Constantine Alexander's blog

Local management helps species adapt to climate change

As the climate changes, habitat specialist species will be forced to either adapt to new conditions or move to more suitable habitat. Now, researchers from the UK have shown how conservationists can use local management practices to help these species expand into new areas with favourable conditions.

One result of climate change is that existing species habitats will become increasingly unsuitable, particularly for habitat specialists. Conservationists can either help these species cope with changing conditions in their existing range, or help them move to new sites. However, few studies have looked at how such 'facilitated range shifts' would work in practice. Those that have tended to look at large landscape-scale habitat management, rather than local management.

To address this, the researchers studied populations of the silver-spotted skipper butterfly (Hesperia comma) in southeast England. H. comma has strict habitat requirements, as females only lay eggs on short tufts of sheep's fescue grass, preferably in warm areas next to bare ground. Higher temperatures also increase egg-laying rates. As a result, rising temperatures have allowed H. comma to expand its range northwards.

The researchers used a general linear model to study how factors such as patch area, vegetation cover and the proportion of sheep's fescue grass, mean August daily maximum temperature and the amount of sunlight the site received affected H. comma populations at 724 patches between 2000 and 2009.

They found that 67 patches were colonised and 48 local extinctions occurred over the study period, as well as 29 temporary colonisations and subsequent extinctions. In particular, populations at the leading edge of the range expansion were most vulnerable to extinction.

The survival of populations of H. comma depended on several site-specific factors which could be influenced by local management practices. Larger patches had higher survival rates, as did higher quality patches with more sheep's fescue grass. Sites with around 15 per cent bare earth also had high survival rates. Survival also depended on climactic factors; populations in warmer, south-facing sites had greater survival chances, as did those which received the most sunlight. Connectivity between patches – a landscape-scale issue – improved both the chances of initial colonisation and survival.

The results suggest that, as population survival in occupied patches is important to long-term range shifts, local management practices can help facilitate range shifts by improving the survival chances of populations at the leading edge of expansion. However, local management practices do not improve the chances of a patch being colonised in the first place. Based on these findings, the researchers proposed management options for sites where either colonisation or survival chances were low. For those where colonisation was a problem, the researchers suggested creating corridors or 'stepping stone' patches between sites to improve connectivity, as well as artificially introducing the butterfly. For sites where survival was low, land managers can increase patch size through habitat restoration or use grazing to improve patch quality.

However, the researchers note that management priorities can change quickly. As climates change, isolated sites may end up better connected to habitable areas, improving the chances of colonisation and suggesting land managers should focus on improving the site to aid survival. Alternatively, sites on the edge of the range where survival rates were low may become more central, so management to improve survival may become less of a priority.

Source: Lawson, C.R., Bennie, J.J., Thomas, C.D., Hodgson, J.A. & Wilson, R.J. (2012). Local and landscape management of an expanding range margin under climate change. Journal of Applied Ecology. 49, p 552 – 561. doi: 10.1111/j.1365-2664.2011.02098.x

Contact: j.j.bennie@exeter.ac.uk

 

 

 

New bat virus could hold key to Hendra virus

Australian scientists have discovered a new virus in bats that could help shed light on how Hendra and Nipah viruses cause disease and death in animals and humans. The new virus - named 'Cedar' after the Queensland location where it was discovered - is a close relative of the deadly Hendra and Nipah viruses.

However, CSIRO's initial studies have discovered one surprising key difference - the Cedar virus does not cause illness in several animal species normally susceptible to Hendra and Nipah.

This tantalising difference may help scientists understand how to better manage and control its deadly cousins. The findings have been announced today in the journal, PLoS Pathogens, published by the Public Library of Science.

Mr Gary Crameri, research scientist with the bat virus team at CSIRO's Australian Animal Health Laboratory in Geelong, Victoria, said the new discovery had significant potential implications for protecting animals and humans from the Hendra and Nipah viruses.

 

"The significance of discovering a new henipavirus that doesn't cause disease is that it may help us narrow down what it is about the genetic makeup of viruses like Hendra and Nipah that does cause disease and death," Mr Crameri said.

"The more that we can learn about bat-borne viruses, the better chance we have of developing anti-virals and vaccines to help protect human health, Australia's livestock industry and our export trade from the threat of current and emerging animal diseases.

"Over 70 per cent of people and animals infected with Hendra and Nipah viruses die. This ranks henipaviruses amongst the deadliest viruses in existence, yet little is known about just how such viruses actually cause disease or death."

It is still too early to rule out the possibility that Cedar virus may cause illness and death in horses or other animals.

The discovery was a result of a close partnership with Biosecurity Queensland which played an important role by collecting and screening samples from bat colonies across Queensland.

