a, 2007 values according to habitat. The linear mixed effect models were performed on data from 2576 non-linear plots surveyed in 2007. b, 2007 values according to habitat and location. The linear mixed effect models were performed on data from 4527 plots (2576 non-linear plots and 1951 linear plots) surveyed in 2007. c, 1978-2007 values according to habitat and year. The linear mixed effect models were performed on data from 768 shared plots surveyed in 1978, 1990, 1998 and 2007. The annual nectar productivity was systematically log10 (x+1) transformed. See Supplementary Table 1 and Supplementary Table 3 for sample sizes.