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  • BIODIVERSITY PROMOTES ECOSYSTEM MULTITASKING

     

    Today, colleagues from around the globe and I published a paper in Nature Communications titled “Biodiversity enhances ecosystem multifunctionality across trophic levels and habitats.” The paper is an important step forward in connecting biological diversity — the variety of organisms living in an ecosystem — to the myriad processes operating in natural, functioning ecosystems. Its worth digging a bit into this analysis, and explaining a little bit about why its important.

    Our report synthesizes across nearly 100 experiments that manipulated biological diversity (the number of species) and measured the consequences for ecosystem functioning — properties and processes that support an ecosystem. Functions include things like growth (biomass production), resource use (consumption), nutrient cycling, and decomposition. Functions often underpin services, or ecosystem properties that benefit humanity. Examples of ecosystem services are fisheries (supported by biomass production), and clean water (supported by nutrient cycling and decomposition). Hence why biodiversity is often implicated in human well-being.

    On top of that, we are losing species. As we continue to exert a dominant influence over the natural world, we destroy and fragment habitats (thinking cutting down the rainforest) and exploit populations (thinking overfishing). The consequence is, unsurprisingly, extinctions, and lots of them. Some estimates suggest that the number of extinctions in the recent past isone thousand times greater than at any point in the history of the planet (aka, the fossil record). So the pressing question is: what are the consequences of losing all these species for ecosystems, and ultimately for us?

    WHAT IS ‘ECOSYSTEM MULTIFUNCTIONALITY’?

    The experiments in our analysis answered this question by directly manipulating diversity and measuring the ecosystem consequences in the form of functions. Controlled experiments such as those included in our analysis are ideal for exploring the effects of diversity loss, because the ecosystem consequences can be directly attributed to changing the number of species.

    There have been hundreds, if not thousands, of experiments to date that have conducted these kinds of manipulations, with more being published every day. However, the vast majority of these have measured only a single ecosystem function (usually standing stock biomass). This is a somewhat simplified view of an ‘ecosystem.’

    If you Google “define: ecosystem” the first definition that pops up is:

    a biological community of interacting organisms and their physical environment.
    (in general use) a complex network or interconnected system.

    The keywords being “complex” and “interconnected.” Ecosystems are comprised of many more functions than biomass, and to truly get at the consequences of diversity loss, we must consider the entirety of this “complex network.”

    Which brings me (finally) to a definition of ecosystem multifunctionality:

    The simultaneous provision of multiple functions in nature.

    Thus, we combed through the hundreds of experiments and chose only those that measured two or more functions, and combined information from those to derive an index of multifunctionality.