Species assembly patterns and protected area effectiveness in times of change : a focus on African avifauna

Coetzee, Bernard Walter Thomas (2013-03)

Thesis (PhD)--Stellenbosch University, 2013.

Thesis

ENGLISH ABSTRACT: The challenge of conserving biodiversity is daunting. Despite some local conservation gains, most indicators of the condition of global biodiversity show declines since the 1970’s, while indicators of the threats to biodiversity all show increases. Humanity has in part responded to the global biodiversity extinction crisis by establishing protected areas (PA) and they are widely considered cornerstones of conservation. However, their efficacy in maintaining biodiversity is much debated. Previous studies have been unable to provide a general answer because of their typically restricted geographic and/or taxonomic focus, or qualitative approach. Using a global meta-analysis with 861 pairwise comparisons inside and outside PAs from 86 studies across five major taxon groups, I tested the hypothesis that PAs achieve significant conservation outcomes measured as higher biodiversity values compared with alternative land covers. I found that globally, PAs typically contain higher abundances of individual species, higher assemblage abundances and higher species richness. Variation in effect sizes among taxa nonetheless underscores that PA efficacy can be context specific. To examine factors driving the context specific nature of PA efficacy, an exact distance, timed point count methodology was used to assess PAs ecological effectiveness in terms of bird assemblages of the Kruger National Park (KNP), South Africa, in the Phalaborwa section. Bird assemblages inside the KNP were compared to matched sites in rural and urban land cover, as well as the connecting habitat matrix outside the KNP. Species richness and abundance were significantly lower inside the KNP compared to other land covers. However, the species assemblages are markedly different. The artificial addition of resources in an otherwise resources poor area, mainly in terms of gardening, provide suitable habitat for a range of species, consistent with the more individuals hypothesis. Large-bodied and ground nesting species are virtually absent outside the KNP. Thus species richness and abundance differences between land cover regions mask insidious changes in species traits. Nonetheless, not formally protected land can contribute positively to the regional biodiversity portfolio. Since an understanding of the mechanisms that structure species assemblages can aid in the consequences of anthropogenic drivers disentangling them, I describe and analyse the body size frequency distributions (BSFDs) of avian assemblages at several spatial scales in the Afrotropical biogeographic realm. I found that the African avifaunal continental BSFD is unimodal and right-skewed. African avifaunal BSFDs are quantitatively dissimilar to the African mammal BSFDs, which are bimodal at all spatial scales. Much of the change in median body size with spatial scale can be captured by a range-weighted null model, suggesting that differential turnover between smaller- and larger-bodied species might explain the shift in the central tendency of the BSFD. My results for the first time quantitatively demonstrate that PAs are a vital component of a global biodiversity conservation strategy. However, I also show that PA ecological effectiveness can be context specific, and understanding which species traits are at risk outside of PAs is critical to predicting their efficacy.

AFRIKAANSE OPSOMMING: Dit is ‘n uitnemende uitdaging om biodiversiteit te bewaar. Ten spyte van sommige sukses op ‘n lokale skaal, dui die meeste indikators aan dat die toestand van globale biodiveristeit afgeneem het vanaf die 1970’s, terwyl bedreigings daartoe toegeneem het. Die mensdom het gedeeltelik reageer op die biodiversiteits uitsterfings krisis deur die uiteensetting en instandhouding van bewaringsgebiede (BG). Hierdie metodiek word wêreldwyd geag as ‘n hoeksteen van bewaring. Die ekologiese doeltreffendheid van BG word egter baie debateer. Vorige studies was geografies beperk of het net op sekere takson groepe gefokus. Vorige studies is ook tipies statisties kwalitatief van aard. As gevolg daarvan het ek ‘n globale meta-analiese gebruik, wat bestaan het uit 861 gepaarde meetings vanaf 86 studies, oor vyf verskillende taksonomiese groepe. Ek het die hipotese getoets dat BG statisties beduidende bewaring laat gekiet in terme van hoër biodiveristeits waardes binnekant hul grense, in kontras met areas buite BG. Ek het gevind dat BG juis hoër waardes van hoër indivuduele spesies hoeveelhede, gemeenskaps hoeveelhede en spesiesrykheid bevat. Tog dui die variasie in effek grootte onder takson groepe aan dat BG effektiwiteit konteks spesifiek is. Aangesien BG effektiwiteit konteks spesifiek is, het ek verder ‘n tydstip, eksakte-afstand punttelling metodiek gevolg om die Kruger Nationale Park (KNP) in Suid Afrika, se ekologiese doeltreffendheid te bepaal. Ek het voëlgemeenskappe binne KNP vergelyk met voëlgemeenskappe buite KNP. Metings is buite die KNP gedoen in tuislande, die stadsgebied van Phalaborwa, asook in die habitat matriks wat die areas verbind. Beide spesiesrykheid en hoeveelheid is hoër buite KNP, maar die voëlgemeenskap struktuur tussen gebiede verskil noemenswaardig. Die uitbreiding van bronne ten opstigte van nesmaak en voeding (meestal deur tuinmaak), bied vir voëls goeie habitat in die stadsgebied, soos verwag kan word uit die meer individue hipotese. Hierdie veranderinge in spesiesrykheid tussen die verskillende areas versteek veranderinge in die spesies einskappe. Voëls met groot liggaamsmassa, veral die wat op die grond nes maak, kom in baie minder getalle voor buite KNP. Tog bied onbewaarde areas ‘n positiewe inpak tot die omgewing se biodiversiteit. ‘n Holistiese begrip van die meganismes wat spesies gemeenskappe struktureer kan help om die menslike invloed daarop uit te lig. Daarvolgens beskryf ek die liggaamsmassa frekwensie verspreiding (LMFV) oor verkillende skale in die Afrotropies biografiese streek. Ek het bevind dat Afrika se voëlgemeenskappe op die kontinentale skaal unimodaal en regs-geskewe is. Afrika se voël LMFV is beduidend verskillend van Afrika soogdier LMFV, wat bimodaal is op verskeie skale. Baie van die verandering in mediaan liggaams massa oor verskillende skale kan verduidelik word met ‘n verspreidings-aangepaste nul-model, wat voorstel dat die verskille in omset van voëls met of klein, of groot liggaamsmassa in die landskap die veranderings in LMFV verduidelik. My studie is die eerste van sy soort wat kwantitatief bepaal dat die gebruik van BG krities is tot ‘n globale bewaringsstrategie. Verder het ek bewys dat BG se ekologiese doeltreffendheid afhang van die kontkes op ‘n lokale skaal, en dat spesies eienskappe geïnkorporeer moet word om BG se doeltreffendheid te bepaal.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/79804
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