		This shows cells infected with Hendra virus (left) and with Cedar virus (right). Hendra virus is the more effective at fusing cells (circled) and spreading its infection. More individual cells remain intact (circled) with Cedar virus and it doesn’t spread nearly as extensively. Credit: CSIRO

"Field work with bats is an essential part of research into identifying new viruses," Dr Hume Field of Biosecurity Queensland said. "Bats are being implicated as the natural host of a growing number of viruses in Australia and overseas, yet they appear to tolerate infection themselves making bat research increasingly important."

Bats have been identified as playing a role in the spread of viruses including Ebola, Marburg, SARS and Melaka yet they are an essential part of our diverse ecosystem through their role as pollinators, seed dispersers and insect regulators.

The discovery is part of ongoing research by CSIRO to target diseases that threaten our animals, people and the environment and is part of CSIRO's wider biosecurity effort. It follows CSIRO's development towards a horse vaccine against Hendra virus.

Contact: Pamela Tyers
Pamela.Tyers@csiro.au
61-488-995-023
CSIRO Australia

 

 

Mapping the future of climate change in Africa

Researchers at the University of Texas at Austin and partner universities create tools to help vulnerable populations adapt to climate change and political instability

		The composite picture highlights areas of chronic insecurity where the four sources of vulnerability coalesce. Credit: Joshua Busby et al.

Our planet's changing climate is devastating communities in Africa through droughts, floods and myriad other disasters.

Using detailed regional climate models and geographic information systems, researchers with the Climate Change and African Political Stability (CCAPS) program developed an online mapping tool that analyzes how climate and other forces interact to threaten the security of African communities.

The program was piloted by the Robert S. Strauss Center for International Security and Law at The University of Texas at Austin in 2009 after receiving a $7.6 million five-year grant from the Minerva Initiative with the Department of Defense, according to Francis J. Gavin, professor of international affairs and director of the Strauss Center.

"The first goal was to look at whether we could more effectively identify what were the causes and locations of vulnerability in Africa, not just climate, but other kinds of vulnerability," Gavin said.

CCAPS comprises nine research teams focusing on various aspects of climate change, their relationship to different types of conflict, the government structures that exist to mitigate them, and the effectiveness of international aid in intervening. Although most CCAPS researchers are based at The University of Texas at Austin, the Strauss Center also works closely with Trinity College Dublin, the College of William and Mary, and the University of North Texas.

"In the beginning these all began as related, but not intimately connected, topics" Gavin said, "and one of the really impressive things about the project is how all these different streams have come together."

Africa is particularly vulnerable to the effects of climate change due to its reliance on rain-fed agriculture and the inability of many of its governments to help communities in times of need.

The region is of increasing importance for U.S. national security, according to Gavin, because of the growth of its population, economic strength and resource importance, and also due to concerns about non-state actors, weakening governments and humanitarian disasters.

		Climate security vulnerability in Somalia is greatest in and around the capital of Mogadishu and the far north. Insecurity in these areas is driven by all four dimensions of vulnerability, but particularly by low resilience and poor governance. Credit: Joshua Busby et al.

Although these issues are too complex to yield a direct causal link between climate change and security concerns, he said, understanding the levels of vulnerability that exist is crucial in comprehending the full effect of this changing paradigm.

The vulnerability mapping program within CCAPS is led by Joshua Busby, assistant professor at the Lyndon B. Johnson School of Public Affairs.

To determine the vulnerability of a given location based on changing climate conditions, Busby and his team looked at four different sources: 1) the degree of physical exposure to climate hazards, 2) population size, 3) household or community resilience, and 4) the quality of governance or presence of political violence.

The first source records the different types of climate hazards which could occur in the area, including droughts, floods, wildfires, storms and coastal inundation. However, their presence alone is not enough to qualify a region as vulnerable.

The second source—population size—determines the number of people who will be impacted by these climate hazards. More people create more demand for resources, potentially making the entire population more vulnerable.

The third source looks at how resilient a community is to adverse effects, analyzing the quality of their education and health, as well as whether they have easy access to food, water and health care.

"If exposure is really bad, it may exceed the capacity of local communities to protect themselves," Busby said, "and then it comes down to whether or not the governments are going to be willing or able to help them."

The final source accounts for the effectiveness of a given government, the amount of accountability present, how integrated it is with the international community, how politically stable it is, and whether there is any political violence present.

Busby and his team combined the four sources of vulnerability and gave them each equal weight, adding them together to form a composite map. Their scores were then divided into a ranking of five equal parts, or quintiles, going from the 20 percent of regions with the lowest vulnerability to the 20 percent with the highest.

The researchers gathered information for the tool from a variety of sources, including historic models of physical exposure from the United Nations Environment Programme (UNEP), population estimates from LandScan, as well as household surveys and governance assessments from the World Bank's World Development and Worldwide Governance Indicators.

