Consequences of eliminating aerial access samples from surveys of forest defoliators in coastal British Columbia

Abstract

Larval populations of forest defoliators in British Columbia are assessed at least once each year by beating trees at scattered permanent sampling stations. These data are supplemented by additional, randomly selected samples. Most stations are reached by road, but aircraft are used to reach some roadless areas. Recently, to economize, large blocks of aircraft access permanent sampling stations were dropped. To learn how this affected the estimates of overall population numbers, we compared past records determined with and without aerial samples and with and without random samples. The northern mainland coast and the west coast of Vancouver Island were selected as test sites. In most instances, defoliator populations as measured at aerial and ground access permanent sampling stations and by random samples rose and declined together, indicating that estimates of population trend would not be seriously affected by dropping aerial and random samples.