Using species distribution models for spatial conservation planning of African Penguins

Geldenhuys, Frieda (2018-03)

Thesis (MSc)--Stellenbosch University, 2018.

Thesis

ENGLISH ABSTRACT: The African penguin Spheniscus demersus inhabits the south-western coast of Africa, between Namibia and Algoa Bay, near Port Elizabeth, South Africa, with the largest colony consisting of about 44% of South Africa’s penguins, found on St. Croix Island. The penguin population is currently at about 2% of the level it was in the 1900s, and is still continuing its strong downward population trajectory. The decrease in the population of African penguins is an early warning indicator of environmental threats, thus studying the factors that affect it is important. The African penguin has been declared Endangered on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species. Due to their population decrease, immediate conservation action is required to prevent this species’ extinction. An understanding of the dynamics and causes of this decrease, is thus of critical importance. The aim of this study is to better understand the effects of drivers of change on the African penguin colonies. The establishment of a sustainable management plan for the African penguin species, by consolidating different approaches, has been investigated. Studies indicate that the drivers of change in the population size include climate change, parasites, pollution (oiling), disease, lack of food resources, predation risk and habitat interference. A large component of this is the anthropogenic impact, especially with human population expansion. As a result of this, ecological traps or scenarios in which organisms settle in habitats of poor quality, due to rapid environmental change, emerge. For example, high plankton populations could indicate high fish populations in an area, although this indicator may be incorrect if the fish have been harvested. This area may thus be an ecological trap for penguins. It is important, for conservation purposes, to be able to identify the ecological traps and differentiate them from sinks or low quality habitats that, on their own, would not have the resources to support a population. The information required to assess the consequences of ecological traps was investigated. Of particular concern are the shifting distributions of forage fish, which may result in a spatial mismatch between the main penguin breeding colonies and their preferred prey. The foraging range of penguins during the breeding season is particularly limited, as foraging trips typically last less than one day. Spatial closures, in the form of marine protected areas, as well as those that permanently prohibit fishing, termed no-take reserves, can be used to manage the fishing effort, and in complementing alternative controls such as quota management. Species Distribution Models (SDMs) have been established in response to these challenges. These are predictive, conceptual models of the abiotic (e.g. physical barriers, climate, lack of resources) and biotic (e.g. competition, predators, parasites) factors influencing the role of habitat suitability in affecting the distribution of species in terms of space, time and scale. To begin with, the demography of the African penguin has been investigated. Thereafter, the modelling method has been described. R statistical programming language has been used to create the SDMs, from the colony location inputs and corresponding environmental data. The Maximum Entropy algorithm used 5 environmental, non-correlated variables and presence-only records (from 33 colonies). The relative contributions of environmental variables, which are ecologically relevant to the species habitat suitability, indicate that sea surface temperature is the largest contributing factor, with 72.4% for annual, 53.2% for summer and 46.9% for winter factors. The second largest contributor for all seasons is mean land temperature. The outputs of this study act as a baseline assessment. Possible areas to relocate or establish African penguin colonies, based on their prey availability, include the old De Hoop colony (which went extinct in 2006) and a site near Plettenberg Bay (which would be a completely new site), according to BirdLife. Camera traps for checking predators, have been in place since November 2016. From this study, it is clear that ongoing research is necessary, mainly due to the shifting distribution of prey, which is caused by climate change and overfishing, in order to model the African penguin colonies. Keywords: African penguins, Conservation, Species Distribution Models, Suitability Maps

