Fig. 1: Location of caves and regional rainfall decrease.

The map shows the location of caves, rainfall samples and the total decrease in annual rainfall for 1971–2010 compared to 1911–197033. See Supplementary Note 1 for description of field sites and stalagmite samples. Inset shows the study area location, full extent of groundwater in the Perth Basin (hatched area) and extent of southwest Australian region (shown by red line joining 30°S, 115°E and 35°S, 120°E). Annual rainfall shown on the inset map shows that the study area is in an important rainfall area of the southern Australian region.