Technical Reviews

Restoration ecology and conservation biology in agriculture (PART I)

Robert L. Bugg

[Note: Part 2, focusing on birds, will appear in Sustainable Agriculture, Vol. 14, No. 1, Winter/Spring 2002.]

The expansion of agriculture has often been at the expense of wildlands, native plants, and wildlife (Gall and Orians 1992, Gall and Staton 1992, Merenlender 2000), yet farms and ranches can be managed such that the impact is lessened. This review covers the basics of restoration ecology and conservation ecology.

For many years, the Natural Resource Conservation Service (formerly known as the Soil Conservation Service) has promoted windbreaks, grassed waterways, tailwater ponds, and other on-farm features that support wildlife (consult Journal of Soil and Water Conservation). Conover (1998) polled 2000 U.S. farmers nationwide on their experience and opinions concerning on-farm wildlife. Twenty-four percent of the 1,347 respondents were reluctant to establish wildlife habitat because of potential damage to crops, while 38 percent of respondents said that they would oppose creation of wildlife refuges near their farms. Farmers noted that damage was especially severe from mammals such as deer, raccoons, and coyotes. Despite these perceived problems, 51 percent of respondents reported that they modified their management to accommodate wildlife, including providing cover for wildlife near fields (39%), providing a water source (38%), leaving crop residue in the field (36%), leaving some crop unharvested (17%), and providing salt licks (12%). Given the willingness of many farmers to alter their practices, there appears to be continuing opportunity to implement on-farm restoration ecology and conservation biology.

The experience of The Nature Conservancy in its Sacramento River Project points up the major role that farmers can play in restoring native vegetation to riparian corridors that adjoin farms, and the importance of in-field management changes to conserve and enhance native bird species (Dawit Zeleke, personal communication). A challenge lies in providing economic incentives and infrastructural support to allow landowners to accommodate, maintain, and enhance or restore ecological parameters on the landscape.

Overview of biodiversity, related sub-disciplines of ecology

Biodiversity refers to the variety of life, but has often mistakenly been equated with species diversity. Franklin (1988) and Noss (1990) depicted a more comprehensive view of biodiversity that encompasses dimensions of composition, structure, and function, and their interaction. Noss (1990) outlined the hierarchies involved in the three main categories of composition, structure, and function:

1. Composition
   1. Landscape Types
      1. Communities, Ecosystems
         1. Species, Populations
            9. Genes
2. Structure
   1. Landscape Patterns
      1. Physiognomy, Habitat Structure
         1. Population Structure
            9. Genetic Structure
3. Function
   1. Landscape Processes, Disturbances; Land-Use Trends
      1. Interspecific Interactions, Ecosystem Processes
         1. Demographic Processes, Life Histories
            9. Genetic Processes

Composition can be assessed through simple species lists from farmland and adjoining wildlands. Structure could be evaluated, for example, through an age-class assessment of wildlands vegetation or a map showing spatial distribution of species of birds. Function would be addressed by a table or figure depicting diets of various birds found on a farm and their use of various habitats on and off the farm. Function would also be addressed by research that determined the roles of various organisms in soil-building and nutrient dynamics on farms. The biodiversity concepts above are interrelated with several subdisciplines and themes, including restoration ecology, conservation biology, landscape ecology, bioindication, target taxa in biological inventories, and ecosystem services, all discussed in brief below.

Restoration ecology may be defined as repair and management of native biodiversity, including composition, structure and function, in a given area. Single or multiple species may be targeted, but typically the emphasis is on complexes of species, based on historical knowledge or speculation about past native communities. Restoration ecology draws on a broad array of experience, knowledge sets and cultural perspectives. Where farmers and managers of forest and rangeland are involved in practical restoration ecology, it can be an important part of active management and can enhance the economic as well as environmental sustainability of the operations.

Conservation biology concerns the maintenance of existing populations of organisms. Ideally, conservation biology and restoration ecology should function in tandem. These fields, as applied in agricultural settings, include but are not limited to in-field management changes to protect sensitive migrant and year-round resident species, riparian zone enhancement, protection of adjoining wildlands, roadside and fieldside native revegetation, and management of hedgerows and windbreaks.

