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Jan
30
2008
Is the writing on the wall for Lake Victoria’s papyrus?
“Darwin’s nightmare” continues at Lake Victoria, according to a report published in Wetlands Ecology and Management. Tanzania National Parks ecologist Yustina Andrew Kiwango and collaborator Eric Wolanski studied the effects the lake’s twin hydroelectric dams – Nalubaale and Kiira – are having on its ecosystem, and as you’d expect things don’t look good. The lack of coordination between the two dams mean that together they draw off too much water, exposing the vulnerable peat wetlands that fringe the lake. These wetlands are swathed in papyrus, which plays two vital ecological roles. It provides juvenile tilapia with safe refuge — until they’re big enough to be caught by the artisan fishermen whose livelihoods depend on them — and draws nutrients out of the severely eutrophicated water. Losing the papyrus would be disastrous for the lake’s inhabitants, including the million or so humans cramped around its shores. Sustainably harvesting it, however, could prove a neat way to clean its polluted waters, Kiwango and Wolanski suggest. Source: Kiwango YA & Wolanski E (2008) Papyrus wetlands, nutrients balance, fisheries collapse, food security, and Lake Victoria level decline in 2000–2006. Wetlands Ecology and Management DOI: 10.1007/s11273-007-9072-4
Image © Frank van den Bergh
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Jan
28
2008
Natural disturbances likely to turn Canada’s forests into carbon source, not sink
Canada has seven percent of the world’s forests, and they are looking like a liability. Far from being a carbon sink, say the Canadian Forest Service authors of a study published in PNAS, climate change will mean they produce a net surplus of carbon in more years than not. To make matters worse, according to Werner Kurz and colleagues, the scale of the emissions is completely unpredictable because they are driven by natural disturbances such as fire and disease outbreaks. Of these, two insect species play the lead roles: the mountain pine beetle Dendroctonus ponderosae and spruce budworm Choristoneura fumiferana. Taking it in turns to wreak havoc upon hundreds of thousands of square kilometres of forest, they force salvage logging operations that bring the trees’ locked-up carbon back into circulation sooner than anticipated. With fire intensities set to worsen in coming decades and the next major budworm outbreak imminent, some creative solutions to the problem of what to do about boreal forests are needed fast. Source: Kurz WA, Stinson G, Rampley GJ, Dymond CC & Neilson ET (2008) Risk of natural disturbances makes future contribution of Canada’s forests to the global carbon cycle highly uncertain. Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.0708133105
Related story in Conservation magazine: That Sinking Feeling
Image © William Ciesla
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Jan
26
2008
Great Apes threatened by the common illnesses of tourists and scientists
Efforts to counter poaching and habitat loss have often focused on eco-tourism and research as sustainable, economically viable alternatives, but a report published in Current Biology suggests they might be just as life-threatening to some of our closest cousins. Post mortem data from chimpanzees Pan troglodytes that died in several respiratory disease outbreaks at the Taï Chimpanzee Research Project, Côte d’Ivoire, revealed the presence of two human paramyxoviruses – human respiratory syncytial virus and human metapneumovirus. Although these viruses rarely trouble healthy adult humans, they are a major cause of mortality among infants in developing countries. The study, carried out by Robert Koch-Institut primatologist Fabian Leendertz and international colleagues, provides the first direct evidence of the widespread transmission of viruses from humans to Great Apes. Molecular analyses suggest the particular viral strains were imported from as far away as Brasil, Asia and North America: such far-flung origins make researchers and eco-tourists the most likely source of infection. Controls must now be put in place to ensure the chimpanzees aren’t destroyed by the action designed to save them. Source: Köndgen S, Kühl H, N’Goran PK, Walsh PD, Schenk S, Ernst N, Biek R, Formenty P, Mätz-Rensing K, Schweiger B, Junglen S, Ellerbrok H, Nitsche A, Briese T, Lipkin WI, Pauli G, Boesch C & Leendertz FH (2008) Pandemic human viruses cause decline of endangered Great Apes. Current Biology DOI: 10.1016/j.cub.2008.01.012
Related story in Conservation magazine: No Easy Way Out
Image © Peter-John Freeman
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Jan
23
2008
Putting mathematics into the mix takes the alchemy out of eradication
