Doctoral Degrees (Conservation Ecology and Entomology)

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Browsing Doctoral Degrees (Conservation Ecology and Entomology) by Author "Bredenhand, Emile"

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    Development of a Biotope Quality Index
    (Stellenbosch : Stellenbosch University, 2014-04) Bredenhand, Emile; Samways, Michael J.; Stellenbosch University. Faculty of AgriSciences. Dept. of Conservation Ecology and Entomology.
    ENGLISH ABSTRACT: As the world’s human population increases, more pressure is placed on the management of natural resources. In response, we need an efficient means of monitoring, not only the quantity of these resources but also their quality. No comprehensive standard metric has been developed to assess environmental quality of a biotope, or to define the nature and extent of environmental degradation at this spatial scale. Currently in conservation management, various landscapes are being evaluated for spatial heterogeneity, by making use of species surrogates such as species richness, relative abundance, diversity indices and phylogenetic indices, as well as environmental surrogates. These values are then used towards conservation, where those systems with high intrinsic heterogeneity are usually considered more important than those with low heterogeneity at least when given the choice between the two. Yet, the actual quality of the biotopes within the landscapes is rarely taken into consideration. This study therefore develops and tests a Biotope Quality Index (BQI) to study this point in depth. The BQI makes use of arthropod assemblages as bioindicators of the level of disturbance within a biotope. Firstly, I summarize the literature on the concept of environmental health, and define it as “An ecosystem is healthy, if it can sustain an optimal number of species with optimal population sizes and their ecological processes, thus providing and optimal heterogeneous sustainable system with sufficient resources, and indicated adequate resistance when under perturbational stress, but still allowing natural succession to take place” Against this background, I then review the use of certain Arthropoda as bioindicators, as arthropods are small, mobile, environmentally sensitive, easily sampled, and readily available. These features together make arthropods good subjects for testing the BQI. I then compare the BQI with diversity indices currently used as surrogates of biotope quality. The outcome was that the BQI stood out as a significantly better indicator than the currently available indices for assessing environmental quality of a biotope. Furthermore, during the selection process, I also tested the use of guilds for BQI evaluation, and found that the scavenger (represented by Formicidae) and decomposer (represented by Collembola) guilds were the most significant. The effect of seasonality was also tested. I found the best results with the BQI were when data are pooled from all seasons of the year. A case study, making use of the BQI evaluation, was conducted at a site in the Cape Floristic Region, South Africa (Jonkershoek Valley). BQI results suggested that the agricultural management and tourism within the locality might have an effect on biotope quality. This study has shown that use of the BQI is a useful and practical management tool for evaluating environmental quality of a biotope towards conservation management.