Fangyuan Hua

Opportunities for biodiversity gains under the world’s largest reforestation programme

Reforestation is a critical means of addressing the environmental and social problems of deforestation. Chinas Grain-for-Green Program (GFGP) is the worlds largest reforestation scheme. Here we provide the first nationwide assessment of the tree composition of GFGP forests and the first combined ecological and economic study aimed at understanding GFGPs biodiversity implications. Across China, GFGP forests are overwhelmingly monocultures or compositionally simple mixed forests. Focusing on birds and bees in Sichuan Province, we find that GFGP reforestation results in modest gains (via mixed forest) and losses (via monocultures) of bird diversity, along with major losses of bee diversity. Moreover, all current modes of GFGP reforestation fall short of restoring biodiversity to levels approximating native forests. However, even within existing modes of reforestation, GFGP can achieve greater biodiversity gains by promoting mixed forests over monocultures; doing so is unlikely to entail major opportunity costs or pose unforeseen economic risks to households.

Measuring the impact of the pet trade on indonesian birds

The trade in wild animals involves one-third of the worlds bird species and thousands of other vertebrate species. Although a few species are imperiled as a result of the wildlife trade, the lack of field studies makes it difficult to gauge how serious a threat it is to biodiversity. We used data on changes in bird abundances across space and time and information from trapper interviews to evaluate the effects of trapping wild birds for the pet trade in Sumatra, Indonesia. To analyze changes in bird abundance over time, we used data gathered over 14 years of repeated bird surveys in a 900-ha forest in southern Sumatra. In northern Sumatra, we surveyed birds along a gradient of trapping accessibility, from the edge of roads to 5 km into the forest interior. We interviewed 49 bird trappers in northern Sumatra to learn which species they targeted and how far they went into the forest to trap. We used prices from Sumatran bird markets as a proxy for demand and, therefore, trapping pressure. Market price was a significant predictor of species declines over time in southern Sumatra (e.g., given a market price increase of approximately

The pet trade's role in defaunation

50, the log change in abundance per year decreased by 0.06 on average). This result indicates a link between the market-based pet trade and community-wide species declines. In northern Sumatra, price and change in abundance were not related to remoteness (distance from the nearest road). However, based on our field surveys, high-value species were rare or absent across this region. The median maximum distance trappers went into the forest each day was 5.0 km. This suggests that trapping has depleted bird populations across our remoteness gradient. We found that less than half of Sumatras remaining forests are >5 km from a major road. Our results suggest that trapping for the pet trade threatens birds in Sumatra. Given the popularity of pet birds across Southeast Asia, additional studies are urgently needed to determine the extent and magnitude of the threat posed by the pet trade.

Understory avifauna exhibits altered mobbing behavior in tropical forest degraded by selective logging

In their Report “The impact of hunting on tropical mammal and bird populations” (14 April, p. [180][1]), A. Benitez-Lopez and colleagues quantify the global impact of hunting on defaunation. However, hunting is only one side of the defaunation crisis. Nonlethal take, particularly wild capture

Functional traits determine heterospecific use of risk-related social information in forest birds of tropical South-East Asia

In understanding the impacts of selective logging on biodiversity, relatively little is known about the critical behavioral link between altered forest conditions and population persistence. Predator-mobbing is a widespread anti-predator behavior in birds that expresses a well-known trade-off influencing prey survival under predation risk. Here, we ask whether the predator-mobbing behavior of understory forest birds is altered by selective logging and associated forest structural changes in the highly endangered lowland rainforest of Sumatra. At four study sites spanning a gradient of logging-induced forest degradation, we used standardized mobbing and owl call playbacks with predator model presentation to elicit the predator-mobbing behavior of understory prey birds, compared birds’ mobbing intensity across sites, and related variation in this intensity to forest vegetation structure. We found that selective logging altered birds’ predator-mobbing intensity (measured by behavioral conspicuousness and propensity to approach the predator) as well as forest structure, and that vegetative changes to canopy and understory were correlated with contrasting responses by the two major bird foraging guilds, gleaning versus flycatching birds. We additionally discuss the implications of our findings for further hypothesis testing pertaining to the impacts of selective logging on the ecological processes underlying prey mobbing behavior, particularly with regards to predator–prey interactions and prey accruement of energy reserves.

The biodiversity benefit of native forest over Grain-for-Green plantations

Abstract In birds and mammals, mobbing calls constitute an important form of social information that can attract numerous sympatric species to localized mobbing aggregations. While such a response is thought to reduce the future predation risk for responding species, there is surprisingly little empirical evidence to support this hypothesis. One way to test the link between predation risk reduction and mobbing attraction involves testing the relationship between species’ attraction to mobbing calls and the functional traits that define their vulnerability to predation risk. Two important traits known to influence prey vulnerability include relative prey‐to‐predator body size ratio and the overlap in space use between predator and prey; in combination, these measures strongly influence prey accessibility, and therefore their vulnerability, to predators. Here, we combine community surveys with behavioral experiments of a diverse bird assemblage in the lowland rainforest of Sumatra to test whether the functional traits of body mass (representing body size) and foraging height (representing space use) can predict species’ attraction to heterospecific mobbing calls. At four forest sites along a gradient of forest degradation, we characterized the resident bird communities using point count and mist‐netting surveys, and determined the species groups attracted to standardized playbacks of mobbing calls produced by five resident bird species of roughly similar body size and foraging height. We found that (1) a large, diverse subcommunity of bird species was attracted to the mobbing calls and (2) responding species (especially the most vigorous respondents) tended to be (a) small (b) mid‐storey foragers (c) with similar trait values as the species producing the mobbing calls. Our findings from the relatively lesser known bird assemblages of tropical Asia add to the growing evidence for the ubiquity of heterospecific information networks in animal communities, and provide empirical support for the long‐standing hypothesis that predation risk reduction is a major benefit of mobbing information networks.

