How will increasing climate variability change plant species diversity?
To most people, global climate change means increases in average temperatures. But scientists are also predicting that climate change will cause increases in rainfall variability-more severe storms and very wet years, but also more extreme droughts. Such changes in rainfall variability might have significant impacts on arid and semi-arid ecosystems. In fact, mathematical theory predicts that climate variability can be important in maintaining species diversity by allowing species to "time-share" one habitat. This theory implies that a change in variability could alter species diversity, but it has been difficult to test due to a lack of appropriate data.
A remarkable dataset from grasslands in western Kansas, USA provides an opportunity to test theory about climate variability and species diversity. For over thirty years starting in the 1930's, all individual plants in permanent quadrats were mapped each year. We can use these data to create a statistical model that describes how each common grass species grows in each year, and how neighboring grasses affect each other's growth. This model then allows us to perform "virtual experiments" to test whether year-to-year variability in climate increases the persistence of each species compared to a hypothetical constant environment. Because mapped datasets like the one from Kansas also exist for a handful of other sites, the study will also ask whether climate variability has a similar influence on species diversity in different arid and semiarid ecosystems. Ultimately, this research will provide a better understanding of how an often ignored aspect of climate change-increasing variability-will influence biodiversity.
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