This data reflects past and present vulnerability, but to understand which places in Africa would be most vulnerable to future climate change, Busby and his team relied on the regional climate model simulations designed by Edward Vizy and Kerry Cook, both members of the CCAPS team from the Jackson School of Geosciences.

		Children in the foothills of Drakensberg mountains in South Africa who still live in traditional rondavels on family homesteads. Credit: Todd G. Smith, CCAPS Program.

Vizy and Cook ran three, 20-year nested simulations of the African continent's climate at the regional scales of 90 and 30 kilometers, using a derivation of the Weather Research and Forecasting Model of the National Center for Atmospheric Research. One was a control simulation representative of the years 1989-2008, and the others represented the climate as it may exist in 2041-2060 and 2081-2100.

"We're adjusting the control simulation's CO2 concentration, model boundary conditions, and sea surface temperatures to increased greenhouse gas forcing scenario conditions derived from atmosphere-ocean global climate models. We re-run the simulation to understand how the climate will operate under a different, warmer state at spatial resolutions needed for regional impact analyses," Vizy said.

Each simulation took two months to complete on the Ranger supercomputer at the Texas Advanced Computing Center (TACC).

"We couldn't run these simulations without the high-performance computing resources at TACC, it would just take too long. If it takes two months running with 200 processors, I can't fathom doing it with one processor," Vizy said.

Researchers input data from these vulnerability maps into an online mapping tool developed by the CCAPS program to integrate its various lines of climate, conflict and aid research. CCAPS's current mapping tool is based on a prototype developed by the team to assess conflict patterns in Africa with the help of researchers at the TACC/ACES Visualization Laboratory (Vislab), according to Ashley Moran, program manager of CCAPS.

"The mapping tool is a key part of our effort to produce new research that could support policy making and the work of practitioners and governments in Africa," Moran said. "We want to communicate this research in ways that are of maximum use to policymakers and researchers."

The initial prototype of the mapping tool used the ArcGIS platform to project data onto maps. Working with its partner Development Gateway, CCAPS expanded the system to incorporate conflict, vulnerability, governance and aid research data.

After completing the first version of their model, Busby and his team carried out the process of ground truthing their maps by visiting local officials and experts in several African countries, such as Kenya and South Africa.

"The experience of talking with local experts was tremendously gratifying," Busby said. "They gave us confidence that the things we're doing in a computer lab setting in Austin do pick up on some of the ground-level expert opinions."

Busby and his team complemented their maps with local perspectives on the kind of impact climate was already having, leading to new insights that could help perfect the model. For example, local experts felt the model did not address areas with chronic water scarcity, an issue the researchers then corrected upon returning home.

According to Busby, the vulnerability maps serve as focal points which can give way to further analysis about the issues they illustrate.

Some of the countries most vulnerable to climate change include Somalia, Sierra Leone, Guinea, Sudan and parts of the Democratic Republic of Congo. Knowing this allows local policymakers to develop security strategies for the future, including early warning systems against floods, investments in drought-resistant agriculture, and alternative livelihoods that might facilitate resource sharing and help prevent future conflicts. The next iteration of the online mapping tool to be released later this year will also incorporate the future projections of climate exposure from the models developed by Vizy and Cook.

The CCAPS team publishes their research in journals like Climate Dynamics and The International Studies Review, carries out regular consultations with the U.S. government and governments in Africa, and participates in conferences sponsored by concerned organizations, such as the United Nations and the United States Africa Command.

"What this project has showed us is that many of the real challenges of the 21st century aren't always in traditional state-to-state interactions, but are transnational in nature and require new ways of dealing with," Gavin said.

Contact: Faith Singer-Villalobos
faith@tacc.utexas.edu
512-663-7237
University of Texas at Austin, Texas Advanced Computing Center

 

 

Notre Dame research into oaks helps us understand climate change

Jeanne Romero-Severson, associate professor of biological sciences at the University of Notre Dame, and her collaborators, are tracking the evolution of the live oaks of eastern North America, seeking to understand how the trees adapted to climate change during glacial periods.

When the ice advanced, the oaks retreated. When the ice retreated the oaks advanced, spreading from tropical to temperate zones, up from Central America and Mexico into the Piedmont Carolinas. The researchers expect the study of live oak migrations and phylogeny will provide clues to the success of the oaks that range up into northern Ontario in Canada.

Oaks originated in southeast Asia before the continents split and migrated both east and west, but North America has far more species than other regions. Researchers have long suspected that repeated climate challenges might have led to this diversity. Previous studies have shown that the live oaks that live in Mexico cannot survive the Carolina winters. This shows that there are genetic differences between the southern live oaks and their northern descendants.

