Climate change

Jul

1

2008
 
 

Cow pharming



Drugged cows produce more milk, cutting greenhouse gas emissions

cowCows might cultivate an image of gentle, vegetarian all-round pleasantness, but don’t be duped: their methane-laden flatus is the source of ten percent of the global annual emissions of this powerful greenhouse gas. Judith Capper and colleagues report a technological solution in this week’s PNAS. The Cornell University researcher has studied the effects of supplementing cow feed with recombinant bovine somatotropin, the main effect of which is to boost milk production. The knock-on effect of this is a reduction of energy input and waste output for a given quantity of milk. The laced cows have a relatively low environmental impact, presenting conservation-minded sorts with a tricky dilemma: should we ditch high impact organic dairy farming for the pharmacologically modified alternative? Source: Capper JL, Castañeda-Gutiérrez, Cady RA & Bauman DE (2008) The environmental impact of recombinant bovine somatotropin (rbST) in dairy production. Proceedings of the National Academy of Sciences USA DOI: 10.1073/pnas.0802446105

Image: © VeSilvio

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Jun

17

2008
 
 

Woe be-toad them



Global analysis could help identify frog species at risk in time to act

going, going, gone A number-crunching study has thrown light on the mysterious global declines in hundreds of amphibian species. Imperial College London researcher Jon Bielby and colleagues collected data on habitat types, species ranges, disease prevalence and a host of other factors to produce a broad scale picture of the health of the world’s frog populations. Of particular note was the finding that aquatic, slowly reproducing species were most susceptible to the fatal Batrachochytrium dendrobatidis fungus. The results, published in Conservation Letters confirm earlier, more restricted findings and should help conservationists decide how to set priorities by enabling them to identify species at risk before it’s too late. Source: Bielby J, Cooper N, Cunningham AA, Garner TWJ & Purvis A (2008) Predicting susceptibility to future declines in the world’s frogs. Conservation Letters DOI: 10.1111/j.1755-263x.2008.00015.x

Image: © Sergey Korotkov

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May

21

2008
 
 

Better aliens



Mammals are more effective invasive species than birds, study finds

kill the pig!According to the “tens rule”, roughly ten percent of introduced species become established and ten percent of those become invasive. Only it doesn’t hold for mammals or birds, according to Jonathan Jeschke’s study, the findings of which are published in Diversity and Distributions. The Ludwig-Maximilians-University, Munich, researcher found that fifty percent of introduced bird species become established, of which 34 percent become invasive. Mammals are even more successful colonists, with an amazing 79 percent finding a permanent home and 63 percent of those going on to become a pain in the proverbial for conservationists. That makes mammals almost fifty times more effective invaders than the tens rule predicts. How wrong can one be? Source: Jeschke JM (2008) Across islands and continents, mammals are more successful invaders than birds. Diversity and Distributions DOI: 10.1111/j.1472-4642.2008.00488.x

Image: Tamara Strelnikova

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May

14

2008
 
 

Our fault? Sure is



Comprehensive analysis links global ecological changes to human activity

melting glaciers are down to usThirty five years’ worth of data covering hundreds of independent studies put beyond reasonable doubt the impact of human activity on the planet, according to a paper published today in Nature. NASA scientist Cynthia Rosenzweig and colleagues collated a diverse array of findings, allowing them to pin down the causes of physical (glacier shrinkage, warmer oceans and so on) and biological (early leaf burst, breeding seasons and algal blooms) changes that have been documented in recent decades. More than 95 percent of some 829 physical, and 90 percent of the nearly 29,000 biological changes they examined were in a direction consistent with a warming climate. If there’s any comfort to be drawn from the findings, it’s that climate warming is overwhelmingly the most important factor influencing changes in the natural world: habitat destruction, overfishing and pollution are mere trifles by comparison, so at least we know which problem to tackle first! Source: Rosenzweig C, Karoly D, Vicarelli M, Neofotis P, Wu Q, Casassa G, Menzel A, Root TL, Estrella N, Seguin B, Tryjanowski P, Liu C, Rawlins S& Imeson A (2008) Attributing physical and biological impacts to anthropogenic climate change. Nature DOI: 10.1038/nature06937

Image © Sburel

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May

5

2008
 
 

Prickly heat



Tropical biodiversity could be most vulnerable to small climate shifts, study warns

better start preying...It’s often touted that the greatest climate change effects will be at higher latitudes – hence all those pictures of stranded polar bears that we’re now worryingly familiar with. However, a study published today in PNAS argues that while the thermal shift at the tropics is likely to be relatively small, many species there are less tolerant to even the tiniest deviation from the more or less uniform temperatures they usually experience. Together with colleagues, Curtis Deutsch and Joshua Tewksbury – climate change scientists at UCLA and Washington universities respectively – assessed the impact of predicted climate change on land-based insects (a particularly speciose and temperature-sensitive group). In the steamy tropics, many bugs live life close to their thermal optimum, meaning increased average temperature could easily spell doom. At higher latitudes survival is a constant battle against the cold, so turning up the heat could be a good thing, at least for creepy crawlies. Unfortunately, the tropics are where it’s at for insect biodiversity… Source: Deutsch CA, Tewksbury JJ, Huey RB, Sheldon KS, Ghalambor CK, Haak DC & Martin PR (2008) Impacts of climate warming on terrestrial ectotherms across latitude. Proceedings of the National Academy of Sciences USA DOI: 10.1073/pnas.0709472105

Image © Chanyut Sribua-rawd

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May

4

2008
 
 

BBQ?