Knowing when to end a campaign to remove an invasive alien species has always been something of a black art. Until now, according to the authors of a paper published recently in the Journal of Applied Ecology. Andrew Solow, senior scientist at Woods Hole Oceanographic Institution, collaborated with a US/UK team of researchers to develop a statistical method for striking the balance between not finishing the job and continuing unnecessarily. The resulting Bayesian model makes use of existing trap data to estimate the time that must elapse, without trapping any further individuals, before a campaign can be declared successful. Solow’s group demonstrate the value of their findings by analyzing trap data from an attempt to remove the Asian musk shrew Suncus murinus from the Mauritian island of Ile aux Aigrettes, which was wound down too early and subsequently failed. The model helpfully declared that the eradication program was indeed wound down too early and subsequently failed. Future campaigns might seek to avoid the same fate by subjecting their trap data to analysis before decisions to scale back are made. Source: Solow A, Seymour A, Beet A & Harris S (2008) The untamed shrew: on the termination of an eradication programme for an introduced species. Journal of Applied Ecology DOI: 10.1111/j.1365-2664.2007.01446.x
Related story in Conservation magazine: Aliens Among Us
Image © Sergey Lavrentev
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Jan
22
2008
Rich countries cause most ecological damage, but poor ones pay for it
There’s more than one kind of foreign debt. Climate change, ozone thinning, agriculture, aquaculture, deforestation and habitat conversion (how that euphemism grates!) all exert negative impacts at a global scale. The problem is that although we all pay the price only a small proportion of us get the benefit. And a group of scientists, led by Thara Srinivasan at the Pacific Ecoinformatics and Computational Ecology Laboratory, Berkeley, California, find that those causing the damage often pay disproportionately less than those who suffer its consequences most directly. Their compilation of World Bank data and Intergovernmental Panel on Climate Change scenarios, published in PNAS this week, reveals many startling gems. For example, the loss of storm protection through the degradation of 35 percent of the world’s mangrove since 1980 is equivalent in monetary value to the planet’s entire aquaculture industry. Yet 96 percent of shrimp are exported to high-income (mangrove-less) countries. On the positive side, Srinivasan and colleagues hope that the framework they have developed will allow the relative level of ecological debts between nations to be more accurately assessed, a crucial first step towards paying them off. Source: Srinivasan UT, Carey SP, Hallstein E, Higgins PAT, Kerr AC, Koteen LE, Smith AB, Watson R, Harte J & Norgaard RB (2008) The debt of nations and the distribution of ecological impacts from human activities. Proceedings of the National Academy of Sciences USA DOI: 10.1073/pnas.0709562104
Image © Laurin Rinder
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Jan
17
2008
A little bit of shrimp farming is OK, environment economists say
The choice between total devastation and total conservation of mangroves is a false one, according to analysis published today in Science. With a team of colleagues, Edward Barbier, a professor of economics at the University of Wyoming, studied the effects of conversion to shrimp aquaculture on a 10 km stretch of Thailand’s mangrove. Because mangroves play such a pivotal role in coastal protection from storms, hurricanes and tsunamis, their economic value is high (compared to the potential cost of disaster recovery in their absence). However, these benefits are only felt locally, whereas the profits from shrimp farms line pockets around the world. Barbier’s group found that a small amount – no more than 20 percent – of farming makes little difference to the protective powers of the mangrove: it’s only at higher levels of degradation that things start to bite. Understanding the impact of shrimp farming properly could help conservation managers achieve a delicate balance between ecosystem protection and keeping the fat cats happy. Source: Barbier EB, Koch EW, Silliman BR, Hacker SD, Wolanski E, Primavera J, Granek EF, Polasky S, Aswani S, Cramer LA, Stoms DM, Kennedy CJ, Bael D, Kappel CV, Perillo GME & Reed DJ (2008) Coastal ecosystem-based management with nonlinear ecological functions and values. Science DOI: 10.1126/science.1150349
Image © David Coleman
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Jan
16
2008
Climate effects on Mediterranean deep-sea fishery revealed
It’s tough being a shrimp. As if being subject to intense harvesting by humans, the deep-sea dwelling Mediterranean species Aristeus antennatus has to endure being swept away by periodic deluges of cold, dense water from above. Barcelona-based marine scientist Joan Company and colleagues, publishing their findings this week in PLoS ONE, analyzed climate data and shrimp harvests in the northwestern Mediterranean. They wanted to understand why, despite intense pressure from – and decadal collapses of – the shrimp fishery, numbers have always bounced back. The answer lies at the sea’s surface: occasional cold, windy, dry winters chill the water and cause it to sink, fast. The resulting underwater torrents, which are laden with organic matter — anyone who’s enjoyed the pleasure of swimming in the Med (you just go through the motions) knows what that means — most likely carry the shrimps to greater depths, effecting an apparent disappearance from their usual haunts. However, the unexpected plumbing of greater depths is probably what saves the little crustacean from extinction – fishing is temporarily halted, and the sudden arrival of nutrients provides a welcome supply of food for the next generation as they find their way back up to the fishing grounds. Current climate change models predict these regenerative events will happen less often, but for now at least they serve to stock deep-sea populations and barbecues alike. Source: Company JB, Puig P, Sardá F, Palanques A, Latasa M & Scharek R (2008) Climate influence on deep sea populations. PLoS ONE DOI: 10.1371/journal.pone.0001431
