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Dataset: A global synthesis of human impacts on the multifunctionality of streams and rivers

Citation

Brauns, Mario et al. (2022), Dataset: A global synthesis of human impacts on the multifunctionality of streams and rivers, Dryad, Dataset, https://doi.org/10.5061/dryad.8pk0p2nqh

Abstract

Human impacts, particularly nutrient pollution and land-use change, have caused significant declines in the quality and quantity of freshwater resources. Most global assessments have concentrated on species diversity and composition, but effects on the multifunctionality of streams and rivers remain unclear. Here, we analyse the most comprehensive compilation of stream ecosystem functions to date to provide an overview of the responses of nutrient uptake, leaf litter decomposition, ecosystem productivity, and food web complexity to six globally pervasive human stressors. We show that human stressors inhibited ecosystem functioning for most stressor-function pairs. Nitrate uptake efficiency was most affected and was inhibited by 347% due to agriculture. However, concomitant negative and positive effects were common even within a given stressor-function pair. Some part of this variability in effect direction could be explained by the structural heterogeneity of the landscape and latitudinal position of the streams. Ranking human stressors by their absolute effects on ecosystem multifunctionality revealed significant effects for all studied stressors, with wastewater effluents (194%), agriculture (148%), and urban land use (137%) having the strongest effects. Our results demonstrate that we are at risk of losing the functional backbone of streams and rivers if human stressors persist in contemporary intensity, and that freshwaters are losing critical ecosystem services that humans rely on. We advocate for more studies on the effects of multiple stressors on ecosystem multifunctionality to improve the functional understanding of human impacts. Finally, freshwater management must shift its focus towards an ecological function-based approach and needs to develop strategies for maintaining or restoring ecosystem functioning of streams and rivers.

Methods

We conducted a systematic literature survey in electronic reference databases (Google Scholar, Scopus, and Web of Science) for papers published in international, indexed journals that studied the effects of human stressors on running water ecosystem functions. We considered the following ecosystem attributes in our initial research: retention of dissolved organic carbon (DOC), dissolved organic nitrogen (DON), ammonia, nitrate and soluble reactive phosphorus (SRP), food web complexity, leaf litter decomposition, secondary production and whole-stream metabolism. Pairwise combinations of stressors and functions were used as keywords (e.g., for the pair food web vs. agriculture: food web AND [freshwater OR river OR stream] AND [agriculture]. We considered all articles and previous meta-analyses published in English until July 31st, 2020. We included primary studies that satisfied the following criteria: (i) they addressed the effect of human stressors on at least one ecosystem function, (ii) they were conducted in the field, i.e., streams, rivers, and streamside channels, (iii) they compared at least one reference and one impacted site, and (iv) they reported means, variation, and sample sizes for reference and impacted conditions.

Funding

Fundação para a Ciência e a Tecnologia, Award: CEEIND/02484/2018

Fundação para a Ciência e a Tecnologia, Award: UIDB/04292/2020

Generalitat de Catalunya, Award: 2017SGR0976