"In Mexico, live oaks do not experience repeated cycles of freezing and thawing," Romero-Severson says. "Are the live oak species that now live further north different species because of this cold tolerance? What about the live oak species that span the tropical-temperate divide? It is logical to assume there is a genetic basis for the ability to survive in those cold temperatures. With four groups of researchers working together, we can tease out how it was that oaks were able to adapt to the climate as they moved north. What were the genetic changes they underwent?"

Romero-Severson focuses on genetics and genomics of the oaks. Andrew Hipp of the Morton Arboretum in Lisle, Ill., is studying their morphological differences; Paul Manos of Duke University is studying their systematics (family trees based on DNA markers); and Jeannine Cavender-Bares of the University of Minnesota is studying their ecophysiology, including the survival of seedlings in cold temperatures. A National Science Foundation grant supports the research.

The team hypothesizes that trees in contact with relatives who could just manage to survive in the cold were able to "capture" from these relatives a few genes favorable for survival in colder climates, without retaining extensive genetic changes that would alter their morphology. Different animal species rarely hybridize in nature and when they do, the offspring are often sterile, like mules. Different forest tree species often make fertile interspecific hybrids, but the parent species remain morphologically distinct.

"It's a mystery to us how oak species can have rampant interspecies hybridization and yet maintain species distinction, but they do," Romero-Severson says. "Favorable gene combinations from one live oak species can be captured by any other live oak species." There might be an "interspecific hybrid screen," a process that retains a relatively small number of good genes that equip the species for successful northward migration, while maintaining all the other genes that determine species identity.

Identification of the genetic changes in the relatively small number of live oak species in the southeastern United States and Mexico can provide clues for study of the more extensive deciduous red and white oaks, which reach from the Caribbean into California to the west and up into Canada from the east. Eastern North America alone has more than two dozen red oak species and close to two dozen white oak species. Some regions in the southeastern United States have the highest concentration of oak species in the world.

"Our hypothesis is that the same set of genes is involved in cold tolerance in all of these species," Romero-Severson says. "We feel that we have defined the problem so carefully that what we learn from these live oaks will help us understand how evolution works, and how natural adaptation arises. Our goal is to understand the role of hybridization in the evolution of forest trees and how forest trees actually respond to rapid climate change."

Romero-Severson, who came to Notre Dame in 2003, is also part of a team of researchers from seven universities with an NSF grant to develop genomics tools for finding the genetic basis for tolerance to the introduced insects and diseases that threaten the nation's hardwood trees.

Contact: Jeanne Romero-Severson
jromeros@nd.edu
574-631-3938
University of Notre Dame

 

 

Extinction risk factors for New Zealand birds today differ from those of the past

Deck of playing cards featuring New Zealand native birds, ca 1950.

What makes some species more prone to extinction? A new study of nearly 300 species of New Zealand birds — from pre-human times to the present — reveals that the keys to survival today differ from those of the past.

The results are important in light of the growing number of studies that try to predict which species could be lost in the future based on what kinds of species are considered most threatened today, said lead author Lindell Bromham of Australian National University.

In the roughly 700 years since humans arrived in the remote islands that make up New Zealand, more than one out of four of New Zealand's native bird species have been wiped out.

Gone are birds such as the massive Haast's eagle, which weighed up to 33 pounds (15kg), and the giant moa, a flightless bird that stood up to ten feet (3m) tall.

Many species were hunted to extinction. Others were eaten by the animals humans brought with them — such as cats, rats and weasels — or pushed off their land as humans cleared and burned forests to make way for farms and pastures.

In a new study, a team of researchers examined whether biological traits such as body size might help scientists predict which species were likely to perish, and whether those risk factors held up over time.

To find out, they analyzed extinction patterns for New Zealand's native birds across four time periods in New Zealand's history, from pre-human times to the present. The data set included 274 species of living and extinct birds, such as ducks, penguins, geese, gulls, pigeons, parakeets and wrens.

The researchers looked for the biological traits that best predicted extinction risk in each time period. After accounting for similarities among closely related species, the researchers found that the traits that make some species more vulnerable today differ from what made species more prone to extinction in the past.

When the researchers compared the last 700 years of human occupation to pre-human times, for example, they found that flightless species such as moa and rails have been consistently hard-hit — presumably because species that can't fly make easy snacks.

"There was no difference in extinction risk between flightless and flighted species until humans arrived," said co-author Robert Lanfear, currently a visiting researcher at the U.S. National Evolutionary Synthesis Center.

Other risk factors for extinction changed with each new wave of human settlement.

In the period after Polynesians appeared until Europeans arrived in the 1820s, for example, bigger species were more likely to die out. According to one study the extinct giant moa — a group of ostrich-like birds that weighed up to 600 pounds (270 kg) — was hunted to extinction within less than one hundred years.

