It has been recently suggested that droughts induced by climate warming reduce the catchment export of colour-forming, and therefore, UV-B protective, DOC to boreal lakes, which in turn may influence the health of resident biota. We determined that the concentration of DOC in 116 Canadian boreal lakes increased in relation to the severity of previous (4-13 yr) catchment forest clearance (reference - buffer strip - wildfire burnt - partial basin clearcut - whole basin clearcut), and was negatively related to water transparency. Removing the landscape influence of catchment drainage ratio showed that lakes within clearcut or burnt watersheds averaged 2 to 3 mg L-1 more DOC than those in reference, undisturbed catchments. Our results suggest the limited possibility that the increased incidence of wildfires coincident with climate warming may partially offset the effects of droughts on catchment export of DOC in the short-term, and thus serve to mitigate the effects of damaging UV-B exposure for selected basins in localized regions. © 2000 Kluwer Academic Publishers. Printed in the Netherlands.