Conservation of invertebrates

Despite the great abundance and seemingly endless number of invertebrate species, they are vulnerable to human caused (anthropogenic) disturbance, potentially influencing invertebrate communities and the ecological services that they provide (Samways 2005). Like all animals invertebrates are interconnected with their environment through a complex food web, and changes in habitat quality and environment can result in population shifts, changes in community composition and structure, loss of functional diversity and species extinctions on a local or perhaps global scale.

There have been great species extinctions in the past, at least five since the Precambrian era (Wilson 1992). However, the loss of species today is related to human activities and is occurring at an alarming rate. Conservative estimates indicate that we will lose up to 20% of global biodiversity by the year 2022, and thereafter we may lose 50% of global biodiversity or more (Wilson 1992). Habitat fragmentation, habitat losses, invasion of exotic species, pollution, global warming, and many other human-induced disruptive phenomena will contribute to these species extinctions (Wilson 1992).

It is imperative that invertebrate biodiversity and the ecological services that invertebrates provide be conserved; for while invertebrates are subject to changes in their environment they in turn shape the environment. Loss of pollinator species may result in reduced seed set, reduced fitness and lower population viability of flowering plants. In specialized plant-pollinator systems, or in fragmented landscapes, the loss of pollinator species or changes in their populations can have serious consequences for the viability of plant species (Buchmann & Nabhan 1996).

Changes in invertebrate herbivore populations or community composition can have profound effects on plant communities. Invertebrate herbivores are relatively inconspicuous compared to vertebrate herbivores. However, they exert considerable top-down regulatory pressure on plant communities, sometimes consuming a significant proportion of plant matter relative to their vertebrate cousins, and thus transferring a significant amount of energy through the food web (Gandar 1982). In arid ecosystems and grasslands, intense herbivory by invertebrates may stimulate primary productivity by providing nutrient rich frass that becomes immediately available to plants (Milton 1995, Belovsky 2000). In contrast, in forest systems productivity may be enhanced or decreased depending on the intensity of herbivory (Schowalter 2000).

The identity and abundance of predator and parasitoid species may indirectly affect floral productivity or composition as a consequence of predation on herbivores. By reducing herbivore populations, primary productivity (plant growth) may increase, decrease or vary depending on which herbivore species are most affected. Such trophic cascades are common in food webs, with changes in upper or lower trophic levels resulting in cascading effects through the food web (Dodson et al. 1998). Consequently, above ground activities such as agricultural or timber production may affect the physical or chemical properties of soils which in turn may affect the invertebrate decomposer community. Earthworms burrow and facilitate water flow and storage, soil aeration, and root development. Soil microfauna, mesofauna and macrofuana help to break-down soil organic matter and recycle nutrients in ecosystems (Wardle 1995, Kladivko 200). Therefore, changes in the decomposer fauna may stimulate changes in the physical and chemical environment (Kladivko 2001) resulting in bottom-up effects on primary producers or higher trophic levels.

References

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J.A., Latchininsky, A.V. and Sergeev, M.G. (eds.), Grasshoppers and grassland health, pp. 7-29.

Kluwer. Dordrecht, The Netherlands. Buchman, S.L. and G.P. Nabhan. 1996. The forgotten pollinators. Island Press, Washington, D.C., USA.

Dodson, S.I., Allen, T.F.H., Carpenter, S.R., Ives, A.R., Jeanne, R.L., Kitchell, J.F., Langson, N.E. and Turner, M.G. 1998. Ecology. Oxford University Press. New York, NY.

Gandar, M.V. 1982. The dynamics and trophic ecology of grasshoppers (Acridoidea) in a South African savanna. Oecologia 54: 370-8.

Kladivko, E. J. 2001. Tillage systems and soil ecology. Soil and Tillage Research 61: 61-76.

Pimentel, D. 1975. Introduction. In Pimentel, D. (eds), Insects, Science & Society, pp. 1-10. Academic Press. New York, NY.

Price, P.W. 1997. Insect ecology. John Wiley and Sons, Inc., New York, NY.

Samways, M.J. 2005. Insect diversity conservation. Cambridge University Press, New York.

Speight, M.R., Hunter, M.D., and Watt, A.D. 1999. Ecology of insects: Concepts and applications. Blackwell Science Ltd, Oxford.

Wardle, D. A. 1995. Impacts of disturbance on detritus food webs in agroecosystems of contrasting tillage and weed management practices, pp. 105-185. In M. Begon and A. H. Fitter [eds.], Advances in Ecological Research. Academic Press, New York, NY.

Wilson, E.O. 1992. The diversity of life. Harvard University Press, Cambridge.