Image © Stephen Coburn
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Jan
14
2008
Climate change slows lizard dispersal, increasing extinction risk
Many species have ways to track their ideal habitat, a useful ability in a rapidly changing environment. However, a study published recently in Global Change Biology suggests it’s not always plain sailing, as it were, when dispersal is behaviorally driven. A long-term study of common lizards Lacerta vivipara, carried out by Manuel Massot, at the Université Pierre et Marie Curie, Paris, and colleagues, revealed a complex interaction between climatic conditions, food availability and dispersal among juveniles. Over a sixteen-year study period, from 1989 to 2004, the probability of juvenile dispersal (moving more than 30 m from their natal site) more than halved. Over the same period, temperatures at the field site in Southern France have risen sharply. This stay-at-home behavior could spell trouble if higher temperatures lead to increased patchiness of suitable habitat, as successive generations will find themselves more isolated and prone to extinction. Source: Massot M, Clobert J & Ferriére R (2008) Climate warming, dispersal inhibition and extinction risk. Global Change Biology DOI: 10.1111/j.1365-24865.2007.01514.x
Image © Steve McWilliam
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Jan
10
2008
Shunned ants in the African savanna show how complex mutualisms can be
The loss of large herbivores can send shock waves throughout a trophic web, according to findings published today in Science. University of Florida biologist Todd Palmer and colleagues carried out a ten-year exclusion experiment in Kenya to study the effect of preventing browsing by elephants, giraffes and other megafauna on the relationships between four ant species and their host acacia trees. Whistling thorn trees Acacia drepanolobium provide several competing species of ants with both food (nectar) and accommodation (modified hollow thorns), in return for varying levels of protection from the unwanted attention of passing herbivores. With them out of the way, however, the plants lowered their “rewards” to the ants. The dominant, most aggressive ant species, Crematogaster mimosae, suffered most, but fought back by turning farmer, carefully tending sap-sucking scale insects. Other changes in the ant-acacia community included a shift in ant species distribution to one dominated by a less aggressive species, C sjostedti. Neglecting their ant guardians finally backfired on the acacias: C sjostedti actively encourages wood-boring cerambycid beetles, which create nesting spaces for the ants to use. The continuing loss of large browsing animals from Africa’s savanna spells equally bad news for the plants on which they feed. Who said plants didn’t like to be eaten? Source: Palmer TM, Stanton ML, Young TP, Goheen JR, Pringle RM & Karban R (2008) Breakdown of an ant-plant mutualism follows the loss of large herbivores from an African savanna. Science DOI: 10.1126/science.1151579
Image © Todd Palmer
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Jan
9
2008
Caribbean coral reefs suffer from the mere presence of humans, study shows
A large-scale study of potential threats to coral reef health has found one that dominates all others: us. Writing in the Proceedings of the Royal Society this week, Camilo Mora and Robert Ginsberg show that human-caused impacts – coastal development, agricultural run-off, fishing pressure and the sheer density of humans living around the Caribbean coastline – exert the strongest influence on coral reef health. Worse, some of these factors work in concert with others. For example, temperature- or disease-triggered coral die-offs allow macroalgal blooms that exceed the ability of the reef’s herbivores to control them. Agricultural fertilizers and sewage-based nutrients finding their way to the sea then fuel the explosive growth, resulting in a feedback loop that is tough to break. The Dalhousie and Miami University duo suggest that now it’s clear that what goes on above the water surface can have a major effect on what goes on below it, perhaps it’s time to consider tougher land-based controls around Marine Protected Areas. A whole-system approach? We need an unprecedented outbreak of common sense first… Source: Mora C & Ginsburg R (2008) A clear human footprint on the Caribbean coral reefs. Proceedings of the Royal Society of London B DOI: 10.1098/rspb.2007.1472
Image © Norbert Rehm
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