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Habitat degradation and loss as key drivers of regional population extinction
Citation:
Heinrichs, J., D. Bender, AND N. Schumaker. Habitat degradation and loss as key drivers of regional population extinction. ECOLOGICAL MODELLING. Elsevier Science BV, Amsterdam, Netherlands, (335):64-73, (2016).
Impact/Purpose:
Human activities impact the quality and pattern of habitats required by wildlife. GIS computer software has made it easy for researchers to obtain maps of habitat pattern extending across large landscapes occupied by wildlife species of interest. But scientists often have little or no information about the variation in habitat quality across these landscapes. This paper identifies general classes of problems for which GIS data describing habitat pattern alone might form a solid foundation upon which predictions about wildlife population viability could be safely based. We also identify general classes of problems for which data on habitat pattern are not enough, and additional information about the quality of these habitat areas must also be acquired before defensible management recommendations can be made.
Description:
Habitat quality is a fundamental driver of species distributions and population outcomes but is often difficult to measure. Further, habitat quality can be abstract, multi-faceted and challenging to compare alongside measures of habitat amount and fragmentation. Consequently, habitat quality is often omitted from many landscape-level habitat analyses or more subjectively represented in resulting habitat management or conservation planning. Yet, the implications of excluding habitat quality from landscape-level responses of species to habitat change are poorly understood. We lack general theory that identifies the conditions under which habitat quality is expected to play a vital role in characterizing local and regional population responses. Using a factorial simulation design, we examined the independent contributions of habitat quality, amount, and fragmentation to population persistence to identify the conditions under which habitat quality might be expected to play a more important role than those of habitat amount or fragmentation. We generated a wide range of fractal landscapes, independently varying in habitat amount, fragmentation, and quality. We simulated interactive animal movement, habitat selection, and persistence for r and K strategist species with short and long dispersal abilities using spatially-explicit individual-based models. Population abundance and extinction risk were recorded through time for each landscape-species combination and used to quantify the relative influence of habitat amount, fragmentation, and landscape quality on population outcomes. We found that habitat degradation influenced extinction risk through a wide range of landscape conditions and species attributes. The most severe extinction responses were observed in scenarios of combined habitat loss and degradation, suggesting that the interactive effects of these variables may greatly affect persistence. Landscape quality modified extinction risks associated with habitat amount-fragmentation thresholds, and we found evidence for quality based extinction thresholds as habitat was degraded. The strength of landscape-level quality on extinction risk outcomes suggests that habitat degradation should be further investigated as a major driver of population responses to landscape change. A more inclusive paradigm may be required to elucidate the general influences landscape change on population extinction. Habitat degradation, along with habitat loss and fragmentation, should be explicitly considered when assessing the implications of landscape change on population extinction.
