Relatively few studies have addressed insects as part of ecosystem conservation or restoration projects. Some endangered insects, such as the Fender's blue butterfly, Icaricia icarioides fenderi, and American burying beetle, Necrophorus americanus, are targets for conservation or restoration efforts (M. Wilson et al. 1997). However, insects also can affect the success of conservation or restoration projects focused on other species or integrated communities.
Loss of key species or functional groups would jeopardize ecosystem integrity and lead to degradation. Xylophages may be particularly threatened as a result of deforestation, forest fragmentation, and conversion of landscapes dominated by old forests with abundant woody litter to landscapes dominated by young forests with little woody litter accumulation. Numerous wood-boring species became extinct as a result of deforestation of Europe during the past 5000 years (Grove 2002). Loss of specialized pollinators or seed dispersers as a result of habitat fragmentation also would threaten the survival of plant mutualists (Powell and Powell 1987, Somanathan et al. 2004, Steffan-Dewenter and Tscharntke 1999). Ants and ground beetles (Carabidae) are important predators in many ecosystems but are sensitive to changes in ecosystem condition, potentially undermining their role as predators (A.Andersen and Majer 2004, Niemela and Spence 1994, Niemela et al. 1992). Such groups should be identified for inclusion in conservation or restoration efforts.
Restoration goals need to address the appropriate historic conditions. For example, clearcut harvest and replanting of ponderosa pine, Pinus ponderosa, or Douglas-fir, Pseudotsuga menziesii, in western North America reflected the early perception of fire as a stand replacing disturbance that burned the forest and created a mineral soil seed bed necessary for establishment of even-aged forest. The resulting even-aged monocultures have supported nearly continuous insect outbreaks as the forests age. More recent research following natural fires in the region demonstrated more complex effects of fire, with patches of surviving trees intermingled with patches burned to mineral soil, resulting in uneven-aged forest structure as forest expanded from the refuges. Consequently, restoration efforts currently focus on thinning and prescribed fire to produce uneven-aged forest structure, and wider tree spacing, often aided by insects (J. Stone et al. 1999). At the same time, restoration of these forests to uneven aged, more widely spaced trees, maintained by a restored low-intensity fire regimen, should improve tree physiological condition and reduce the likelihood of future insect outbreaks (Kolb et al. 1998).
Restoration also requires attention to critical site conditions. Planted seedlings may be insufficient for forest restoration on harsh sites. Amaranthus and Perry (1987) demonstrated that transfer of biologically active soil (containing invertebrates and microorganisms necessary for maintenance of soil fertility) from established conifer plantations significantly increased the survival and growth of seedlings on clearcut harvested sites by up to 50% compared to seedlings planted directly into clearcut soils from which soil biota had disappeared as a result of overstory removal and exposure to heat and desiccation. Similarly, flooding a depression may not be sufficient for wetland restoration. Attention to water flux and predisposing substrate conditions may be necessary for reestablishment of wetland vegetation. For example, S. C. Brown et al. (1997) found that transplantation of wetland soil resulted in significantly faster and more prolific plant growth and macroinvertebrate colonization. Insects often serve as useful indicators of ecosystem conditions and restoration success (A. Andersen and Majer 2004).
Second, restoration of some ecosystems requires attention to insect mutual-ists necessary for reproduction and survival of target species. Research on the ecology of pollination and seed dispersal has demonstrated the critical role insects play in the persistence of understory and sparsely distributed plant species (Chapter 13). If necessary pollinators or seed dispersers disappear in isolated refuges (e.g., Fig. 13.3), other means must be found to ensure reproduction and recruitment of target plant species. For example, evaluation and promotion of alternate pollinators or seed dispersers may be necessary, recognizing that such species may be less efficient than those that co-evolved with a particular plant species.
Finally, restoration success can be threatened by invasive species. Invasive plants can outcompete target plants, requiring consideration of insect herbivores as biological control agents. Invasive insects also can create problems. For example, red imported fire ants, Solenopsis invicta, negatively affect populations of ground-nesting birds, small mammals, and reptiles and can discourage larger animals from entering infested areas (C. Allen et al. 2004). Introduced diseases, such as insect-vectored plague and West Nile virus, can decimate wildlife populations (Marra et al. 2004, Stapp et al. 2004), requiring consideration of tactics to reduce vector or pathogen abundance to ensure successful conservation or restoration of vulnerable species. At the same time, invasive species are not necessarily detrimental to restoration efforts and may, in some cases, contribute to restoration success (Ewel and Putz 2004).
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