of us and typically avoid humans—their biggest cause of death, aside from roads—Wilmers wanted to know what factors govern their decisions. He and his team figured the cats would steer clear of neighborhoods, where they’d risk seeing their nemesis in various activities, more than roads, where traffic can be sporadic. And they predicted the cats would respond differently depending on their reproductive status. If running into humans meant losing a meal, that would prove less costly from an evolutionary perspective, than if it meant losing a chance to mate or raise young—since, as any evolutionary biologist will tell you, we exist primarily to reproduce.
The team combined their GPS data with field visits to determine whether cats were simply going about their business—that is, feeding (based on the analysis of GPS data and confirmed by finding prey remains) or moving about the landscape (GPS readings not linked to kill or den sites)—or engaged in reproductive behavior—denning (indicated by a female staying within a spot and making repeated return visits) or communicating (indicated by “scrapes,” urine-soaked leaves and debris mounded with the hind feet, the puma version of “here’s my number”).
As predicted, the cats’ response to developments varied with their reproductive status. The data collected on their 20 collared pumas (12 females and 8 males) showed that the animals give human developments a wider berth when engaged in reproductive behaviors. Given how frequently human run-ins result in death for pumas around the Bay Area, it’s not surprising that evolutionary pressures selected against placing the next generation at risk. Similarly, the cats seem to have learned that placing their calling card near trails leaves them vulnerable to destruction by hikers and bikers.
Still, it appears that taking care of large cubs makes mom willing to take more risks. The team found that females with dependent young showed higher tolerance for residential developments than males, possibly because they can’t afford to be choosy about where they find prey. Still, one male in the study did go near developments—a young male seeking new territory—an extremely risky behavior that the sexually immature male shot in Berkeley’s Gourmet Ghetto learned too late.
There’s no doubt that our behavior influences the big cats’ behavior. If you live on the edge of puma habitat and plant lush gardens, you’ll attract deer—and likely their ancient predator. If you don’t safeguard your goats and sheep in enclosed pens at night, you’re just asking for trouble. An astonishing eight of the 11 adult pumas the team studied were shot for attacking livestock.
By understanding where, when and how pumas use their increasingly fragmented habitat, Wilmers and his team can predict how they might respond as development continues. They can also predict, and hopefully mitigate, likely conflicts between humans and the increasingly boxed-in carnivores. But ecologists, even the best ecologists, can do only so much. They need the rest of us to decide whether we’re ready to reverse the trophic downgrading of the planet before it’s too late.
European Union countries should step up their conservation efforts and fully implement the EU Biodiversity Strategy to 2020 to prevent species from going extinct, according to a recent analysis of the European Red List coordinated by IUCN.
The analysis presents a detailed overview of species threatened at the European level in all 27 EU Member States. It shows that the highest share of species threatened in the European Union can be found in the Mediterranean region which hosts most of Europe’s biodiversity.
“Thanks to its bioclimatic conditions, the Mediterranean region is a recognized global hotspot for biodiversity, hosting a large number and extraordinary variety of species,” says Antonio Troya, Director of IUCN Centre for Mediterranean Cooperation. “The survival of many of these species is at risk as their habitats are being negatively impacted by human activities. This is a major challenge that European policy-makers shall address. The IUCN Red List of Threatened Species™ can be an important tool to analyse species population trends to guide effective policy and action at different levels”.
Spain, Portugal and Greece host the highest proportion of species threatened with extinction at the European level and should act with the greatest urgency. Of the 2,233 species assessed which occur in Spain, 21% are considered threatened at the European level. Fifteen percent of the 1,215 European species occurring in Portugal are threatened, and the same is true for 14% of the 1,684 European species found in Greece.
Of the species assessed so far, freshwater species – including fishes, molluscs and amphibians – are at the highest risk, with species such as the European Eel (Anguilla anguilla) and the Freshwater Pearl Mussel (Margaritifera margaritifera) being particularly threatened. The status of terrestrial molluscs, dragonflies and mammals, such as the European Mink (Mustela lutreola) also raises significant concern. Species are mainly threatened by the loss, fragmentation and degradation of their habitat, due in large part to agricultural and urban expansion, construction of dams and water pollution.
While effective conservation action in the Mediterranean is needed urgently, the study calls on all EU Member States to take adequate measures to reverse the current population declines, in order to avoid species going extinct.
“Species can be saved from extinction, but this requires a combination of sound research and greater coordinated efforts,” saysAna Nieto, Regional Biodiversity Conservation Officer at IUCN. “All EU Heads of State and Government have committed to halting biodiversity loss and the degradation of ecosystem services by 2020. Considerable conservation investment is needed from these countries and the EU to achieve this target and assure a long-term improvement in the status of European species.”
EU nature conservation policies are among the most advanced globally. The Birds and Habitats Directives have led to successful recovery of many species.
“Conservation works,” says Simon Stuart, Chair of IUCN Species Survival Commission. “The increase in the population of the Iberian Lynx (Lynx pardinus) in Southern Spain from 94 individuals in 2002 to 312 in 2011 is a case in point. The EU and Member States need to continue to act to protect Europe’s invaluable natural heritage. IUCN stands ready to provide the science and support needed to scale up these efforts.”
For more information or to set up interviews, please contact:
Liza Drius, Communications Officer, IUCN European Union Representative Office, Tel: +32 2 739 0318, liza.drius@iucn.org
About the analysis
The study is based on the data from the European Red Listsupported by the European Commission. It presents the proportion of species which are threatened at the European level for each EU Member State. The present analysis does not provide information on the status of the species at the national level (i.e. in each individual country), but rather on the level of threat for species groups at the European level (i.e. across the whole European continent, but excluding the EU overseas entities). National and sub-national Red Lists can be cross-checked to identify the status of species at the national level. More detailed information and all 27 country fact sheets can be found here.
Which EU Member State hosts the highest proportion of species threatened at the European level?
The above graph shows the proportion of species threatened at the European level for each EU Member State, based upon the ten European Red Lists produced so far. See here the results of the assessments conducted until 2011. Overall, the most threatened species groups assessed so far in Europe are freshwater fishes, freshwater molluscs and amphibians.
Between Thorn Bushes and Claws 