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Atmospheric CO2 and Sap-Feeding Herbivores
Docherty, M., Wade, F.A., Hurst, D.K., Whittaker, J.B. and Lea, P.J.  1997.  Responses of tree sap-feeding herbivores to elevated CO2Global Change Biology 3: 51-59.

What was done
Saplings of beech and sycamore were grown in glasshouses receiving atmospheric CO2 concentrations of 350 and 600 ppm.  During this exposure, groups of three sap-feeding aphid species and two sap-feeding leafhopper species were allowed to feed on the saplings to determine the effects of atmospheric CO2 enrichment on their feeding habits and growth responses.

What was learned
Overall, elevated CO2 had few significant effects on the feeding and performance of these insect herbivores.  There was, however, a non-significant tendency for elevated CO2 to reduce the individual weights and population sizes of aphids growing on CO2-enriched saplings.

What it means
As the atmospheric CO2 concentration increases, the feeding and growth patterns of sap-feeding insect herbivores - like aphids and leafhoppers - will likely be little affected.  Indeed, with respect to the aphid species, the authors concluded that "aphid populations on both beech and sycamore would not alter in response to any CO2-induced changes in plant quality."  Nonetheless, their data revealed non-significant CO2-induced reductions in individual aphid weights and population sizes, suggesting that future increases in the air's CO2 content might reduce feeding pressures on beech and sycamore saplings caused by these insect groups.

Reviewed 27 March 2002