Amphibian conservation in an urban park : a spatial approach to quantifying threats to Anura on the Cape peninsula

Thesis (MSc)--Stellenbosch University, 2017.

ENGLISH ABSTRACT: Species’ threat assessments produce generalized threat impact scores, often by considering regional-scale representations of threats. Cities, on the other hand, produce municipal-scale, high resolution data that are proxies for threats; furthermore, cities in mega-diverse regions are home to a high number of threatened species. Prioritization of conservation action is biased for where more information is known (about the ecosystem), and where a positive outcome can be anticipated. Eight Cape peninsula amphibian species have a threatened conservation status. They are isolated on highlands or are restricted to remnant and suburban habitats, dependent on both urban and protected terrestrial and freshwater habitats found in the City of Cape Town and Table Mountain National Park. In Chapter Two, I used spatial data (shapefiles) to represent threats in a Geographic Information System to spatially define threats to eight amphibian species (five lowland, three upland). I used two approaches: weighted and un-weighted by a threat impact-score, to produce five indices of local threats. The Micro Frog (Microbatrachella capensis) is assessed as the most threatened peninsula frog species by three of the five indices considered. The results show that for lowland species, the threat-class of greatest extent is ‘Residential and commercial development’. The three lowland species most exposed to this threat are M. capensis (100% exposed to potential development), Breviceps gibbosus (55.6% of its 8.5 km2 putative peninsula distribution), and Sclerophrys pantherina (38.4% of its 199.7 km2 distribution). The Compounded and the General Threat Index correlate to the (global) Redlist Index (P < 0.05); but no correlation to the regional Red Listing, indicating congruency of threats and threat status. The Critically Endangered Table Mountain Ghost Frog (Heleophryne rosei) is torrent adapted, and found only on the Table Mountain massif. CapeNature monitors tadpoles, and SANParks monitors (selected) stream parameters. In Chapter Three, I analyse water-habitat monitoring data (controlled for altitude) to show where threats of habitat alteration, drought, or temperature extremes may affect the H. rosei metapopulation. Permanence of water-flow and water temperature are shown to be very highly significant predictors of tadpole presence (p = 0.0005, r = 0.78). The lower the water temperature, the more likely tadpoles are present. Streams with a mean summer temperature greater than 17.2°C (n=3) at 400 to 300 meters above sea level were found to have no tadpoles at this altitude. Permanence of water flow is significant, as tadpoles need more than one year to reach metamorphosis. Summer water temperatures over an average of 17.2°C should be a red-flag for management authorities responsible for bulk-water supply, threat mitigation efforts, and biodiversity conservation. Spatial indices of threat are useful to illustrate the relative exposure to threats at a local (city) scale. Threats to different lowland amphibians are similar (e.g. residential and commercial development), which varies from the mutual threats to different upland amphibians. Fundamental to stream species’ conservation is water supply and demand management, while upland terrestrial species are most affected by veld age and invasive alien flora. Some threats are common for both areas (e.g. invasive alien species). Key words: Threat impact score, threatened areas, GIS, habitat loss, amphibians, Table Mountain National Park, Cape Town, environmental water requirement, water temperature, habitat.

AFRIKAANSE OPSOMMING: Spesies bedreigingsassesserings produseer algemene bedreigingsimpakte, dikwels deur die oorweging van streeksskaalse voorstellings van bedreigings in ag te neem. Stede, aan die ander kant, produseer munisipale skaal, hoë resolusie data wat voorstellings vir bedreigings bied. Daarbenewens is stede in mega-diverse gebiede die tuiste van 'n groot aantal bedreigde spesies. Agt Kaapse skiereiland amfibiese spesies het 'n bedreigde bewaringsstatus. Hulle is geïsoleerd op hooglande of beperk tot residensiële en voorstedelike habitats, afhangende van beide stedelike en beskermde land- en varswaterhabitats wat in die Stad Kaapstad en Tafelberg Nasionale Park gevind word. In Hoofstuk twee word ruimtelike data (Shapefiles) gebruik om bedreigings in 'n geografiese inligtingstelsel voor te stel om bedreigings vir agt amfibiese spesies (vyf laaglande, drie hooglande) ruimtelik te definieer. Twee benaderings word gebruik: geweegde en ongeweegde deur 'n bedreigingsimpak-telling om vyf indekse van plaaslike bedreigings te produseer. Die mikro padda (Microbatrachella capensis) word beskou as die mees bedreigde skiereiland padda spesies deur drie van die vyf indekse wat oorweeg word. Die resultate toon dat vir laaglandspesies die bedreigingsklas die grootste mate 'Residensiële en kommersiële ontwikkeling' is. Die drie laaglandse spesies wat die meeste bedreig word, is M. capensis (100% blootgestel aan potensiële ontwikkeling), Breviceps gibbosus (55,6% van sy vermeende skiereiland verspreiding van 8.5 km2) en Sclerophrys pantherina (38,4% van sy verspreiding van 199,7 km2). Die saamgestelde en die algemene bedreigingsindeks korreleer met die (globale) Redlist Indeks (P <0.05), maar daar is geen korrelasie met die plaaslike Redlist, wat dui op kongruensie van bedreigings en bedreigingsstatus. Die kritiek bedreigde Tafelberg spook padda (Heleophryne rosei) is aangepas tot vining vloeiende water, en word net op die Tafelberg-massief gevind. CapeNature moniteer padda vissie getalle, en SANParke moniteer geselekteerde water kwaliteit stroomparameters. In hoofstuk drie, ontleed ek water-habitat monitering data (beheer vir die hoogte) om te wys waar bedreigings van habitat verandering, droogte of temperatuur uiterstes die metapopulasie van H. rosei kan beïnvloed. Permanensie van watervloei en watertemperatuur word getoon as baie hoogs betekenisvolle voorspellers van die teenwoordigheid van die padda vissies (p = 0.0005, r = 0.78). Hoe laer die watertemperatuur, hoe meer waarskynlik is die teenwoordigheid van padda vissies. Strome met 'n gemiddelde somertemperatuur van meer as 17.2°C (n = 3) by 400 tot 300 meter bo seespieël het gevind dat daar geen padda vissies op hierdie hoogte is nie. Permanensie van watervloei is beduidend, aangesien padda vissies meer as een jaar nodig het om metamorfose te bereik. Somerwatertemperature oor 'n gemiddelde van 17.2°C moet 'n rooi vlag wees vir bestuursowerhede wat verantwoordelik is vir grootmaatwatervoorsiening, bedreigingsbeperkingspogings en biodiversiteitsbewaring. Ruimtelike indikse van bedreiging is nuttig om die relatiewe blootstelling aan bedreigings op 'n plaaslike (stad) skaal te illustreer. Bedreigings vir verskillende laerlandse amfibieë is soortgelyk (bv. Residensiële en kommersiële ontwikkeling), maar wissel van die onderlinge bedreigings vir verskillende amfibieë in hoërliggende gebiede. Fundamenteel tot die bewaring van varswater spesies is die bestuur van watervoorsiening en -aanvraag, terwyl die veldleeftyd en indringerplante die grootste invloed het op hoogliggende spesies. Sommige bedreigings is algemeen vir beide gebiede (bv. Indringerplante). Sleutelwoorde: Bedreigingsklas, bedreigde gebiede, GIS, habitatverlies, amfibieë, Tafelberg Nasionale Park, Kaapstad, omgewingswatervereiste, watertemperatuur, habitat.