Effect of Ecosystem Changes on Air-Borne and Vegetation-Dwelling Arthropods in Agu-Awka Area of Awka

By Animal Research International, University Of Nigeria, Nsukka.


Man often causes ecosystem changes due to activities such as agricultural clearing, rangeland grazing, urbanisation, road construction and mining (Majer and Beeston, 1996). Such activities can affect genetic diversity, species diversity and ecosystem diversity (WRI, IUCN and UNEP, 1992). Loss of biodiversity is a great problem of environmental and ecological consequences and humanity depends on biodiversity for fuel, food medicine and raw materials. The continuous removal of forests for various agricultural and industrial purposes has caused the loss and degradation of the primary tropical forests, leaving only man-made ones. This destruction causes extinction or loss of richness for those species whose habitats have been altered by man (Adebayo, 1995).
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The study on the impact of ecosystem changes on air-borne and vegetation-dwelling arthropods was carried out in the Agu-Awka area of Awka, Anambra State capital. Areas investigated were roadsides, cultivated agricultural, built-up, uncultivated agricultural and forest sites using the sweep net for arthropods on vegetation and the sticky trap for ar-borne flyng arthropods The forest site acted as control. Ecosystem changes from close forest to open environments reduced species richness for vegetation-dwelling arthropods but increased the species richness of ar-borne arthropods. For the vegetation-dwelling fauna, the forest site recorded 14 species while the disturbed built-up sites had only4 species. The differences between the sites were significant (P < 0.05). For the air-borne arthropods, there were no species in the forest while the highest number of species (7) was recorded in the uncultivated agricultural sites. The differences over the study sites for air-borne species were not significant (P > 0.05). The ecosystem change decreased significantly the species abundance of vegetation-dwelling arthropods fom 42 in the forest to 14 in the built-up sites (P < 0.05), while the species abundance of air-borne fauna was significantly increased from 0 in the forest to 43 in the uncultivated agricultural sites (P > 0.05). The species diversity for the vegetation-dwelling arthropods decreased significantly from 0.856 in the forest to 0.384 in the built-up sites (P < 0.05), while it increased significantly from 0.000 in the forest to 0.611 in the uncultivated agricultural sites for the air-borne arthropods (P < 0.05). For the vegetation-dwelling arthropods, 6 insect species and 6 spider species were dominant in the sites that had undergone environmental changes while 1 insect species and 3 spider species were dominant in the forest. For theair-borne fauna, no species was found in the forest while 7 insect species weedominant in the sites which had experienced ecosystem changes.


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