A scientific critique of the two-degree climate change target

The world's governments agreed to limit global mean temperature change to below 2-derees C compared with pr-industrial levels in the years following the 2009 climate conference in Copenhagen. This 2-degrees C warming target is perceived by the pulic as a universally accepted goal, identified by scientists as a safe limit that avoids dangerous climate change. This perception is incorrect: no scientific assessment has clearly justified or defended the 2-degrees C target as a safe level of warming, and indeed, this is not a problem that science alone can address. We argue that global temperature is the best climate target quantity, but it is unclear what level can be consiered safe. The 2-degrees C target is useful for anchoring discussions, but has been ineffective in triggering the required emission reductions; debates on considering a lower target are strongly at odds with the current real-world level of action. These debates are moot, however, as the decisions that need to be taken now to limit warming to 1.5 or 2 degrees C are very similar. We need to agree how to start, not where to end mitigation

Ecological character displacement in the face of gene flow: Evidence from two species of nightingales

<p>Abstract</p> <p>Background</p> <p>Ecological character displacement is a process of phenotypic differentiation of sympatric populations caused by interspecific competition. Such differentiation could facilitate speciation by enhancing reproductive isolation between incipient species, although empirical evidence for it at early stages of divergence when gene flow still occurs between the species is relatively scarce. Here we studied patterns of morphological variation in sympatric and allopatric populations of two hybridizing species of birds, the Common Nightingale (<it>Luscinia megarhynchos</it>) and the Thrush Nightingale (<it>L. luscinia</it>).</p> <p>Results</p> <p>We conducted principal component (PC) analysis of morphological traits and found that nightingale species converged in overall body size (PC1) and diverged in relative bill size (PC3) in sympatry. Closer analysis of morphological variation along geographical gradients revealed that the convergence in body size can be attributed largely to increasing body size with increasing latitude, a phenomenon known as Bergmann's rule. In contrast, interspecific interactions contributed significantly to the observed divergence in relative bill size, even after controlling for the effects of geographical gradients. We suggest that the divergence in bill size most likely reflects segregation of feeding niches between the species in sympatry.</p> <p>Conclusions</p> <p>Our results suggest that interspecific competition for food resources can drive species divergence even in the face of ongoing hybridization. Such divergence may enhance reproductive isolation between the species and thus contribute to speciation.</p

A comparison of point counts with a new acoustic sampling method: a case study of a bird community from the montane forests of Mount Cameroon

Acoustic signals are frequently used for estimating avian species richness, abundance and community composition. However, sampling by traditional methods of bird surveys is often limited by availability of experienced researchers in the field, especially in the tropics. New bioacoustic approaches offer some solutions to such limitations and provide opportunities for more extensive spatial and temporal sampling. In our study, we compared results of traditional point counts with simultaneous acoustic samples obtained by automated soundscape recording units in the montane forest of Mount Cameroon. We showed that the estimates of species richness, abundance and community composition based on point counts and post-hoc laboratory listening to acoustic samples are very similar, especially for a distance limited up to 50 m. Species that were frequently missed during both point counts and listening to acoustic samples were typically those with relatively quiet songs. Abundances were rather underestimated by listening to acoustic samples in the most abundant species, including those occurring in flocks and species with low singing activity. Despite some possible biases, we demonstrated that the method based on listening to acoustic samples is relatively effective and offers a useful alternative approach for surveying Afromontane bird communities.Keywords: abundance, automatic recording units, montane forest, point count, species richness, species turnove

Where is the greatest impact of uncontrolled HIV infection on AIDS and non-AIDS events in HIV?

Objective:The extent to which controlled and uncontrolled HIV interact with ageing, European region of care and calendar year of follow-up is largely unknown.Method:EuroSIDA participants were followed after 1 January 2001 and grouped according to current HIV progression risk; high risk (CD4(+) cell count 350/l, viral load 10000 copies/ml), low risk (CD4(+) cell count 500 cells/l, viral load <50 copies/ml) and intermediate (other combinations). Poisson regression investigated interactions between HIV progression risk, age, European region of care and year of follow-up and incidence of AIDS or non-AIDS events.Results:A total of 16839 persons were included with 136688 person-years of follow-up. In persons aged 30 years or less, those at high risk had a six-fold increased incidence of non-AIDS compared with those at low risk, compared with a two-to-three-fold increase in older persons (P=0.0004, interaction). In Eastern Europe, those at highest risk of non-AIDS had a 12-fold increased incidence compared with a two-to-four-fold difference in all other regions (P=0.0029, interaction). Those at high risk of non-AIDS during 2001-2004 had a two-fold increased incidence compared with those at low risk, increasing to a five-fold increase between 2013 and 2016 (P <0.0001, interaction). Differences among high, intermediate and low risk of AIDS were similar across age groups, year of follow-up and Europe (P=0.57, 0.060 and 0.090, respectively, interaction).Conclusion:Factors other than optimal control of HIV become increasingly important with ageing for predicting non-AIDS, whereas differences across Europe reflect differences in patient management as well as underlying socioeconomic circumstances. The differences between those at high, intermediate and low risk of non-AIDS between 2013 and 2016 likely reflects better quality of car