Helpers in colonial cooperatively breeding sociable weavers <Emphasis Type="Italic">Philetairus socius</Emphasis> contribute to buffer the effects of adverse breeding conditions

Some studies on the effects of helpers in cooperatively breeding vertebrates show a positive effect of helper presence on reproductive output whereas others find no effect. One possibility for this discrepancy is that helpers may have a positive effect when breeding conditions are adverse, while their effect might go unnoticed under good conditions. We investigate this hypothesis on sociable weavers Philetairus socius, a colonial cooperatively breeding passerine that inhabits a semi-arid region where breeding conditions vary markedly. We used multivariate mixed models to analyse the effect of helpers on reproduction under contrasting environmental and social conditions while controlling for parental and colony identity. We found that reproductive success in sociable weavers was primarily influenced by nest predation and rainfall. In addition, colony size was negatively associated with hatching and fledging success and number of young fledged per season. Helpers had a less prominent but significant influence on feeding rates and reproductive outcome. In agreement with expectations, the presence of helpers counteracted some of the negative effects of breeding in periods of low rainfall or in large colonies and was also associated with an increased number of young fledged per season. Our results illustrate that the effect of helpers might be detectable mostly under unfavourable conditions, but can contribute to improve reproductive performance in those situations.     

Valuing high-seas ecosystem conservation

The high seas provide a variety of ecosystem services that benefit society. There have, however, been few attempts to quantify the human welfare impacts of changes to the delivery of these benefits. We assessed the values of several key ecosystem service benefits derived from protecting ecosystems in the high seas of the Flemish Cap through choice experiments conducted in Canada, Norway, and Scotland. Rather than solely eliciting public willingness to pay, we also explored the determinants of variance in the estimates of willingness to pay. We aimed to determine how much respondents were willing to pay for high-seas ecosystems conservation, which factors influence individuals’ willingness to pay, and whether individuals in Canada had a higher willingness to pay relative to those living in Norway and Scotland. This latter point captures distance-decay effects. On average, the public placed positive value on conserving high-seas ecosystems and on developing economic activities related to the exploitation and exploration of marine resources, despite a lack of awareness and familiarity with these environments. Distance-decay effects on willingness to pay were not clear. Scots had the highest willingness to pay and the Norwegians the lowest willingness to pay for all attributes, with the only exception being willingness to pay for a large increase in new jobs, in which case Canadians’ willingness to pay was higher than Scots’. The public's willingness to pay was influenced by sociodemographic characteristics and their perceptions of high-seas ecosystems. Our results provide evidence of the impacts of high-seas governance on human welfare and that improved governance could increase the value people place on high-seas ecosystems and the services they produce.     

Does information on the interdependence of climate adaptation measures stimulate collaboration? A case study analysis

A key issue in implementing adaptation strategies at the landscape level is that landowners take measures on their land collectively. We explored the role of information in collective decision-making in a landscape planning process in the Baakse Beek region, the Netherlands. Information was provided on (a) the degree to which measures contribute to multiple purposes, (b) whether they are beneficial to stakeholders representing different sectors of land use, and (c) the need for landscape-level implementation of adaptation measures. Our analysis suggests that the negotiation process resulted in collective decisions for more collaborative adaptation measures than could be expected from individual preferences previous to the planning session. Based on the results, it is plausible that the provided information enhanced integrative agreements by leading stakeholders to realize that they were mutually interdependent, both in acquiring individual benefits as well as in implementing the measures at the landscape level. Our findings are significant in the context of the emerging insight that targeted information provision for climate adaptation of landscapes can support collaboration between the relevant stakeholders.     

Spatial and temporal trends in water quality in a Mediterranean temporary river impacted by sewage effluents

This paper analyzes how changes in hydrological conditions can affect the water quality of a temporary river that receives direct inputs of sewage effluents. Data from 12 spatial surveys of the Vène river were examined. Physico-chemical parameters, major ion, and nutrient concentrations were measured. Analyses of variance (ANOVA) and multivariate analyses were performed. ANOVA revealed significant spatial differences for conductivity and major ion but no significant spatial differences for nutrient concentrations even if higher average concentrations were observed at stations located downstream from sewage effluent discharge points. Significant temporal differences were observed among all the parameters. Karstic springs had a marked dilution effect on the direct disposal of sewage effluents. During high-flow periods, nutrient concentrations were high to moderate whereas nutrient concentrations ranged from moderate to bad at stations located downstream from the direct inputs of sewage effluents during low-flow periods. Principal component analysis showed that water quality parameters that explained the water quality of the Vène river were highly dependent on hydrological conditions. Cluster analysis showed that when the karstic springs were flowing, water quality was homogeneous all along the river, whereas when karstic springs were dry, water quality at the monitoring stations was more fragmented. These results underline the importance of considering hydrological conditions when monitoring the water quality of temporary rivers. In view of the pollution observed in the Vène river, “good water chemical status” can probably only be achieved by improving the management of sewage effluents during low-flow periods.     

Photoreactivity of humic substances: relationship between fluorescence and singlet oxygen production

Humic substances are natural compounds abundantly present in the environment. They play a significant role in the natural attenuation of pollution in surface water due to their capacity to generate reactive species upon solar light excitation. Finding physico chemical parameters related to this property would be of a great help in the prediction studies of the organic pollutants fate. In this work, we investigated relationships between the ability of the humic substances to produce singlet oxygen and their fluorescence properties. For this, a series of sixteen humic acids, fulvic acids, and water-extractable organic matter from soils were studied. The steady-state singlet oxygen concentrations in the irradiated humic substances solutions were measured by monitoring the loss of furfuryl alcohol added as a singlet oxygen scavenger. The emission spectra of the sixteen samples were also recorded. Values of the steady-state singlet oxygen concentrations and the emission intensities showed significant variations among the humic samples and a parallel increase. Thus, here we demonstrate that the rate of singlet oxygen production and the emission intensity of the humic samples are correlated, the best correlation being obtained for emission wavelengths between 500 and 580 nm. This correlation which was never reported until now can be used to estimate the singlet oxygen-production capacity of the humic substances based on their fluorescent properties.