Assessing the distribution and drivers of mangrove dieback in Kakadu National Park, northern Australia

Asbridge, Emma; Bartolo, Renée E.; Finlayson, C. Max; Lucas, Richard; Rogers, Kerrylee; Woodroffe, Colin D.

doi:10.1016/j.ecss.2019.106353

Cited by 52 publications

(46 citation statements)

References 40 publications

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“…Over 7000 ha of mangroves along ∼ 1000 km of the Gulf of Carpentaria coastline in Australia experienced mass mortality during the summer in 2015-2016 (Duke et al, 2017), the most extensive mangrove forest dieback ever recorded due to natural causes (Sippo et al, 2018). At the same time, there were coinciding mangrove mass mortality events in Exmouth, Western Australia (Lovelock et al, 2017), and Kakadu National Park, Northern Territory (Asbridge et al, 2019). The climate in the Gulf region is wet-dry tropical with mean annual precipitation ranging from approximately 600 to 900 mm.…”

Section: Study Sitementioning

confidence: 99%

“…In most cases, recovery of mangroves primarily relies on the recruitment of seedlings (Smith et al, 1994;Krauss and Osland, 2019). Disturbances in mangrove forests not only affect recruitment but can also change the cycling of C, N and S. Loss of mangrove trees and root structures can change organic matter inputs, sediment oxygenation and degradation of sediment organic matter, with consequences for benthic assemblages (Sweetman et al, 2010;Bernardino et al, 2018;Harada et al, 2019), the coastal carbon cycle (Jeffrey et al, 2019;Sippo et al, 2020b), sediment C and N stocks (Adame et al, 2018), microbial assemblages, and associated nutrient processes, e.g. nitrogen fixation and sulfate reduction (Sjöling et al, 2005).…”

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confidence: 99%

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Stable isotopes track the ecological and biogeochemical legacy of mass mangrove forest dieback in the Gulf of Carpentaria, Australia

Harada¹,

Connolly²,

Fry³

et al. 2020

Biogeosciences

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Abstract. A combination of elemental analysis, bulk stable isotope analysis (bulk SIA) and compound-specific stable isotope analysis of amino acids (CSIA-AA) was used to assess and monitor carbon (C), nitrogen (N) and sulfur (S) cycling of a mangrove ecosystem that suffered mass dieback of trees in the Gulf of Carpentaria, Australia in 2015–2016, attributed to an extreme drought event. Three field campaigns were conducted 8, 20 and 32 months after the event over a period from 2016 to 2018 to obtain biological time-series data. Invertebrates and associated organic matter including mangroves and sediments from the impacted ecosystem showed enrichment in 13C, 15N and 34S relative to those from an adjacent unimpacted reference ecosystem, likely indicating lower mangrove carbon fixation, lower nitrogen fixation and lower sulfate reduction in the impacted ecosystem. For example, invertebrates representing the feeding types of grazing, leaf feeding and algae feeding were more 13C enriched at the impacted site, by 1.7 ‰–4.1 ‰, and these differences did not change over the period from 2016 to 2018. The CSIA-AA data indicated widespread 13C enrichment across five essential amino acids and all groups sampled (except filter feeders) within the impacted site. The seedling density increased from 0.2 m−2 in 2016 to 7.1 m−2 in 2018 in the impacted forest, suggesting recovery of the vegetation. Recovery of CNS cycling, however, was not evident even after 32 months, suggesting a biogeochemical legacy of the mortality event. Continued monitoring of the post-dieback forest is required to predict the long-term trajectory of ecosystem recovery. This study shows that time-series SIA can track biogeochemical changes over time and evaluate recovery of an impacted ecosystem from an extreme event.

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Section: Study Sitementioning

confidence: 99%

mentioning

confidence: 99%

Stable isotopes track the ecological and biogeochemical legacy of mass mangrove forest dieback in the Gulf of Carpentaria, Australia

Harada¹,

Connolly²,

Fry³

et al. 2020

Biogeosciences

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“…This extreme climatic event drove the largest recorded mangrove mortality event (∼ 1000 km coastline, ∼ 7400 ha) attributed to natural causes (Duke et al, 2017;Harris et al, 2017;Sippo et al, 2018) and led to extensive changes in the coastal carbon cycle (Sippo et al, 2019(Sippo et al, , 2020 and coastal food webs (Harada et al, 2020). Two other large-scale mangrove dieback events occurred at the same time: one in Exmouth (Lovelock et al, 2017) and the other in Kakadu National Park, Australia (Asbridge et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

