Ulrike Proske

The palaeoenvironmental development of the northeastern Vietnamese Mekong River Delta since the mid Holocene

Three radiocarbon-dated sediment cores from the northeastern Vietnamese Mekong River Delta have been analysed with a multiproxy approach (grain size, pollen and spores, macro-charcoal, carbon content) to unravel the palaeoenvironmental history of the region since the mid Holocene. During the mid-Holocene sea-level highstand a diverse, zoned and widespread mangrove belt (dominated by Rhizophora) covered the extended tidal flats. The subsequent regression and coeval delta progradation led to the rapid development of a back-mangrove community dominated by Ceriops and Bruguiera but also represented locally by e.g. Kandelia, Excoecaria and Phoenix. Along rivers this community seems to have endured even when the adjoining floodplain had already shifted to freshwater vegetation. Generally this freshwater vegetation has a strong swamp signature but locally Arecaceae, Fabaceae, Moraceae/ Urticaceae and Myrsinaceae are important and mirror the geomorphological diversity of the delta plain. The macro-charcoal record implies that natural burning of vegetation occurred throughout the records, however, the occurrence of the highest amounts of macro-charcoal particles is linked with modern human activity.

Island ecosystem and biodiversity dynamics in northeastern Australia during the Holocene: Unravelling short-term impacts and long-term drivers

Vegetation changes of tropical Lizard Island (Great Barrier Reef World Heritage Area, Australia) over the last 8000 years are derived from palaeoenvironmental analysis of a 475 cm long sediment core. During early-Holocene sea-level rise, flooding of the continental shelf and thus isolation of Lizard Island, the pollen record shows the gradual establishment of a mangrove forest paralleled by contraction of the near-coastal palm and grass-dominated vegetation. Subsequently, mid-Holocene relative environmental stability supported a diverse, Rhizophora-dominated mangrove and open, mixed sclerophyll vegetation inland. Around 6000 years ago, a profound disturbance of the mangrove is recorded by a siliciclastic layer and we hypothesise that this deposit documents the impact of a storm or cyclone. Postevent environmental conditions were strongly altered with enhanced estuarine conditions supporting a Sonneratia and Bruguiera-dominated mangrove forest. During late-Holocene sea-level fall and stabilisation, progradation and contraction of the mangrove forest was paralleled by the expansion of a palm-dominated swamp. Freshwater taxa continued to dominate the record, however, a distinct disturbance signal from anthropogenic activity is recorded in the last century. Although Sonneratia dominated the post-event mangrove, late-Holocene environmental instability led to the extinction of this genus on the island. Local environmental changes in the freshwater swamp and rainforest also led to the loss of Arenga and Ilex from the island’s ecosystems. Our record implies that long-term ecosystem and biodiversity change on Lizard Island is: (a) primarily reflected in the spatial extent of the island’s vegetation communities and the species dominance within them and (b) driven by an interplay between climate, sea-level and potentially human activity. In addition, a short-term impact provoked the reconfiguration of the mangrove, potentially causing long-term ecosystem instability and thus impacting on mangrove biodiversity development on the Great Barrier Reef islands.

Assessing wetland degradation and loss of ecosystem services in the Niger Delta, Nigeria

The Niger Delta, being the most extensive freshwater wetland and aquatic ecosystem in West Africa, provides numerous services both to local people and to the West African economy. Ongoing environmental pressure exerted by large-scale oil extraction and illegal timber logging, however, are suspected to have had a substantial impact on the Delta’s ecosystems over the last decades. Knowledge on impact of these activities on the region’s wetlands now or in the past is scarce and patchy. To address this lack of knowledge, this study assesses spatiotemporal changes in two wetlands in the region by using satellite data from 1984 to 2011 and GIS methods. The results show that both wetlands have experienced substantial degradation, particularly with respect to the area of forest lost. Although comprehensive environmental protection laws were introduced in 1988, ecosystem services of up to US

The palaeo-environmental history of Big Willum Swamp, Weipa: An environmental context for the archaeological record

65 million in value were lost over the study period. The introduction of new legislation in 2007, however, is potentially a first step towards a more ‘wise use’ of wetlands in Nigeria.

Using X-ray fluorescence core scanning to assess acid sulfate soils

Abstract The environmental history of Big Willum (Waandriipayn) Swamp and the surrounding landscape is reconstructed for the last 8000 years through the analysis of pollen, charcoal and mineral magnetics. The data provide a Holocene record of vegetation and fire in an area where few records exist. Swamp initiation at Big Willum began prior to 8000 cal. BP, with swamp–like conditions maintained until 2200 cal. BP, after which it became a permanent deep water body, reaching its present day extent between 600–400 cal. BP. From 7000–1200 cal. BP the surrounding woodland was essentially stable. Fire is present throughout the record, with only one period of pronounced burning outside of the historic period, at around 1000 cal. BP, leading to a slightly more open understorey/woodland. The hydrological change at 2200 cal. BP that led to Big Willum becoming a more permanent water body overlaps with the end of the most intensive period of shell mound formation and the commencement of earth mound building at nearby Wathayn. This is suggestive that change in, or diversification of, mound types may in part be linked to environmental transformations in the late Holocene. One possibility is that greater water security allowed for increasing and more permanent exploitation of inland locations.

Early growth stage of a large delta - Transformation from estuarine-platform to deltaic-progradational conditions (the northeastern Mekong River Delta, Vietnam)

During the formation of acid sulfate soils (ASS), several chemical elements in the sediment are mobilised. These elements are removed from the sediment or become enriched as precipitates in distinct horizons. The stratigraphic depth in which these precipitates accumulate is element-specific and is located either within the oxidised or in a transitional zonebetweentheoxidisedandthereducedzone.AimofthisstudyistodemonstratehowX-ray fluorescencecorescanning, together with detailed sediment descriptions, can be used to perform an initial assessment of these different zones in ASS in a fast and cost-effective manner. We measured the chemical element signatures of K, Fe, Pb, Sr, Zn, Ni, Y, Mn and Ca in two sediment cores from Western Australia where ASS are suspected to occur. The oxidised zone in both cores is characterised by the occurrence of jarosite, which is indicated by pale straw yellow mottling and synchronous peaks in Fe/ Ti, K/Ti, Pb/Ti and Sr/Ti, and of other secondary Fe-oxides, which are indicated by reddish mottling and synchronous peaks in Fe/Ti and Pb/Ti. The transition zone into reduced material is marked by synchronous peaks in Zn/Ti, Ni/Ti, Y/Ti and Mn/Ti. Based on these characteristic signatures, we broadly estimated the depth of the oxidised and the transitional zone at both sites.