Does spatial scale affect the pattern of mangrove change under different rainfall regimes? An example in southeast Queensland, Australia

Abstract

The aim of this study was to investigate the interactions of natural and anthropogenic variables at different spatial scales related to changes in mangrove distribution during a relatively wet period (1972)(1973)(1974)(1975)(1976)(1977)(1978)(1979)(1980)(1981)(1982)(1983)(1984)(1985)(1986)(1987)(1988)(1989)(1990)) and a dry period (1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004) in subtropical eastern Australia. Previous research has demonstrated that mangroves are encroaching into salt marsh. Mangrove spatial change in southeast Queensland is related generally to landscape variables especially during the relatively wet period. What has not been explored is the spatial scale of the influence under the two rainfall regimes (wet and dry) and that is the aim of this paper. Ten sites were examined at different levels of resolution including catchment, sub-catchment and two buffer zones (1000 and 500 m), under the period of relatively higher and lower rainfall. Land use was ascertained from Landsat satellite imagery using Maximum Likelihood Classification techniques. Partial least squares regression analysis was used to study the relationships between the predictor variables and the rate of change in the mangrove distribution. The research has found that the impact of land use/cover on the encroachment of mangrove into saltmarsh can vary and appears to be related to rainfall patterns, which in turn affect hydrological connectivity. A major finding of this research was that the changing spatial patterns of mangroves during the wet period was more a function of land use/cover pattern and population density at the sub-catchment level, whereas during drier periods it was more affected by the local effects of nearby land use/cover in buffer zones.

Rainfall and its possible hysteresis effect on the proportional cover of tropical tidal-wetland mangroves and saltmarsh–saltpans

“…Several physical and climate drivers are recognised for their ability to limit and influence processes within coastal-estuarine wetland habitats (Duke et al 1998). These specifically include rising sea levels leading to upland encroachment (Jiang et al 2015;Lovelock et al 2015), increases in temperature, driving species shifts to higher latitudes (Osland et al 2013;Saintilan et al 2014), and variations in rainfall, affecting vegetation cover within the tidal-zone habitat (Eslami-Andargoli et al 2013;Osland et al 2014Osland et al , 2016. Although these studies and others have made substantive contributions, fundamental gaps remain in our understanding of how tidal-wetland ecosystems respond to change, and how particular drivers specifically influence ecosystem processes.…”

“…(2) Rainfall-influenced changes to mangrove v. saltmarsh vegetation within the latitudinal limits of mangroves, where mangrove expansion was linked primarily to wetter conditions (Duke et al 2003;Gilman et al 2008;Eslami-Andargoli et al 2013;Duke 2014). The alternate scenario is that mangrove loss or retreat is linked to drought and decreased precipitation (Duke et al 2003;Gilman et al 2008;Duke 2014;.…”

The impact of encroachment of mangroves into saltmarshes on saltwater mosquito habitats

“…It is beyond the scope of this paper to address the human land use planning issue, but population and land use are also drivers of mangrove encroachment into saltmarshes, especially when close to the wetland (e.g., Eslami‐Andergoli et al ). Land use planning in Queensland under the Sustainable Planning Act (2009) is intended to manage the ‘effects of development on the environment’ (Section 3b).…”

“…Mangrove spatial changes, land cover, and population changes were calculated as % change per year for each site, for both periods 1972–1990 and 1990–2004, using aerial photographs for mangrove mapping, Landsat satellite imagery was used for land use, and Australian Bureau of Census data for population (Eslami‐Andargoli et al , ).…”

Land‐based and climatic stressors of mangrove cover change in the Auckland Region, New Zealand

“…Significant increases of mangrove area along the Pacific coast of Mexico have been associated with sea‐level rise and warm surface waters during El Niño (López‐Medellín et al, ). Oceanic factors differ both between and within estuaries, in particular between the estuary mouth (downstream) and upstream estuary regions (Duke et al, , ; Eslami‐Andargoli, Dale, & Sipe, ; Hayes et al, ; Spier, Gerum, Noernberg, & Lana, ).…”