Identifying knowledge gaps on simultaneous above- and belowground organism responses to global change

Hendrik Mohr , Esme Ashe-Jepson, Malte Jochum

Global change affects all terrestrial organisms regardless if they live above or below the ground. Even though they are strongly linked by various direct and indirect interactions, organisms can respond very differently to global change stressors, due to different features of above- and belowground compartments. Many different organism groups have shown declines in diversity, abundance or biomass which goes hand in hand with the loss of important ecosystem services. However, to date, the extent to which above- and belowground organisms are studied simultaneously in global change research has not systematically been studied. This makes it difficult to assess knowledge gaps and research deficits in this area. Here we present a systematic literature overview on well-covered research areas and knowledge gaps on how global change stressors affect above- and belowground organisms in terrestrial ecosystems. We found an underrepresentation of tropical areas and non-agricultural ecosystems, like wetlands and deserts. For global change stressors we identified knowledge gaps on many aspects, including non-agricultural pollutants, extreme weather events, and direct exploitation, while we overall observed a strong focus on invertebrates compared to other organism groups. Many combinations of organism groups and stressors were poorly or not at all covered. Our results regarding study design and focal biodiversity metrics suggest a lack of studies investigating future scenarios as well as direct linkages of organism presence with ecosystem functioning. Closing the knowledge gaps that we identified will be the key to lift our knowledge from how single groups respond to global change to how whole communities and ecosystems will be altered. This knowledge could not only significantly improve conservation measures but might also offer relevant economic and societal benefits via agricultural advancements and provision of ecosystem services.