We reviewed 148 assessments of animal source food (ASF) production for livestock, aquaculture, and capture fisheries that measured four metrics of environmental impact (energy use, greenhouse‐gas emissions, release of nutrients, and acidifying compounds) and standardized these per unit of protein production. We also examined additional literature on freshwater demand, pesticide use, and antibiotic use. There are up to 100‐fold differences in impacts between specific products and, in some cases, for the same product, depending on the production method being used. The lowest impact production methods were small pelagic fisheries and mollusk aquaculture, whereas the highest impact production methods were beef production and catfish aquaculture. Many production methods have not been evaluated, limiting our analysis to the range of studies that have been published. Regulatory restrictions on ASF production methods, as well as consumer guidance, should consider the relative environmental impact of these systems, since, currently, there appears to be little relationship between regulatory restrictions and impact in most developed countries.

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Watersheds are complex mosaics of habitats whose conditions vary across space and time as landscape features filter overriding climate forcing, yet the extent to which the reliability of ecosystem services depends on these dynamics remains unknown. We quantified how shifting habitat mosaics are expressed across a range of spatial scales within a large, free-flowing river, and how they stabilize the production of Pacific salmon that support valuable fisheries. The strontium isotope records of ear stones (otoliths) show that the relative productivity of locations across the river network, as both natal- and juvenile-rearing habitat, varies widely among years and that this variability is expressed across a broad range of spatial scales, ultimately stabilizing the interannual production of fish at the scale of the entire basin.

Tributaries of the Colorado River Basin, historically home to a complex of endemic omnivores collectively referred to as the 'three species'; flannelmouth sucker (Catostomus latipinnis), bluehead sucker (C. discobolus) and roundtail chub (Gila robusta), have experienced the establishment of numerous non-native fish species. In this study, we examine the impacts of the trophic ecology of non-native fishes on the 'three species' in the San Rafael River, Utah, USA. We employ a suite of abundance comparisons, stable isotope techniques and size-at-age back-calculation analyses to compare food web structure and growth rates of the 'three species' in study areas with and without established populations of non-native species. We found that the 'three species' are more abundant in areas with few non-native fishes present, regardless of habitat complexity. Stable isotope analyses indicate non-native fishes lengthen the food chain by 0.5 trophic positions. Further, the trophic niche spaces of the native fishes shift and are narrower in the presence of non-native fishes, as several non-native species' trophic niche spaces overlap almost entirely with each of the 'three species' (bluehead sucker and flannelmouth sucker 100%, roundtail chub 98.5%) indicating strong potential for competition. However, the 'three species' demonstrated no evidence of reduced growth in the presence of these non-native fishes. Collectively, these results suggest that while non-native fishes alter the food web structure presenting novel sources of predation and competition, mechanisms other than competition are controlling the size-structure of 'three species' populations in the San Rafael River.