Abstract
Understanding threatened species diversity is important for long-term conservation planning. Geodiversity-the diversity of Earth surface materials, forms, and processes-may be a useful biodiversity surrogate for conservation and have conservation value itself. Geodiversity and species richness relationships have been demonstrated; establishing whether geodiversity relates to threatened species' diversity and distribution pattern is a logical next step for conservation. We used 4 geodiversity variables (rock-type and soil-type richness, geomorphological diversity, and hydrological feature diversity) and 4 climatic and topographic variables to model threatened species diversity across 31 of Finland's national parks. We also analyzed rarity-weighted richness (a measure of site complementarity) of threatened vascular plants, fungi, bryophytes, and all species combined. Our 1-km2 resolution data set included 271 threatened species from 16 major taxa. We modeled threatened species richness (raw and rarity weighted) with boosted regression trees. Climatic variables, especially the annual temperature sum above 5 °C, dominated our models, which is consistent with the critical role of temperature in this boreal environment. Geodiversity added significant explanatory power. High geodiversity values were consistently associated with high threatened species richness across taxa. The combined effect of geodiversity variables was even more pronounced in the rarity-weighted richness analyses (except for fungi) than in those for species richness. Geodiversity measures correlated most strongly with species richness (raw and rarity weighted) of threatened vascular plants and bryophytes and were weakest for molluscs, lichens, and mammals. Although simple measures of topography improve biodiversity modeling, our results suggest that geodiversity data relating to geology, landforms, and hydrology are also worth including. This reinforces recent arguments that conserving nature's stage is an important principle in conservation.
Highlights
Land-use and climate change threaten species globally (Mantyka-Pringle et al 2015)
We modeled the relationship between the physical environment and both threatened species richness and rarity-weighted richness (RWR) at 1-km2 grain size across 31 protected areas of Finland
Growing-degree days and mean precipitation were usually the dominant predictors of threatened species richness; elevational range and topographic wetness index (TWI) range were important for threatened vascular plants and bryophytes, respectively (Table 3)
Summary
Land-use and climate change threaten species globally (Mantyka-Pringle et al 2015). It is increasingly important to understand and conserve species’ diversity and distributions. Numerous researchers have explored how abiotic factors are related to species’ diversity and distributions (Lawler et al 2015), and the relationship between environmental heterogeneity and species richness has been established across multiple taxa and spatial scales (Stein et al 2014). Vascular plants are commonly studied and typically have strong relationships with climatic variables and topographic heterogeneity (Field et al 2009), whereas the effect of abiotic conditions is less known for rare species in other taxonomic groups (e.g., Virkkala et al 2005; Anderson & Ferree 2010)
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