Browsing by Subject "Urbanisation"

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    Current patterns of habitat transformation and future threats to biodiversity in terrestrial ecosystems of the Cape Floristic Region, South Africa
    (2003) Rouget, Mathieu; Richardson, David M; Cowling, Richard M; Lloyd, J Wendy; Lombard, Amanda T
    The formulation of an effective strategic plan for biodiversity conservation in the Cape Floristic Region (CFR) requires an assessment of the current situation with regard to habitat transformation, and an explicit framework for predicting the likelihood of remaining habitat (i.e. that potentially available for conservation) being transformed. This paper presents the results of a detailed assessment of the current and future extent of three important factors that threaten biodiversity in the CFR: cultivation for intensive agriculture (including commercial forestry plantations), urbanisation, and stands of invasive (self-sown) alien trees and shrubs. The extent of habitat transformation was mapped at the scale of 1:250,000, using primarily satellite imagery. We compared models derived from a rule-based approach relying on expert knowledge and a regression-tree technique to identify other areas likely to be affected by these factors in future. Cultivation for agriculture has transformed 25.9% of the CFR and dense stands of woody alien plants and urban areas each cover 1.6%. Both models predict that at least 30% of the currently remaining natural vegetation could be transformed within 20 years. There was an overall accuracy of 73% between both models although significant differences were found for some habitat types. Spatial predictions of future agriculture threats derived from the rule-based approach were overestimated relative to the statistical approach, whereas future alien spread was underestimated. Threat assessment was used to derive conservation targets for subsequent stages of conservation planning for the CFR. The importance of integrating vulnerability knowledge into conservation planning is discussed. The choice of vulnerability analysis (future habitat degradation and/or impact on biological entities) and methods will depend on the complexity of the threatening processes and the availability of spatial data.
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    Is multiple nest building an adequate strategy to cope with inter-species nest usurpation?
    (2016) Sumasgutner, Petra; Millán, Juan; CURTIS, ODETTE; Koelsag, Ann; AMAR, ARJUN
    Abstract Background Black sparrowhawks (Accipiter melanoleucus) recently colonised the Cape Peninsula, South Africa, where the species faces competition for their nest sites from Egyptian geese (Alopochen aegyptiaca) which frequently usurp black sparrowhawk nests. In this paper, we test the hypothesis that multiple nest building by black sparrowhawks is a strategy to cope with this competitor, based on a 14-year long term data set. Results Two main results support the hypothesis: first, the numbers of intact nests per breeding season in black sparrowhawk territories increased as levels of geese interactions increased, specifically when usurpation occurred. Usurpation occurred significantly more often at nests later in the season, and may provide a further explanation for the advancement of the black sparrowhawk breeding season towards earlier breeding attempts which results in an overall extension of the breeding period (over 9 months) that has been found in our study population. Second, nest usurpation had a negative impact on black sparrowhawks’ reproductive performance at the ‘nest’ level, but not at the ‘territory’ level when multiple nests were available within the same breeding season, suggesting that this strategy was effective for dealing with this competitor. However, our results do not rule out long term negative consequences of these interactions, for example, reduced adult survival rates or reduced lifetime reproductive success, due to the higher energy demand required to build several nests each breeding season. Conclusions Our results suggest that black sparrowhawks avoid direct conflict with this large and aggressive competitor and instead choose the passive strategy in allocating more resources to multiple nest building. Our research further highlights the importance of behavioural plasticity, which might be especially important for city-dwelling species in the face of global urbanisation.
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    Urbanisation in Botswana: social intercations among the residents of Broadhurst, Gaborone
    (2004) Lesetedi, Gwen N; Lincoln, David
    This study examines the extent of social interaction among the residents of the Broadhurst area of Gaborone.