AFRIKAANSE OPSOMMING: Die Afrika pikkewyn Spheniscus demersus bewoon die suid-westelike kus van Afrika, tussen Namibië en Algoa Baai, naby Port Elizabeth, Suid-Afrika, waar die grootste kolonie bestaan uit omtrent 44% van Suid Afrika se pikkewyne, te vinde by St. Croix Eiland. Die pikkewyn bevolking is tans ongeveer 2% van die vlak wat dit was in die 1900s, en is steeds op ’n sterk afwaartse bevolkingstrajek. Die afname van die bevolking Afrika pikkewyne is ’n vroeë waarskuwings-aanwyser van omgewings-bedreigings. Dus is die bestudering van faktore wat dit beïnvloed baie belangrik. Die Afrika pikkewyn is nou geklassifiseer as Bedreig op die Internasionale Unie vir die Bewaring van die Natuur (IUBN) Rooi Lys van Bedreigde Spesies. Weens hul bevolkingsafname word onmiddellike bewarings-aksies vereis om hierdie spesie se uitsterwing te verhoed. ’n Begrip van die dinamika en oorsake van hierdie afname, is dus van kritieke belang. Die doel van die studie is om die uitwerking van die aandrywers van verandering op die Afrika pikkewyn kolonies beter te verstaan. Die vestiging van ’n volhoubare bestuursplan vir die Afrika pikkewyn spesie, deur van verskillende benaderings gebruik te maak, is ondersoek. Studies dui daarop dat die aandrywers van hierdie verandering in bevolkingsgrootte, insluit klimaatsverandering, parasiete, besoedeling (met olie), siekte, gebrek aan voedselbronne, roofdier vyande risiko en habitat inmenging. ’n Groot komponent hiervan is die antropogeniese impak, veral met die menslike bevolkingsaanwas. As gevolg hiervan, ontstaan ekologiese slagysters of scenarios waar organismes gaan bly in habitats wat van swak gehalte is, weens die vinnige omgewingsverandering. Byvoorbeeld, hoë plankton bevolkings kan ’n aanwyser wees dat daar hoë visbevolkings in ’n spesifieke area behoort te wees, maar hierdie aanwyser kan verkeerd wees as die vis grootliks ge-oes is. So ’n gebied kan dus ’n ekologiese slagyster vir pikkewyne wees. Dit is belangrik vir bewaringsdoeleindes, om in staat te wees om ekologiese slagysters te identifiseer en om hul te onderskei van sinkgate of lae gehalte habitats wat, op hul eie, nie die hulpbronne sou hê om ’n bevolking te onderhou nie. Die informasie was benodig word om die gevolge van die ekologiese slagysters te evalueer, is bestudeer. Van besondere belang is die veranderende verspreiding van prooivis, wat tot gevolg kan hê dat daar ’n verkeerde ruimtelike paring is tussen die hoof pikkewyn broeikolonies en hul voorkeur prooi. Die jag reikwydte van pikkewyne gedurende die broeiseioen is besonder beperk, aangesien jag uitstappies tipies korter as een dag is. Ruimtelike sluitings, in die vorm van mariene beskermde areas, sowel as daardie gebiede wat visvangs permanent verbied, genoem geen-vangs reservate, kan gebruik word om visvangpogings te bestuur, wat dan alternatiewe beheermatreëls soos voorgeskrewe kwotas kan aanvul. Spesies Distribusie Modelle (SDMs) is opgestel in reaksie op hierdie uitdagings. Hierdie is voorspellende, konseptuele modelle van die abiotiese (bv. fisieke versperrings, klimaat, gebrek aan bronne) en biotiese (bv. kompetisie, roofvyande, parasiete) faktore wat die rol van habitat geskiktheid beïnvloed deur die verspreiding van die spesies te raak in terme van ruimte, tyd en skaal. Om mee te begin, word die demografie van die Afrika pikkewyn ondersoek. Daarna word die modelleringsmetode beskryf. R statistiese programmeringstaal gebruik om die SDMs te skep, vanuit die kolonie ligging invoere en ooreenkomstige omgewingsdata. Die Maksimum Entropie algoritme gebruik 5 omgewing, nie-korrelerende veranderlikes en teenwoordigheid-alleen rekords (van 33 kolonies). Die relatiewe bydraes van omgewingsveranderlikes, wat ekologies relevant is tot die spesie habitat geskiktheid, dui aan dat see oppervlak temperatuur die grootste bydraende faktor, met 72.4% vir jaarliks, 53.2% vir somer en 46.9% vir winter faktore is. Die tweede grootste bydraer vir alle seisoene is gemiddelde landstemperature. Die resultate van die studie kan beskou word as ’n basislyn studie. Moontlike areas wat ondersoek word om die Afrika pikkewyn kolonies te verskuif of vestig, gebaseer op hul prooi beskikbaarheid, is die ou De Hoop kolonie (wat in 2006 uitgesterf het) en ’n area naby Plettenbergbaai (wat ’n totaal nuwe area sal wees), volgens BirdLife. Kamera lokvalle om die predatore te kontroleer is al geplaas vanaf November 2016. Uit hierdie studie sien ek dat deurlopende navorsing benodig word, veral as gevolg van die veranderende verspreiding van hul prooivis, wat veroorsaak word deur klimaatsverandering en oorbevissing, om die Afrika pikkewyn kolonies te modelleer. Sleutelwoorde: Afrika pikkewyne, Bewaring, Spesies Verspreiding Modelle, Geskiktheidslandkaarte

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