Abstract
Urbanisation results in a marked modification of habitats and influences several ecological processes, some of which give rise to beneficial ecological services. Natural pest control, the effect of predators on prey is one of such services. We quantified changes in the incidence of predation with increasing levels of urbanisation using artificial caterpillars made of green plasticine. Potential preda- tors can be identified by the attack marks they leave on these artificial caterpillars. We conducted this study from May to October 2010 around the city of Soro (Zealand, Denmark), in forests along an urbanisation gradient (rural-suburban-urban). Artificial caterpil - lars were placed on the ground in order to obtain an estimate of the incidence of predation at ground level. Half (50%) of the 1398 cat- erpillars were attacked and 28.8% of the bites were those of chewing insects. We attributed the majority of these to carabids, the most common group of ground-active arthropods. Chewing insects exerted the greatest predation pressure in the original forest (52.1%), with lower values recorded in the suburban (10.1%) and urban (16.4%) forest fragments. Ants were responsible for only 4.7% of the attacks in forest, 11.3% in suburban and 16.4% in urban forest fragments. Mammals exerted the highest predation pressure in suburban habitats (22.2% vs. 4.9% in forest, and 8.1% in urban forest fragments).
Highlights
Ecological servicesBiodiversity provides several benefits, termed ecological or ecosystem services, which are essential for human survival (Millennium Ecosystem Assessment, 2005)
In our study we did not focus on any particular predator, but exploited the characteristic signs left by different predators in the malleable surface of the artificial caterpillars
We found differences in the incidence of predation along the urbanisation gradient
Summary
Biodiversity provides several benefits, termed ecological or ecosystem services, which are essential for human survival (Millennium Ecosystem Assessment, 2005). The continued increase in the human population is accompanied by marked modifications of natural areas resulting in a reduction in biodiversity, which usually negatively affects the services provided (Carpenter et al, 2009). Even if the consequences of these effects are known, the quantification of ecological services is difficult and changes in the numbers of useful organisms are often used as a proxy for the level of services they provide (Isbell et al, 2011). Considering the environmental and economic importance of the well-being of ecosystem services for humans, it is important to identify and accurately measure ecosystem services (Layke et al, 2012; Liss et al, 2013)
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