Data from: The effects of land use on downstream water quality and biodiversity in a changing tropical mosaic landscape

Land use and other human activities often degrade downstream water
quality, with consequences for ecosystem services and freshwater
biodiversity. Understanding the relative effects of different land-use
types across large spatial scales, however, remains challenging in
heterogeneous landscapes. We investigated how landscape composition
influences stream water quality and aquatic biodiversity in 46 catchments
with perennial streams draining mosaic landscapes managed by smallholder
farmers in southwest Ethiopia. Specifically, we assessed whether coffee
agroforestry landscapes have intermediate effects on stream biodiversity
compared to forests and agricultural lands. We measured multiple water
quality parameters and sampled stream macroinvertebrates, while
quantifying land-use proportions, settlement density, and an index
representing the number and proximity of coffee washing stations within
each catchment. Streams draining forest-dominated landscapes exhibited
better water quality, characterized by higher dissolved oxygen and lower
turbidity and nutrient concentrations, than those draining agroforestry-
or agriculture-dominated landscapes. Elevated concentrations of
Escherichia coli were detected in most streams, particularly in
agroforestry landscapes. Macroinvertebrate community composition varied
widely, with pollution-sensitive taxa dominating cleaner streams and
tolerant taxa prevailing in more degraded systems. These patterns were
more pronounced when considering the direct effects of settlement density
and coffee washing stations, although some taxonomic groups showed
inconsistent responses. Our results indicate that water chemistry alone
does not fully capture land-use impacts on stream condition, underscoring
the importance of incorporating biodiversity assessments. Given the
reliance of local communities on these streams and the risks to freshwater
biodiversity, our findings highlight the urgent need for mitigation
measures, particularly in agriculture- and agroforestry-dominated
landscapes, with a focus on reducing waste inputs from settlements and wet
coffee washing stations.