Predation risk shaped by habitat and landscape complexity in urban environments

Abstract

Habitat loss and modification are hallmarks of anthropogenic ecosystems, but the consequences for ecosystem functioning and service provisioning often remain unclear. Understanding these links in cities is complicated by strong but fine‐scale differences in habitat structure among green space patches, and a high variance in habitat amount across urban landscapes. We used airborne laser scanning data to disentangle the effects of 3D woody habitat heterogeneity of urban home gardens, and woody habitat amount at four landscape spatial scales (50, 100, 250, and 500 m), on the predation risk of artificial sentinel prey by birds and arthropods. In both predator groups, and at all the investigated spatial scales, cross‐scale interactive effects between garden habitat heterogeneity and habitat amount in the urban landscape were the main drivers of predation. Risk of predation by birds was highest in heterogeneous garden habitats, but only in densely built urban landscapes where habitat amount was low to intermediate (10%–20%) at large spatial scales (250–500 m). It dropped independently of garden habitat heterogeneity when habitat amount became too low (<10%) at small (50–100 m) spatial scales. In contrast, risk of predation by arthropods mostly peaked in homogeneous garden habitats when habitat amount was intermediate (20%) at large spatial scales. Our findings show that the ability of urban green space patches, such as gardens, to sustain ecosystem functions in cities mainly depends on cross‐scale interactive effects with larger scale habitat amount. In birds, predation activity can increase when high patch‐scale habitat heterogeneity contrasts with reduced larger scale habitat amount, suggesting concentration effects. Yet, thresholds exist under which ecosystem functioning drops independently of habitat structure. Synthesis and applications. The potential of small‐scale interventions to enhance habitat heterogeneity (e.g., by planting native trees with understorey shrubs) for restoring ecosystem functions, such as bird predation, in urban areas is dependent on wider landscape habitat structure. Urban planning should therefore adopt a multiscale approach to sustain and restore ecosystem functions and services; a simple but still not broadly recognized finding. Airborne laser scanning is a useful tool to infer habitat structure across a hierarchy of scales in spatially heterogeneous anthropogenic ecosystems.

Litter decomposition driven by soil fauna, plant diversity and soil management in urban gardens

“…While above-ground BEF relationships are often shaped by an interaction of local-scale (e.g. vegetation structure ) and landscapescale factors (Angold et al, 2006;Frey et al, 2018a), our understanding of how such multi-scale factors affect the belowground BEF relationships is still limited (Lin and Egerer, 2018). For example, recent studies of ecosystems services rarely addressed the high spatial heterogeneity and complexity of urban soils (Ziter and Turner, 2018), and neither consider the variety of direct and indirect anthropogenic influences across spatial scales (Enloe et al, 2015), nor the role of different aspects of biodiversity (Schwarz et al, 2017).…”

I Can See You: Temporal Variation in Ant Aggressiveness Towards Herbivores under Continuous Provision of High- or Low-quality Food Sources

“…We observed an extremely high proportion of attacked caterpillars during the whole experiment: 84.25% in only two days. Studies conducted in different environments, such as tropical savanna, urban area and tropical forest, that left models exposed for over four days observed attack marks on only 11.7, 16.2 and 20.9% of caterpillars, respectively (Moreno & Ferro, 2012;Leles et al, 2017;Frey et al, 2018). Therefore, our study demonstrated that caterpillar models can be used efficiently to explore the relationships between ants, the resources provided by plant species and herbivorous insects.…”

“…birds, reptiles or chewing insects) (Low et al, 2014) (Fig 1B). These models have already provided useful information about the effects of plant and vegetation structure (Leles et al, 2017;Frey et al, 2018) and caterpillar characteristics (Hossie & Sherratt, 2012) on the relationships between caterpillars and their natural enemies. Ants have been shown to be responsible for most of the attacks on dummy caterpillars (Roslin et al, 2017), evidence that caterpillar models are efficient tools to assess the ants' response towards herbivorous arthropods (Leles et al, 2017).…”

Towards an integrative approach to evaluate the environmental ecosystem services provided by urban forest

“…Since many ecosystem functions ultimately rely on interactions between primary producers (plants) and other trophic levels (e.g. pollinators, soil decomposers, and herbivores), the redundancy and resilience framework (e.g., Elmqvist et al 2003) should be extended to multi-trophic systems (Lavorel et al 2013) and include metrics of biotic interactions (for measuring functional redundancy and response diversity) as indicators of functionally resilient urban ecosystems (e.g., Frey et al 2018;Tresch et al 2019).…”