A study of 16 streams in eastern North America shows that riparian deforestation causes channel narrowing, which reduces the total amount of stream habitat and ecosystem per unit channel length and compromises in-stream processing of pollutants. Wide forest reaches had more macroinvertebrates, total ecosystem processing of organic matter, and nitrogen uptake per unit channel length than contiguous narrow deforested reaches. Stream narrowing nullified any potential advantages of deforestation regarding abundance of fish, quality of dissolved organic matter, and pesticide degradation. These findings show that forested stream channels have a wider and more natural configuration, which significantly affects the total in-stream amount and activity of the ecosystem, including the processing of pollutants. The results reinforce both current policy of the United States that endorses riparian forest buffers as best management practice and federal and state programs that subsidize riparian reforestation for stream restoration and water quality. Not only do forest buffers prevent nonpoint source pollutants from entering small streams, they also enhance the in-stream processing of both nonpoint and point source pollutants, thereby reducing their impact on downstream rivers and estuaries.

Aquatic insect secondary production, emergence, and export of adults to the adjacent terrestrial ecosystem were assessed in Sycamore Creek, Arizona, by means of benthic sampling, emergence traps, and catch-nets that passively sampled adults falling into the stream .. Annual secon~ary production was 120.9 ± 18.0 g·m-2 ·yr-' and emergence was 23.1 g·m-2 ·yr-' (m dry mass umts). The ratio of annual emergence to annual production (EI P) varied among taxa and ranged from 2 to 29%. Chironomids comprised 48.2% ofproduction and 59.7% of emergence and mayflies accounted for 45.9 and 19 .2%, respectively. Approximately 3% of emergent insect biomass returned to the stream; thus 22.4 g·m-2 ·yr-' was transferred to the adjacent terrestrial ecosystem. The transfer of a significant portion of aquatic insect biomass to the terrestrial habitat reduced insects available to stream insectivores while providing prey for insectivores in neighboring terrestrial ecosystems.

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