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Dec
21
2007
Giraffes have at least eleven genetically distinct populations, but how many species?
Not all giraffes Giraffa camelopardalis are the same, according to a report published online today in BMC Biology. Despite large differences in pelage markings, ossicone (those antler-like thingys) number and mitochondrial variation, taxonomists have struggled to agree on how many species there are. Previous accounts have given one or two, broken up into several subspecies. However, UCLA biologist Robert Wayne and colleagues present genetic and phylogeographic evidence for the existence of at least six distinct African giraffe lineages, of which five contain genetically discrete populations. The conservation implications are profound: of the estimated 110000 wild giraffes left, only 100 belong to the West African clade, found in a single area of Niger. The current “Lower Risk” IUCN Red List classification needs looking at again: giraffe conservation just got trickier. Source: Brown DM, Brenneman RA, Koepfli K-P, Pollinger JP, Mila B, Georgiadis NJ, Louis EE Jr, Grether GF, Jacobs DK & Wayne RK (2007) Extensive population genetic structure in the giraffe. BMC Biology DOI: 10.1186/1741-7007-5-57
Image © Graeme Purdy
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Dec
21
2007
Measures of land use change are missing the most important cause of fragmentation
Urban sprawl is thought to be a major cause of habitat fragmentation with major consequences for wildlife, but according to a study published this week in PNAS measuring landscape patterns isn’t easy. Worse, say the report’s authors Elena Irwin and Nancy Bockstael, the National Land Cover Dataset is biased towards under-recording low-density residential development. For example, the 2001 NCLD only recognizes around a quarter of 0.5–5 acre housing lots as being developed. Using Maryland Department of Planning’s land use maps, compiled from aerial photography and geocoded tax data, Irwin and Bockstael found that between 1973 and 2000 those areas suffering most fragmentation were relatively far from urban centers. The simultaneous rise in low-density residential development in those areas is no coincidence: there’s only so many houses one can build in the country before there’s no country left. Source: Irwin EG & Bockstael NE (2007) The evolution of urban sprawl: evidence of spatial heterogeneity and increasing land fragmentation. Proceedings of the National Academy of Sciences USA DOI: 10.1073/pnas.0705527105
Image © fotoVoyager
Read more on Community-based conservation, Economics and conservation, Habitat, Monitoring, Socio-political issues | 8 Comments
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Dec
20
2007
Removal of one key predator releases another, experiment shows
Farmers really don’t love European badgers Meles meles enough. Decades of blaming the UK’s largest native predator for transmitting bovine TB led to the establishment of a controversial, “definitive” experiment: the Randomised Badger Culling Trial. While the UK government continues to ignore the study’s unequivocal findings (despite having designed and bankrolled it), scientists have been piggybacking it to make other discoveries. For example, a group led by the Central Science Laboratory’s Iain Trewby report in Biology Letters that in areas where badgers were eliminated red fox Vulpes vulpes numbers increased substantially. It’s a classic example of mesopredator release – foxes and badgers share diets and sometimes dens, but foxes are punier – although a rarity in being so clear-cut. The findings reinforce questions about the impact of predator removal on prey species: some conservation efforts have come tragically unstuck in this way. With robust experimental results, however, conservation managers can design policies driven by science rather than blind faith. It’s a pity politicians can’t do the same. Source: Trewby ID, Wilson GJ, Delahay RJ, Walker N, Young R, Davison J, Cheeseman C, Robertson PA, Gorman ML & McDonald RA (2007) Experimental evidence of competitive release in sympatric carnivores. Biology Letters DOI: 10.1098/rsbl.2007.0516
Image © Suzann Julien
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Dec
16
2007
Habitat fragmentation is more painful when larvae and adults have different needs
Having different habitat requirements at different life stages solves all sorts of life’s problems – such as avoiding predators and competition with one’s own species – but it can also create them, especially when humans are taken into the equation. Writing in Science this week, Brazilian scientists — led by Carlos Roberto Fonseca — illustrate the effects of what they call “habitat split”. Terrestrial amphibians whose larvae require aquatic habitat are now often forced to leave forest fragments to find suitable water bodies in which to reproduce, whereas in the past the two habitats graded into one another. The same goes for the metamorphosed juveniles, who face a dangerous trek back to the forest. The separation of habitat types, primarily due to anthropogenic disturbance, could be why those species with aquatic larvae are suffering worse population declines than those whose entire life cycle is completed in the same place. Source: Becker CG, Fonseca CR, Haddad CFB, Batista RF & Prado PI (2007) Habitat split and the global decline of amphibians. Science DOI: 10.1126/science.1149374
Image © Mark Kostich
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Dec
13
2007
Salmon farms pose a greater threat to wild stocks than the fisheries they replace
