Quat. Int. 173-174, 153–160 (2007)

Credit: Clive Carter

Spruce trees in Britain face threats from human development and pests. A new study shows that climate change may be giving one particular insect pest an upper hand.

In the UK, infestations of the green spruce aphid (Elatobium abietinum) have resulted in large losses of spruce foliage and height both during the active infestation and in subsequent years. Angus Westgarth-Smith at Brunel University and colleagues analysed the timing of spring aphid flight period and changes in population size over the last four decades. For 41 years, insects were collected daily in a large suction trap located about 30 kilometres north of London. Over this period, the average number of aphids and length of time they were drinking plant sap increased steadily.

The largest populations and earliest onsets of aphid activity were associated with years with a positive North Atlantic Oscillation (NAO) index. Positive NAO values correspond to warmer atmospheric conditions over Britain. Global warming is thought to increase NAO variability, shifting the system to more positive values. This will probably increase aphid activity, further harming the spruce population.