The researchers were surprised to find that after Europeans arrived, size was no longer a factor. Instead, species having males and females of different color were the hardest hit —possibly because those species were prized for museum collections.

Today, species that nest on the ground and lay only a few eggs at a time are considered most threatened, including the iconic kiwi, and a giant flightless parrot called the kakapo — two birds found only in New Zealand.

Why do the extinction risk factors for New Zealand birds living today differ from those of the past? Size, for example, was only associated with extinction risk in the period after Polynesians arrived but before European settlement.

"It could be that that's when birds were most heavily hunted for food," Bromham said. "Or it might be that all the largest birds went extinct soon after human arrival, so now there are no longer enough large species to spot the raised extinction risk!"

"If extinction has already caused the loss of a susceptible trait, then this trait may no longer be relevant to surviving species even though it is still the original cause of past extinctions. This is known as an 'extinction-filter'," explained co-author Phillip Cassey of the University of Adelaide in Australia.

For studies of extinction risk, the results mean we should proceed with caution when analyzing different time periods. "We can't guarantee that the patterns we detect in contemporary extinction risk are the same as those that have caused extinctions in the past, or will be the ones that are most important in the future," Bromham said.

Marcel Cardillo of Australian National University and Gillian Gibb of Massey University in New Zealand were also authors on this study. The team's findings were published online on August 1, 2012 in the journal Proceedings of the Royal Society B.

CITATION: Bromham, L., R. Lanfear, et al. (2012). "Reconstructing past species assemblages reveals the changing patterns and drivers of extinction through time." Proceedings of the Royal Society B. http://dx.doi.org/10.1098/rspb.2012.1437.

The National Evolutionary Synthesis Center (NESCent) is a nonprofit science center dedicated to cross-disciplinary research in evolution. Funded by the U.S. National Science Foundation, NESCent is jointly operated by Duke University, The University of North Carolina at Chapel Hill, and North Carolina State University.

Contact: Robin Ann Smith
rsmith@nescent.org
919-668-4544
National Evolutionary Synthesis Center (NESCent)

 

 

Deep-sea squid can 'jettison arms' as defensive tactic

Octopoteuthis deletron

A postdoctoral researcher at the University of Rhode Island has observed a never-before-seen defensive strategy used by a small species of deep-sea squid in which the animal counter-attacks a predator and then leaves the tips of its arms attached to the predator as a distraction.

Stephanie Bush said that when the foot-long octopus squid (Octopoteuthis deletron) found deep in the northeast Pacific Ocean "jettisons its arms" in self-defense, the bioluminescent tips continue to twitch and glow, creating a diversion that enables the squid to escape from predators.

"If a predator is trying to attack them, they may dig the hooks on their arms into the predator's skin. Then the squid jets away and leaves its arm tips stuck to the predator," explained Bush. "The wriggling, bioluminescing arms might give the predator pause enough to allow the squid to get away."

The discovery was published in the July issue of the journal Marine Ecology Progress Series.

While Bush was a graduate researcher working with the Midwater Ecology Lab at the Monterey Bay Aquarium Research Institute, she observed that many octopus squid had arms of different lengths. Scientists had speculated that they may release their arms, just as lizards can release their tails when attacked, but no one had seen it happen. Using a remotely operated vehicle in the Monterey Bay Submarine Canyon off the coast of California, Bush poked at a squid with a bottlebrush.

"The very first time we tried it, the squid spread its arms wide and it was lighting up like fireworks," she said. "It then came forward and grabbed the bottlebrush and jetted backwards, leaving two arms on the bottlebrush. We think the hooks on its arms latched onto the bristles of the brush, and that was enough for the arms to just pop off."

The squid are able to re-grow their missing arms.

"There is definitely an energy cost associated with this behavior, but the cost is less than being dead," Bush said.

In further experiments, Bush found that some octopus squid appeared hesitant to sacrifice their limbs, but some did so after being prodded several times. When she provoked seven other squid species similarly, none dropped their arm tips.

Bush's research on squid began in 2003 when she decided to investigate the assumptions that some scientists had made about deep-sea animals.

"Scientists had assumed that squid living in the deep-sea would not release ink as a defensive measure, but all the species I've observed did release ink," she said. "They assumed that because they're in the dark all day every day that they're not doing the same things that shallow water squids are doing. They also assumed that deep-sea squid don't change color because of the dark, but they do."

The URI scientist's current research focuses on a tiny squid that lives in the Gulf of California that migrates every day from the dark depths where there is little oxygen to the surface waters to feed. She is examining their oxygen consumption rates and how increasing water temperatures will affect their survival.

"They're a really abundant species in the Gulf, so presumably if they are that abundant, they must be feeding on lots of different things and there must be lots of things feeding on them," Bush said. "They could be very important to the health of the ecosystem."

