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Limited functional redundancy in vertebrate scavenger guilds fails to compensate for the loss of raptors from urbanized sandy beaches
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posted on 2015-01-01, 00:00 authored by C M Huijbers, T A Schlacher, D S Schoeman, A D Olds, Mike WestonMike Weston, R M ConnollyAim: Globally, urbanization is one of the most widespread, intense and ecologically destructive forms of landscape transformation, and it is often concentrated in coastal areas. Theoretically, species losses attributable to urbanization are predicted not to alter overall ecosystem function if functional redundancy (i.e. replacement of function by alternative species) compensates for such losses. Here, we test this expectation by measuring how coastal urbanization affects scavenger guilds on sandy beaches and whether changes in guild composition result either in an overall loss of scavenging efficiency, or in functional compensation under alternative guild structures, maintaining net ecosystem functioning. Location: Fourteen beaches along the east coast of Australia with variable levels of urbanization. Methods: Scavenging communities and rates of carrion removal were determined using motion-triggered cameras at the beach-dune interface. Results: A substantial shift in the community structure of vertebrate scavengers was associated with gradients in urbanization. Iconic and functionally important raptors declined precipitously in abundance on urban beaches. Importantly, other vertebrates usually associated with urban settings (e.g. dogs, foxes, corvids) did not functionally replace raptors. In areas where < 15% of the abutting land had been developed into urban areas, carcass removal by scavengers was often complete, but always > 70%. Conversely, on beaches bordering coastal cities with < 40% of natural vegetation remaining, two-thirds of fish carcasses remained uneaten by scavengers. Raptors removed 70-100% of all deployed fish carcasses from beaches with < 8% urban land cover, but this number dropped significantly with greater levels of urbanization and was not compensated by other scavenger species in urban settings. Main conclusions: There is limited functional redundancy in vertebrate scavenger communities of sandy beach ecosystems, which impacts the system's capacity to mitigate the ecological consequences of detrimental landscape transformations.
History
Journal
Diversity and Distributions: a journal of conservation biogeographyVolume
21Issue
1Pagination
55 - 63Publisher
WileyLocation
London, Eng.Publisher DOI
ISSN
1472-4642eISSN
1472-4642Language
engPublication classification
C Journal article; C1 Refereed article in a scholarly journalCopyright notice
2015, WileyUsage metrics
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No categories selectedKeywords
CarrionCoastal managementFunctional lossHuman impactsSandy beachesScavengingUrbanizationScience & TechnologyLife Sciences & BiomedicineBiodiversity ConservationEcologyBiodiversity & ConservationEnvironmental Sciences & EcologyLAND-USE INTENSIFICATIONRESPONSE DIVERSITYVULPES-VULPESBIODIVERSITYECOSYSTEMSIMPACTSCONSERVATIONHABITATBIRDS
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