Abstract
Human land use and climate change are regarded as the main driving forces of present-day and future species extinction. They may potentially lead to a profound reorganisation of the composition and structure of natural communities throughout the world. However, studies that explicitly investigate both forms of impact—land use and climate change—are uncommon. Here, we quantify community change of Dutch breeding bird communities over the past 25 years using time lag analysis. We evaluate the chronological sequence of the community temperature index (CTI) which reflects community response to temperature increase (increasing CTI indicates an increase in relative abundance of more southerly species), and the temporal trend of the community specialisation index (CSI) which reflects community response to land use change (declining CSI indicates an increase of generalist species). We show that the breeding bird fauna underwent distinct directional change accompanied by significant changes both in CTI and CSI which suggests a causal connection between climate and land use change and bird community change. The assemblages of particular breeding habitats neither changed at the same speed and nor were they equally affected by climate versus land use changes. In the rapidly changing farmland community, CTI and CSI both declined slightly. In contrast, CTI increased in the more slowly changing forest and heath communities, while CSI remained stable. Coastal assemblages experienced both an increase in CTI and a decline in CSI. Wetland birds experienced the fastest community change of all breeding habitat assemblages but neither CTI nor CSI showed a significant trend. Overall, our results suggest that the interaction between climate and land use changes differs between habitats, and that comparing trends in CSI and CTI may be useful in tracking the impact of each determinant.
Highlights
Among the various anthropogenic factors that are responsible for the extinction of species and the decline of biodiversity, two are considered to have an overwhelming importance, and they have received particular attention in the last few decades: global climatic change [1] and the destruction, fragmentation and disturbance of habitats [2,3]
The magnitude of directional change in the time series differed between the habitat communities
Directional change in Dutch bird fauna We showed that the Dutch breeding bird fauna underwent distinct directional change between 1984 and 2009
Summary
Among the various anthropogenic factors that are responsible for the extinction of species and the decline of biodiversity, two are considered to have an overwhelming importance, and they have received particular attention in the last few decades: global climatic change [1] and the destruction, fragmentation and disturbance of habitats [2,3]. Human land use is regarded to be the main driving force of present-day species extinction, climate change is expected to become at least important in the coming decades [4]. The interaction between climate change and habitat loss has been called a ‘‘deadly anthropogenic cocktail’’ [5], and projected future extinction rates are commonly based on the degree of land use and climate change [6]. They will potentially lead to a profound reorganisation of the composition and structure of natural communities throughout the world. A formal analysis investigating the long-term change in community composition and dynamics in the face of land use and land cover change (LUCC; see Table 1 for an explanation of all acronyms used in this paper) and climate change is still lacking
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