Ecological Impacts of Invasive Forest Insects

and Their Control Products: Which are Worse?

Dr D. Kreutzweiser - Canadian Forest Service, Natural Resources Canada, Sault Ste Marie.

• When: Wednesday Jan 23, 2013 at 12:00PM
• Where: Science Boardroom - N1046

Abstract:  The exotic invasive insect, emerald ash borer (EAB), is rapidly spreading through eastern North America and causing extensive mortality of ash trees. Many of these trees are in riparian (shoreline) areas that provide critical refuge habitats, movement corridors, and other ecological services including the support of a rich biodiversity and the protection of aquatic ecosystem health. We conducted microcosm experiments to test effects of systemic insecticides for control of EAB on non-target, leaf-decomposing organisms. We then designed field studies to compare a no-intervention option, to determine impacts of the insect pest on riparian forests and some of the ecosystem services they provide. Preliminary results indicate that EAB causes rapid and extensive mortality of all ash tree species in riparian areas. When ash trees compose about 30% or more of riparian forests, this mortality causes large and sudden canopy openings. Light penetration to forest floors is measurably increased, forest floor vegetation proliferates, incursions by invasive plants are about doubled, and nitrogen cycling in riparian soils is increased by about 4 times above baseline rates. Across our riparian plots, ash is always among the top 4 tree species contributing leaf litter to forest floors and adjacent water bodies, with an average contribution of 20% and ranging to 45%. Ash litter inputs have a distinct seasonal trend; always among the earliest inputs. Among litter from the 6 most common riparian trees, ash is preferred (decomposed) by aquatic invertebrates as first or second choice in selection microcosms. Further endpoints, including invertebrate communities on in-situ leaf packs with or without ash, are being assessed and will be reported. We show that risks posed by effective insecticides are quantifiable and manageable. Conversely, risks posed by the insect, if left unchecked, appear to threaten the ecological function of riparian forests in terms of canopy cover and shading, forest plant biodiversity, soil nitrogen cycling, leaf litter inputs, and the food web dynamics of adjacent water bodies, probably for several decades at least.

Bio: 

Dr. Kreutzweiser is a Research Scientist in aquatic ecology and ecotoxicology with the Canadian Forest Service (CFS) of Natural Resources Canada, and an Adjunct Professor in Biology at Laurentian University. He leads a research team at the CFS lab in Sault Ste Marie that investigates the ecological impacts of forest management activities and pesticides on aquatic ecosystems. His main focus is on understanding ecological linkages between forest watersheds and receiving waters, the susceptibilities and resilience of those linkages to disturbances, and the development of forest management policies and practices to mitigate potential harmful effects.