Invertebrates: Why They Matter
Invertebrates such as insects, spiders, snails and slugs comprise the lion's share (>90%) of all animal species found on earth and contribute greatly to global biological diversity and to the health of our environment (Samways 2005, Wilson 1991). Invertebrates and especially insects perform a disproportionate number of ecological functions (e.g. predation, herbivory, omnivory, detritivory, etc.) and consequently provide many beneficial services including plant pollination, seed dispersal, pest control, nutrient addition, decomposition of organic matter (e.g. dung and carrion) and nutrient cycling (Speight et al. 1999).
In some ecosystems insects have such influence over the biophysical characteristics of their environment that they are termed "ecosystem engineers" (Price 1997), redistributing vast quantities or soil or organic matter and thus shaping the landscape. This is not surprising given the biomass of invertebrates which often exceeds that of vertebrates by many fold (Pimentel 1975, Wilson 1991). The biomass of ants alone equals that of all humans.
Invertebrates move vast amounts of energy through food webs by providing food resources for fish, birds, bats, and other wildlife and biota including invertebrates. Hence, without invertebrates, food webs would likely consist of fewer trophic levels and fewer trophic linkages, and the world as we know it would simply cease to exist (Samways 2005)!