Multiple stages of tree seedling recruitment are altered in tropical forests degraded by selective logging

Aim China’s Grain-for-Green Program (GFGP) is the largest reforestation program in the world and has been operating since 1999. The GFGP has promoted the establishment of tree plantations over the preservation of diverse native forest. In a previous study (Hua et al. 2016, Nat Comms 7:12717), we showed that native forest supports higher species richnesses of birds and bees than do GFGP plantations. We also showed that ‘mixed-plantation’ GFGP plantations, which are mostly made up of two to five neighboring monoculture stands of different tree species, planted in checkboard fashion, support a level of bird (but not bee) species richness that is higher than any of the individual GFGP monocultures, although still below that of native forest. To better protect terrestrial biodiversity, which is an important objective of China’s land-sustainability spending, we recommended that the GFGP should firstly prioritize native forest conservation and regeneration and secondly promote checkerboard planting arrangements over monocultures. Here, we use metabarcoding of arthropod biodiversity to test the generality of these results and policy recommendations. Location Sichuan, China Methods We used COI-amplicon sequencing (‘metabarcoding’) of bulk samples of arthropods that were collected with pan traps in native forest, cropland, mixed plantations, and monocultures. Results Native forest supports the highest overall levels of arthropod species richness and diversity, followed by cropland and mixed plantations, followed by bamboo monoculture, followed by the other monocultures. Also, the arthropod community in mixed plantations shares more species with native forest than do any of the monocultures. Together, these results show a biodiversity value of mixed plantations for arthropods that is higher than that previously indicated by bees alone. Main conclusion These results strengthen our original policy recommendations of (1) promoting the conservation and expansion of native forest and (2) promoting mixed-plantation arrangements. The value of this added metabarcoding-based analysis is that these policy prescriptions are now also based on a dataset that includes over 500 species-resolution taxa, ranging across the Arthropoda.

Bluebirds Perceive Prey Switching by Cooper's Hawks Across an Urban Gradient and Adjust Reproductive Effort

Abstract Tropical forest degradation is a global environmental issue. In degraded forests, seedling recruitment of canopy trees is vital for forest regeneration and recovery. We investigated how selective logging, a pervasive driver of tropical forest degradation, impacts canopy tree seedling recruitment, focusing on an endemic dipterocarp Dryobalanops lanceolata in Sabah, Borneo. During a mast‐fruiting event in intensively logged and nearby unlogged forest, we examined four stages of the seedling recruitment process: seed production, seed predation, and negative density‐dependent germination and seedling survival. Our results suggest that each stage of the seedling recruitment process is altered in logged forest. The seed crop of D. lanceolata trees in logged forest was one‐third smaller than that produced by trees in unlogged forest. The functional role of vertebrates in seed predation increased in logged forest while that of non‐vertebrates declined. Seeds in logged forest were less likely to germinate than those in unlogged forest. Germination increased with local‐scale conspecific seed density in unlogged forest, but seedling survival tended to decline. However, both germination and seedling survival increased with local‐scale conspecific seed density in logged forest. Notably, seed crop size, germination, and seedling survival tended to increase for larger trees in both unlogged and logged forests, suggesting that sustainable timber extraction and silvicultural practices designed to minimize damage to the residual stand are important to prevent seedling recruitment failure. Overall, these impacts sustained by several aspects of seedling recruitment in a mast‐fruiting year suggest that intensive selective logging may affect long‐term population dynamics of D. lanceolata. It is necessary to establish if other dipterocarp species, many of which are threatened by the timber trade, are similarly affected in tropical forests degraded by intensive selective logging.

Increased perception of predation risk to adults and offspring alters avian reproductive strategy and performance

ABSTRACT Urban-adapting carnivorous predators such as the Coopers hawk appear to be adjusting their diet in urban areas to mostly include larger-bodied adult birds rather than nest contents, compared to Coopers hawks in natural areas. If adult prey in urban areas are relatively more threatened by predation relative to their offspring and non-urban adults, then life-history theory predicts contrasting shifts in urban vs. non-urban reproductive behavior and effort. We tested whether urban and non-urban Eastern bluebirds exhibited contrasting reproductive effort consistent with shifts in the relative risk perception of adult vs. nest predation. At urban sites, Eastern bluebirds using nest boxes exposed to broadcasts of Coopers hawk vocalizations exhibited enhanced reproductive parameters compared to controls, whereas the opposite trend occurred in box-nesting bluebirds at non-urban sites. As predicted by theory, given prey life-stage switching by a dominant predator, increased perception of predation risk from hawks led to opposing reproductive strategies in urban vs. non-urban habitats. Results align with increasing evidence that urban predation pressures, prey risk perception, and reproductive investment patterns are distinct from those of natural habitats.