Biodiversity-ecosystem functioning (BEF) literature is dominated by investigations conducted in temperate grassland ecosystems under homogenous environmental conditions. Consequently, studies concerned with the functional importance of higher trophic levels, or with the role of environmental conditions in shaping BEF relationships, are comparatively uncommon. To address this, we assessed dung beetle diversity-functioning relationships in situ, in a field experiment in the Brazilian Amazon. Dung beetles perform a number of ecological functions in habitats across the globe; in tropical forests they play a key role in the secondary dispersal of seeds. We therefore experimentally tested how the functional diversity of dung beetle communities affects seed dispersal and how BEF relationships varied with environmental context, by replicating the experiments under contrasting soil conditions. Relationships between dung beetle diversity and function were examined using diversity indices calculated using continuous morphological traits of the individuals involved in experiments, and functioning was measured as the dispersion of artificial seeds throughout the soil profile and the probability of burial. Ninety experimental plots were established across three distinct primary forest sites. We collected, identified, and measured almost 2000 beetles, and sieved around 11 Mg of soil to quantify the dispersion of 1800 seed mimics. There was a significant effect of dung beetle functional diversity on both seed dispersion and seed burial, although this depended on environmental context, with the strength or direction of responses differing across the contrasting soils. Regardless of soil type, functional richness, but not species richness, predicted seed dispersion. We therefore advocate the use of functional diversity indices over taxonomic approaches in dung beetle-focused BEF investigations. Furthermore, we highlight the difficulties in generalizing BEF relationships, even considering a single function within the same ecosystem.

Tropical rainforest regions are urbanizing rapidly, yet the role of emerging metropolises in driving wildlife overharvesting in forests and inland waters is unknown. We present evidence of a large defaunation shadow around a rainforest metropolis. Using interviews with 392 rural fishers, we show that fishing has severely depleted a large-bodied keystone fish species, tambaqui (Colossoma macropomum), with an impact extending over 1,000 km from the rainforest city of Manaus (population 2.1 million). There was strong evidence of defaunation within this area, including a 50% reduction in body size and catch rate (catch per unit effort). Our findings link these declines to city-based boats that provide rural fishers with reliable access to fish buyers and ice and likely impact rural fisher livelihoods and flooded forest biodiversity. This empirical evidence that urban markets can defaunate deep into rainforest wilderness has implications for other urbanizing socioecological systems.ecological footprint | fishing down | overfishing | urbanization | freshwater biodiversity

1. Billions of people rely on harvesting wildlife for food, and must contend with catch rates that vary in space (e.g. overharvesting near communities) and time (e.g. seasonal migrations). Yet, research has overlooked potential linkages between reduced wildlife catch rates (catch-per-unit-effort) and food security. Moreover, assumptions that people living in biologically rich environments are food secure lack empirical testing. This is problematic given that food security rests on having stable access to sufficient food, rather than there being sufficient food.2. We examine spatiotemporal variation in fish catch rates and perceived food security among rural communities in Amazonian flooded forests. We also assess social inequities in food insecurity. We used structured interviews to collect data on fishing, hunting, chicken and beef consumption, and perceptions of food security.We did so during 556 household visits along a spatial gradient (1,267 km) of commercial fishing pressure, during high-and low-water seasons.3. We provide the first empirical evidence of simultaneous seasonal crashes in wildlife catch rates and food insecurity. During the high-water season, fish catch rates were 73% lower, and the probability of not eating for a whole day was four times higher. With a third of households skipping meals and a sixth not eating for a whole day during this season, food security can be classed as severe. However, less-deprived households tended to avoid severe food insecurity. Fish catch rates and perceived food security did not vary along a spatial gradient of commercial overfishing. River-dwelling Amazonians increased fishing and hunting efforts during the high-water season, without eating more chicken and beef, emphasizing the importance of stable access to wild fish and bushmeat.4. This study shows how wildlife catch rates and food security can crash seasonally and simultaneously, demonstrating the fallacies of environmental and social policies which assume stability of food availability in resource-rich areas. Our results have implications for degraded habitats where falls in catch rates also occur. This suggests that overharvesting, as with other causes of reduced catch rates, could cause food insecurity in wildlife-reliant populations. | 469People and Nature TREGIDGO ET al.