Climate change is causing drying streamflow regimes in south-western Australia (SWA). Processing rates of jarrah leaves (Eucalyptus marginata; primary carbon source) were measured in two always-perennial and two were-perennial, now-seasonal headwater streams, then compared to research conducted by Bunn (1988) when all streams were perennial. Mesh bags contained tasty jarrah leaves: large mesh allowed invertebrate access and small mesh excluded them. These results examine the identities and relative contributions of shredding macroinvertebrates, and other processes (leaching and microbial/ fungal colonisation) to leaf breakdown under climate change.