The Sand Lizard in the Amsterdam Water Supply Dunes: 20 years of monitoring. Since 1993, the Sand Lizard (Lacerta agilis) has been monitored on 28 transects in the Amsterdam Water Supply Dunes (AWD). These transects are visited 7 times a year as part of the National Monitoring Network for Reptiles. All adult and juvenile lizards are counted; counting only takes place when weather conditions are favourable. Since the official start of monitoring in 1994, volunteers have made 1436 visits during which they observed 8045 adult and sub-adult lizards and 740 juveniles. The indices calculated by Statistics Netherlands (CBS) using the TRIM software package, show a moderate increase in L. agilis in the AWD. Trends of Sand Lizard also increase in the rest of the dunes, on inland heaths, and in the Netherlands as a whole.