Human disturbance impact on shorebirds at Muizenberg Beach, South Africa, during and prior to the COVID-19 lockdown

Lewis, Jemma Elizabeth

Human disturbance impact on shorebirds at Muizenberg Beach, South Africa, during and prior to the COVID-19 lockdown

Master Thesis

2021

Abstract

The impact of humans on the natural environment has been so extensive that the scientific community has defined a new geological era: the Anthropocene. Coastal ecosystems rank amongst the most threatened of global habitats due to high urban human population density and demand for socio-ecological services provided by the coast. Sandy beach ecosystems are prominent constituents of coastal regions and sought after for their recreational value, but these systems are understudied relative to more charismatic marine habitats such as coral reefs and kelp forests. Human disturbance has been identified as one of the most serious threats to sandy beach ecosystems, but several knowledge gaps prevail, including its effects on shorebirds. The 2020 global COVID-19 pandemic resulted in a period of abnormally limited human mobility that has been coined the ‘anthropause'. In South Africa, a national lockdown commenced on 27 March 2020 and consisted of five levels to combat the pandemic. Specifically, lockdown levels 5, 4, and 3 did not permit human presence in public areas, including beaches. The aim of this study was to understand the impact of human disturbance during and prior to the COVID-19 lockdown on shorebird abundance and community structure on Muizenberg Beach, South Africa (34°06.3′S 18°28.3′E), using two approaches. The first approach used photographic data to compare shorebird numbers across five lockdown levels in 2020 with equivalent periods in 2019 (prior to the pandemic) to determine the effects of contrasting levels of human abundance on shorebirds. Results from this component indicated that shorebird abundance was negatively related to human abundance and year, but positively associated with the lockdown levels. Most importantly, greatest shorebird abundance across the study were recorded under lockdown levels 5 and 4, when there were virtually no humans on the beach. Similarly, the lowest bird abundance was recorded under lockdown level 1, when human abundance was greatest for 2020. The second approach implemented in this study was based on in situ counts of shorebirds on Muizenberg Beach between lockdown levels 3 and 1 in 2020, to understand how intermediate to moderate levels of lockdown influenced shorebird community structure. PERMANOVA analysis indicated that while a significant difference in the shorebird community structure among lockdown levels was detected, it was secondary relative to zonal variation. SIMPER analysis showed Larus dominicanus (Kelp Gull) to be the dominant shorebird species, contributing the most to community structure within all three lockdown levels. Significant differences in community indices and L. dominicanus abundance were detected between zones but not lockdown levels, apart from the Shannon-Wiener diversity metric. In general, the minor effects of lockdown levels 3 to 1 on the shorebird community were attributed to high human numbers on the beach and low species variation across the respective lockdown levels. Overall, results indicate a strong negative relationship between shorebird and human abundance on Muizenberg Beach over a two-year period prior to, and including, periods of enforced lockdown. At intermediate to moderate levels, however, lockdown had minimal effects on community structure. In a global context, findings provide valuable information on human impacts on sandy beach shorebirds and suggest that closure for two months may positively impact bird communities within urban beach ecosystems.

Keywords

Applied Ocean Sciences

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