Long-held suspicions that fish farms act as disease reservoirs for wild populations are well founded, according to findings published this week in Science. University of Alberta mathematical biologist Marty Krkošek and colleagues show that outbreaks of salmon lice Lepeophtheirus salmonis among wild pink salmon Oncorhynchus gorbuscha populations — the direct result of infestations within the open-net aquaculture pens the juveniles must swim past on their migration to the sea — can bring virtual extinction in just four generations. The pressure wild stocks are placed under by the disease risk from fish farms is much greater than that caused by over-exploitative harvesting: the very factor that prompted aquaculture in the first place. It’s surely time for a re-think on fish farming. Source: Krkošek M, Ford JS, Morton A, Lele S, Myers RA & Lewis MA (2007) Declining wild salmon populations in relation to parasites from farm salmon. Science DOI: 10.1126/science.1148744
Related stories in Conservation magazine: Salmon Farms Create Deadly Clouds of Sea Lice | 10 Solutions to Save the Ocean
Image © David Hyde
Read more on Economics and conservation, Endangered species, Fresh water, Marine, Monitoring, Restoration, Socio-political issues, Tools and technology | 2 Comments
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Dec
12
2007
Higher atmospheric CO2 leads to… higher atmospheric CO2
The atmospheric fallout of climate change – higher carbon dioxide levels, temperatures and shifting rainfall – is predicted to result in higher rates of leaf litterfall. The results of a five-year field experiment, published this week in PLoS ONE, suggest the extra leaf litter will make things worse by increasing soil respiration. In turn, say University of Cambridge biologist Emma Sayer and colleagues, more of the soil’s carbon will find its way into the atmosphere. If only we had a way to get rid of the extra leaf litter… Source: Sayer EJ, Powers JS & Tanner EVJ (2007) Increased litterfall in tropical forests boosts the transfer of soil CO2 to the atmosphere. PLoS ONE DOI: 10.1371/journal.pone.0001299
Image © Alain Lacroix
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Dec
12
2007
Bear predation drives fish to old age, study finds
The annual feast enjoyed by brown bears Ursus arctos as spawning sockeye salmon Oncorhynchus nerka migrate up river affects the rate at which the fish age, research published in PLoS ONE suggests. Stephanie Carlson – currently at the University of California at Santa Cruz – and co-workers studied salmon senescence in rivers under several different levels of bear predation. Like us, bears prefer to eat fresher, healthier fish, but their extra vitality makes them harder to catch. Consequently, it’s only in smaller streams — where struggling salmon are more vulnerable — that bears are able to exercise a choice: in larger rivers it’s literally survival of the fittest. However, the researchers found that where bears kill mostly exhausted, worn out fish, those populations aged more slowly, as measured by a suite of tell-tale traits. The findings suggest that fussy ursine eating habits are more important than their overall hit rate on the evolution of salmon dodderiness. Source: Carlson SM, Hilborn R, Hendry AP & Quinn TP (2007) Predation by bears drives senescence in natural populations of salmon. PLoS ONE DOI: 10.1371/journal.pone.0001286
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Dec
10
2007
Island data show that mesopredators are released… sometimes
Removing introduced cats Felis cattus allowed introduced rats Rattus exulans to wreak havoc on two high-altitude native island Cook’s petrel Pterodroma cookii populations, according to a study of long-term data published this week in PNAS. The University of Auckland’s Matt Rayner and fellow New Zealand biologists found that exterminating the top level predators from Little Barrier Island in 1980 resulted in a steady drop in chick production until 2004, when the rats followed the cats’ fateful footsteps. In the few years since there has been a dramatic boost in petrel numbers, freed at last from their twin alien predators. The counterintuitive, theoretically beguiling idea that removing top predators can lead to a fall in prey numbers — a phenomenon known as mesopredator release — has seldom been put to the test in the real world, and Rayner’s findings sound a cautious note: at another, low-altitude site, rat presence made little difference to petrel chick production, possibly because there were plenty of alternative food sources. It might be a dog eat dog world, but it’s not a simple one. Source: Rayner MJ, Hauber ME, Imber MJ, Stamp RK & Clout MN (2007) Spatial heterogeneity of mesopredator release within an oceanic island system. Proceedings of the National Academy of Sciences USA DOI: 10.1073/pnas.0707414105
Related story in Conservation magazine: Us Or Them
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Dec
6
2007
Different perspective could conserve fish and fishers alike
Win-win situations are as rare in conservation as mermaid scales, but the authors of a paper published this week in Science think they’ve found a solution to the problem of overfishing that could make everyone happy. Eventually. Australian National University economist Quentin Grafton and colleagues put forward a surprisingly simple proposition: change focus from the maximum sustainable yield to the maximum economic yield. The latter takes the costs of fishing into account, such as rising fuel prices, and demands higher fish stock levels. In a nutshell, more fish in the sea means less time spent searching for them, resulting in lower costs and thus higher profits. So, by catching fewer fish now and allowing populations to recover, fishers should enjoy greater profits in the future. Can it really be that easy? Source: Grafton RQ, Kompas T & Hilborn RW (2007) Economics of overexploitation revisited. Science DOI: 10.1126/science.1146017
Related story in Conservation magazine: 10 Solutions to Save the Ocean
Image © Luis Alvarez
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