The subdisciplines of restoration ecology and conservation biology were reviewed and compared by Young (2000). Restoration ecology has been mainly botanically oriented to date, emphasizing small-scale, replicated, manipulative experiments on re-establishment of native plants from areas in which they have been removed. Several studies have concerned re-establishment of native plants on the edges of farms (Bugg et al. 1997, Bugg et al. 1998, Brown and Bugg 2001).

Conservation biology, by contrast, has focused on protection of existing habitats, communities, and populations. Modifying rice production practices to accommodate waterfowl would be an example of conservation biology in agriculture. In many cases, conservation biology has involved the development and management of natural preserves and has focused on so-called charismatic species that attract much public interest, such as certain large mammals.

Landscape ecology relates geographic features and their modification to behavior, distribution, dispersal, interaction, and survival of species. Concepts of special interest in this field are corridors, connectivity, patchiness, patch size, fine- vs. coarse-grain interspersion of different habitat types (mesh size), mobility, and territoriality. Habitat fragmentation may impair biological control of agricultural pests (Kruess and Tscharntke, 1994), a point of special interest to organic farmers. Corridor and connectivity issues are still poorly researched and understood, as documented in Jodi Hilty’s doctoral dissertation (Hilty, in prep.). Usher and Keiller (1998) found that configuration of restored woodlands on organic farms significantly influenced the diversity and abundance of geometrid moths that use understory forest plants as hosts. More compact woodlands were superior to linear woodlands in this respect.

Bioindication is the assessment of population changes in one or a few, select species to infer effects of various practices and pollutants on larger organismal complexes or communities. Bioindicator species are much better understood for freshwater aquatic than for terrestrial systems. The use of arthropod bioindicators in agricultural systems has gotten little attention, although ants have been suggested as likely bioindicators (Peck et al. 1998). Amphibia have been suggested as especially sensitive to environmental perturbation, and several Californian amphibia are believed to be declining in part because of agricultural chemicals, especially organophosphorus insecticides (Davidson et al. 2001, Sparling et al. 2001). Perhaps such species could serve as bioindicators of agrochemical overuse.

A related theme is the use of species assemblages as indicators of environmental heterogeneity. Using multivariate statistics, Kremen (1992) found that butterfly assemblages in the rainforest of Madagascar were good indicators of environmental heterogeneity due to topographic/moisture gradient, of limited value in reflecting human-induced disturbance, and poor indicators of plant diversity. Target taxon analysis, a refinement of the above approach, uses species-rich, closely related groups of organisms to index environmental heterogeneity. This can streamline biotic inventories and aid in conservation planning. In Madagascar, Kremen (1994) found that species in the subgenus of Henotesia were as good or better than the entire butterfly fauna in reflecting various environmental gradients. Claire Kremen (personal communication) points out that this approach has yet to be widely tested or applied. In discussing criteria for indicator species, Hilty and Merenlender (2000) wrote that most vertebrates are mobile generalists with unknown environmental tolerances and correlations with ecosystem changes. Most invertebrate taxa lack known correlations to ecosystem changes, but may satisfy other criteria. However, inefficiencies can arise when higher invertebrate taxa comprising many species are often recommended, with varying attributes, and including superfluous species.

Ecosystem services are benefits that humans derive from native biota and the systems that comprise them (Daily, 1997). For example, the Forgotten Pollinators Campaign has centered on the roles of bees, bats, and other organisms in pollinating crops that are important to humans, and the preservation of wildlands to avoid losing or reducing these services (Buchman and Nabhan, 1996; see also Allen-Wardell et al. 1998).

For discussion of varied aspects of biotic diversity in agroecosystems, consult the special issue of Agriculture, Ecosystems and Environment edited by Paoletti and Pimentel (1992).

