Understanding Biodiversity: New Research
Biodiversity is a hot topic for scientists and activists looking to conserve and better understand our ecosystems, but how do we define it? Many people use “biodiversity” as a synonym for “species richness,” but an effective assessment of a landscape’s biological organisms would need to include phylogenetic, genetic, functional, and genomic diversity, among other factors. Many of these dimensions of biodiversity are less commonly investigated, including functional diversity, or the variation of species’ traits and their function within a system. For plant species these functional traits can include the ability to fix nitrogen or not, what their rates of photosynthesis are, and much more.
Recently, Shahid Naeem, Professor of Ecology at Columbia University, and colleagues, published a paper that presents a new, multi-dimensional framework for research by examining three dimensions of biodiversity: (1) taxonomic diversity, or simply, the number of species and their relative abundance; (2) functional diversity; and (3) phylogenetic diversity, or the diversity of evolutionary history within the species. Phylogenetic diversity takes both the more recent and the “deeper” branches of the evolutionary tree into account, which is important because ancient organisms have a longer track record of adapting to environmental change.
Naeem and colleagues first established that the majority of biodiversity studies published over the past 15 years have focused on taxonomic diversity alone. This focus, they argued, limits the conclusions that can be drawn and sometimes misses important ways that biodiversity matters.
Naeem's team used their new framework to assess biodiversity at Black Rock Forest by examining understory vegetation both inside and outside of deer exclosures located on long-term plots within the forest. The exclosures are fenced-in areas that prevent deer from browsing, allowing the vegetation to grow unhindered. Vegetation data, gathered over two years, quantified plant productivity within 240 plots (120 within and 120 outside of the exclosures).
These scientists discovered that in the plots outside of the exclosures -- in other words, the areas exposed to deer browse -- the plots with higher functional diversity had higher productivity, or plant growth, as measured by cover. Having higher functional diversity, such as leaf thickness, strategies for nutrient uptake, and use of light, is thus beneficial for landscapes. However, within the deer exclosures, plant cover could not be explained by this functional diversity, and in fact, was controlled by other factors not examined in this study.
Because taxonomic diversity is not substantively different across the 240 plots, an analysis that focused solely on this dimension would have yielded little insight, and missed a chance for deeper understanding of the processes inherent to productivity. As demonstrated by these Consortium scientists, biodiversity is a multi-dimensional concept. The better we understand the complexity of biodiversity in what Naeem and colleagues have called “the heyday of contemporary mass extinction,” the better chance we will have of managing the consequences and strengthening the case for preventing further losses.