DOI: 10.5061/dryad.8pk0p2nqh
title: Dataset: A global synthesis of human impacts on the multifunctionality of streams and rivers

description: 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.
description: 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 31<sup>st</sup>, 2020. We included primary
 studies that satisfied the following criteria: (<em>i</em>)
 they addressed the effect of human stressors on at least one ecosystem
 function, (<em>ii</em>) they were conducted in the
 field, i.e., streams,
 rivers, and streamside channels, (<em>iii</em>) they compared
 at least one reference and one impacted site, and
 (<em>iv</em>) they reported means, variation, and sample sizes
 for reference and impacted conditions.