Some communities are susceptible to invasions and some are not. Why? Elton suggested in 1958 that the ability of the community to withstand invading species – its biotic resistance – depends on the number of resident species. Later contributors have emphasized the habitat's ability to support species, as well as the contribution of individual species to the resistance. In this study we use information from 184 introductions of Arctic char into Swedish lakes to study both abiotic and biotic aspects of the resident community's ability to resist introductions.

Many arid and semi‐arid landscapes around the world are affected by a shift from grassland to shrubland vegetation, presumably induced by climate warming, increasing atmospheric CO₂concentrations, and/or changing land use. This major change in vegetation cover is likely sustained by positive feedbacks with the physical environment. Recent research has focused on a feedback with microclimate, whereby cold intolerant shrubs increase the minimum nocturnal temperatures in their surroundings.

Cumulative human impacts across the world's oceans are considerable. We therefore examined a single model taxonomic group, the penguins (Spheniscidae), to explore how marine species and communities might be at risk of decline or extinction in the southern hemisphere. We sought to determine the most important threats to penguins and to suggest means to mitigate these threats. Our review has relevance to other taxonomic groups in the southern hemisphere and in northern latitudes, where human impacts are greater.