Building trust in science and evidence-based decision-making depends heavily on the credibility of studies and their findings. Researchers employ many different study designs that vary in their risk of bias to evaluate the true effect of interventions or impacts. Here, we empirically quantify, on a large scale, the prevalence of different study designs and the magnitude of bias in their estimates. Randomised designs and controlled observational designs with pre-intervention sampling were used by just 23% of intervention studies in biodiversity conservation, and 36% of intervention studies in social science. We demonstrate, through pairwise within-study comparisons across 49 environmental datasets, that these types of designs usually give less biased estimates than simpler observational designs. We propose a model-based approach to combine study estimates that may suffer from different levels of study design bias, discuss the implications for evidence synthesis, and how to facilitate the use of more credible study designs.

Do young children think that plants deserve morally-based respect or, on the contrary, do they feel that respect for plant life is nothing more than another behavioural norm similar to, for instance, one that states that you should not pick your nose in public? This study examines how dilemmas involving environmental, moral and socio-conventional situations are comprehended in early childhood so as to investigate the issue of whether young children attach a significant degree of severity to transgressions against plant life in comparison with disregarding socially accepted rules. Additionally, young children’s judgements are put into perspective alongside their understanding of the concept of living things in order to shed light on the role that grasping essential biological notions might play in the emergence of young children’s assessments of actions that pose a threat to the environment. The sample of the study consists of 328 children (162 girls and 166 boys) who attend Early Years Education or Primary Education and the data examined comes from the individual interviews conducted with the children. The results are discussed in connection with the current understanding of the source of ethical judgements which emphasises the importance that emotions seem to play in the construction of moral thinking.

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Streams in the Aiako Harria Natural Park (Basque Country, Spain) have excellent water quality, but are physically impoverished after centuries of snagging. In an attempt to restore channel complexity and ecosystem functioning, especially in-channel retention of sediments and organic matter, large woody debris (LWD) was introduced into four mountain streams (channel width 3-13 m) following a before ⁄ after, control ⁄ impact (BACI) design. Logs were introduced by means of hand-held machinery and located uncabled, mimicking the natural amount and disposition of LWD in streams. Floods disrupted most of the structures at the large stream, but caused little damage to those in the small ones. Only minnow and brown trout inhabit in the area. Before wood addition, trout densities were fairly high in the small streams, low in the large one, where recruitment seemed very poor. In the small tributaries, trout populations showed a strong imbalance towards young fish, adults being only found in the spawning season. Wood addition produced some interesting trends in trout, although statistical significance was low as a result of large environmental variability. Fish densities showed small changes, but biomass increased, especially in the spawning season. Also, there was a trend towards more aged 2 + or larger, thus suggesting wood addition improved adult habitat. Although restoring LWD is extremely unusual in Spain, the changes in physical habitat and the trends in fish populations detected in the present project suggest it is worth making more experiments, at least in safe settings where there is no risk of flooding or damaging properties.