, 2001a). For most study catchments, 210Pb-based background lake sedimentation rates (1900–1952 medians) ranged from about 20–200 g m−2 a−1 (Fig. 2). Only the mountainous catchment regions, excluding the Vancouver Island-Insular Mountains, contained a significant number of lakes with background rates exceeding 200 g m−2 a−1. A few lakes in the Coast and Skeena mountains exhibited very high background

rates (>1000 g m−2 a−1). Relatively low rates (<20 g m−2 a−1) were observed for most of the Insular Mountain lake catchments. Environmental changes experienced by the lake catchments in the study are described by our suite of land use and climate change variables PR-171 clinical trial (Table 1). Cumulative intensities of land use increased steadily for study catchments overall, especially shown by the trends in road density (Fig. 3). For Anti-infection Compound Library the

late 20th century, averaged road densities were highest for the Insular Mountains (up to 1.90 km km−2) and lowest for the Coast Mountains (up to 0.26 km km−2). By the end of the century, other region catchments had intermediate road densities ranging between 0.46 and 0.80 km km−2. Land use histories for individual study catchments were temporarily variable. The percentage of unroaded catchments over the period of analysis ranged from 0 to 44% for the Insular and Coast mountain regions, respectively. Road densities in excess of 2 km km−2 were observed for several Insular almost Mountain catchments, one Nechako Plateau catchment, and one Nass Basin catchment. Land use variables are all positively correlated,

with highest correlations occurring between road and cut density and between seismic cutline and hydrocarbon well density (Foothills-Alberta Plateau region only). Temperature and precipitation differences among regions and individual lake catchments are related to elevation, continentality, and orographic setting. Temperature data show interdecadal fluctuations and an increasing trend since the mid 20th century for all regions (Fig. 3). Precipitation has increased slightly over the same period and high correlations are observed among temperature and precipitation change variables. Minor regional differences in climate fluctuations include reduced interdecadal variability in highly continental (i.e. Foothills and Alberta Plateau) temperatures during the open-water season and in coastal (i.e. Insular and Coast mountain) temperatures during the closed-water season, as well as greater interdecadal variability in coastal precipitation between seasons and regions. Sedimentation trends during the second half of the 20th century are highly variable between lake catchments (Fig.