“…Mangroves provide a wide range of ecosystem services, including nursery habitat, carbon sequestration and coastal protection (Barbier et al, 2011;Donato et al, 2011). Climate change is a major threat to mangroves, which adds to existing stressors imposed by deforestation and over-exploitation (Hamilton and Casey, 2016;Richards and Friess, 2016).…”

Section: Introductionmentioning

confidence: 99%

Reconstructing extreme climatic and geochemical conditions during the largest natural mangrove dieback on record

et al. 2020

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Abstract. A massive mangrove dieback event occurred in 2015–2016 along ∼1000 km of pristine coastline in the Gulf of Carpentaria, Australia. Here, we use sediment and wood chronologies to gain insights into geochemical and climatic changes related to this dieback. The unique combination of low rainfall and low sea level observed during the dieback event had been unprecedented in the preceding 3 decades. A combination of iron (Fe) chronologies in wood and sediment, wood density and estimates of mangrove water use efficiency all imply lower water availability within the dead mangrove forest. Wood and sediment chronologies suggest a rapid, large mobilization of sedimentary Fe, which is consistent with redox transitions promoted by changes in soil moisture content. Elemental analysis of wood cross sections revealed a 30- to 90-fold increase in Fe concentrations in dead mangroves just prior to their mortality. Mangrove wood uptake of Fe during the dieback is consistent with large apparent losses of Fe from sediments, which potentially caused an outwelling of Fe to the ocean. Although Fe toxicity may also have played a role in the dieback, this possibility requires further study. We suggest that differences in wood and sedimentary Fe between living and dead forest areas reflect sediment redox transitions that are, in turn, associated with regional variability in groundwater flows. Overall, our observations provide multiple lines of evidence that the forest dieback was driven by low water availability coinciding with a strong El Niño–Southern Oscillation (ENSO) event and was associated with climate change.

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“…Such climatic variables have been reported as drivers of mangrove variability at local and regional scales 2 . Most notably, temperature, salinity and precipitation have been consistently reported as constraining abiotic variables in mangrove forest condition, and distribution 3 , and when altered have resulted in tree mortality 4 , change in species composition, and loss or reduction in function (e.g., ability to store carbon) 5 .…”

Section: Introductionmentioning

confidence: 99%

ENSO feedback drives variations in dieback at a marginal mangrove site

Hickey

Radford

Callow

et al. 2021

Sci Rep

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Ocean–atmosphere climatic interactions, such as those resulting from El Niño Southern Oscillation (ENSO) are known to influence sea level, sea surface temperature, air temperature, and rainfall in the western Pacific region, through to the north-west Australian Ningaloo coast. Mangroves are ecologically important refuges for biodiversity and a rich store of blue carbon. Locations such as the study site (Mangrove Bay, a World Heritage Site within Ningaloo Marine Park and Cape Range National Park) are at the aridity range-limit which means trees are small in stature, forests small in area, and are potentially susceptible to climate variability such as ENSO that brings lower sea level and higher temperature. Here we explore the relationship between mangrove dieback, and canopy condition with climatic variables and the Southern Oscillation Index (SOI)—a measure of ENSO intensity, through remote sensing classification of Landsat satellite missions across a 29 year period at a north-west Australian site. We find that the SOI, and seasonal mean minimum temperature are strongly correlated to mangrove green canopy (as indicator of live canopy) area. This understanding of climate variations and mangrove temporal heterogeneity (patterns of abundance and condition) highlights the sensitivity and dynamics of this mangrove forest and recommends further research in other arid and semi-arid tropical regions at mangrove range-limits to ascertain the extent of this relationship.

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Assessing the distribution and drivers of mangrove dieback in Kakadu National Park, northern Australia

Cited by 52 publications

References 40 publications

Stable isotopes track the ecological and biogeochemical legacy of mass mangrove forest dieback in the Gulf of Carpentaria, Australia

Stable isotopes track the ecological and biogeochemical legacy of mass mangrove forest dieback in the Gulf of Carpentaria, Australia

Reconstructing extreme climatic and geochemical conditions during the largest natural mangrove dieback on record

ENSO feedback drives variations in dieback at a marginal mangrove site

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