Charcoal isn’t quite the carbon lockup we hoped for

plans to use biochar might go up in smokeCurious stuff, charcoal. Sure, when a wildfire sweeps through a forest plenty of carbon finds its way into the atmosphere, but what gets left behind is highly resistant to further loss – though not inert, it’s a tough nut for most living organisms to crack. Alas, not for microbes, say the authors of a brief communication in this week’s Science. Reporting the results of a ten-year experiment, David Wardle and colleagues at the Swedish University of Agricultural Sciences found that charcoal on its own does indeed cling tenaciously to its carbon. However, when mixed with humus it apparently serves to enhance microbial activity, which in turn leads to greater carbon loss. So whilst charcoal is a great store of carbon on one hand, it promotes loss of carbon from forest soil on the other. Wardle’s findings go some way towards explaining the loss of ecosystem carbon that typically follows a forest fire, but throw doubt on plans to use biochar as a means of storing excess carbon. Source: Wardle DA, Nilsson M-C & Zackrisson O (2008) Fire-derived charcoal causes loss of forest humus. Science USA DOI: 10.1126/science.1154960

Image © Peterguess

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May

3

2008
 
 

Nor any drop to breathe



Oxygen disappears from the world’s tropical oceans, consequences ahead

open waterParts of the world’s oceans contain little oxygen, and those areas are getting bigger, according to findings published this week in Science. Lothar Stramma, a marine scientist at Universität Kiel, Germany, and colleagues constructed a 50-year time line of dissolved oxygen concentrations at depths of up to 2000 metres. The found that parts of the eastern tropical Atlantic and equatorial Pacific oceans have been becoming increasingly oxygen poor, a phenomenon most likely linked to climate change – atmospheric carbon dioxide levels in particular. Of course, that’s a problem for organisms that inhabit those regions, and it will probably impact on our fisheries. Source: Stramma L, Johnson GC, Sprintall J & Mohrholz V (2008) Expanding oxygen-minimum zones in the tropical oceans. Science USA DOI: 10.1126/science.1153847

Image © Alessia Giangrande

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Apr

23

2008
 
 

Black days ahead



Climate change helps native beetle devastate forest carbon sink

small but deadlyA tiny beetle the size of a grain of rice could affect carbon emissions to the tune of 270 megatonnes by 2020, according to a study of British Columbia’s forests. The findings of Natural Resources Canada forestry experts Werner Kurz and colleagues, published this week in Nature, chronicle the latest Dendroctonus ponderosae outbreak, which is an order of magnitude greater than anything previously observed. The figures are staggering: 130000 square km were attacked by the end of 2006, resulting in the loss of some 435 million cubic m of timber. This raises the status of the beetle as an important factor in carbon sequestration plans, as the current outbreak has shifted the forest from being a carbon sink to a major carbon source. The worst of it is that climate change, brought about largely by there being too much carbon in the atmosphere already, has allowed the beetle to expand its range into areas that were previously off limits. Future models of forest carbon flow need to take into account not only the very large (fire, drought, wind) but also the very small (bugs) things that influence them. Source: Kurz WA, Dymond CC, Stinson G, Rampley GJ, Neilson ET, Carroll AL, Ebata T & Safranyik L (2008) Mountain pine beetle and forest carbon feedback to climate change. Nature DOI: 10.1038/nature06777

Image © Doug Linton

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Apr

15

2008
 
 

Major headache



Scientists still grapple with big question: are trees carbon source or sink?

Major oak -- there's a lot of carbon in Sherwood!Forests account for a huge chunk — around one fifth — of the world’s carbon dioxide emissions. So it stands to reason that by avoiding cutting trees down, say, in the Amazon, we can reduce those emissions by leaving carbon in situ. Take the logic one step further and planting new forests suddenly seems like the dream answer to our atmospheric woes. Rik Leemans and colleagues blow a hole in that one: writing in Carbon Balance and Management, the Wageningen University and Netherlands Environmental Assessment Agency collaborators highlight the infinite complexities of the issue. Demands for agricultural land tussle with those for carbon plantations, questions hang over whether those plantations should be temporary or permanent, and the value of “social potential” — the additional benefits that include nature conservation — are every bit as hard to pin down as the amount of carbon a forest actually stores. But there is some good news. Although plantations take around twenty years to compensate for the carbon emissions during their establishment, thereafter they can — if planted in the right place and managed in the right way — help in the battle to lower those dreaded parts per million in the sky. The question is… by how much? Source: van Minnen JG, Strengers BJ, Eickhout B, Swart RJ & Leemans R (2008) Quantifying the effectiveness of climate change mitigation through forest plantations and carbon sequestration with an integrated land-use model. Carbon Balance and Management DOI: tba, but download here

Image © Nick Atkinson

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Apr

7

2008
 
 

Larger than life



Big mammals go extinct faster than more highly-strung little ones

wish I was a red squirrelWith hearts beating ten to the dozen and precious little by way of stored bodyfat reserves, you’d expect small mammals to be most susceptible to that grimmest of reapers, extinction. Yet the ability to sleep in times of stress could be the thing that saves them whilst their larger cousins are dropping like flies, according to a Scandinavian group of scientists led by University of Oslo researcher Nils Chr. Stenseth. Writing in PNAS this week, they present their findings from a large group of fossils from the Neogene Old World: large mammals have shorter “duration times” – they evolve more often, but also die out faster – than small mammals. Although our mega-mammalian taxonomic bias could perhaps explain this observation, there’s a more concrete possibility. The longest-lived groups of these fossils are littered with moles, mice, hamsters and flying squirrels, animals that typically exhibit “sleep-or-hide” – hibernating or burrowing – habits to weather out the worst of times. Us big guys just keel over. Source: Liow LH, Fortelius M, Bingham E, Lintulaakso K, Mannila H, Flynn L & Stenseth NC (2008) Higher origination and extinction rates in larger mammals. Proceedings of the National Academy of Sciences USA DOI: 10.1073/pnas.0709763105

Image © Rick Wylie

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