Modelling the responses of wildlife to human disturbance: An evaluation of alternative management scenarios for black-crowned night-herons

The impact of anthropogenic disturbance on wildlife is increasing becoming a source of concern as the popularity of outdoor recreation rises. There is now more pressure on site managers to simultaneously ensure the continued persistence of wildlife and provide recreational opportunities. Using ‘Simulation of Disturbance Activities’, a model designed to investigate the impact of recreational disturbance on wildlife, we demonstrate how a simulation modelling approach can effectively inform such management decisions. As an example, we explored the implications of various design and management options for a proposed recreational area containing a historic breeding bird colony. By manipulating the proximity, orientation and intensity of recreation, we were able to evaluate the impact of recreational activities on the behaviour of black-crowned night-heron nestlings (Nycticorax nycticorax). Using a classification and regression tree (CART) procedure to analyse simulation output, we explored the dynamics of multiple strategies in concert. Our analysis revealed that there are inherent advantages in implementing multiple strategies as opposed to any single strategy. Nestlings were not disturbed by recreation when bird-watching facility placement (proximity and orientation) and type were considered in combination. In comparison, proximity alone only led to a <10% reduction in disturbance. Thus we demonstrate how simulation models based on customised empirical data can bridge the gap between field studies and active management, enabling users to test novel management scenarios that are otherwise logistically difficult. Furthermore, such models potentially have broad application in understanding human-wildlife interactions (e.g. exploring the implications of roads on wildlife, probability of bird strikes around airports, etc.). They therefore represent a valuable decision-making tool in the ecological design of urban infrastructures.     

PCDD/F and "Dioxin-like" PCB emissions from iron ore sintering plants in the UK

Investigations have been carried out at the three Corus UK sinter plants over the period 2002-2004 to characterise the emissions of both 2,3,7,8-PCDD/Fs and WHO-12 PCBs, to estimate annual mass releases of these organic micro-pollutants using the I-TEF and WHO-TEF schemes, and to investigate the formation of PCBs in the iron ore sintering process. Results showed that the sintering of iron ore produces a characteristic WHO-12 PCB and PCDD/F congener pattern that is substantially the same for all UK sinter plants. With regard to WHO-12 PCBs, the most abundant congeners were typically PCBs 118 (6-9 ngNm(-3)), 105 (2-4 ngNm(-3)) and 77 (2-3 ngNm(-3)). All other WHO-12 PCBs were also detected at concentrations around 1 ngNm(-3). All sinter plants investigated exhibited very similar TEQ concentrations. WHO-12 PCB emissions were in the range 0.042-0.111 ngWHO-TEQNm(-3), whereas PCDD/F emissions ranged from 0.39 to 1.62 ngWHO-TEQNm(-3). PCDF congeners were the main contributors to the overall TEQ in sintering emissions (ca. 85%). Amongst WHO-12 PCBs, PCB 126 was the only noteworthy contributor to total TEQ (ca. 5-7%), a similar contribution to that from PCDDs. Based on the measurements that Corus UK has undertaken at these three sinter plants, annual mass releases of WHO-12 PCBs and PCDD/Fs have been calculated. For UK sinter plants, a total mass release of 29.5 g WHO-TEQ per annum [WHO-12 PCBs+PCDD/Fs] has been estimated, representing 9% of the total PCDD/F emissions to the UK atmosphere. Measurements were also carried out at a UK sinter plant to determine the windleg emission profile of WHO-12 PCBs. Results showed that WHO-12 PCBs were formed in the same regions of the sinter strand as 2,3,7,8-PCDD/Fs, indicating that there was a strong correlation between the formation of WHO-12 PCBs and PCDD/Fs in the iron ore sintering process.     

Valuing long run ecological consequences and irreversibilities

In this paper we consider the special nature and implications, for economic theory and policy, of resource uses that involve adverse effects on the physical environment that are difficult or impossible to reverse. Distinctions are drawn between reversible and irreversible activities, between replaceable and irreplaceable resources. The existence of an “irreversibility premium” is demonstrated under certain plausible conditions, including uncertainty and shifting time perspective.     

New Zealand Farmer Narratives of the Benefits of Reduced Human Intervention During Lambing in Extensive Farming Systems

Easy-care or natural lambing pertainsto those sheep able to successfully lamb andrear at least one lamb without human assistancein a difficult environment. Such sheep may havea higher survival rate, lower lamb mortality,and require less shepherding at lambing thanother sheep breeds or strains. The farmer orshepherd account of easy-care lambing revealsseveral themes. Firstly, stock were bred tosurvive or suit local environments orconditions, particularly steep hill country inNew Zealand. This involved extensive culling ofundesirable dams, regardless of how well theymight perform in traits other than the abilityto survive and to produce live lambs atweaning. Sheep that did have problems wereoften assisted, recorded or marked and thenculled at an appropriate time; thus bothartificial (culling) and natural selection wereused. Secondly, natural selection enabled theimportant traits to be identified and they weresubsequently incorporated into artificialselection programs. Thirdly, the practice wasnecessitated by the impracticality ofsupervising lambing in difficult terrain andthe cost of skilled farm labor. Finally, it wasacknowledged that disturbance at lambingcreated problems and most importantly, theeasy-care approach reduced some of the problemstraditionally associated with lambing.Easy-care lambing systems thus aim to minimizesome of the detrimental effects associated withcarefully supervised lambing in someenvironments, by selecting sheep to suit boththat environment and modern farm management.They overcame pervasive influences our culturallegacy was exerting on the way we interact withanimals, and may have produced a system more inkeeping with the biology of the animal in anextensive environment.