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Effects of landscape and patch-level attributes on regional population persistence
Citation:
Heinrichs, J. A., D. J. Bender, D. I. Gummer, AND N. H. SCHUMAKER. Effects of landscape and patch-level attributes on regional population persistence. Journal for Nature Conservation. ELSEVIER, AMSTERDAM, Holland, 26:56-64, (2015).
Impact/Purpose:
Habitat patch size and isolation are often described as the key habitat variables influencing population dynamics.
Description:
Habitat patch size and isolation are often described as the key habitat variables influencing population dynamics. Yet habitat quality may also play an important role in influencing the regional persistence of spatially structured populations as the value or density of resources within habitats can affect the capacity of habitats to support individuals. To examine the relative importance of patch size, quality, and isolation on the regional persistence of endangered Ord’s kangaroo rats (Dipodomys ordii) in Alberta, we conducted habitat removal simulations using a spatially explicit population model. Groups of habitat patches were selected for removal based on their size, quality, and isolation characteristics, and the resulting risk of regional population extinction was measured. A proportional hazards model was used to assess the relative importance of each habitat variable. Patch-based variables contributed to the risk of population extinction, despite the dominant influence of landscape variables (particularly quality and habitat amount). The highest ranked variables all related to habitat quantity and/or quality, suggesting that kangaroo rat persistence is heavily influenced by habitat capacity, and less influenced by habitat configuration. Results indicate that both landscape considerations and the attributes of constituent patches should be of vital interest for kangaroo rat conservation. While linear or proportional relationships between patch area and local population size are often assumed, the influence of patch quality outweighed that of patch area, suggesting that such assumptions may not be appropriate in landscapes of heterogeneous habitat quality. The removal of low quality habitats (road margins) actually increased persistence, suggesting that the prioritization of habitats based only on patch size and isolation may jeopardize persistence by promoting the preservation and proliferation of low quality or detrimental sinks. Conservation planning should consider the potential influence of habitat 23 quality in landscapes where differences in resources or population density may be important.