Stream order-dependent ecological impacts of agricultural and urban land
use across ecoregions
Abstract
Why have ecological targets for the majority of water bodies in Europe
not been met despite decades of water protection programs? We
hypothesize that restoration strategies have not adequately accounted
for whole-river network perspectives, including interactions between
stream orders, spatial patterns of pollutant sources, and
ecoregion-dependent susceptibility. We used high-resolution data from
Germany to identify relationships between urban wastewater-river
discharge fraction (UDF), agricultural land use fraction (ALF), and
ecological status by stream order across three ecoregions. We found
ecological status of good or better in less than 8% of all river
sections with the highest proportions in low-order streams and complete
disappearance at higher orders. Increasing ALF impaired the ecological
status for river reaches across all stream orders. In contrast,
relationships between UDF and ecological status impairment were
significant only in low-order streams, independent from ecoregion.
Concentrating integrative restoration efforts in low-order streams would
maximize the potential to mitigate anthropogenic impacts.