Contact: Todd McLeish
tmcleish@uri.edu
401-874-7892
University of Rhode Island

 

Economy of arm autotomy in the mesopelagic squid Octopoteuthis
Octopoteuthis deletron autotomizes 2 arms onto a bottle-brush that is attached to an arm of the remotely operated vehicle (ROV) 'Ventana' on October 22, 2008, at 830 m depth. The 2 arms remain attached to the bottle-brush, and then 1 arm detaches and thrashes for 10 s before ceasing movement. The terminal photophore of the thrashing arm is white, therefore it is presumably bioluminescent.

 

Cuckoo tricks to beat the neighborhood watch

New research explains why female cuckoos have evolved different guises

To minimise the chance of being recognised and thus attacked by the birds they are trying to parasitize, female cuckoos have evolved different guises. The new research, funded by the Natural Environment Research Council, was published today, 03 August, in the journal Science.

The common cuckoo (Cuculus canorus) lays its eggs in the nests of other birds. On hatching, the young cuckoo ejects the host's eggs and chicks from the nest, so the hosts end up raising a cuckoo chick rather than a brood of their own. To fight back, reed warblers (a common host across Europe) have a first line of defence: they attack, or 'mob', the female cuckoo, which reduces the chance that their nest is parasitized.

Some female common cuckoos are grey and hawk-like, and previous research has shown that their resemblance to hawks reduces host bird attack. However, other females are bright rufous (brownish-red). The presence of alternate colour morphs in the same species is rare in birds, but frequent among the females of parasitic cuckoo species. The new research shows that this is another cuckoo trick: cuckoos combat reed warbler mobbing by coming in different guises.

Cuckoos are secretive. To widen their source of information about local cuckoo activity, reed warblers eavesdrop on the mobbing behaviour of their neighbours. In the study, the researchers manipulated local frequencies of the more common grey colour cuckoo and the less common (in the United Kingdom) rufous colour cuckoo by placing models of the birds at neighbouring nests. They then recorded how the experience of watching neighbours mob changed reed warbler responses back at their own nest.

They found that reed warblers increased their mobbing, but only to the cuckoo morph that their neighbours had mobbed. Therefore, as one cuckoo morph increases in frequency, local host populations will become alerted specifically to that morph. This means the alternate morph will be more likely to slip past host defences and lay undetected. This is the first time that 'social learning' has been documented in the evolution of mimicry as well as the evolution of different observable characteristics - such as colour - in the same species (called polymorphism).

Dr Rose Thorogood, of the University of Cambridge and co-author on the paper, said: "When mimetic disguises become less effective, evolving a polymorphism can be a successful trick. Our research shows that individuals assess disguises not only from personal experience, but also by observing others. However, because their learning is so specific, this social learning then selects for alternative cuckoo disguises and the arms race continues."

Professor Nick Davies, of the University of Cambridge and co-author on the paper, added: "It's well known that cuckoos have evolved various egg types which mimic those of their hosts in order to combat rejection. This research shows that cuckoos have also evolved alternate female morphs to sneak through the hosts' defences. This explains why many species which use mimicry, such as the cuckoo, evolve different guises."

1. The paper 'Cuckoos combat socially transmitted defences of reed warbler hosts with a plumage polymorphism' will be published in the 03 August edition of Science.
2. The work was funded by the Natural Environment Research Council (NERC) is the UK's main agency for funding and managing world-class research, training and knowledge exchange in the environmental sciences. It coordinates some of the world's most exciting research projects, tackling major issues such as climate change, food security, environmental influences on human health, the genetic make-up of life on earth, and much more. NERC receives around £300 million a year from the government's science budget, which it uses to fund research and training in universities and its own research centres. 

Contact: Genevieve Maul
Genevieve.maul@admin.cam.ac.uk
44-012-237-65542
University of Cambridge

 

 

 

Aerial photos reveal dynamic ice sheet

Despite the current and rapid melting of the Greenland Ice Sheet, it remains far from certain just when we will have reached a point when scientists will be able to predict its disappearance. Recent research conducted by the University of Copenhagen in conjunction with the Technical University of Denmark (DTU) and the Danish National Survey and Cadastre (KMS) in collaboration with an international team of scientists reports that this is not the first time in recent history that the ice sheet has been in retreat and then stabilised again. The researchers' results have just been published in Science, the renowned American scientific journal.

