Another study linked infected forests with plantings from the Sweetwater Nursery in Waipoua Forest by the New Zealand Forest Service in the 1950s. The only forest that has been regularly monitored for kauri dieback using a scientifically peer reviewed methodology is the Waitākere Ranges. Between 2011 and 2016 the infection rate of kauri trees in the ranges doubled, from 8% to 19%. In the Waitākeres 58% of large areas of kauri ecosystem over 5 hectares have some state of infection.[16][17] An independent review of the epidemiology of the Kauri study, found that the Auckland data is of limited use if we want to conduct an analysis to identify factors associated with PTA being present.