Persistence of wetlands on North Stradbroke Island (south‐east Queensland, Australia) during the last glacial cycle: implications for Quaternary science and biogeography

Abstract

Few Australian wetlands have persisted since the Last Glacial Maximum, with fewer still in existence through the entire last glacial cycle. The absence of wetlands, which itself indicates periods of moisture deficit, means there are few continuous climate and environmental change records covering this critical period. The lack of wetland persistence also raises the question of how plant and animal species that require permanent wetlands survived the last glacial cycle. Sixteen wetlands have been cored and dated on North Stradbroke Island (Minjerribah) – a large east Australian sand island – with basal dates reported from 10 sites for the first time. These wetlands range in age to over 200 000 years old, with six dating to the Last Glacial Maximum or earlier. There is no evidence of a stratigraphic discontinuity in the radiocarbon‐based age–depth profiles, suggesting continuous deposition of highly organic sediment through the period covered by these ages (c. 40 ka). The persistence of these wetlands suggests that for much of the last 40 000 years, and for perhaps much longer, the regional moisture balance has been positive. Over the last glacial cycle, persistently wet conditions may have provided a refuge from regional drying, and thus contributed to the high genetic diversity of rainforest plants in the region. Vegetation and climate records from these sites will allow hypothesis testing about the drivers of both local and regional climate variability. Copyright © 2017 John Wiley & Sons, Ltd.

Late Quaternary records and chronology of environmental change in the Southern Hemisphere – a contribution to SHAPE

“…The paper by Tibby et al . () is highly informative in this context, showing that North Stradbroke Island (south‐east Queensland) is unusual for Australia in maintaining wetlands throughout the LGM and for the past 100 000 years. This area at least retained positive effective moisture throughout this time and may therefore have acted as a refuge for aquatic plants and animals as well as favouring human population during the LGM.…”

“…The regional differences reported by these various studies illustrate the challenges of reconstructing complex precipitation patterns at the continental scale, and highlight a need to develop more robust proxies while concomitantly improving the dating of LGM records. The paper by Tibby et al (2017) is highly informative in this context, showing that North Stradbroke Island (south-east Queensland) is unusual for Australia in maintaining wetlands throughout the LGM and for the past 100 000 years. This area at least retained positive effective moisture throughout this time and may therefore have acted as a refuge for aquatic plants and animals as well as favouring human population during the LGM.…”

Groundwater mean residence times of a subtropical barrier sand island

“…The island is an important part of the coastal environment in south-east Queensland and provides a vital groundwater resource, recreational space for large urban areas and, most importantly, unique coastal ecosystems with many freshwater wetlands, lakes and marine coastal environments . The island also plays a major role in the palaeoclimate reconstructions for the east coast of Australia, as some of the longest sediment records have been extracted from the North Stradbroke Island wetlands (Barr et al, 2013(Barr et al, , 2019Tibby et al, 2016Tibby et al, , 2017. Apart from a small number of government reports (Leach, 2011), there are few studies on the groundwater resources of the island, and, to the best of our knowledge, there is no prior work on MRTs on large Early Quaternary subtropical islands.…”

Velvet worm (Phylum Onychophora) on a sand island, in a wetland: Flushed from a Pleistocene refuge by recent rainfall?

“…The answer remains uncertain, but there are several compelling lines of evidence that may explain this unusual situation. The palaeoecology of Welsby Lagoon has been studied, which has shown it to have continuously accrued wetland sediments for at least the past 80 000 years, making it one of the oldest continuous wetlands in Australia (Barr et al ; Tibby et al ; Cadd et al ). It retained a positive moisture balance even during the last glacial maximum, regarded as the driest period in the history of the Australian continent, probably because of its links to groundwater as a buffer from rainfall deficit (Cadd et al ).…”

“…Given this history, it is feasible that the perpetually moist microhabitats associated with the wetland have sustained a relic onychophoran population from an era of more widespread regional rainforest cover, which may have provided more widespread onychophoran habitat than is present today on the island. Groundwater‐fed wetlands have been identified previously as evolutionary refugia for moisture‐dependent biota (Davis et al ), and the wetlands of North Stradbroke Island have been considered to be important examples of such refugia (Tibby et al ).…”