Riparian Restoration Improves Physical Habitat but Not Ecosystem Functioning to Reference Levels in Urban Neotropical Streams

Urbanization modifies stream ecosystems through changes in land use and water quality, with particularly understudied effects in tropical regions. This study evaluates how the conservation status (reference, restored, and impacted) influences nutrient enrichment and organic matter decomposition—key indicators of ecosystem function—across five Neotropical streams in southeastern Brazil. We found large differences in nutrient availability, with impacted streams exhibiting 22.7‐fold higher ammonium (1259.5 vs. 43.4 μg L −1 ) and 7.3‐fold higher total dissolved phosphorus (425.9 vs. 55.7 μg L −1 ) concentrations than the reference stream. Functional assessments using cotton strip assays showed average decomposition coefficients in impacted streams (0.158 day −1 ) exceeded reference conditions (0.034 day −1 ) by 4.6‐fold, with restored streams displaying intermediate values (0.093 day −1 ). Despite the limited number of streams, those with > 50% urban cover showed markedly higher decomposition rates and nutrient concentrations compared to less urbanized sites. Restored streams achieved near‐reference habitat quality (Rapid Habitat Diversity Assessment RHDA scores: 63–64 vs. 65) but maintained intermediate nutrient levels and decomposition rates, indicating persistent watershed‐scale influences. The studied Neotropical streams respond nonlinearly to land use intensity, with watershed management being equally critical as reach‐scale restoration for maintaining ecosystem processes. These findings provide empirical support for implementing integrated urban planning approaches that address both local habitat quality and landscape‐scale connectivity in Neotropical regions undergoing rapid development.