Describing the findings, University of Copenhagen Associate Professor Kurt H. Kjær at Professor Eske Willerslevs Centre for GeoGenetics at the Natural History Museum of Denmark asserts:

"That air temperatures have increased and melting has intensified is relatively well-understood. On the other hand, the UN's climate panel, the IPCC, has for many years called for greater knowledge in relation to the other major effect on the Greenland Ice Sheet - the 'thinning of the ice sheet' which is the effect of the largest glaciers in Greenland flowing faster into the ocean than previously measured. Over the past three years a number of scientific articles have addressed the issue and pointed to a sea-level rise of one metre or more. These reports presuppose that the melting will accelerate to the same degree as during the past decade. This is a question to which we have been able to provide a qualified answer. It turns out that the ice sheet, in relation to this point, behaves more dynamically and is able to more quickly stabilise itself in comparison to what many other models and computer calculations otherwise predict."

Denmark under water

No less than 240 billion tons of fresh water escape their solid state within the Greenland Ice Sheet and runoff or discharge as icebergs into the world's oceans each year. This amount corresponds to a 5.6 meter annual rise in water level if distributed over the surface area of Denmark, an area of approximately 43,000 km2.

Current melting attributable to global warming is so great that some experts warn that we are headed towards an irreversible "tipping point" - a point at which the global climate is permanently transformed, a point at which low-lying cities and coastal zones around the world will be seriously threatened in 100 years time.

As recently as one year ago this scenario was presented in Copenhagen at a scientific conference organised by the Arctic Council, the University of Copenhagen and Aarhus University, a conference involving over 400 climate researchers from 20 countries.

A problem to be taken more than seriously

Among the somber tones and gloomier outlooks, the recent research findings out of the University of Copenhagen and the Technical University of Denmark (DTU) in conjunction with an international team of researchers, show that the Greenland Ice Sheet is more robust than researchers have otherwise been able to predict using models and computer-based calculations.

The new research findings were obtained by combining contemporary satellite data with old aerial photographs of the ice sheet in northwestern Greenland, one of two hotspots for ice sheet thinning and heavy glacial melt runoff.

Senior researcher Shfaqat Abbas Khan of the Technical University of Denmark (DTU) says of the research results:

"We've used a combination of old aerial photographs from the 80's to construct a digital elevation map and recent satellite data. In this way we've been able to gain an overview of the thinning of the ice sheet over the last 30 years in northwestern Greenland. We are the first who have been able to show that the Greenland Ice Sheet was on as a dramatic diet at the end of the 80's as it is today. On the positive side our results show that despite a significant thinning in peripheral regions from 1985-1992; the thinning slowed and then died out."

Old photos

Associate Professor Kurt H. Kjær of the University of Copenhagen had the idea to create new and comparable elevation models of the ice sheet along a 700 km long stretch of the northwestern Greenland coast using the old photos. This provided researchers with a relatively simple way of revealing more of the ice sheet's secrets in comparison to other new methods.

Kurt H. Kjær says:

"Our results show that the thinning of the ice sheet at the end of the 80's and beginning of the 90's eased over a 4-8 year period, after which a period of stability occurred until 2003. Our conclusion is therefore, that if we judged against longer periods of time, the current thinning of the ice sheet is likely to ease within an 8-year period."

"These variations in the amount of thinning that we are able to document since the 80's make it difficult to predict how much the world's oceans will rise over a longer period of time - a century for instance - as a result of Greenland glacial melt-water runoff. However, it is certain that many of the present calculations and computer models of ice sheet conditions that built upon a short range of years since 2000 must be reassessed. It is too early to proclaim the 'ice sheet's future doom' and subsequent contribution to serious water problems for the world. In this context it should be mentioned that the Greenland bedrock rises as the ice sheet in the peripheral regions and especially near the coast is in retreat and becoming thinner. This highlights the enormous forces that are at play in Greenland and of how difficult it is to predict what it means for Greenland as well as the rest of the world," says Associate Professor Kurt H. Kjær of the Natural History Museum of Denmark, University of Copenhagen.

Contact: Kurt Kjær
kurtk@snm.ku.dk
45-30-58-97-30
University of Copenhagen

 

 

Study finds healthy seafood comes from sustainable fish

Seafood Watch Program

When ordering seafood, the options are many and so are some of the things you might consider in what you order. Is your fish healthy? Is it safe? Is it harvested responsibly? While there are many services and rankings offered to help you decide – there’s even an iPhone app – a group of researchers have found a simple rule of thumb applies.

“If the fish is sustainable, then it is likely to be healthy to eat too,” said Leah Gerber, an associate professor and senior sustainability scientist at Arizona State University.

Gerber and colleagues ran an analysis of existing literature on fish to see which choices are consistently healthier and which are high in mercury or overfished. Their findings are published in today’s (Aug. 2) early on-line version of the Frontiers in Ecology and the Environment, a publication of the Ecological Society of America.

In “Sustaining seafood for public health,” Gerber and fellow authors – Roxanne Karimi, Stony Brook University, Stony Brook, N.Y., and Timothy Fitzgerald of the Environmental Defense Fund, Washington, DC – state that their analysis is the first to bring together several types of sustainability rankings, along with species specific health metrics, including omega-3 fatty acid and mercury content.