References Cited

• Allen-Wardell, G., P. Bernhardt, R. Bitner, A. Burquez, S. Buchmann, J. Cane, P.A. Cox, V. Dalton, P. Feinsinger, M. Ingram, D. Inouye, C.E. Jones, K. Kennedy, P. Kevan, H. Koopowitz, R. Medellin, S. Medellin-Morales, G.P. Nabhan, B. Pavlik, V. Tepedino, P. Torchio and S. Walker. 1998. The potential consequences of pollinator declines on the conservation of biodiversity and stability of food crop yields. Conservation Biology 12:8-17.
• Brown, C.S. and R.L. Bugg. 2001. Effects of established perennial grasses on introduction of native forbs in California. Restoration Ecology 9:38-48.
• Buchmann, S. L. and G. P. Nabhan. 1996. The forgotten pollinators. Island Press/ Shearwater Books, Washington, D.C./Covelo, Calif.
• Bugg, R.L., J.H. Anderson, C.D. Thomsen, and J. Chandler. 1998. Farmscaping: restoring native biodiversity to agricultural settings. Pp. 339-374 in: Pickett, C.H. and R.L. Bugg [Eds.], Enhancing biological control: habitat management to promote natural enemies of agricultural pests. University of California Press, Berkeley, CA.
• Bugg, R.L., C.S. Brown and J.H. Anderson. 1997. Restoring native perennial grasses to rural roadsides in the Sacramento Valley of California: establishment and evaluation. Restoration Ecology 5:214-228.
• Conover, M.R. 1998. Perceptions of American agricultural producers about wildlife on their farms and ranches. Wildlife Society Bulletin 26:597-604.
• Daily, G.C., ed. 1997. Nature's services: societal dependence on natural ecosystems. Island Press, Washington, DC.
• Davidson C., H.B. Shaffer and M.R. Jennings. 2001. Declines of the California red-legged frog: Climate, UV-B, habitat, and pesticides hypotheses. Ecological Applications 11(2):464-479.
• Franklin, J.F. 1988. Structural and functional diversity in temperate forests. Pp. 166-175 in: E.O. Wilson, ed. Biodiversity. National Academy Press. Washington, D.C.
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• Gall, G.A.E. and M. Staton. 1992. Integrating conservation biology and agricultural production - conclusions. Agriculture Ecosystems and Environment 42: 217-230.
• Hilty, J.A. in prep. The role of ecological corridors. In Wildlife Use of Riparian Corridors in the Oak Woodland and Vineyard Landscape. Ph.D. Dissertation, Department of Environmental Science, Policy, or Management. University of California, Berkeley. Berkeley, Calif.
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• Kremen, C. 1994. Biological inventory using target taxa: a case study of the butterflies of Madagascar. Ecol. Appl. 4:407-422.
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• Merenlender, A. M. 2000. Mapping vineyard expansion provides information on agriculture and the environment. California Agric. 54(3):7-12.
• Noss, R. 1990. Indicators for monitoring biodiversity: a hierarchical approach. Conserv. Biol. 4:355-364.
• Paoletti, M.G. and D. Pimentel. (Guest Editors). 1992. Biotic diversity in agroecosystems. Special issue of Agric. Ecosystems Environment. 40.
• Peck S.L., B. McQuaid and C.L. Campbell. 1998. Using ant species (Hymenoptera: Formicidae) as a biological indicator of agroecosystem condition. Environ. Entomol. 27:1102-1110.
• Santer, L. (Editor). 1995. BIOS for Almonds: A Practical Guide to Biologically Integrated Orchard Systems Management. Community Alliance with Family Farmers Foundation, Davis, California / Almond Board of California, Modesto, Calif.
• Sparling, D.W., G.M. Fellers and L.L. McConnell. 2001. Pesticides and amphibian population declines in California, USA. Environmental Toxicology and Chemistry 20(7):1591-1595.
• Usher, M.B. and S.W.J. Keiller. 1998. The Macrolepidoptera of farm woodlands: determinants of diversity and community structure Biodiversity and Conservation 7(6): 725-748.
• Young, T.P. 2000. Restoration ecology and conservation biology. Biol. Conserv. 92:73-83.