title: Mechanisms underpinning climatic impacts on natural populations: altered species interactions are more important than direct effects.
abstract: Shifts in species' distribution and abundance in response to climate change have been well documented, but the underpinning processes are still poorly understood. We present the results of a systematic literature review and meta-analysis investigating the frequency and importance of different mechanisms by which climate has impacted natural populations. Most studies were from temperate latitudes of North America and Europe; almost half investigated bird populations. We found significantly greater support for indirect, biotic mechanisms than direct, abiotic mechanisms as mediators of the impact of climate on populations. In addition, biotic effects tended to have greater support than abiotic factors in studies of species from higher trophic levels. For primary consumers, the impact of climate was equally mediated by biotic and abiotic mechanisms, whereas for higher level consumers the mechanisms were most frequently biotic, such as predation or food availability. Biotic mechanisms were more frequently supported in studies that reported a directional trend in climate than in studies with no such climatic change, although sample sizes for this comparison were small. We call for more mechanistic studies of climate change impacts on populations, particularly in tropical systems.
authors.affiliation: British Trust for Ornithology, The Nunnery, Thetford IP24 2PU, UK.
authors.forename: Nancy
authors.initials: N
authors.lastname: Ockendon
authors.forename: David J
authors.initials: DJ
authors.lastname: Baker
authors.forename: Jamie A
authors.initials: JA
authors.lastname: Carr
authors.forename: Elizabeth C
authors.initials: EC
authors.lastname: White
authors.forename: Rosamunde E A
authors.initials: RE
authors.lastname: Almond
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Amano
authors.forename: Esther
authors.initials: E
authors.lastname: Bertram
authors.forename: Richard B
authors.initials: RB
authors.lastname: Bradbury
authors.forename: Cassie
authors.initials: C
authors.lastname: Bradley
authors.forename: Stuart H M
authors.initials: SH
authors.lastname: Butchart
authors.forename: Nathalie
authors.initials: N
authors.lastname: Doswald
authors.forename: Wendy
authors.initials: W
authors.lastname: Foden
authors.forename: David J C
authors.initials: DJ
authors.lastname: Gill
authors.forename: Rhys E
authors.initials: RE
authors.lastname: Green
authors.forename: William J
authors.initials: WJ
authors.lastname: Sutherland
authors.forename: Edmund V J
authors.initials: EV
authors.lastname: Tanner
authors.forename: James W
authors.initials: JW
authors.lastname: Pearce-Higgins
mesh_terms: D000818:Animals; D058448:Biota; D001717:Birds / Q000502:physiology; D057231:Climate Change; D005060:Europe; D005399:Fishes / Q000502:physiology; D007448:Invertebrates / Q000502:physiology; D008322:Mammals / Q000502:physiology; D009656:North America; D018521:Plant Physiological Phenomena; D011157:Population Dynamics
keywords: abiotic; biotic; climate change; mechanism; meta-analysis; trophic level