“In general, larger longer-lived fish are more likely to have exposure to toxins due to the length of their lives and their place on the food chain,” Gerber explained. “So you might be best served to stay away from them – like Bluefin Tuna or Sturgeon. Besides, these stocks have been depleted by fishing.”

Safer choices might be Alaskan Pollock or Atlantic Mackerel, said Gerber, a conservation biologist and sushi lover. In fact, the research grew out of her interest in knowing more about the fish she was eating and the choices she and her friends made when dining on fish.

In one experience, Gerber said, friends ordered Bluefin Tuna to her dismay.

“That my socially- and health-conscious friends did not know Bluefin was taboo made me think about how complicated it has become to decide what seafood to eat,” she recalled. “How do seafood consumers make informed decisions based on ecological risk, health risks (mercury), and health benefits (omegas).

So Gerber, Karimi and Fitzgerald began digging in the literature and developed a database on both ecological and health metrics of seafood.

“We used the database to look for patterns of similarity between ecological and health metrics, and found that in general, choosing healthy seafood also means that you are choosing sustainable seafood,” Gerber said. “Great news for sushi-lovers! Choose the sustainable options and you also are boosting omega-3 intake, without risking mercury poisoning.”

Next up for Gerber is to help develop a tool that can be used to guide seafood consumers to smarter choices in what they eat.

“We want to help people choose fish that are both eco-friendly and healthy,” she said.

Contact: Skip Derra
skip.derra@asu.edu
480-965-4823
Arizona State University

 

 

Stanford expert brings climate change science to heated Capitol Hill

Now's the time to prepare for the heat waves, heavy rains and droughts that climate change will bring, says Stanford's Chris Field, a noted climate researcher.

Speaking Wednesday at a contentious U.S. Senate hearing on climate change, Stanford's Chris Field, an expert on climate change, offered a stark yet hopeful analogy.

Just as speeding increases the chance of having a car accident, climate change intensifies the risk of heat waves, droughts and heavy precipitation, said Field, a senior fellow at the Stanford Woods Institute for the Environment. He testified before the Senate Committee on Environment and Public Works.Speaking Wednesday at a contentious U.S. Senate hearing on climate change, Stanford's Chris Field, an expert on climate change, offered a stark yet hopeful analogy.

"We can point clearly to the causal mechanism, but it's still difficult to predict exactly when or where the crisis – either the accident from speeding in a car or the disaster that's related to climate change – will occur, he said. "But still, we can have high confidence in the driving mechanism."

Or, as Field put it later in his testimony, "It is critical to understand that the link between climate change and the kinds of extremes that lead to disasters is clear."

Although we can't be certain that staying within the speed limit will prevent a crash, we know it will decrease the risk. Similarly, Field said, we can reduce the risk of a weather-related disaster with measures such as disaster preparations, early warning systems and well-built infrastructure.

While climate change's role in tornadoes and hurricanes remains unknown, Field said, "the pattern is increasingly clear" when it comes to heat waves, heavy rains and droughts.

The hearing came on the heels of months of intense heat waves and massive wildfires. A disastrous drought still affects more of the U.S. than any drought in almost 25 years. Last year alone, the U.S. endured 14 climate-related disasters that each wreaked at least a billion dollars in damage, according to written testimony Field prepared for the hearing.

Field is a Stanford professor of biology and environmental Earth system science and director of the Department of Global Ecology at the Carnegie Institution for Science. He was part of a group of researchers who shared the 2007 Nobel Peace Prize for their climate change work with the United Nations Intergovernmental Panel on Climate Change (IPCC). Field is co-chair of an IPCC working group that recently released a special report entitled "Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation."

Citing studies from the IPCC, the U.S. National Academy of Sciences and the U.S. National Oceanic and Atmospheric Administration (NOAA), among other scientific organizations, Field told the committee that climate change will lead to more frequent and intense extreme weather that affects larger areas and lasts longer. This, Field said, is a recipe for "unprecedented extreme weather and climate events."

At the hearing's close, Field explained his objective. "What we're trying to do is provide sufficient information for policymakers to make good decisions to try to figure out ways to avoid the damages that come from climate change without providing unacceptable costs to the rest of society. And we're really trying to find smart ways to move forward, recognizing what's happening, recognizing what the risks are and that there are consequences of using the atmosphere as a dump for greenhouse gasses just the same way there are consequences of making changes in the economy that are intended to alleviate those damages."

• Watch the Hearing video
• Download Chris Field's prepared testimony
• IPCC report

Contact: Christine Harrison
christine.harrison@stanford.edu
650-725-8240
Stanford University