The majority of the examples in Section 3.3 are from studies mimicking projected conditions in the year 2100 that report the responses of an individual species or strain to multiple drivers. This powerful generic experimental approach has largely been restricted to single species because it is logistically complex to conduct experiments that straddle multiple trophic levels, and that also include more than two drivers ; the need for multiple replicates, drivers and treatment levels greatly increase the work required . It is challenging to apply this experimental approach to communities or ecosystems . To date, most research on community or ecosystem response to climate-induced drivers has been in large-volume  mesocosms , or at natural analogues such as CO2 seeps, in which only one driver  is altered  in Figure Box 3.1.1). Only very recently have two drivers been incorporated into climate-change manipulation studies examining responses of primary producers to secondary consumers  in Figure Box 3.1.1a; Nagelkerken et al., 2020). Therefore, 'natural experiments' from the geological past  provide insights into how food webs and their constituents respond to complex change involving multiple drivers. Contemporary observations are occasionally long enough  to capture community responses to complex climate change. For example, Brun et al.  reported a shift in zooplankton community structure in the North Atlantic , with major biogeochemical ramifications.
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Climate Change 2022: Impacts, Adaptation and Vulnerability
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